forked from Imagelibrary/binutils-gdb
f17015417643be9d6cb03b840edbb9d8952671ec
134 Commits
| Author | SHA1 | Message | Date | |
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Nick Alcock
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f170154176 |
libctf: drop unnecessary macro
Every use of this macro has been deleted. |
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Nick Alcock
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9ea8bea7f0 |
libctf: link: BTF support
This is in two parts, one new API function and one change. New API: +int ctf_link_output_is_btf (ctf_dict_t *); Changed API: unsigned char *ctf_link_write (ctf_dict_t *, size_t *size, - size_t threshold); + size_t threshold, int *is_btf); The idea here is that callers can call ctf_link_output_is_btf on a ctf_link()ed (deduplicated) dict to tell whether a link will yield BTF-compatible output before actually generating that output, so they can e.g. decide whether to avoid trying to compress the dict if they know it would be BTF otherwise (since compressing a dict renders it non-BTF-compatible). ctf_link_write() gains an optional is_btf output parameter that reports whether the dict that was finally generated is actually BTF after all, perhaps because the caller didn't call ctf_link_output_is_btf or wants to be robust against possible future changes that may add other reasons why a written-out dict can't be BTF at the last minute. These are simple wrappers around already-existing machinery earlier in this series. |
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Nick Alcock
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5ec23dfb74 |
libctf: strings: no external strings in BTF
One of the things BTF doesn't have is the concept of external strings which can be shared with the ELF strtab. Therefore, even if the linker has reported strings which the dict is reusing, when we generate the strtab for a BTF dict we should emit those strings into it (and we should certainly not cause the presence of external strings to prevent BTF emission!) Note that since already-written strtab entries are never erased, writing a dict as BTF and then CTF will cause external strings to be emitted even for the CTF. This sort of repeated writing in different formats seems to be very rare: in any case, the problem can be avoided by simply doing the CTF writeout first (the following BTF writeout will spot the missing external- in-CTF strings and add them). We also throw away the internal-only function ctf_strraw_explicit(), which was used to add strings with a hardwired strtab: it was only ever used to write out the variable section, which is gone in v4. |
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Nick Alcock
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c14bdfc7a4 |
libctf: serialize: kind suppression and prohibition
The CTF serialization machinery decides whether to write out a dict as BTF or CTF (or, in LIBCTF_BTM_BTF mode, whether to write out a dict or fail with ECTF_NOTBTF) in part by looking at the type kinds in the dictionary. It is possible that you'd like to extend this check and ban specific type kinds from the dictionary (possibly even if it's CTF); it's also possible that you'd like to *not* fail even if a CTF-only kind is found, but rather replace it with a still-valid stub (CTF_K_UNKNOWN / BTF_KIND_UNKNOWN) and keep going. (The kernel's btfarchive machinery does this to ensure that the compiler and previous link stages have emitted only valid BTF type kinds.) ctf_write_suppress_kind supports both these use cases: +int ctf_write_suppress_kind (ctf_dict_t *fp, int kind, int prohibited); This commit adds only the core population code: the actual suppression is spread across the serializer and will be added in the next commits. |
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Nick Alcock
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2c5f74300a |
libctf: serialize: user control over BTF-versus-CTF writeout
We need some way for users to declare that they want BTF or CTF in
particular to be written out when they ask for it, or that they don't mind
which. Adding this to all the ctf_write functions (like the compression
threshold already is) would be a bit of a nightmare: there are a great many
of them and this doesn't seem like something people would want to change
on a per-dict basis (even if we did, we'd need to think about archives and
linking, which work on a higher level than single dicts).
So we repurpose an unused, vestigial existing function, ctf_version(), which
was originally intended to do some sort of rather unclear API switching at
runtime, to allow switching between different CTF file format versions (not
yet supported, you have to pass CTF_VERSION) and BTF writeout modes:
/* BTF/CTF writeout version info.
ctf_btf_mode has three levels:
- LIBCTF_BTM_ALWAYS writes out full-blown CTFv4 at all times
- LIBCTF_BTM_POSSIBLE writes out CTFv4 if needed to avoid information loss,
BTF otherwise. If compressing, the same as LIBCTF_BTM_ALWAYS.
- LIBCTF_BTM_BTF writes out BTF always, and errors otherwise.
Note that no attempt is made to downgrade existing CTF dicts to BTF: if you
read in a CTF dict and turn on LIBCTF_BTM_POSSIBLE, you'll get a CTF dict; if
you turn on LIBCTF_BTM_BTF, you'll get an unconditional error. Thus, this is
really useful only when reading in BTF dicts or when creating new dicts. */
typedef enum ctf_btf_mode
{
LIBCTF_BTM_BTF = 0,
LIBCTF_BTM_POSSIBLE = 1,
LIBCTF_BTM_ALWAYS = 2
} ctf_btf_mode_t;
/* Set the CTF library client version to the specified version: this is the
version of dicts written out by the ctf_write* functions. If version is
zero, we just return the default library version number. The BTF version
(for CTFv4 and above) is indicated via btf_hdr_len, also zero for "no
change".
You can influence what type kinds are written out to a CTFv4 dict via the
ctf_write_suppress_kind() function. */
extern int ctf_version (int ctf_version_, size_t btf_hdr_len,
ctf_btf_mode_t btf_mode);
(We retain the ctf_version_ stuff to leave space in the API to let the
library possibly do file format downgrades in future, since we've already
had requests for such things from users.)
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Nick Alcock
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f782340ba5 |
libctf, serialize: preparatory steps
The new serializer is quite a lot more customizable than the old, because it can write out BTF as well as CTF: you can ask to write out BTF or fail, write out CTF if required to avoid information loss, otherwise BTF, or always write out CTF. Callers often need to find out whether a dict could be written out as BTF before deciding how to write it out (because a dict can never be written out as BTF if it is compressed, a caller might well want to ask if there is anything else that prevents BTF writeout -- say, slices, conflicting types, or CTF_K_BIG -- before deciding whether to compress it). GNU ld will do this whenever it is passed only BTF sections on the input. Figuring out whether a dict can be written out as BTF is quite expensive: we have to traverse all the types and check them, including every member of every struct. So we'd rather do that work only once. This means making a lot of state once private to ctf_preserialize public enough that another function can initialize it; and since the whole API is available after calling this function and before serializing, we should probably arrange that if we do things we know will invalidate the results of all this checking, we are forced to do it again. This commit does that, moving all the existing serialization state into a new ctf_serialize_t and adding to it. Several functions grow force_ctf arguments that allow the caller to force CTF emission even if the type section looks BTFish: the writeout code and archive creation use this to force CTF emission if we are compressing, and archive creation uses it to force CTF emission if a CTF multi-member archive is in use, because BTF doesn't support archives at all so there's no point maintaining BTF compatibility in that case. The ctf_write* functions gain support for writing out BTF headers as well as CTF, depending on whether what was ultimately written out was actually BTF or not. Even more than most commits in this series, there is no way this is going to compile right now: we're in the middle of a major transition, completed in the next few commits. |
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Nick Alcock
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fb8917ac21 |
libctf, create, types: type and decl tags
These are a little more fiddly than previous kinds, because their namespacing rules are odd: they have names (so presumably we want an API to look them up by name), but the names are not unique (they don't need to be, because they are not entities you can refer to from C), so many distinct tags in the same TU can have the same name. Type tags only refer to a type ID: decl tags refer to a specific function parameter or structure member via a zero-indexed "component index". The name tables for these things are a hash of name to a set of type IDs; rather different from all the other named entities in libctf. As a consequence, they can presently be looked up only using their own dedicated functions, not using ctf_lookup_by_name et al. (It's not clear if this restriction could ever be lifted: ctf_lookup_by_name and friends return a type ID, not a set of them.) They are similar enough to each other that we can at least have one function to look up both type and decl tags if you don't care about their component_idx and only want a type ID: ctf_tag. (And one to iterate over them, ctf_tag_next). (A caveat: because tags aren't widely used or generated yet, much of this is more or less untested and/or supposition and will need testing later.) New API, more or less the minimum needed because it's not entirely clear how these things will be used: +ctf_id_t ctf_tag (ctf_dict_t *, ctf_id_t tag); +ctf_id_t ctf_decl_tag (ctf_dict_t *, ctf_id_t decl_tag, + int64_t *component_idx); +ctf_id_t ctf_tag_next (ctf_dict_t *, const char *tag, ctf_next_t **); +ctf_id_t ctf_add_type_tag (ctf_dict_t *, uint32_t, ctf_id_t, const char *); +ctf_id_t ctf_add_decl_type_tag (ctf_dict_t *, uint32_t, ctf_id_t, const char *); +ctf_id_t ctf_add_decl_tag (ctf_dict_t *, uint32_t, ctf_id_t, const char *, + int component_idx); |
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Nick Alcock
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a632f3ed33 |
libctf, types: ctf_type_kind_{iter,next} et al
These new functions let you iterate over types by kind, letting you get all
variables, all enums, all datasecs, etc. (This is amenable to future
optimization, and some is expected shortly.)
We also add new iternal functions ctf_type_kind_{forwarded_,unsliced_,}tp
which are like the corresponding non-_tp functions except that they
take a ctf_type_t rather than a type ID: doing this allows the deduplicator
to use these nearly-public functions more. The public ctf_type_kind*
functions are reimplemented in terms of these.
This machinery is the principal place where the magic encoding of forwards
is encoded.
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Nick Alcock
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ea21a1b2ae |
libctf: create, types: variables and datasecs (REVIEW NEEDED)
This is an area of significant difference from CTFv3. The API changes significantly, with quite a few additions to allow creation and querying of these new datasec entities: -typedef int ctf_variable_f (const char *name, ctf_id_t type, void *arg); +typedef int ctf_variable_f (ctf_dict_t *, const char *name, ctf_id_t type, + void *arg); +typedef int ctf_datasec_var_f (ctf_dict_t *fp, ctf_id_t type, size_t offset, + size_t datasec_size, void *arg); +/* Search a datasec for a variable covering a given offset. + + Errors with ECTF_NODATASEC if not found. */ + +ctf_id_t ctf_datasec_var_offset (ctf_dict_t *fp, ctf_id_t datasec, + uint32_t offset); + +/* Return the datasec that a given variable appears in, or ECTF_NODATASEC if + none. */ + +ctf_id_t ctf_variable_datasec (ctf_dict_t *fp, ctf_id_t var); +int ctf_datasec_var_iter (ctf_dict_t *, ctf_id_t, ctf_datasec_var_f *, + void *); +ctf_id_t ctf_datasec_var_next (ctf_dict_t *, ctf_id_t, ctf_next_t **, + size_t *size, size_t *offset); -int ctf_add_variable (ctf_dict_t *, const char *, ctf_id_t); +/* ctf_add_variable adds variables to no datasec at all; + ctf_add_section_variable adds them to the given datasec, or to no datasec at + all if the datasec is NULL. */ + +ctf_id_t ctf_add_variable (ctf_dict_t *, const char *, int linkage, ctf_id_t); +ctf_id_t ctf_add_section_variable (ctf_dict_t *, uint32_t, + const char *datasec, const char *name, + int linkage, ctf_id_t type, + size_t size, size_t offset); We tie datasecs quite closely to variables at addition (and, as should become clear later, dedup) time: you never create datasecs, you only create variables *in* datasecs, and the datasec springs into existence when you do so: datasecs are always found in the same dict as the variables they contain (the variables are never in the parent if the datasec is in a child or anything). We keep track of the variable->datasec mapping in ctf_var_datasecs (populating it at addition and open time), to allow ctf_variable_datasec to work at reasonable speed. (But, as yet, there are no tests of this function at all.) The datasecs are created unsorted (to avoid variable addition becoming O(n^2)) and sorted at serialization time, and when ctf_datasec_var_offset is invoked. We reuse the natural-alignment code from struct addition to get a plausible offset in datasecs if an alignment of -1 is specified: maybe this is unnecessary now (it was originally added when ctf_add_variable added variables to a "default datasec", while now it just leaves them out of all datasecs, like externs are). One constraint of this is that we currently prohibit the addition of nonrepresentable-typed variables, because we can't tell what their natural alignment is: if we dropped the whole "align" and just required everyone adding a variable to a datasec to specify an offset, we could drop that restriction. WDYT? One additional caveat: right now, ctf_lookup_variable() looks up the type of a variable (because when it was invented, variables were not entities in themselves that you could look up). This name is confusing as hell as a result. It might be less confusing to make it return the CTF_K_VAR, but that would be awful to adapt callers to, since both are represented with ctf_id_t's, so the compiler wouldn't warn about the needed change at all... I've vacillated on this three or four times now. |
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Nick Alcock
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4a4312b684 |
libctf: types: ctf_type_resolve_nonrepresentable
This new internal function allows us to say "resolve a type to its base type, but treat type 0 like BTF, returning 0 if it is found rather than erroring with ECTF_NONREPRESENTABLE". Used in the next commit. |
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Nick Alcock
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20e6f72dc7 |
libctf: create: structure and union member addition
There is one API addition here:
int ctf_add_member_bitfield (ctf_dict_t *, ctf_id_t souid,
const char *, ctf_id_t type,
unsigned long bit_offset,
int bit_width);
SoU addition handles the representational changes for bitfields and for
CTF_K_BIG structs (i.e. all structs you can add members to), errors out if
you add bitfields to structs that aren't created with the
CTF_ADD_STRUCT_BITFIELDS flag, and arranges to add padding as needed if
there is too much of a gap for the offsets to encode in one hop (that
part is still untested).
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Nick Alcock
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05a2970ad1 |
libctf: create, lookup: delete DVDs; ctf_lookup_by_kind
Variable handling in BTF and CTFv4 works quite differently from in CTFv3. Rather than a separate section containing sorted, bsearchable variables, they are simply named entities like types, stored in CTF_K_VARs. As a first stage towards migrating to this, delete most references to the ctf_varent_t and ctf_dvdef_t, including the DVD lookup code, all the linking code, and quite a lot of the serialization code. Note: CTF_LINK_OMIT_VARIABLES_SECTION, and the whole "delete variables that already exist in the symtypetabs section" stuff, has yet to be reimplemented. We can implement CTF_LINK_OMIT_VARIABLES_SECTION by simply excising all CTF_K_VARs at deduplication time if requested. (Note: symtypetabs should still point directly at the type, not at the CTF_K_VAR.) (Symtypetabs in general need a bit more thought -- perhaps we can now store them in a separate .ctf.symtypetab section with its own little four-entry header for the symtypetabs and their indexes, making .ctf even more like .BTF; the only difference would then be that .ctf could include prefix types, CTF_K_FLOAT, and external string refs. For later discussion.) We also add ctf_lookup_by_kind() at this stage (because it is hopelessly diff-entangled with ctf_lookup_variable): this looks up a type of a particular kind, without needing a per-kind lookup function for it, nor needing to hack around adding string prefixes (so you can do ctf_lookup_by_kind (fp, CTF_K_STRUCT, "foo") rather than having to do ctf_lookup_by_name (fp, "struct foo"): often this is more convenient, and anything that reduces string buffer manipulation in C is good.) |
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Nick Alcock
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64b65a0a34 |
libctf: types: struct/union member querying and iteration
This commit revises ctf_member_next, ctf_member_iter, ctf_member_count, and
ctf_member_info for the new CTFv4 world. This also pulls in a bunch of
infrastructure used by most of the type querying functions, and fundamental
changes to the way DTD records are represented in libctf (ctf-create not yet
adjusted). Other type querying functions affected by changes in struct
representation are also changed.
There are some API changes here: new bit-width fields in ctf_member_f,
ctf_membinfo_t and ctf_member_next, and a fix to the type of the offset in
ctf_member_f, ctf_membinfo_t and and ctf_member_count. (ctf_member_next got
the offset type right already.)
ctf_member_f also gets a new ctf_dict_t arg so that you can actually use
the member type it passes in without having to package up and pass in the
dict type yourself (a frequent need). This change is later echoed in most
of the rest of the *_f typedefs.
typedef struct ctf_membinfo
{
ctf_id_t ctm_type; /* Type of struct or union member. */
- unsigned long ctm_offset; /* Offset of member in bits. */
+ size_t ctm_offset; /* Offset of member in bits. */
+ int ctm_bit_width; /* Width of member in bits: -1: not bitfield */
} ctf_membinfo_t;
-typedef int ctf_member_f (const char *name, ctf_id_t membtype,
- unsigned long offset, void *arg);
+typedef int ctf_member_f (ctf_dict_t *, const char *name, ctf_id_t membtype,
+ size_t offset, int bit_width, void *arg);
extern ssize_t ctf_member_next (ctf_dict_t *, ctf_id_t, ctf_next_t **,
const char **name, ctf_id_t *membtype,
- int flags);
+ int *bit_width, int flags);
-int ctf_member_count (ctf_dict_t *, ctf_id_t);
+ssize_t ctf_member_count (ctf_dict_t *, ctf_id_t);
The DTD changes are that where before the ctf_dtdef_t had a dtd_data which
was the ctf_type_t type node for a type, and a separate dtd_vlen which was
the vlen buffer which (in the final serialized representation) would
directly follow that type, now it has one single buffer, dtd_buf, which
consists of a stream of one or more ctf_type_t nodes, followed by a vlen,
as it will appear in the final serialized form. This buffer has internal
pointers into it: dtd_data is a pointer to the last ctf_type_t in the stream
(the true type node, after all prefixes), and dtd_vlen is a pointer to the
vlen (precisely one ctf_type_t after the dtd_data). This representation is
nice because it means there is even less distinction between a dynamic type
added by ctf_add_*() and a static one read directly out of a dict: you can
traverse the entire type without caring where it came from, simplifying
most of the type querying functions.
(There are a few more things in there which will be useful mostly when
adding new types: their uses will be seen later.)
Two new nontrivial functions exist (one of which is annoyingly tangled up in
the diff, sorry about that): ctf_find_prefix, which hunts down a given
prefix (if it exists) among the possibly many that may exist on a type (so
you can ask it to find the CTF_K_BIG prefix for a type if it exists, and
it'll return you a pointer to its ctf_type_t record), and ctf_vlen, which
you hand a type ID and its ctf_type_t *, and it gives you back a pointer to
its vlen and tells you how long it is. (This is one of only two places left
in ctf-types.c which cares whether a type is dynamic or not. The other has
yet to be added). Almost every function in ctf-types.c will end up calling
ctf_lookup_by_id and ctf_vlen in turn.
ctf_next_t has changed significantly: the ctn_type member is split in two so
that we can tell whether a given iterator works using types or indexes, and
we gain the ability to iterate over enum64s, DTDs themselves, and datasecs
(most of this will only be used in later commits).
The old internal function ctf_struct_member, which handled the distinction
between ctf_member_t and ctf_lmember_t, is gone. Instead we have new code
that handles the different representation of bitfield versus non-bitfield
structs and unions, and more code to handle the different representation of
CTF_K_BIG structs and unions (their offsets are the distance from the last
offset, rather than the distance from the start of the structure).
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Nick Alcock
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ad13b7d44f |
libctf: CTFv4: type opening
The majority of this commit rejigs the core type table opening code for CTFv4: there are a few ancillary bits it drags in, indicated below. The internal definition of a child dict (that may not have type or string lookups performed in it until ctf_open time) used to be 'has a cth_parent_name', but since BTF doesn't have one of those at all, we add an additional check: a dict the first byte of whose strtab is not 0 must be a child. (If *either* is true, this is a child dict, which allows for the possibility of CTF dicts with non-deduplicated strtabs -- thus with leading \0's -- to exist in future.) The initial sweep through the type table in init_static_types (to size the name-table lookup hashes) also now checks for various types which indicate that this must be a CTF dict, in addition to being adjusted to cater for new CTFv4 representations of things like forwards. (At this early stage, we cannot rely on the functions in ctf-type.c to abstract over this for us.) We make some new hashtables for new namespace-like things: datasecs and type and decl tags. The main name-population loop in init_static_types_names_internal takes prefixes into account, looking for the name on the suffix type (where the name is always found). LSTRUCT handling is removed (they no longer exist); ENUM64s, enum forwards, VARs, datasecs, and type and decl tags get their names suitably populated. Some buggy code which tried to populate the name tables for cvr-quals (which are nameless) was dropped. We add an extra pass which traverses all datasecs and keeps track of which datasec each var is instantiated in (if any) in a new ctf_var_datasecs hash table. (This uses a number of type-querying functions which don't yet exist: they'll be added in the upcoming commits.) We handle the type 0 == void case by pointing the first element of ctf_txlate at a type read in named "void" (making type 0 an alias to it), or, if one doesn't exist, creating a new one (outside the type table and dtd arrays), and pointing type 0 at that. Since it is numbered 0 and not in the type table or dtd arrays, it will never be written out at serialization time, but since it is *present*, libctf consumers who expect the void type to have an integral definition rather than being a magic number will get what they expect. |
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Nick Alcock
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f7d05ab342 |
libctf: CTFv4: core opening (other than the type table)
This commit modifies the core opening code to handle opening CTFv4 and BTF. Much of the back-compatibility side is left for later and is currently untested, as is the type table side of things. We keep the v3 header (if any) stashed away in ctf_dict_t.ctf_v3_header, for the sake of the CTF dumper; we "upgrade" the BTF header to CTF (so that the rest of the code can ignore the distinction, and so that you can do CTFish things like adding symtypetab entries even to things opened as BTF), but keep note of the fact that it was opened as BTF in ctf_dict_t.ctf_opened_btf, so that things like ctf_import can allow for the absence of the various parent-length fields. A couple of ctf_dict_t fields are renamed for consistency with the headers' names for them (ctf_parname becomes ctf_parent_name; ctf_dynparname becomes ctf_dyn_parent_name; ctf_cuname becomes ctf_cu_name). Not all users are yet adjusted. |
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Nick Alcock
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99e9ab4828 |
libctf: adjust foreign-endian byteswapping for v4
Split into a separate commit because it's not yet really tested. Callers not yet adjusted. |
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Nick Alcock
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2ef9554023 |
libctf: ctf-lookup: support prefixes in ctf_lookup_by_id
ctf_lookup_by_id now has a new optional suffix argument, which, if set, returns the suffix of a prefixed type: the ctf_type_t it returns remains (as ever) the first one in the type (i.e. it may be a prefix type). This is most convenient because the prefix is the ctf_type_t that LCTF_KIND and other LCTF functions taking ctf_type_t's expect. Callers not yet adjusted. |
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Nick Alcock
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a80b903b45 |
libctf: simplify ctf_txlate
Before now, this critical internal structure was an array mapping from a type ID to the type index of the type with that ID. This was critical for the old world in which ctf_update() reserialized the entire dict, so things moved around in memory all the time: but these days, a ctf_type_t * never moves after creation, so we can just make ctf_txlate an array of ctf_type_t * and be done with it. This lets us point type indexes anywhere in memory, not just to entries in the ctf_buf, which means we can have synthetic ones for various purposes. And we will. |
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Nick Alcock
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1d70873382 |
libctf: dynhash/dynset: a bit of const-correctness
A pile of dynhash and dynset functions were requiring non-const hashes/sets unnecessarily. Fix them. |
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Nick Alcock
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40aea6c596 |
libctf: ctf_next_t.ctn_size: make a size_t
Literally every single user would rather this is a size_t, rather than an ssize_t. Change it. |
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Nick Alcock
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6a4a485c7b |
libctf: adapt core dictops for v4 and prefix types
The heart of libctf's reading code is the ctf_dictops_t and the functions it provides for reading various things no matter what the CTF version in use: these are called via LCTF_*() macros that translate into calls into the dictops. The introduction of prefix types in v4 requires changes here: in particular, we want the ability to get the type kind of whatever ctf_type_t we are looking at (the 'unprefixed' kind), as well as the ability to get the type kind taking prefixes into account: and more generally we want the ability to both look at a given prefix and look at the type as a whole. So several ctf_dictops_t entries are added for this (ctfo_get_prefixed_kind, ctfo_get_prefixed_vlen). This means API changes (no callers yet adjusted, it'll happen as we go), because the existing macros were mostly called with e.g. a ctt_info value and returned a type kind, while now we need to be called with the actual ctf_type_t itself, so we can possibly walk beyond it to find the real type record. ctfo_get_vbytes needs adjusting for this. We also add names to most of the ctf_type_t parameters, because suddenly we can have up to three of them: one relating to the first entry in the type record (which may be a prefix, usually called 'prefix'), one relating to the true type record (which may be a suffix, so usually called 'suffix'), and one possibly relating to some intermediate record if we have multiple prefixes (usually called 'tp'). There is one horrible special case in here: the vlen of the new CTF_K_FUNC_LINKAGE kind (equivalent to BTF_KIND_FUNC) is always zero: it reuses the vlen field to encode the linkage (!). BTF is rife with ugly hacks like this. |
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Nick Alcock
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ab3ad58be9 |
libctf: don't warn about unused fp in ctf_assert
When hash debugging is enabled and NDEBUG is not set, ctf_assert() translates into a true assert(). Don't leave the fp parameter unused in this case (which can cause compiler errors when -Werror is also on). |
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Nick Alcock
|
b5d3790c66 |
libctf: consecutive ctf_id_t assignment
This change modifies type ID assignment in CTF so that it works like BTF: rather than flipping the high bit on for types in child dicts, types ascend directly from IDs in the parent to IDs in the child, without interruption (so type 0x4 in the parent is immediately followed by 0x5 in all children). Doing this while retaining useful semantics for modification of parents is challenging. By definition, child type IDs are not known until the parent is written out, but we don't want to find ourselves constrained to adding types to the parent in one go, followed by all child types: that would make the deduplicator a nightmare and would frankly make the entire ctf_add*() interface next to useless: all existing clients that add types at all add types to both parents and children without regard for ordering, and breaking that would probably necessitate redesigning all of them. So we have to be a litle cleverer. We approach this the same way as we approach strings in the recent refs rework: if a parent has children attached (or has ever had them attached since it was created or last read in), any new types created in the parent are assigned provisional IDs starting at the very top of the type space and working down. (Their indexes in the internal libctf arrays remain unchanged, so we don't suddenly need multigigabyte indexes!). At writeout (preserialization) time, we traverse the type table (and all other table containing type IDs) and assign refs to every type ID in exactly the same way we assign refs to every string offset (just a different set of refs -- we don't want to update type IDs with string offset values!). For a parent dict with children, these refs are real entities in memory: pointers to the memory locations where type IDs are stored, tracked in the DTD of each type. As we traverse the type table, we assign real IDs to each type (by simple incrementation), storing those IDs in a new dtd_final_type field in the DTD for each type. Once the type table and all other tables containing type IDs are fully traversed, we update all the refs and overwrite the IDs currently residing in each with the final IDs for each type. That fixes up IDs in the parent dict itself (including forward references in structs and the like: that's why the ref updates only happen at the end); but what about child dicts' references, both to parent types and to their own? We add armouring to enforce that parent dicts are always serialized before their children (which ctf-link.c already does, because it's a precondition for strtab deduplication), and then arrange that when a ref is added to a type whose ID has been assigned (has a dtd_final_type), we just immediately do an update rather than storing a ref for later updating. Since the parent is already serialized, all parent type IDs have a dtd_final_type by this point, and all parent IDs in the children are properly updated. The child types can now be renumbered now we now the number of types in the parent, and their refs updated identically to what was just done with the parent. One wrinkle: before the child refs are updated, while we are working over the child's type section, the type IDs in the child start from 1 (or something like that), which might seem to overlap the parent IDs. But this is not the case: when you serialize the parent, the IDs written out to disk are changed, but the only change to the representation in memory is that we remember a dtd_final_type for each type (and use it to update all the child type refs): its ID in memory is the same as it always was, a nonoverlapping provisional ID higher than any other valid ID. We enforce all of this by asserting that when you add a ref to a type, the memory location that is modified must be in the buffer being serialized: the code will not let you accidentally modify the actual DTDs in memory. We track the number of types in the parent in a new CTFv4 (not BTF) header field (the dumper is updated): we will also use this to open CTFv3 child dicts without change by simply declaring for them that the parent dict has 2^31 types in it (or 2^15, for v2 and below): the IDs in the children then naturally come out right with no other changes needed. (Right now, opening CTFv3 child dicts requires extra compatibility code that has not been written, but that code will no longer need to worry about type ID differences.) Various things are newly forbidden: - you cannot ctf_import() a child into a parent if you already ctf_add()ed types to the child, because all its IDs would change (and since you already cannot ctf_add() types to a child that hasn't had its parent imported, this in practice means only that ctf_create() must be followed immediately by a ctf_import() if this is a new child, which all sane clients were doing anyway). - You cannot import a child into a parent which has the wrong number of (non-provisional) types, again because all its IDs would be wrong: because parents only add types in the provisional space if children are attached to it, this would break the not unknown case of opening an archive, adding types to the parent, and only then importing children into it, so we add a special case: archive members which are not children in an archive with more than one member always pretend to have at least one child, so type additions in them are always provisional even before you ctf_import anything. In practice, this does exactly what we want, since all archives so far are created by the linker and have one parent and N children of that parent. Because this introduces huge gaps between index and type ID for provisional types, some extra assertions are added to ensure that the internal ctf_type_to_index() is only ever called on types in the current dict (never a parent dict): before now, this was just taken on trust, and it was often wrong (which at best led to wrong results, as wrong array indexes were used, and at worst to a buffer overflow). When hash debugging is on (suggesting that the user doesn't mind expensive checks), every ctf_type_to_index() triggers a ctf_index_to_type() to make sure that the operations are proper inverses. Lots and lots of tests are added to verify that assignment works and that updating of every type kind works fine -- existing tests suffice for type IDs in the variable and symtypetab sections. The ld-ctf tests get a bunch of largely display-based updates: various tests refer to 0x8... type IDs, which no longer exist, and because the IDs are shorter all the spacing and alignment has changed. |
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Nick Alcock
|
beccf36b88 |
libctf: move string deduplication into ctf-archive
This means that any archive containing dicts can get its strings dedupped together, rather than only those that are ctf_linked. (For now, we are still constrained to ctf_linked archives, since fixing that requires further changes to ctf_dedup_strings: but this gives us the first half of what is necessary.) libctf/ * ctf-link.c (ctf_link_write): Move string dedup into... * ctf-archive.c (ctf_arc_preserialize): ... this new function. (ctf_arc_write_fd): Call it. |
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Nick Alcock
|
a480362d88 |
libctf: string: refs rework
This commit moves provisional (not-yet-serialized) string refs towards the
scheme to be used for CTF IDs in the future. In particular
- provisional string offsets now count downwards from just under the
external string offset space (all bits on but the high bit). This makes
it possible to detect an overflowing strtab, and also makes it trivial to
determine whether any string offset (ref) updates were missed -- where
before we might get a slightly corrupted or incorrect string, we now get
a huge high strtab offset corresponding to no string, and an error is
emitted at read time.
- refs are emitted at serialization time during the pass through the types.
They are strictly associated with the newly-written-out buffer: the
existing opened CTF dict is not changed, though it does still get the new
strtab so that new refs to the same string can just refer directly to it.
The provisional strtab hash table that contains these strings is not
deleted after serialization (because we might serialize again): instead,
we keep track in the parent of the lowest-yet-used ("latest") provisional
strtab offset, and any strtab offset above that, but not external
(high-bit-on) is considered provisional.
This is sort-of-enforced by moving most of the ref-addition function
declarations (including ctf_str_add_ref) to a new ctf-ref.h, which is
not included by ctf-create.c or ctf-open.c.
- because we don't add refs when adding types, we don't need to handle the
case where we add things to expanding vlens (enums, struct members) and
have to realloc() them. So the entire painful movable refs system can
just be deleted, along with the ability to remove refs piecemeal at all
(purging all of them is still possible). Strings added during type
addition are added via ctf_str_add(), which adds no refs: the strings are
picked up at serialization time and refs to their final, serialized
resting place added. The DTDs never have any refs in them, and their
provisional strtab offsets are never updated by the ref system.
This caused several bugs to fall out of the earlier work and get fixed.
In particular, attempts to look up a string in a child dict now search
the parent's provisional strtab too: we add some extra special casing
for the null string so we don't need to worry about deduplication
moving it somewhere other than offset zero.
Finally, the optimization that removes an unreferenced synthetic external
strtab (the record of the strings the linker has told us about, kept around
internally for lookup during late serialization) is faulty: references to a
strtab entry will only produce CTF-level refs if their value might change,
and an external string's offset won't change, so it produces no refs: worse
yet, even if we did get a ref (say, if the string was originally believed
to be internal and only later were we told that the linker knew about it
too), when we serialize a strtab, all its refs are dropped (since they've
been updated and can no longer change); so if we serialized it a second
time, its synthetic external strtab would be considered empty and dropped,
even though the same external strings as before still exist, referencing
it. We must keep the synthetic external strtab around as long as external
strings exist that reference it, i.e. for the life of the dict.
One benefit of all this: now we're emitting provisional string offsets at
a really high value, it's out of the way of the consecutive, deduplicated
string offsets in child dicts. So we can drop the constraint that you
cannot add strings to a dict with children, which allows us to add types
freely to parent dicts again. What you can't do is write that dict out
again: when we serialize, we currently update the dict being serialized
with the updated strtabs: when you write a dict out, its provisional
strings become real strings, and suddenly the offsets would overlap once
more. But opening a dict and its children, adding to it, and then
writing it out again is rare indeed, and we have a workaround: anyone
wanting to do this can just use ctf_link instead.
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Nick Alcock
|
97a72b2a35 |
libctf: create: fix vlen / vbytes confusion
The initial_vlen parameter to ctf_add_generic is misnamed: it's not the initial vlen (the initial number of members of a struct, etc), but rather the initial size of the vlen region. We have a term for that, vbytes: use it. Amazingly this doesn't seem to have caused any bugs to creep in. |
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Nick Alcock
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dc93d01ff2 |
libctf: de-macroize LCTF_TYPE_TO_INDEX / LCTF_INDEX_TO_TYPE
Making these functions is unnecessary right now, but will become much clearer shortly. While we're at it, we can drop the third child argument to LCTF_INDEX_TO_TYPE: it's only used for nontrivial purposes that aren't literally the same as getting the result from the fp in one place, in ctf_lookup_by_name_internal, and that place is easily fixed by just looking in the right dictionary in the first place. |
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Nick Alcock
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b875301e74 |
libctf: drop LCTF_TYPE_ISPARENT/LCTF_TYPE_ISCHILD
Parent/child determination is about to become rather more complex, making a macro impractical. Use the ctf_type_isparent/ischild function calls everywhere and remove the macro. Make them more const-correct too, to make them more widely usable. While we're about it, change several places that hand-implemented ctf_get_dict() to call it instead, and armour several functions against the null returns that were always possible in this case (but previously unprotected-against). |
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Nick Alcock
|
9835747b21 |
libctf: generalize the ref system
Despite the removal of the separate movable ref list, the ref system as a whole is more than complex enough to be worth generalizing now that we are adding different kinds of ref. Refs now are lists of uint32_t * which can be updated through the pointer for all entries in the list and moved to new sites for all pointers in a given range: they are no longer references to string offsets in particular and can be references to other uint32_t-sized things instead (note that ctf_id_t is a typedef to a uint32_t). ctf-string.c has been adjusted accordingly (the adjustments are tiny, more or less just turning a bunch of references to atom into &atom->csa_refs). |
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Nick Alcock
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21f748e1e3 |
libctf, string: delete separate movable ref storage again
This was added last year to let us maintain a backpointer to the movable refs dynhash in movable ref atoms without spending space for the backpointer on the majority of (non-movable) refs and also without causing an atom which had some refs movable and some refs not movable to dereference unallocated storage when freed. The backpointer's only purpose was to let us locate the ctf_str_movable_refs dynhash during item freeing, when we had nothing but a pointer to the atom being freed. Now we have a proper freeing arg, we don't need the backpointer at all: we can just pass a pointer to the dict in to the atoms dynhash as a freeing arg for the atom freeing functions, and throw the whole backpointer and separate movable ref list complexity away. |
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Nick Alcock
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6a6a3cc9c2 |
libctf, hash: add support for freeing functions taking an arg
There are a bunch of places in libctf where the code is complicated by the fact that freeing a hash key or value requires access to the dict: more generally, they want an arg pointer to *something*. But for the sake of being able to use free() as a freeing function, we can't do this at all times. We also don't want to bloat up the hash itself with an arg value unless necessary (in the same way we already avoid storing the key or value freeing functions unless at least one of them is specified). So from the outside this change is simple: add a new ctf_dynhash_create_arg which takes a new sort of freeing function which takes an argument. Internally, we store the arg only when the key or owner is set, and cast from the one freeing function to the other iff the arg is non-NULL. This means it's impossible to pass a value that may or may not be NULL to the freeing function, but that's harmless for all current uses, and allows significant simplifications elsewhere. |
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Nick Alcock
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4d2d5afa60 |
libctf: actually deduplicate the strtab
This commit finally implements strtab deduplication, putting together all
the pieces assembled in the earlier commits.
The magic is entirely localized to ctf_link_write, which preserializes all
the dicts (parent first), and calls ctf_dedup_strings on the parent.
(The error paths get tweaked a bit too.)
Calling ctf_dedup_strings has implications elsewhere: the lifetime rules for
the inputs versus outputs change a bit now that the child output dicts
contain references to the parent dict's atoms table. We also pre-purge
movable refs from all the deduplicated strings before freeing any of this
because movable refs contain backreferences into the dict they came from,
which means the parent contains references to all the children! Purging
the refs first makes those references go away so we can free the children
without creating any wild pointers, even temporarily.
There's a new testcase that identifies a regression whereby offset 0 (the
null string) and index 0 (in children now often the parent dict name,
".ctf") got mixed up, leading to anonymous structs and unions getting the
not entirely C-valid name ".ctf" instead.
May other testcases get adjusted to no longer depend on the precise layout
of the strtab.
TODO: add new tests to verify that strings are actually being deduplicated.
libctf/
* ctf-link.c (ctf_link_write): Deduplicate strings.
* ctf-open.c (ctf_dict_close): Free refs, then the link outputs,
then the out cu_mapping, then the inputs, in that order.
* ctf-string.c (ctf_str_purge_refs): Not static any more.
* ctf-impl.h: Declare it.
ld/
* testsuite/ld-ctf/conflicting-cycle-2.A-1.d: Don't depend on
strtab contents.
* testsuite/ld-ctf/conflicting-cycle-2.A-2.d: Likewise.
* testsuite/ld-ctf/conflicting-cycle-2.parent.d: Likewise.
* testsuite/ld-ctf/conflicting-cycle-3.C-1.d: Likewise.
* testsuite/ld-ctf/conflicting-cycle-3.C-2.d: Likewise.
* testsuite/ld-ctf/anonymous-conflicts*: New test.
|
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Nick Alcock
|
9daceda796 |
libctf: dedup: add strtab deduplicator
This is a pretty simple two-phase process (count duplicates that are actually going to end up in the strtab and aren't e.g. strings without refs, strings with external refs etc, and move them into the parent) with one wrinkle: we sorta-abuse the csa_external_offset field in the deduplicated child atom (normally used to indicate that this string is located in the ELF strtab) to indicate that this atom is in the *parent*. If you think of "external" as meaning simply "is in some other strtab, we don't care which one", this still makes enough sense to not need to change the name, I hope. This is still not called from anywhere, so strings are (still!) not deduplicated, and none of the dedup machinery added in earlier commits does anything yet. libctf/ * ctf-dedup.c (ctf_dedup_emit_struct_members): Note that strtab dedup happens (well) after struct member emission. (ctf_dedup_strings): New. * ctf-impl.h (ctf_dedup_strings): Declare. |
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Nick Alcock
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3bec4f1f3c |
include, libctf: string lookup and writeout of a parent-shared strtab
The next stage of strtab sharing is actual lookup of strings in such
strtabs, interning of strings in such strtabs and writing out of
such strtabs (but not actually figuring out which strings should
be shared: that's next).
We introduce several new internal ctf_str_* API functions to augment the
existing rather large set: ctf_str_add_copy, which adds a string and always
makes a copy of it (used when deduplicating to stop dedupped strings holding
permanent references on the input dicts), and ctf_str_no_dedup_ref (which
adds a ref to a string while preventing it from ever being deduplicated,
used for header fields like the parent name, which is the same for almost
all child dicts but had still better not be stored in the parent!).
ctf_strraw_explicit, the ultimate underlying "look up a string" function
that backs ctf_strptr et al, gains the ability to automatically find strings
in the parent if the offset is < cth_parent_strlen, and generally make all
offsets parent-relative (so something at offset 1 in the child strlen will
need to be looked up at offset 257 if cth_parent_strlen is 256). This
suffices to paste together the parent and child from the perspective
of lookup.
We do quite a lot of new checks in here, simply because it's called all over
the place and it's preferable to emit a nice error into the ctf_err_warning
stream if things go wrong. Among other things this traps cases where you
accidentally added a string to the parent, throwing off all the offsets.
Completely invalid offsets also now add a message to the err_warning
stream.
Insertion of new atoms (the deduplicated entities underlying strings in a
given dict), already a flag-heavy operation, gains more flags, corresponding
to the new ctf_str_add_copy and ctf_str_no_dedup_ref functions: atom
addition also checks the ctf_max_children set by ctf_import and prevents
addition of new atoms to any dicts with ctf_imported children and an
already-serialized strtab.
strtab writeout gains more checks as well: you can't write out a strtab for
a child dict whose parent hasn't been serialized yet (and thus doesn't have
a serialized strtab itself); you can't write it out if the child already
depended on a shared parent strtab and that strtab has changed length. The
null atom at offset 0 is only written to the parent strtab; and ref updating
changes to look up offsets in the parent's atoms table iff a new
CTF_STR_ATOM_IN_PARENT flag is set on the atom (this will be set by
deduplication to ensure that serializing a dict will update all its refs
properly even though a bunch of them have moved to the parent dict).
None of this actually has any *effect* yet because no string deduplication
is being carried out, and the cth_parent_strlen is still locked at 0.
include/
* ctf-api.h (_CTF_ERRORS) [ECTF_NOTSERIALIZED]: New.
(ECTF_NERR): Updated.
libctf/
* ctf-impl.h (CTF_STR_ATOM_IN_PARENT): New.
(CTF_STR_ATOM_NO_DEDUP): Likewise.
(ctf_str_add_no_dedup_ref): New.
(ctf_str_add_copy): New.
* ctf-string.c (ctf_strraw_explicit): Look in parents if necessary:
use parent-relative offsets.
(ctf_strptr_validate): Avoid duplicating errors.
(ctf_str_create_atoms): Update comment.
(CTF_STR_COPY): New.
(CTF_STR_NO_DEDUP): Likewise.
(ctf_str_add_ref_internal): Use them, setting the corresponding
csa_flags, prohibiting addition to serialized parents, and copying
strings if so requested.
(ctf_str_add): Turn into a wrapper around...
(ctf_str_add_flagged): ... this new function. The offset is now
parent-relative.
(ctf_str_add_ref): Likewise.
(ctf_str_add_movable_ref): Likewise.
(ctf_str_add_copy): New.
(ctf_str_add_no_dedup_ref): New.
(ctf_str_write_strtab): Prohibit writes when the parent has
changed length or is not serialized. Only write the null atom
to parent strtabs. Chase refs to the parent if necessary.
|
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Nick Alcock
|
a14fb397b2 |
libctf: tear opening and serialization in two
The next stage in sharing the strtab involves tearing two core parts
of libctf into two pieces.
Large parts of init_static_types, called at open time, involve traversing
the types table and initializing the hashtabs used by the type name lookup
functions and the enumerator conflicting checks. If the string table is
partly located in the parent dict, this is obviously not going to work: so
split out that code into a new init_static_types_names function (which
also means moving the wrapper around init_static_types that was used
to simplify the enumerator code into being a wrapper around
init_static_types_names instead) and call that from init_static_types
(for parent dicts, and < v4 dicts), and from ctf_import (for v4 dicts).
At the same time as doing this we arrange to set LCTF_NO_STR (recently
introduced) iff this is a v4 child dict with a nonzero cth_parent_strlen:
this then blocks more or less everything that involves string operations
until a ctf_import has actually imported the strtab it depends on. (No
string oeprations that actually use this have been introduced yet, but
since no string deduplication is happening yet either this is harmless.)
For v4 dicts, at import time we also validate that the cth_parent_strlen has
the same value as the parent's strlen (zero is also a valid value,
indicating a non-shared strtab, as is commonplace in older dicts, dicts
emitted by the compiler, parent dicts etc). This makes ctf_import more
complex, so we simplify things again by dropping all the repeated code in
the obscure used-only-by-ctf_link ctf_import_unref and turning both into
wrappers around an internal function. We prohibit repeated ctf_imports
(except of NULL or the same dict repeatedly), and set up some new fields
which will be used later to prevent people from adding strings to parent
dicts with pre-existing serialized strtabs once they have children imported
into them (which would change their string length and corrupt all those
strtabs).
Serialization also needs to be torn in two. The problem here is that
currently serialization does too much: it emits everything including the
strtab, does things that depend on the strtab being finalized (notably
variable table sorting), and then writes it out. Much of this emission
itself involves strtab writes, so the strtab is not actually complete until
halfway through ctf_serialize. But when deduplicating, we want to use
machinery in ctf-link and ctf-dedup to deduplicate the strtab after it is
complete, and only then write it out.
We could do this via having ctf_serialize call some sort of horrible
callback, but it seems much simpler to just cut ctf_serialize in two,
and introduce a new ctf_preserialize which can optionally be called to do
all this "everything but the strtab" work. (If it's not called,
ctf_serialize calls it itself.)
This means pulling some internal variables out of ctf_serialize into the
ctf_dict_t, and slightly abusing LCTF_NO_STR to mean (in addition to its
"no, you can't do much between opening a child dict and importing its
parent" semantics), "no, you can't do much between calling ctf_preserialize
and ctf_serialize". The requirements of both are not quite identical -- you
definitely can do things that involve string lookups after ctf_preserialize
-- but it serves to stop callers from accidentally adding more types after
the types table has been written out, and that's good enough.
ctf_preserialize isn't public API anyway.
libctf/
* ctf-impl.h (struct ctf_dict) [ctf_serializing_buf]: New.
[ctf_serializing_buf_size]: Likewise.
[ctf_serializing_vars]: Likewise.
[ctf_serializing_nvars]: Likewise.
[ctf_max_children]: Likewise.
(LCTF_PRESERIALIZED): New.
(ctf_preserialize): New.
(ctf_depreserialize): New.
* ctf-open.c (init_static_types): Rename to...
(init_static_types_names): ... this, wrapping a different
function.
(init_static_types_internal): Rename to...
(init_static_types): ... this, and set LCTF_NO_STR if neecessary.
Tear out the name-lookup guts into...
(init_static_types_names_internal): ... this new function. Fix a few
comment typos.
(ctf_bufopen): Emphasise that you cannot rely on looking up strings
at any point in ctf_bufopen any more.
(ctf_dict_close): Free ctf_serializing_buf.
(ctf_import): Turn into a wrapper, calling...
(ctf_import_internal): ... this. Prohibit repeated ctf_imports of
different parent dicts, or "unimporting" by setting it back to NULL
again. Validate the parent we do import using cth_parent_strlen.
Call init_static_types_names if the strtab is shared with the
parent.
(ctf_import_unref): Turn into a wrapper.
* ctf-serialize.c (ctf_serialize): Split out everything before
strtab serialization into...
(ctf_preserialize): ... this new function.
(ctf_depreserialize): New, undo preserialization on error.
|
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Nick Alcock
|
70d05ab0b2 |
libctf: add mechanism to prohibit most operations without a strtab
We are about to add machinery that deduplicates a child dict's strtab
against its parent. Obviously if you open such a dict but do not import its
parent, all strtab lookups must fail: so add an LCTF_NO_STR flag that is set
in that window and make most operations fail if it's not set. (Two more
that will be set in future commits are serialization and string lookup
itself.)
Notably, not all symbol lookup is impossible in this window: you can still
look up by symbol index, as long as this dict is not using an indexed
strtypetab (which obviously requires string lookups to get the symbol name).
include/
* ctf-api.h (_CTF_ERRORS) [ECTF_HASPARENT]: New.
[ECTF_WRONGPARENT]: Likewise.
(ECTF_NERR): Update.
Update comments to note the new limitations on ctf_import et al.
libctf/
* ctf-impl.h (LCTF_NO_STR): New.
* ctf-create.c (ctf_rollback): Error out when LCTF_NO_STR.
(ctf_add_generic): Likewise.
(ctf_add_struct_sized): Likewise.
(ctf_add_union_sized): Likewise.
(ctf_add_enum): Likewise.
(ctf_add_forward): Likewise.
(ctf_add_unknown): Likewise.
(ctf_add_enumerator): Likewise.
(ctf_add_member_offset): Likewise.
(ctf_add_variable): Likewise.
(ctf_add_funcobjt_sym_forced): Likewise.
(ctf_add_type): Likewise (on either dict).
* ctf-dump.c (ctf_dump): Likewise.
* ctf-lookup.c (ctf_lookup_by_name): Likewise.
(ctf_lookup_variable): Likewise. Likewise.
(ctf_lookup_enumerator): Likewise.
(ctf_lookup_enumerator_next): Likewise.
(ctf_symbol_next): Likewise.
(ctf_lookup_by_sym_or_name): Likewise, if doing indexed lookups.
* ctf-types.c (ctf_member_next): Likewise.
(ctf_enum_next): Likewise.
(ctf_type_aname): Likewise.
(ctf_type_name_raw): Likewise.
(ctf_type_compat): Likewise, for either dict.
(ctf_member_info): Likewise.
(ctf_enum_name): Likewise.
(ctf_enum_value): Likewise.
(ctf_type_rvisit): Likewise.
(ctf_variable_next): Note that we don't need to test LCTF_NO_STR.
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Nick Alcock
|
9a74ab12c8 |
include, libctf: start work on libctf v4
This format is a superset of BTF, but for now we just do the minimum to
declare a new file format version, without actually introducing any format
changes.
From now on, we refuse to reserialize CTFv1 dicts: these have a distinct
parent/child boundary which obviously cannot change upon reserialization
(that would change the type IDs): instead, we encoded this by stuffing in
a unique CTF version for such dicts. We can't do that now we have one
version for all CTFv4 dicts, and testing such old dicts is very hard these
days anyway, and is not automated: so just drop support for writing them out
entirely. (You still *can* write them out, but you have to do a full-blown
ctf_link, which generates an all-new fresh dict and recomputes type IDs as
part of deduplication.)
To prevent this extremely-not-ready format escaping into the wild, add a
new mechanism whereby any format version higher than the new #define
CTF_STABLE_VERSION cannot be serialized unless I_KNOW_LIBCTF_IS_UNSTABLE is
set in the environment.
include/
* ctf-api.h (_CTF_ERRORS) [ECTF_CTFVERS_NO_SERIALIZE]: New.
[ECTF_UNSTABLE]: New.
(ECTF_NERR): Update.
* ctf.h: Small comment improvements..
(ctf_header_v3): New, copy of ctf_header.
(CTF_VERSION_4): New.
(CTF_VERSION): Now CTF_VERSION_4.
(CTF_STABLE_VERSION): Still 4, CTF_VERSION_3.
ld/
* testsuite/ld-ctf/*.d: Update to CTF_VERSION_4.
libctf/
* ctf-impl.h (LCTF_NO_SERIALIZE): New.
* ctf-dump.c (ctf_dump_header): Add CTF_VERSION_4.
* ctf-open.c (ctf_dictops): Likewise.
(upgrade_header): Rename to...
(upgrade_header_v2): ... this.
(upgrade_header_v3): New.
(upgrade_types): Support upgrading from CTF_VERSION_3.
Turn on LCTF_NO_SERIALIZE for CTFv1.
(init_static_types_internal): Upgrade all types tables older than
* CTF_VERSION_4.
(ctf_bufopen): Support CTF_VERSION_4: error out if we forget to
update this switch in future. Add header upgrading from v3 and
below. Improve comments slightly.
* ctf-serialize.c (ctf_serialize): Block serialization of unstable
file formats, and of file formats for which LCTF_NO_SERIALIZE is
turned on (v1).
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Alan Modra
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e8e7cf2abe | Update year range in copyright notice of binutils files | ||
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Nick Alcock
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6da9267482 |
libctf, include: add ctf_dict_set_flag: less enum dup checking by default
The recent change to detect duplicate enum values and return ECTF_DUPLICATE when found turns out to perturb a great many callers. In particular, the pahole-created kernel BTF has the same problem we historically did, and gleefully emits duplicated enum constants in profusion. Handling the resulting duplicate errors from BTF -> CTF converters reasonably is unreasonably difficult (it amounts to forcing them to skip some types or reimplement the deduplicator). So let's step back a bit. What we care about mostly is that the deduplicator treat enums with conflicting enumeration constants as conflicting types: programs that want to look up enumeration constant -> value mappings using the new APIs to do so might well want the same checks to apply to any ctf_add_* operations they carry out (and since they're *using* the new APIs, added at the same time as this restriction was imposed, there is likely to be no negative consequence of this). So we want some way to allow processes that know about duplicate detection to opt into it, while allowing everyone else to stay clear of it: but we want ctf_link to get this behaviour even if its caller has opted out. So add a new concept to the API: dict-wide CTF flags, set via ctf_dict_set_flag, obtained via ctf_dict_get_flag. They are not bitflags but simple arbitrary integers and an on/off value, stored in an unspecified manner (the one current flag, we translate into an LCTF_* flag value in the internal ctf_dict ctf_flags word). If you pass in an invalid flag or value you get a new ECTF_BADFLAG error, so the caller can easily tell whether flags added in future are valid with a particular libctf or not. We check this flag in ctf_add_enumerator, and set it around the link (including on child per-CU dicts). The newish enumerator-iteration test is souped up to check the semantics of the flag as well. The fact that the flag can be set and unset at any time has curious consequences. You can unset the flag, insert a pile of duplicates, then set it and expect the new duplicates to be detected, not only by ctf_add_enumerator but also by ctf_lookup_enumerator. This means we now have to maintain the ctf_names and conflicting_enums enum-duplication tracking as new enums are added, not purely as the dict is opened. Move that code out of init_static_types_internal and into a new ctf_track_enumerator function that addition can also call. (None of this affects the file format or serialization machinery, which has to be able to handle duplicate enumeration constants no matter what.) include/ * ctf-api.h (CTF_ERRORS) [ECTF_BADFLAG]: New. (ECTF_NERR): Update. (CTF_STRICT_NO_DUP_ENUMERATORS): New flag. (ctf_dict_set_flag): New function. (ctf_dict_get_flag): Likewise. libctf/ * ctf-impl.h (LCTF_STRICT_NO_DUP_ENUMERATORS): New flag. (ctf_track_enumerator): Declare. * ctf-dedup.c (ctf_dedup_emit_type): Set it. * ctf-link.c (ctf_create_per_cu): Likewise. (ctf_link_deduplicating_per_cu): Likewise. (ctf_link): Likewise. (ctf_link_write): Likewise. * ctf-subr.c (ctf_dict_set_flag): New function. (ctf_dict_get_flag): New function. * ctf-open.c (init_static_types_internal): Move enum tracking to... * ctf-create.c (ctf_track_enumerator): ... this new function. (ctf_add_enumerator): Call it. * libctf.ver: Add the new functions. * testsuite/libctf-lookup/enumerator-iteration.c: Test them. |
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Nick Alcock
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36c771b179 |
libctf: fix CTF dict compression
Commit
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Nick Alcock
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b404bf7270 |
libctf, string: split the movable refs out of the ref list
In commit
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Nick Alcock
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68720e03f5 |
libctf, dedup: drop unnecessary arg from ctf_dedup()
The PARENTS arg is carefully passed down through all the layers of hash
functions and then never used for anything. (In the distant past it was
used for cycle detection, but the algorithm eventually committed doesn't
need to do cycle detection...)
The PARENTS arg is still used by ctf_dedup_emit(), but even there we can
loosen the requirements and state that you can just leave entries
corresponding to dicts with no parents at zero (which will be useful
in an upcoming commit).
libctf/
* ctf-dedup.c (ctf_dedup_hash_type): Drop PARENTS arg.
(ctf_dedup_rhash_type): Likewise.
(ctf_dedup): Likewise.
(ctf_dedup_emit_struct_members): Mention what you can do to
PARENTS entries for parent dicts.
* ctf-impl.h (ctf_dedup): Adjust accordingly.
* ctf-link.c (ctf_link_deduplicating_per_cu): Likewise.
(ctf_link_deduplicating): Likewise.
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Nick Alcock
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2fa4b6e6df |
libctf, include: new functions for looking up enumerators
Three new functions for looking up the enum type containing a given
enumeration constant, and optionally that constant's value.
The simplest, ctf_lookup_enumerator, looks up a root-visible enumerator by
name in one dict: if the dict contains multiple such constants (which is
possible for dicts created by older versions of the libctf deduplicator),
ECTF_DUPLICATE is returned.
The next simplest, ctf_lookup_enumerator_next, is an iterator which returns
all enumerators with a given name in a given dict, whether root-visible or
not.
The most elaborate, ctf_arc_lookup_enumerator_next, finds all
enumerators with a given name across all dicts in an entire CTF archive,
whether root-visible or not, starting looking in the shared parent dict;
opened dicts are cached (as with all other ctf_arc_*lookup functions) so
that repeated use does not incur repeated opening costs.
All three of these return enumerator values as int64_t: unfortunately, API
compatibility concerns prevent us from doing the same with the other older
enum-related functions, which all return enumerator constant values as ints.
We may be forced to add symbol-versioning compatibility aliases that fix the
other functions in due course, bumping the soname for platforms that do not
support such things.
ctf_arc_lookup_enumerator_next is implemented as a nested ctf_archive_next
iterator, and inside that, a nested ctf_lookup_enumerator_next iterator
within each dict. To aid in this, add support to ctf_next_t iterators for
iterators that are implemented in terms of two simultaneous nested iterators
at once. (It has always been possible for callers to use as many nested or
semi-overlapping ctf_next_t iterators as they need, which is one of the
advantages of this style over the _iter style that calls a function for each
thing iterated over: the iterator change here permits *ctf_next_t iterators
themselves* to be implemented by iterating using multiple other iterators as
part of their internal operation, transparently to the caller.)
Also add a testcase that tests all these functions (which is fairly easy
because ctf_arc_lookup_enumerator_next is implemented in terms of
ctf_lookup_enumerator_next) in addition to enumeration addition in
ctf_open()ed dicts, ctf_add_enumerator duplicate enumerator addition, and
conflicting enumerator constant deduplication.
include/
* ctf-api.h (ctf_lookup_enumerator): New.
(ctf_lookup_enumerator_next): Likewise.
(ctf_arc_lookup_enumerator_next): Likewise.
libctf/
* libctf.ver: Add them.
* ctf-impl.h (ctf_next_t) <ctn_next_inner>: New.
* ctf-util.c (ctf_next_copy): Copy it.
(ctf_next_destroy): Destroy it.
* ctf-lookup.c (ctf_lookup_enumerator): New.
(ctf_lookup_enumerator_next): New.
* ctf-archive.c (ctf_arc_lookup_enumerator_next): New.
* testsuite/libctf-lookup/enumerator-iteration.*: New test.
* testsuite/libctf-lookup/enum-ctf-2.c: New test CTF, used by the
above.
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Nick Alcock
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4bbc4b1f5c |
libctf: make the ctf_next ctn_fp non-const
This was always an error, because the ctn_fp routinely has errors set on it, which is not something you can (or should) do to a const object. libctf/ * ctf-impl.h (ctf_next_) <cu.ctn_fp>: Make non-const. |
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Nick Alcock
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6e09d4a6e6 |
libctf: prohibit addition of enums with overlapping enumerator constants
libctf has long prohibited addition of enums with overlapping constants in a
single enum, but now that we are properly considering enums with overlapping
constants to be conflciting types, we can go further and prohibit addition
of enumeration constants to a dict if they already exist in any enum in that
dict: the same rules as C itself.
We do this in a fashion vaguely similar to what we just did in the
deduplicator, by considering enumeration constants as identifiers and adding
them to the core type/identifier namespace, ctf_dict_t.ctf_names. This is a
little fiddly, because we do not want to prohibit opening of existing dicts
into which the deduplicator has stuffed enums with overlapping constants!
We just want to prohibit the addition of *new* enumerators that violate that
rule. Even then, it's fine to add overlapping enumerator constants as long
as at least one of them is in a non-root type. (This is essential for
proper deduplicator operation in cu-mapped mode, where multiple compilation
units can be smashed into one dict, with conflicting types marked as
hidden: these types may well contain overlapping enumerators.)
So, at open time, keep track of all enums observed, then do a third pass
through the enums alone, adding each enumerator either to the ctf_names
table as a mapping from the enumerator name to the enum it is part of (if
not already present), or to a new ctf_conflicting_enums hashtable that
tracks observed duplicates. (The latter is not used yet, but will be soon.)
(We need to do a third pass because it's quite possible to have an enum
containing an enumerator FOO followed by a type FOO: since they're processed
in order, the enumerator would be processed before the type, and at that
stage it seems nonconflicting. The easiest fix is to run through the
enumerators after all type names are interned.)
At ctf_add_enumerator time, if the enumerator to which we are adding a type
is root-visible, check for an already-present name and error out if found,
then intern the new name in the ctf_names table as is done at open time.
(We retain the existing code which scans the enum itself for duplicates
because it is still an error to add an enumerator twice to a
non-root-visible enum type; but we only need to do this if the enum is
non-root-visible, so the cost of enum addition is reduced.)
Tested in an upcoming commit.
libctf/
* ctf-impl.h (ctf_dict_t) <ctf_names>: Augment comment.
<ctf_conflicting_enums>: New.
(ctf_dynset_elements): New.
* ctf-hash.c (ctf_dynset_elements): Implement it.
* ctf-open.c (init_static_types): Split body into...
(init_static_types_internal): ... here. Count enumerators;
keep track of observed enums in pass 2; populate ctf_names and
ctf_conflicting_enums with enumerators in a third pass.
(ctf_dict_close): Free ctf_conflicting_enums.
* ctf-create.c (ctf_add_enumerator): Prohibit addition of duplicate
enumerators in root-visible enum types.
include/
* ctf-api.h (CTF_ADD_NONROOT): Describe what non-rootness
means for enumeration constants.
(ctf_add_enumerator): The name is not a misnomer.
We now require that enumerators have unique names.
Document the non-rootness of enumerators.
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Nick Alcock
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f8da1a05db |
libctf: dedup: enums with overlapping enumerators are conflicting
The CTF deduplicator was not considering enumerators inside enum types to be
things that caused type conflicts, so if the following two TUs were linked
together, you would end up with the following in the resulting dict:
1.c:
enum foo { A, B };
2.c:
enum bar { A, B };
linked:
enum foo { A, B };
enum bar { A, B };
This does work -- but it's not something that's valid C, and the general
point of the shared dict is that it is something that you could potentially
get from any valid C TU.
So consider such types to be conflicting, but obviously don't consider
actually identical enums to be conflicting, even though they too have (all)
their identifiers in common. This involves surprisingly little code. The
deduplicator detects conflicting types by counting types in a hash table of
hash tables:
decorated identifier -> (type hash -> count)
where the COUNT is the number of times a given hash has been observed: any
name with more than one hash associated with it is considered conflicting
(the count is used to identify the most common such name for promotion to
the shared dict).
Before now, those identifiers were all the identifiers of types (possibly
decorated with their namespace on the front for enumerator identifiers), but
we can equally well put *enumeration constant names* in there, undecorated
like the identifiers of types in the global namespace, with the type hash
being the hash of each enum containing that enumerator. The existing
conflicting-type-detection code will then accurately identify distinct enums
with enumeration constants in common. The enum that contains the most
commonly-appearing enumerators will be promoted to the shared dict.
libctf/
* ctf-impl.h (ctf_dedup_t) <cd_name_counts>: Extend comment.
* ctf-dedup.c (ctf_dedup_count_name): New, split out of...
(ctf_dedup_populate_mappings): ... here. Call it for all
* enumeration constants in an enum as well as types.
ld/
* testsuite/ld-ctf/enum-3.c: New test CTF.
* testsuite/ld-ctf/enum-4.c: Likewise.
* testsuite/ld-ctf/overlapping-enums.d: New test.
* testsuite/ld-ctf/overlapping-enums-2.d: Likewise.
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Nick Alcock
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483546ce4f |
libctf: make ctf_serialize() actually serialize
ctf_serialize() evolved from the old ctf_update(), which mutated the in-memory CTF dict to make all the dynamic in-memory types into static, unchanging written-to-the-dict types (by deserializing and reserializing it): back in the days when you could only do type lookups on static types, this meant you could see all the types you added recently, at the small, small cost of making it impossible to change those older types ever again and inducing an amortized O(n^2) cost if you actually wanted to add references to types you added at arbitrary times to later types. It also reset things so that ctf_discard() would throw away only types you added after the most recent ctf_update() call. Some time ago this was all changed so that you could look up dynamic types just as easily as static types: ctf_update() changed so that only its visible side-effect of affecting ctf_discard() remained: the old ctf_update() was renamed to ctf_serialize(), made internal to libctf, and called from the various functions that wrote files out. ... but it was still working by serializing and deserializing the entire dict, swapping out its guts with the newly-serialized copy in an invasive and horrible fashion that coupled ctf_serialize() to almost every field in the ctf_dict_t. This is totally useless, and fixing it is easy: just rip all that code out and have ctf_serialize return a serialized representation, and let everything use that directly. This simplifies most of its callers significantly. (It also points up another bug: ctf_gzwrite() failed to call ctf_serialize() at all, so it would only ever work for a dict you just ctf_write_mem()ed yourself, just for its invisible side-effect of serializing the dict!) This lets us simplify away a bunch of internal-only open-side functionality for overriding the syn_ext_strtab and some just-added functionality for forcing in an existing atoms table, without loss of functionality, and lets us lift the restriction on reserializing a dict that was ctf_open()ed rather than being ctf_create()d: it's now perfectly OK to open a dict, modify it (except for adding members to existing structs, unions, or enums, which fails with -ECTF_RDONLY), and write it out again, just as one would expect. libctf/ * ctf-serialize.c (ctf_symtypetab_sect_sizes): Fix typos. (ctf_type_sect_size): Add static type sizes too. (ctf_serialize): Return the new dict rather than updating the existing dict. No longer fail for dicts with static types; copy them onto the start of the new types table. (ctf_gzwrite): Actually serialize before gzwriting. (ctf_write_mem): Improve forced (test-mode) endian-flipping: flip dicts even if they are too small to be compressed. Improve confusing variable naming. * ctf-archive.c (arc_write_one_ctf): Don't bother to call ctf_serialize: both the functions we call do so. * ctf-string.c (ctf_str_create_atoms): Drop serializing case (atoms arg). * ctf-open.c (ctf_simple_open): Call ctf_bufopen directly. (ctf_simple_open_internal): Delete. (ctf_bufopen_internal): Delete/rename to ctf_bufopen: no longer bother with syn_ext_strtab or forced atoms table, serialization no longer needs them. * ctf-create.c (ctf_create): Call ctf_bufopen directly. * ctf-impl.h (ctf_str_create_atoms): Drop atoms arg. (ctf_simple_open_internal): Delete. (ctf_bufopen_internal): Likewise. (ctf_serialize): Adjust. * testsuite/libctf-lookup/add-to-opened.c: Adjust now that this is supposed to work. |
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Nick Alcock
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cf9da3b0b6 |
libctf: rethink strtab writeout
This commit finally adjusts strtab writeout so that repeated writeouts, or writeouts of a dict that was read in earlier, only sorts the portion of the strtab that was newly added. There are three intertwined changes here: - pull the contents of strtabs from newly ctf_bufopened dicts into the atoms table, so that future additions will reuse the existing offset etc rather than adding new identical strings - allow the internal ctf_bufopen done by serialization to contribute its existing atoms table, so that existing atoms can be used for the remainder of the open process (like name table construction): this atoms table currente gets thrown away in the mass reassignment done later in ctf_serialize in any case, but it needs to be there during the open. - rewrite ctf_str_write_strtab so that a) it uses iterators rather than ctf_*_iter, reducing pointless structures which serve no other purpose than to implement ordinary variable scope, but more clunkily, and b) retains the existing strtab on the front of the new one, with its sort retained, rather than resorting, so all existing already-written strtab offsets remain valid across the call. This latter change finally permits repeated serializations, and reserializations of ctf_open()ed dicts, to work, but for now we keep the code that prevents that because serialization is about to change again in a way that will make it more obvious that doing such things is safe, and we can take it out then. (There are also some smaller changes like moving the purge of the refs table into ctf_str_write_strtab(), since that's where the changes happen that invalidate it, rather than doing it in ctf_serialize(). We also prohibit something that has never worked, opening a dict and then reporting symbols to it via ctf_link_add_strtab() et al: you must do that to newly-created dicts which have had stuff ctf_link()ed into them. This is very unlikely ever to be a problem in practice: linkers just don't do that sort of thing.) libctf/ * ctf-create.c (ctf_create): Add (temporary) atoms arg. * ctf-impl.h (struct ctf_dict.ctf_dynstrtab): New. (ctf_str_create_atoms): Adjust. (ctf_str_write_strtab): Likewise. (ctf_simple_open_internal): Likewise. * ctf-open.c (ctf_simple_open_internal): Add atoms arg. (ctf_bufopen): Likewise. (ctf_bufopen_internal): Initialize just enough of an atoms table: pre-init from the atoms arg if supplied. (ctf_simple_open): Adjust. * ctf-serialize.c (ctf_serialize): Constify the strtab. Move ref list purging into ctf_str_write_strtab. Initialize the new dict with the old dict's atoms table. Accept the new strtab from ctf_str_write_strtab. Adjust for addition of ctf_dynstrtab. * ctf-string.c (ctf_strraw_explicit): Improve comments. (ctf_str_create_atoms): Prepopulate from an existing atoms table, or alternatively pull in all strings from the strtab and turn them into atoms. (ctf_str_free_atoms): Free the dynstrtab and its strtab. (struct ctf_strtab_write_state): Remove. (ctf_str_count_strtab): Fold this... (ctf_str_populate_sorttab): ... and this... (ctf_str_write_strtab): ... into this. Prepend existing strings to the strtab rather than resorting them (and wrecking their offsets). Keep the dynstrtab updated. Update refs for all atoms with refs, whether or not they are strings newly added to the strtab. |
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Nick Alcock
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149ce5c263 |
libctf: replace 'pending refs' abstraction
A few years ago we introduced a 'pending refs' abstraction to fix one
problem: serializing a dict, then changing it would tend to corrupt the dict
because the strtab sort we do on strtab writeout (to improve compression
efficiency) would modify the offset of any strings that sorted
lexicographically earlier in the strtab: so we added a new restriction that
all strings are added only at serialization time, and maintained a set of
'pending' refs that were added earlier, whose offsets we could update (like
other refs) at writeout time.
This was in hindsight seriously problematic for maintenance (because
serialization has to traverse all strings in all datatypes in the entire
dict), and has become impossible to sustain now that we can read in existing
dicts, modify them, and reserialize them again. We really don't want to
have to dig through the entire dict we jut read in just in order to dig out
all its strtab offsets, then *change* it, just for the sake of a sort that
adds a frankly trivial amount of compression efficiency.
Sorting *is* still worthwhile -- but it sacrifices very little to only sort
newly-added portions of the strtab, reusing older portions as necessary.
As a first stage in this, discard the whole "pending refs" abstraction and
replace it with "movable" refs, which are exactly like all other refs
(addresses containing the strtab offset of some string, which are updated
wiht the final strtab offset on serialization) except that we track them in
a reverse dict so that we can move the refs around (which we do whenever we
realloc() a buffer containing a bunch of structure members or something when
we add members to the structure).
libctf/
* ctf-create.c (ctf_add_enumerator): Call ctf_str_move_refs; add
a movable ref.
(ctf_add_member_offset): Likewise.
* ctf-util.c (ctf_realloc): Delete.
* ctf-serialize.c (ctf_serialize): No longer use it. Adjust to
new fields.
* ctf-string.c (ctf_str_purge_atom_refs): Purge movable refs.
(ctf_str_free_atom): Free freeable atoms' strings.
(ctf_str_create_atoms): Create the movable refs dynhash if needed.
(ctf_str_free_atoms): Destroy it.
(CTF_STR_MOVABLE): Switch (back) from ints to flags (see previous
reversion). Add new flag.
(aref_create): New, populate movable refs if need be.
(ctf_str_add_ref_internal): Switch back to flags, update refs
directly for nonprovisional strings (with already-known fixed offsets);
create refs via aref_create. Allocate strings only if not within an
mmapped strtab.
(ctf_str_add_movable_ref): New.
(ctf_str_add): Adjust to CTF_STR_* reintroduction.
(ctf_str_add_external): LIkewise.
(ctf_str_move_refs): New, move refs via ctf_str_movable_refs
backpointer.
(ctf_str_purge_refs): Drop ctf_str_num_refs.
(ctf_str_update_refs): Fix indentation.
* ctf-impl.h (struct ctf_str_atom_movable): New.
(struct ctf_dict.ctf_str_num_refs): Drop.
(struct ctf_dict.ctf_str_movable_refs): New.
(ctf_str_add_movable_ref): Declare.
(ctf_str_move_refs): Likewise.
(ctf_realloc): Drop.
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Nick Alcock
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3301ddba1b |
Revert "libctf: do not corrupt strings across ctf_serialize"
This reverts commit
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