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* Check in Fred Fish's changes in these modules. Fred

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will make ChangeLog entries for all of them.
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John Gilmore
1992-02-22 01:46:16 +00:00
parent 8e48d87af6
commit 1ab3bf1b14
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gdb/minsyms.c Normal file
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/* GDB routines for manipulating the minimal symbol tables.
Copyright 1992 Free Software Foundation, Inc.
Contributed by Cygnus Support, using pieces from other GDB modules.
This file is part of GDB.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
/* This file contains support routines for creating, manipulating, and
destroying minimal symbol tables.
Minimal symbol tables are used to hold some very basic information about
all defined global symbols (text, data, bss, abs, etc). The only two
required pieces of information are the symbol's name and the address
associated with that symbol.
In many cases, even if a file was compiled with no special options for
debugging at all, as long as was not stripped it will contain sufficient
information to build useful minimal symbol tables using this structure.
Even when a file contains enough debugging information to build a full
symbol table, these minimal symbols are still useful for quickly mapping
between names and addresses, and vice versa. They are also sometimes used
to figure out what full symbol table entries need to be read in. */
#include <stdio.h>
#include "defs.h"
#include "symtab.h"
#include "bfd.h"
#include "symfile.h"
/* Accumulate the minimal symbols for each objfile in bunches of BUNCH_SIZE.
At the end, copy them all into one newly allocated location on an objfile's
symbol obstack. */
#define BUNCH_SIZE 127
struct msym_bunch
{
struct msym_bunch *next;
struct minimal_symbol contents[BUNCH_SIZE];
};
/* Bunch currently being filled up.
The next field points to chain of filled bunches. */
static struct msym_bunch *msym_bunch;
/* Number of slots filled in current bunch. */
static int msym_bunch_index;
/* Total number of minimal symbols recorded so far for the objfile. */
static int msym_count;
/* Prototypes for local functions. */
static int
compare_minimal_symbols PARAMS ((const void *, const void *));
static int
compact_minimal_symbols PARAMS ((struct minimal_symbol *, int));
/* Call the function specified by FUNC for each currently available minimal
symbol, for as long as this function continues to return NULL. If the
function ever returns non-NULL, then the iteration over the minimal
symbols is terminated,, the result is returned to the caller.
The function called has full control over the form and content of the
information returned via the non-NULL result, which may be as simple as a
pointer to the minimal symbol that the iteration terminated on, or as
complex as a pointer to a private structure containing multiple results. */
PTR
iterate_over_msymbols (func, arg1, arg2, arg3)
PTR (*func) PARAMS ((struct objfile *, struct minimal_symbol *,
PTR, PTR, PTR));
PTR arg1;
PTR arg2;
PTR arg3;
{
register struct objfile *objfile;
register struct minimal_symbol *msymbol;
char *result = NULL;
for (objfile = object_files;
objfile != NULL && result == NULL;
objfile = objfile -> next)
{
for (msymbol = objfile -> msymbols;
msymbol != NULL && msymbol -> name != NULL && result == NULL;
msymbol++)
{
result = (*func)(objfile, msymbol, arg1, arg2, arg3);
}
}
return (result);
}
/* Look through all the current minimal symbol tables and find the first
minimal symbol that matches NAME. If OBJF is non-NULL, it specifies a
particular objfile and the search is limited to that objfile. Returns
a pointer to the minimal symbol that matches, or NULL if no match is found.
Note: One instance where their may be duplicate minimal symbols with
the same name is when the symbol tables for a shared library and the
symbol tables for an executable contain global symbols with the same
names (the dynamic linker deals with the duplication). */
struct minimal_symbol *
lookup_minimal_symbol (name, objf)
register const char *name;
struct objfile *objf;
{
struct objfile *objfile;
struct minimal_symbol *msymbol;
struct minimal_symbol *found_symbol = NULL;
for (objfile = object_files;
objfile != NULL && found_symbol == NULL;
objfile = objfile -> next)
{
if (objf == NULL || objf == objfile)
{
for (msymbol = objfile -> msymbols;
msymbol != NULL && msymbol -> name != NULL &&
found_symbol == NULL;
msymbol++)
{
if (strcmp (msymbol -> name, name) == 0)
{
found_symbol = msymbol;
}
}
}
}
return (found_symbol);
}
/* Search through the minimal symbol table for each objfile and find the
symbol whose address is the largest address that is still less than or
equal to PC. Returns a pointer to the minimal symbol if such a symbol
is found, or NULL if PC is not in a suitable range. Note that we need
to look through ALL the minimal symbol tables before deciding on the
symbol that comes closest to the specified PC. */
struct minimal_symbol *
lookup_minimal_symbol_by_pc (pc)
register CORE_ADDR pc;
{
register int lo;
register int hi;
register int new;
register struct objfile *objfile;
register struct minimal_symbol *msymbol;
register struct minimal_symbol *best_symbol = NULL;
for (objfile = object_files;
objfile != NULL;
objfile = objfile -> next)
{
/* If this objfile has a minimal symbol table, go search it using
a binary search. Note that a minimal symbol table always consists
of at least two symbols, a "real" symbol and the terminating
"null symbol". If there are no real symbols, then there is no
minimal symbol table at all. */
if ((msymbol = objfile -> msymbols) != NULL)
{
lo = 0;
hi = objfile -> minimal_symbol_count - 2;
/* This code assumes that the minimal symbols are sorted by
ascending address values. If the pc value is greater than or
equal to the first symbol's address, then some symbol in this
minimal symbol table is a suitable candidate for being the
"best" symbol. This includes the last real symbol, for cases
where the pc value is larger than any address in this vector.
By iterating until the address associated with the current
hi index (the endpoint of the test interval) is less than
or equal to the desired pc value, we accomplish two things:
(1) the case where the pc value is larger than any minimal
symbol address is trivially solved, (2) the address associated
with the hi index is always the one we want when the interation
terminates. In essence, we are iterating the test interval
down until the pc value is pushed out of it from the high end.
Warning: this code is trickier than it would appear at first. */
if (pc >= msymbol[lo].address)
{
while (msymbol[hi].address > pc)
{
/* pc is still strictly less than highest address */
/* Note "new" will always be >= lo */
new = (lo + hi) / 2;
if ((msymbol[new].address >= pc) || (lo == new))
{
hi = new;
}
else
{
lo = new;
}
}
/* The minimal symbol indexed by hi now is the best one in this
objfile's minimal symbol table. See if it is the best one
overall. */
if ((best_symbol == NULL) ||
(best_symbol -> address < msymbol[hi].address))
{
best_symbol = &msymbol[hi];
}
}
}
}
return (best_symbol);
}
/* Prepare to start collecting minimal symbols. Note that presetting
msym_bunch_index to BUNCH_SIZE causes the first call to save a minimal
symbol to allocate the memory for the first bunch. */
void
init_minimal_symbol_collection ()
{
msym_count = 0;
msym_bunch = NULL;
msym_bunch_index = BUNCH_SIZE;
}
void
prim_record_minimal_symbol (name, address, ms_type)
const char *name;
CORE_ADDR address;
enum minimal_symbol_type ms_type;
{
register struct msym_bunch *new;
if (msym_bunch_index == BUNCH_SIZE)
{
new = (struct msym_bunch *) xmalloc (sizeof (struct msym_bunch));
msym_bunch_index = 0;
new -> next = msym_bunch;
msym_bunch = new;
}
msym_bunch -> contents[msym_bunch_index].name = (char *) name;
msym_bunch -> contents[msym_bunch_index].address = address;
msym_bunch -> contents[msym_bunch_index].info = NULL;
msym_bunch -> contents[msym_bunch_index].type = ms_type;
msym_bunch_index++;
msym_count++;
}
/* Compare two minimal symbols by address and return a signed result based
on unsigned comparisons, so that we sort into unsigned numeric order. */
static int
compare_minimal_symbols (fn1p, fn2p)
const PTR fn1p;
const PTR fn2p;
{
register const struct minimal_symbol *fn1;
register const struct minimal_symbol *fn2;
fn1 = (const struct minimal_symbol *) fn1p;
fn2 = (const struct minimal_symbol *) fn2p;
if (fn1 -> address < fn2 -> address)
{
return (-1);
}
else if (fn1 -> address > fn2 -> address)
{
return (1);
}
else
{
return (0);
}
}
/* Discard the currently collected minimal symbols, if any. If we wish
to save them for later use, we must have already copied them somewhere
else before calling this function.
FIXME: We could allocate the minimal symbol bunches on their own
obstack and then simply blow the obstack away when we are done with
it. Is it worth the extra trouble though? */
/* ARGSUSED */
void
discard_minimal_symbols (foo)
int foo;
{
register struct msym_bunch *next;
while (msym_bunch != NULL)
{
next = msym_bunch -> next;
free (msym_bunch);
msym_bunch = next;
}
}
/* Compact duplicate entries out of a minimal symbol table by walking
through the table and compacting out entries with duplicate addresses
and matching names.
When files contain multiple sources of symbol information, it is
possible for the minimal symbol table to contain many duplicate entries.
As an example, SVR4 systems use ELF formatted object files, which
usually contain at least two different types of symbol tables (a
standard ELF one and a smaller dynamic linking table), as well as
DWARF debugging information for files compiled with -g.
Without compacting, the minimal symbol table for gdb itself contains
over a 1000 duplicates, about a third of the total table size. Aside
from the potential trap of not noticing that two successive entries
identify the same location, this duplication impacts the time required
to linearly scan the table, which is done in a number of places. So
just do one linear scan here and toss out the duplicates.
Note that we are not concerned here about recovering the space that
is potentially freed up, because the strings themselves are allocated
on the symbol_obstack, and will get automatically freed when the symbol
table is freed. Also, the unused minimal symbols at the end of the
compacted region will get freed automatically as well by whomever
is responsible for deallocating the entire minimal symbol table. We
can't diddle with the pointer anywhy, so don't worry about the
wasted space.
Also note we only go up to the next to last entry within the loop
and then copy the last entry explicitly after the loop terminates.
Since the different sources of information for each symbol may
have different levels of "completeness", we may have duplicates
that have one entry with type "mst_unknown" and the other with a
known type. So if the one we are leaving alone has type mst_unknown,
overwrite its type with the type from the one we are compacting out. */
static int
compact_minimal_symbols (msymbol, mcount)
struct minimal_symbol *msymbol;
int mcount;
{
struct minimal_symbol *copyfrom;
struct minimal_symbol *copyto;
if (mcount > 0)
{
copyfrom = copyto = msymbol;
while (copyfrom < msymbol + mcount - 1)
{
if (copyfrom -> address == (copyfrom + 1) -> address
&& (strcmp (copyfrom -> name, (copyfrom + 1) -> name) == 0))
{
if ((copyfrom + 1) -> type == mst_unknown)
{
(copyfrom + 1) -> type = copyfrom -> type;
}
copyfrom++;
}
else
{
*copyto++ = *copyfrom++;
}
}
*copyto++ = *copyfrom++;
mcount = copyto - msymbol;
}
return (mcount);
}
/* INCLINK nonzero means bunches are from an incrementally-linked file.
Add them to the existing bunches.
Otherwise INCLINK is zero, and we start from scratch.
FIXME: INCLINK is currently unused, and is a holdover from when all
these symbols were stored in a shared, globally available table. If
it turns out we still need to be able to incrementally add minimal
symbols to an existing minimal symbol table for a given objfile, then
we will need to slightly modify this code so that when INCLINK is
nonzero we copy the existing table to a work area that is allocated
large enough for all the symbols and add the new ones to the end. */
void
install_minimal_symbols (inclink, objfile)
int inclink;
struct objfile *objfile;
{
register int bindex;
register int mcount;
register struct msym_bunch *bunch;
register struct minimal_symbol *msymbols;
int nbytes;
if (msym_count > 0)
{
/* Allocate a temporary work area into which we will gather the
bunches of minimal symbols, sort them, and then compact out
duplicate entries. Once we have a final table, it will be attached
to the specified objfile. */
msymbols = (struct minimal_symbol *)
xmalloc (msym_count * sizeof (struct minimal_symbol));
mcount = 0;
/* Walk through the list of minimal symbol bunches, adding each symbol
to the new contiguous array of symbols. Note that we start with the
current, possibly partially filled bunch (thus we use the current
msym_bunch_index for the first bunch we copy over), and thereafter
each bunch is full. */
for (bunch = msym_bunch; bunch != NULL; bunch = bunch -> next)
{
for (bindex = 0; bindex < msym_bunch_index; bindex++, mcount++)
{
msymbols[mcount] = bunch -> contents[bindex];
#ifdef NAMES_HAVE_UNDERSCORE
if (msymbols[mcount].name[0] == '_')
{
msymbols[mcount].name++;
}
#endif
#ifdef SOME_NAMES_HAVE_DOT
if (msymbols[mcount].name[0] == '.')
{
msymbols[mcount].name++;
}
#endif
}
msym_bunch_index = BUNCH_SIZE;
}
/* Sort the minimal symbols by address. */
qsort (msymbols, mcount, sizeof (struct minimal_symbol),
compare_minimal_symbols);
/* Compact out any duplicates. The table is reallocated to a
smaller size, even though it is unnecessary here, as we are just
going to move everything to an obstack anyway. */
mcount = compact_minimal_symbols (msymbols, mcount);
/* Attach the minimal symbol table to the specified objfile, allocating
the table entries in the symbol_obstack. Note that the strings them-
selves are already located in the symbol_obstack. We also terminate
the minimal symbol table with a "null symbol", which is *not* included
in the size of the table. This makes it easier to find the end of
the table when we are handed a pointer to some symbol in the middle
of it. */
objfile -> minimal_symbol_count = mcount;
nbytes = (mcount + 1) * sizeof (struct minimal_symbol);
objfile -> msymbols = (struct minimal_symbol *)
obstack_alloc (&objfile -> symbol_obstack, nbytes);
memcpy (objfile -> msymbols, msymbols, nbytes);
free (msymbols);
/* Zero out the fields in the "null symbol" allocated at the end
of the array. Note that the symbol count does *not* include
this null symbol, which is why it is indexed by mcount and not
mcount-1. */
objfile -> msymbols[mcount].name = NULL;
objfile -> msymbols[mcount].address = 0;
objfile -> msymbols[mcount].info = NULL;
objfile -> msymbols[mcount].type = mst_unknown;
}
}