While running this test on an emulator, I noticed we're failing to match the
output message when "memory-tag check" is issued with no arguments. That's
because I coded the message using "error" and missed a period at the end. Other
similar messages are issued with error_no_arg.
This patch changes that call to use error_no_arg.
Tested on aarch64-linux Ubuntu 20.04/22.04.
This changes dwarf2_fde to use the unrelocated_addr type. This
pointed out a latent bug in dwarf2_frame_cache, where a relocated
address is compared to an unrelocated address.
A few spots in dwarf2_frame_cache use:
cache->per_objfile->objfile->text_section_offset ()
... and a subsequent patch will add more, so move this into a local
variable.
unrelocated_addr is currently defined in symtab.h, but in order to
avoid having to include that in more places, I wanted to move the type
elsewhere. I considered defs.h, but it seemed reasonable to have it
next to CORE_ADDR, which is what this patch does.
dwarf2_record_block_ranges is only ever called with the text section
offset, so this patch removes the parameter entirely. This makes a
subsequent patch a little simpler.
History Of This Patch
=====================
This commit aims to address PR gdb/21699. There have now been a
couple of attempts to fix this issue. Simon originally posted two
patches back in 2021:
https://sourceware.org/pipermail/gdb-patches/2021-July/180894.htmlhttps://sourceware.org/pipermail/gdb-patches/2021-July/180896.html
Before Pedro then posted a version of his own:
https://sourceware.org/pipermail/gdb-patches/2021-July/180970.html
After this the conversation halted. Then in 2023 I (Andrew) also took
a look at this bug and posted two versions:
https://sourceware.org/pipermail/gdb-patches/2023-April/198570.htmlhttps://sourceware.org/pipermail/gdb-patches/2023-April/198680.html
The approach taken in my first patch was pretty similar to what Simon
originally posted back in 2021. My second attempt was only a slight
variation on the first.
Pedro then pointed out his older patch, and so we arrive at this
patch. The GDB changes here are mostly Pedro's work, but updated by
me (Andrew), any mistakes are mine.
The tests here are a combinations of everyone's work, and the commit
message is new, but copies bits from everyone's earlier work.
Problem Description
===================
Bug PR gdb/21699 makes the observation that using $_as_string with
GDB's printf can cause GDB to print unexpected data from the
inferior. The reproducer is pretty simple:
#include <stddef.h>
static char arena[100];
/* Override malloc() so value_coerce_to_target() gets a known
pointer, and we know we"ll see an error if $_as_string() gives
a string that isn't null terminated. */
void
*malloc (size_t size)
{
memset (arena, 'x', sizeof (arena));
if (size > sizeof (arena))
return NULL;
return arena;
}
int
main ()
{
return 0;
}
And then in a GDB session:
$ gdb -q test
Reading symbols from /tmp/test...
(gdb) start
Temporary breakpoint 1 at 0x4004c8: file test.c, line 17.
Starting program: /tmp/test
Temporary breakpoint 1, main () at test.c:17
17 return 0;
(gdb) printf "%s\n", $_as_string("hello")
"hello"xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
(gdb) quit
The problem above is caused by how value_cstring is used within
py-value.c, but once we understand the issue then it turns out that
value_cstring is used in an unexpected way in many places within GDB.
Within py-value.c we have a null-terminated C-style string. We then
pass a pointer to this string, along with the length of this
string (so not including the null-character) to value_cstring.
In value_cstring GDB allocates an array value of the given character
type, and copies in requested number of characters. However
value_cstring does not add a null-character of its own. This means
that the value created by calling value_cstring is only
null-terminated if the null-character is included in the passed in
length. In py-value.c this is not the case, and indeed, in most uses
of value_cstring, this is not the case.
When GDB tries to print one of these strings the value contents are
pushed to the inferior, and then read back as a C-style string, that
is, GDB reads inferior memory until it finds a null-terminator. For
the py-value.c case, no null-terminator is pushed into the inferior,
so GDB will continue reading inferior memory until a null-terminator
is found, with unpredictable results.
Patch Description
=================
The first thing this patch does is better define what the arguments
for the two function value_cstring and value_string should represent.
The comments in the header file are updated to describe whether the
length argument should, or should not, include a null-character.
Also, the data argument is changed to type gdb_byte. The functions as
they currently exist will handle wide-characters, in which case more
than one 'char' would be needed for each character. As such using
gdb_byte seems to make more sense.
To avoid adding casts throughout GDB, I've also added an overload that
still takes a 'char *', but asserts that the character type being used
is of size '1'.
The value_cstring function is now responsible for adding a null
character at the end of the string value it creates.
However, once we start looking at how value_cstring is used, we
realise there's another, related, problem. Not every language's
strings are null terminated. Fortran and Ada strings, for example,
are just an array of characters, GDB already has the function
value_string which can be used to create such values.
Consider this example using current GDB:
(gdb) set language ada
(gdb) p $_gdb_setting("arch")
$1 = (97, 117, 116, 111)
(gdb) ptype $
type = array (1 .. 4) of char
(gdb) p $_gdb_maint_setting("test-settings string")
$2 = (0)
(gdb) ptype $
type = array (1 .. 1) of char
This shows two problems, first, the $_gdb_setting and
$_gdb_maint_setting functions are calling value_cstring using the
builtin_char character, rather than a language appropriate type. In
the first call, the 'arch' case, the value_cstring call doesn't
include the null character, so the returned array only contains the
expected characters. But, in the $_gdb_maint_setting example we do
end up including the null-character, even though this is not expected
for Ada strings.
This commit adds a new language method language_defn::value_string,
this function takes a pointer and length and creates a language
appropriate value that represents the string. For C, C++, etc this
will be a null-terminated string (by calling value_cstring), and for
Fortran and Ada this can be a bounded array of characters with no null
terminator. Additionally, this new language_defn::value_string
function is responsible for selecting a language appropriate character
type.
After this commit the only calls to value_cstring are from the C
expression evaluator and from the default language_defn::value_string.
And the only calls to value_string are from Fortan, Ada, and ObjectC
related code.
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=21699
Co-Authored-By: Simon Marchi <simon.marchi@efficios.com>
Co-Authored-By: Andrew Burgess <aburgess@redhat.com>
Co-Authored-By: Pedro Alves <pedro@palves.net>
Approved-By: Simon Marchi <simon.marchi@efficios.com>
Fix grammar in some comments and docs:
- machines that doesn't -> machines that don't
- its a -> it's a
- its the -> it's the
- if does its not -> if it does it's not
- one more instructions if doesn't match ->
one more instruction if it doesn't match
- it's own -> its own
- it's first -> its first
- it's pointer -> its pointer
I also came across "it's performance" in gdb/stubs/*-stub.c in the HP public
domain notice, I've left that alone.
Tested on x86_64-linux.
In microblaze_analyze_prologue in gdb/microblaze-tdep.c I came across:
...
microblaze_debug ("got addi r1,r1,%d; contnuing\n", imm);
...
Fix this by using "continuing".
Reviewed-By: Tom Tromey <tom@tromey.com>
In gdb/python/py-value.c, in the value_object_methods array I noticed:
...
{ "const_value", valpy_const_value, METH_NOARGS,
"Return a 'const' qualied version of the same value." },
...
Fix the qualied -> qualified typo.
Reviewed-By: Tom Tromey <tom@tromey.com>
In gdb/guile/scm-value.c, I noticed in the value_functions array initializer:
...
{ "value-optimized-out?", 1, 0, 0,
as_a_scm_t_subr (gdbscm_value_optimized_out_p),
"\
Return #t if the value has been optimizd out." },
...
There's a typo in the doc string.
Fix this by using "optimized".
Reviewed-By: Tom Tromey <tom@tromey.com>
I noticed:
...
(gdb) help show tui tab-width
Show the tab witdh, in characters, for the TUI.
This variable controls how many spaces are used to display a tab character.
...
a typo: "witdh".
Fix this by using "width" instead.
Reviewed-By: Tom Tromey <tom@tromey.com>
I noticed a typo:
...
(gdb) help maint info target-sections
List GDB's internal section table.
Print the current targets section list. This is a sub-set of all
sections, from all objects currently loaded. Usually the ALLOC
sectoins.
...
Fix this by using "sections".
Reviewed-By: Tom Tromey <tom@tromey.com>
I noticed here:
...
(gdb) help maint set ignore-prologue-end-flag
Set if the PROLOGUE-END flag is ignored.
The PROLOGUE-END flag from the line-table entries is used to place \
breakpoints past the prologue of functions. Disabeling its use use forces \
the use of prologue scanners.
...
a typo in "Disabeling" and accidental word repetition "use use".
Fix by replacing with "Disabling" and "use".
Reviewed-By: Tom Tromey <tom@tromey.com>
In compile_object_load in gdb/compile/compile-object-load.c I came across:
...
"Connectiong ELF symbol \"%s\" to the .toc section (%s)\n",
...
Fix this typo by using "Connecting" instead.
Reviewed-By: Tom Tromey <tom@tromey.com>
Two functions use the argument name bounds_prefered_p.
This misspells "preferred".
Fix this by using bounds_preferred_p instead.
Tested on x86_64-linux.
Reviewed-By: Tom Tromey <tom@tromey.com>
Caught this during emulator testing.
Fix the constants. They should be 0xa and 0xb as opposed to 0x10 and
0x11. There was a thinko while defining them.
Obvious enough.
Tested on aarch64-linux Ubuntu 20.04/22.04.
I found the documentation for -dprintf-insert a bit unclear. It
didn't mention the possibility of multiple arguments, and I also
noticed that it implied that the format parameter is optional, which
it is not.
While looking into this I also noticed a few comments in the
implementation that could also be improved.
Then, I noticed a repeated call to strlen in a loop condition, so I
fixed this up as well.
Reviewed-By: Eli Zaretskii <eliz@gnu.org>
I noticed a couple instance of this warning when rebuilding the gdb
info files:
warning: undefined flag: GDB
The problem is that the wrong argument was passed to @value. This
patch fixes the problem.
When running the test-case gdb.tui/wrap-line.exp with a build configured with
--disable-tui, we run into:
...
(gdb) PASS: gdb.tui/wrap-line.exp: width-hard-coded: set width 50
tui new-layout command-layout cmd 1^M
Undefined command: "tui". Try "help".^M
(gdb) ERROR: Undefined command "tui new-layout command-layout cmd 1".
...
Fix this by guarding the command with allow_tui_tests.
Tested on x86_64-linux.
When running test-case gdb.tui/pr30056.exp with target board
native-extended-gdbserver, I run into:
...
Quit^[[K^M^[[B(gdb) PASS: gdb.tui/pr30056.exp: Control-C
Remote debugging from host ::1, port 38810^M
^M(failed reverse-i-search)`xyz': ^M(gdb) target extended-remote \
localhost:2346^[[7GWARNING: Timed out waiting for EOF in server after \
monitor exit
...
This is due to the fact that ^C doesn't abort the reverse-i-search. This
appears to be due to a readline problem. A PR is open about this: PR
cli/30498.
Add a KFAIL for the PR, and ensure that the isearch is aborted by using ^G,
such that we have a responsive prompt to handle the "monitor exit" command
that native-extended-gdbserver issues.
Tested on x86_64-linux.
I added a cmd-only layout:
...
(gdb) tui new-layout cmd cmd 1
...
and set it:
...
(gdb) layout cmd
...
which gave me the expect result: only the cmd window in the screen.
However, after going back to layout src:
...
(gdb) layout src
...
I got a source window with only one line in it, and the cmd window taking most
of the screen.
I traced this back to tui_set_layout, where for both the old and the new
layout the fingerprint of the cmd window in the layout is taken. If the
fingerprint is the same, an effort will be done to preserve the command
window size.
The fingerprint is "VC" for both the old (cmd) and new (src) layouts, which
explains the behaviour.
I think this is essentially a bug in the finger print calculation, and it
should be "C" for the cmd layout.
Fix this by not adding a V or H in the fingerprint if the list size is one.
Tested on x86_64-linux.
Reviewed-By: Tom Tromey <tom@tromey.com>
This commit adds a new format for the printf and dprintf commands:
'%V'. This new format takes any GDB expression and formats it as a
string, just as GDB would for a 'print' command, e.g.:
(gdb) print a1
$a = {2, 4, 6, 8, 10, 12, 14, 16, 18, 20}
(gdb) printf "%V\n", a1
{2, 4, 6, 8, 10, 12, 14, 16, 18, 20}
(gdb)
It is also possible to pass the same options to %V as you might pass
to the print command, e.g.:
(gdb) print -elements 3 -- a1
$4 = {2, 4, 6...}
(gdb) printf "%V[-elements 3]\n", a1
{2, 4, 6...}
(gdb)
This new feature would effectively replace an existing feature of GDB,
the $_as_string builtin convenience function. However, the
$_as_string function has a few problems which this new feature solves:
1. $_as_string doesn't currently work when the inferior is not
running, e.g:
(gdb) printf "%s", $_as_string(a1)
You can't do that without a process to debug.
(gdb)
The reason for this is that $_as_string returns a value object with
string type. When we try to print this we call value_as_address,
which ends up trying to push the string into the inferior's address
space.
Clearly we could solve this problem, the string data exists in GDB, so
there's no reason why we have to push it into the inferior, but this
is an existing problem that would need solving.
2. $_as_string suffers from the fact that C degrades arrays to
pointers, e.g.:
(gdb) printf "%s\n", $_as_string(a1)
0x404260 <a1>
(gdb)
The implementation of $_as_string is passed a gdb.Value object that is
a pointer, it doesn't understand that it's actually an array. Solving
this would be harder than issue #1 I think. The whole array to
pointer transformation is part of our expression evaluation. And in
most cases this is exactly what we want. It's not clear to me how
we'd (easily) tell GDB that we didn't want this reduction in _some_
cases. But I'm sure this is solvable if we really wanted to.
3. $_as_string is a gdb.Function sub-class, and as such is passed
gdb.Value objects. There's no super convenient way to pass formatting
options to $_as_string. By this I mean that the new %V feature
supports print formatting options. Ideally, we might want to add this
feature to $_as_string, we might imagine it working something like:
(gdb) printf "%s\n", $_as_string(a1,
elements = 3,
array_indexes = True)
where the first item is the value to print, while the remaining
options are the print formatting options. However, this relies on
Python calling syntax, which isn't something that convenience
functions handle. We could possibly rely on strictly positional
arguments, like:
(gdb) printf "%s\n", $_as_string(a1, 3, 1)
But that's clearly terrible as there's far more print formatting
options, and if you needed to set the 9th option you'd need to fill in
all the previous options.
And right now, the only way to pass these options to a gdb.Function is
to have GDB first convert them all into gdb.Value objects, which is
really overkill for what we want.
The new %V format solves all these problems: the string is computed
and printed entirely on the GDB side, we are able to print arrays as
actual arrays rather than pointers, and we can pass named format
arguments.
Finally, the $_as_string is sold in the manual as allowing users to
print the string representation of flag enums, so given:
enum flags
{
FLAG_A = (1 << 0),
FLAG_B = (1 << 1),
FLAG_C = (1 << 1)
};
enum flags ff = FLAG_B;
We can:
(gdb) printf "%s\n", $_as_string(ff)
FLAG_B
This works just fine with %V too:
(gdb) printf "%V\n", ff
FLAG_B
So all functionality of $_as_string is replaced by %V. I'm not
proposing to remove $_as_string, there might be users currently
depending on it, but I am proposing that we don't push $_as_string in
the documentation.
As %V is a feature of printf, GDB's dprintf breakpoints naturally gain
access to this feature too. dprintf breakpoints can be operated in
three different styles 'gdb' (use GDB's printf), 'call' (call a
function in the inferior), or 'agent' (perform the dprintf on the
remote).
The use of '%V' will work just fine when dprintf-style is 'gdb'.
When dprintf-style is 'call' the format string and arguments are
passed to an inferior function (printf by default). In this case GDB
doesn't prevent use of '%V', but the documentation makes it clear that
support for '%V' will depend on the inferior function being called.
I chose this approach because the current implementation doesn't place
any restrictions on the format string when operating in 'call' style.
That is, the user might already be calling a function that supports
custom print format specifiers (maybe including '%V') so, I claim, it
would be wrong to block use of '%V' in this case. The documentation
does make it clear that users shouldn't expect this to "just work"
though.
When dprintf-style is 'agent' then GDB does no support the use of
'%V' (right now). This is handled at the point when GDB tries to
process the format string and send the dprintf command to the remote,
here's an example:
Reading symbols from /tmp/hello.x...
(gdb) dprintf call_me, "%V", a1
Dprintf 1 at 0x401152: file /tmp/hello.c, line 8.
(gdb) set sysroot /
(gdb) target remote | gdbserver --once - /tmp/hello.x
Remote debugging using | gdbserver --once - /tmp/hello.x
stdin/stdout redirected
Process /tmp/hello.x created; pid = 3088822
Remote debugging using stdio
Reading symbols from /lib64/ld-linux-x86-64.so.2...
(No debugging symbols found in /lib64/ld-linux-x86-64.so.2)
0x00007ffff7fd3110 in _start () from /lib64/ld-linux-x86-64.so.2
(gdb) set dprintf-style agent
(gdb) c
Continuing.
Unrecognized format specifier 'V' in printf
Command aborted.
(gdb)
This is exactly how GDB would handle any other invalid format
specifier, for example:
Reading symbols from /tmp/hello.x...
(gdb) dprintf call_me, "%Q", a1
Dprintf 1 at 0x401152: file /tmp/hello.c, line 8.
(gdb) set sysroot /
(gdb) target remote | gdbserver --once - /tmp/hello.x
Remote debugging using | gdbserver --once - /tmp/hello.x
stdin/stdout redirected
Process /tmp/hello.x created; pid = 3089193
Remote debugging using stdio
Reading symbols from /lib64/ld-linux-x86-64.so.2...
(No debugging symbols found in /lib64/ld-linux-x86-64.so.2)
0x00007ffff7fd3110 in _start () from /lib64/ld-linux-x86-64.so.2
(gdb) set dprintf-style agent
(gdb) c
Continuing.
Unrecognized format specifier 'Q' in printf
Command aborted.
(gdb)
The error message isn't the greatest, but improving that can be put
off for another day I hope.
Reviewed-By: Eli Zaretskii <eliz@gnu.org>
Acked-By: Simon Marchi <simon.marchi@efficios.com>
Same idea as previous patches, but for about_to_proceed. We only need
(and want, as far as the mi_interp implementation is concerned) to
notify the interpreter that caused the proceed.
Change-Id: Id259bca10dbc3d43d46607ff7b95243a9cbe2f89
Same idea as previous patches, but for inferior_disappeared.
For symmetry with on_inferior_appeared, I named this one
on_inferior_disappeared, despite the observer being called
inferior_exit. This is called when detaching an inferior, so I think
that calling it "disappeared" is a bit less misleading (the observer
should probably be renamed later).
Change-Id: I372101586bc9454997953c1e540a2a6685f53ef6
Same idea as previous patches, but for inferior_added.
mi_interp::init avoided using mi_inferior_added, since, as the comment
used to say, it would notify all MI interpreters. Now, it's easy to
only notify the new interpreter, so it's possible to just call the
on_inferior_added method in mi_interp::init.
Change-Id: I0eddbd5367217d1c982516982089913019ef309f
