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binutils-gdb/gdb/minsyms.c

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/* GDB routines for manipulating the minimal symbol tables.
Copyright (C) 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001,
2002, 2003, 2004, 2007, 2008 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 3 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, see <http://www.gnu.org/licenses/>. */
/* 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 "defs.h"
#include <ctype.h>
#include "gdb_string.h"
#include "symtab.h"
#include "bfd.h"
#include "symfile.h"
#include "objfiles.h"
#include "demangle.h"
#include "value.h"
#include "cp-abi.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;
/* Compute a hash code based using the same criteria as `strcmp_iw'. */
unsigned int
msymbol_hash_iw (const char *string)
{
unsigned int hash = 0;
while (*string && *string != '(')
{
while (isspace (*string))
++string;
if (*string && *string != '(')
{
hash = hash * 67 + *string - 113;
++string;
}
}
return hash;
}
/* Compute a hash code for a string. */
unsigned int
msymbol_hash (const char *string)
{
unsigned int hash = 0;
for (; *string; ++string)
hash = hash * 67 + *string - 113;
return hash;
}
/* Add the minimal symbol SYM to an objfile's minsym hash table, TABLE. */
void
add_minsym_to_hash_table (struct minimal_symbol *sym,
struct minimal_symbol **table)
{
if (sym->hash_next == NULL)
{
unsigned int hash
= msymbol_hash (SYMBOL_LINKAGE_NAME (sym)) % MINIMAL_SYMBOL_HASH_SIZE;
sym->hash_next = table[hash];
table[hash] = sym;
}
}
/* Add the minimal symbol SYM to an objfile's minsym demangled hash table,
TABLE. */
static void
add_minsym_to_demangled_hash_table (struct minimal_symbol *sym,
struct minimal_symbol **table)
{
if (sym->demangled_hash_next == NULL)
{
unsigned int hash = msymbol_hash_iw (SYMBOL_DEMANGLED_NAME (sym)) % MINIMAL_SYMBOL_HASH_SIZE;
sym->demangled_hash_next = table[hash];
table[hash] = sym;
}
}
/* Return OBJFILE where minimal symbol SYM is defined. */
struct objfile *
msymbol_objfile (struct minimal_symbol *sym)
{
struct objfile *objf;
struct minimal_symbol *tsym;
unsigned int hash
= msymbol_hash (SYMBOL_LINKAGE_NAME (sym)) % MINIMAL_SYMBOL_HASH_SIZE;
for (objf = object_files; objf; objf = objf->next)
for (tsym = objf->msymbol_hash[hash]; tsym; tsym = tsym->hash_next)
if (tsym == sym)
return objf;
/* We should always be able to find the objfile ... */
internal_error (__FILE__, __LINE__, _("failed internal consistency check"));
}
/* Look through all the current minimal symbol tables and find the
first minimal symbol that matches NAME. If OBJF is non-NULL, limit
the search to that objfile. If SFILE is non-NULL, the only file-scope
symbols considered will be from that source file (global symbols are
still preferred). Returns a pointer to the minimal symbol that
matches, or NULL if no match is found.
Note: One instance where there 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).
It's also possible to have minimal symbols with different mangled
names, but identical demangled names. For example, the GNU C++ v3
ABI requires the generation of two (or perhaps three) copies of
constructor functions --- "in-charge", "not-in-charge", and
"allocate" copies; destructors may be duplicated as well.
Obviously, there must be distinct mangled names for each of these,
but the demangled names are all the same: S::S or S::~S. */
struct minimal_symbol *
lookup_minimal_symbol (const char *name, const char *sfile,
struct objfile *objf)
{
struct objfile *objfile;
struct minimal_symbol *msymbol;
struct minimal_symbol *found_symbol = NULL;
struct minimal_symbol *found_file_symbol = NULL;
struct minimal_symbol *trampoline_symbol = NULL;
unsigned int hash = msymbol_hash (name) % MINIMAL_SYMBOL_HASH_SIZE;
unsigned int dem_hash = msymbol_hash_iw (name) % MINIMAL_SYMBOL_HASH_SIZE;
if (sfile != NULL)
{
char *p = strrchr (sfile, '/');
if (p != NULL)
sfile = p + 1;
}
for (objfile = object_files;
objfile != NULL && found_symbol == NULL;
objfile = objfile->next)
{
if (objf == NULL || objf == objfile
|| objf->separate_debug_objfile == objfile)
{
/* Do two passes: the first over the ordinary hash table,
and the second over the demangled hash table. */
int pass;
for (pass = 1; pass <= 2 && found_symbol == NULL; pass++)
{
/* Select hash list according to pass. */
if (pass == 1)
msymbol = objfile->msymbol_hash[hash];
else
msymbol = objfile->msymbol_demangled_hash[dem_hash];
while (msymbol != NULL && found_symbol == NULL)
{
/* FIXME: carlton/2003-02-27: This is an unholy
mixture of linkage names and natural names. If
you want to test the linkage names with strcmp,
do that. If you want to test the natural names
with strcmp_iw, use SYMBOL_MATCHES_NATURAL_NAME. */
if (strcmp (DEPRECATED_SYMBOL_NAME (msymbol), (name)) == 0
|| (SYMBOL_DEMANGLED_NAME (msymbol) != NULL
&& strcmp_iw (SYMBOL_DEMANGLED_NAME (msymbol),
(name)) == 0))
{
switch (MSYMBOL_TYPE (msymbol))
{
case mst_file_text:
case mst_file_data:
case mst_file_bss:
if (sfile == NULL
|| strcmp (msymbol->filename, sfile) == 0)
found_file_symbol = msymbol;
break;
case mst_solib_trampoline:
/* If a trampoline symbol is found, we prefer to
keep looking for the *real* symbol. If the
actual symbol is not found, then we'll use the
trampoline entry. */
if (trampoline_symbol == NULL)
trampoline_symbol = msymbol;
break;
case mst_unknown:
default:
found_symbol = msymbol;
break;
}
}
/* Find the next symbol on the hash chain. */
if (pass == 1)
msymbol = msymbol->hash_next;
else
msymbol = msymbol->demangled_hash_next;
}
}
}
}
/* External symbols are best. */
if (found_symbol)
return found_symbol;
/* File-local symbols are next best. */
if (found_file_symbol)
return found_file_symbol;
/* Symbols for shared library trampolines are next best. */
if (trampoline_symbol)
return trampoline_symbol;
return NULL;
}
/* Look through all the current minimal symbol tables and find the
first minimal symbol that matches NAME and has text type. If OBJF
is non-NULL, limit the search to that objfile. Returns a pointer
to the minimal symbol that matches, or NULL if no match is found.
This function only searches the mangled (linkage) names. */
struct minimal_symbol *
lookup_minimal_symbol_text (const char *name, struct objfile *objf)
{
struct objfile *objfile;
struct minimal_symbol *msymbol;
struct minimal_symbol *found_symbol = NULL;
struct minimal_symbol *found_file_symbol = NULL;
unsigned int hash = msymbol_hash (name) % MINIMAL_SYMBOL_HASH_SIZE;
for (objfile = object_files;
objfile != NULL && found_symbol == NULL;
objfile = objfile->next)
{
if (objf == NULL || objf == objfile
|| objf->separate_debug_objfile == objfile)
{
for (msymbol = objfile->msymbol_hash[hash];
msymbol != NULL && found_symbol == NULL;
msymbol = msymbol->hash_next)
{
if (strcmp (SYMBOL_LINKAGE_NAME (msymbol), name) == 0 &&
(MSYMBOL_TYPE (msymbol) == mst_text ||
MSYMBOL_TYPE (msymbol) == mst_file_text))
{
switch (MSYMBOL_TYPE (msymbol))
{
case mst_file_text:
found_file_symbol = msymbol;
break;
default:
found_symbol = msymbol;
break;
}
}
}
}
}
/* External symbols are best. */
if (found_symbol)
return found_symbol;
/* File-local symbols are next best. */
if (found_file_symbol)
return found_file_symbol;
return NULL;
}
/* Look through all the current minimal symbol tables and find the
first minimal symbol that matches NAME and is a solib trampoline.
If OBJF is non-NULL, limit the search to that objfile. Returns a
pointer to the minimal symbol that matches, or NULL if no match is
found.
This function only searches the mangled (linkage) names. */
struct minimal_symbol *
lookup_minimal_symbol_solib_trampoline (const char *name,
struct objfile *objf)
{
struct objfile *objfile;
struct minimal_symbol *msymbol;
struct minimal_symbol *found_symbol = NULL;
unsigned int hash = msymbol_hash (name) % MINIMAL_SYMBOL_HASH_SIZE;
for (objfile = object_files;
objfile != NULL && found_symbol == NULL;
objfile = objfile->next)
{
if (objf == NULL || objf == objfile
|| objf->separate_debug_objfile == objfile)
{
for (msymbol = objfile->msymbol_hash[hash];
msymbol != NULL && found_symbol == NULL;
msymbol = msymbol->hash_next)
{
if (strcmp (SYMBOL_LINKAGE_NAME (msymbol), name) == 0 &&
MSYMBOL_TYPE (msymbol) == mst_solib_trampoline)
return msymbol;
}
}
}
return NULL;
}
/* 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, and matches SECTION (if non-NULL). 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. This is because objfiles can
overlap, for example objfile A has .text at 0x100 and .data at
0x40000 and objfile B has .text at 0x234 and .data at 0x40048. */
struct minimal_symbol *
lookup_minimal_symbol_by_pc_section (CORE_ADDR pc, asection *section)
{
int lo;
int hi;
int new;
struct objfile *objfile;
struct minimal_symbol *msymbol;
struct minimal_symbol *best_symbol = NULL;
struct obj_section *pc_section;
/* PC has to be in a known section. This ensures that anything
beyond the end of the last segment doesn't appear to be part of
the last function in the last segment. */
pc_section = find_pc_section (pc);
if (pc_section == NULL)
return NULL;
/* We can not require the symbol found to be in pc_section, because
e.g. IRIX 6.5 mdebug relies on this code returning an absolute
symbol - but find_pc_section won't return an absolute section and
hence the code below would skip over absolute symbols. We can
still take advantage of the call to find_pc_section, though - the
object file still must match. In case we have separate debug
files, search both the file and its separate debug file. There's
no telling which one will have the minimal symbols. */
objfile = pc_section->objfile;
if (objfile->separate_debug_objfile)
objfile = objfile->separate_debug_objfile;
for (; objfile != NULL; objfile = objfile->separate_debug_objfile_backlink)
{
/* 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 (objfile->minimal_symbol_count > 0)
{
int best_zero_sized = -1;
msymbol = objfile->msymbols;
lo = 0;
hi = objfile->minimal_symbol_count - 1;
/* 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. */
/* Should also require that pc is <= end of objfile. FIXME! */
if (pc >= SYMBOL_VALUE_ADDRESS (&msymbol[lo]))
{
while (SYMBOL_VALUE_ADDRESS (&msymbol[hi]) > pc)
{
/* pc is still strictly less than highest address */
/* Note "new" will always be >= lo */
new = (lo + hi) / 2;
if ((SYMBOL_VALUE_ADDRESS (&msymbol[new]) >= pc) ||
(lo == new))
{
hi = new;
}
else
{
lo = new;
}
}
/* If we have multiple symbols at the same address, we want
hi to point to the last one. That way we can find the
right symbol if it has an index greater than hi. */
while (hi < objfile->minimal_symbol_count - 1
&& (SYMBOL_VALUE_ADDRESS (&msymbol[hi])
== SYMBOL_VALUE_ADDRESS (&msymbol[hi + 1])))
hi++;
/* Skip various undesirable symbols. */
while (hi >= 0)
{
/* Skip any absolute symbols. This is apparently
what adb and dbx do, and is needed for the CM-5.
There are two known possible problems: (1) on
ELF, apparently end, edata, etc. are absolute.
Not sure ignoring them here is a big deal, but if
we want to use them, the fix would go in
elfread.c. (2) I think shared library entry
points on the NeXT are absolute. If we want
special handling for this it probably should be
triggered by a special mst_abs_or_lib or some
such. */
if (msymbol[hi].type == mst_abs)
{
hi--;
continue;
}
/* If SECTION was specified, skip any symbol from
wrong section. */
if (section
/* Some types of debug info, such as COFF,
don't fill the bfd_section member, so don't
throw away symbols on those platforms. */
&& SYMBOL_BFD_SECTION (&msymbol[hi]) != NULL
&& (!matching_bfd_sections
(SYMBOL_BFD_SECTION (&msymbol[hi]), section)))
{
hi--;
continue;
}
/* If the minimal symbol has a zero size, save it
but keep scanning backwards looking for one with
a non-zero size. A zero size may mean that the
symbol isn't an object or function (e.g. a
label), or it may just mean that the size was not
specified. */
if (MSYMBOL_SIZE (&msymbol[hi]) == 0
&& best_zero_sized == -1)
{
best_zero_sized = hi;
hi--;
continue;
}
/* If we are past the end of the current symbol, try
the previous symbol if it has a larger overlapping
size. This happens on i686-pc-linux-gnu with glibc;
the nocancel variants of system calls are inside
the cancellable variants, but both have sizes. */
if (hi > 0
&& MSYMBOL_SIZE (&msymbol[hi]) != 0
&& pc >= (SYMBOL_VALUE_ADDRESS (&msymbol[hi])
+ MSYMBOL_SIZE (&msymbol[hi]))
&& pc < (SYMBOL_VALUE_ADDRESS (&msymbol[hi - 1])
+ MSYMBOL_SIZE (&msymbol[hi - 1])))
{
hi--;
continue;
}
/* Otherwise, this symbol must be as good as we're going
to get. */
break;
}
/* If HI has a zero size, and best_zero_sized is set,
then we had two or more zero-sized symbols; prefer
the first one we found (which may have a higher
address). Also, if we ran off the end, be sure
to back up. */
if (best_zero_sized != -1
&& (hi < 0 || MSYMBOL_SIZE (&msymbol[hi]) == 0))
hi = best_zero_sized;
/* If the minimal symbol has a non-zero size, and this
PC appears to be outside the symbol's contents, then
refuse to use this symbol. If we found a zero-sized
symbol with an address greater than this symbol's,
use that instead. We assume that if symbols have
specified sizes, they do not overlap. */
if (hi >= 0
&& MSYMBOL_SIZE (&msymbol[hi]) != 0
&& pc >= (SYMBOL_VALUE_ADDRESS (&msymbol[hi])
+ MSYMBOL_SIZE (&msymbol[hi])))
{
if (best_zero_sized != -1)
hi = best_zero_sized;
else
/* Go on to the next object file. */
continue;
}
/* 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 (hi >= 0
&& ((best_symbol == NULL) ||
(SYMBOL_VALUE_ADDRESS (best_symbol) <
SYMBOL_VALUE_ADDRESS (&msymbol[hi]))))
{
best_symbol = &msymbol[hi];
}
}
}
}
return (best_symbol);
}
/* Backward compatibility: search through the minimal symbol table
for a matching PC (no section given) */
struct minimal_symbol *
lookup_minimal_symbol_by_pc (CORE_ADDR pc)
{
/* NOTE: cagney/2004-01-27: This was using find_pc_mapped_section to
force the section but that (well unless you're doing overlay
debugging) always returns NULL making the call somewhat useless. */
struct obj_section *section = find_pc_section (pc);
if (section == NULL)
return NULL;
return lookup_minimal_symbol_by_pc_section (pc, section->the_bfd_section);
}
/* Return leading symbol character for a BFD. If BFD is NULL,
return the leading symbol character from the main objfile. */
static int get_symbol_leading_char (bfd *);
static int
get_symbol_leading_char (bfd *abfd)
{
if (abfd != NULL)
return bfd_get_symbol_leading_char (abfd);
if (symfile_objfile != NULL && symfile_objfile->obfd != NULL)
return bfd_get_symbol_leading_char (symfile_objfile->obfd);
return 0;
}
/* 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 (void)
{
msym_count = 0;
msym_bunch = NULL;
msym_bunch_index = BUNCH_SIZE;
}
void
prim_record_minimal_symbol (const char *name, CORE_ADDR address,
enum minimal_symbol_type ms_type,
struct objfile *objfile)
{
int section;
switch (ms_type)
{
case mst_text:
case mst_file_text:
case mst_solib_trampoline:
section = SECT_OFF_TEXT (objfile);
break;
case mst_data:
case mst_file_data:
section = SECT_OFF_DATA (objfile);
break;
case mst_bss:
case mst_file_bss:
section = SECT_OFF_BSS (objfile);
break;
default:
section = -1;
}
prim_record_minimal_symbol_and_info (name, address, ms_type,
NULL, section, NULL, objfile);
}
/* Record a minimal symbol in the msym bunches. Returns the symbol
newly created. */
struct minimal_symbol *
prim_record_minimal_symbol_and_info (const char *name, CORE_ADDR address,
enum minimal_symbol_type ms_type,
char *info, int section,
asection *bfd_section,
struct objfile *objfile)
{
struct msym_bunch *new;
struct minimal_symbol *msymbol;
/* Don't put gcc_compiled, __gnu_compiled_cplus, and friends into
the minimal symbols, because if there is also another symbol
at the same address (e.g. the first function of the file),
lookup_minimal_symbol_by_pc would have no way of getting the
right one. */
if (ms_type == mst_file_text && name[0] == 'g'
&& (strcmp (name, GCC_COMPILED_FLAG_SYMBOL) == 0
|| strcmp (name, GCC2_COMPILED_FLAG_SYMBOL) == 0))
return (NULL);
/* It's safe to strip the leading char here once, since the name
is also stored stripped in the minimal symbol table. */
if (name[0] == get_symbol_leading_char (objfile->obfd))
++name;
if (ms_type == mst_file_text && strncmp (name, "__gnu_compiled", 14) == 0)
return (NULL);
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;
}
msymbol = &msym_bunch->contents[msym_bunch_index];
SYMBOL_INIT_LANGUAGE_SPECIFIC (msymbol, language_unknown);
SYMBOL_LANGUAGE (msymbol) = language_auto;
SYMBOL_SET_NAMES (msymbol, (char *)name, strlen (name), objfile);
SYMBOL_VALUE_ADDRESS (msymbol) = address;
SYMBOL_SECTION (msymbol) = section;
SYMBOL_BFD_SECTION (msymbol) = bfd_section;
MSYMBOL_TYPE (msymbol) = ms_type;
/* FIXME: This info, if it remains, needs its own field. */
MSYMBOL_INFO (msymbol) = info; /* FIXME! */
MSYMBOL_SIZE (msymbol) = 0;
/* The hash pointers must be cleared! If they're not,
add_minsym_to_hash_table will NOT add this msymbol to the hash table. */
msymbol->hash_next = NULL;
msymbol->demangled_hash_next = NULL;
msym_bunch_index++;
msym_count++;
OBJSTAT (objfile, n_minsyms++);
return msymbol;
}
/* Compare two minimal symbols by address and return a signed result based
on unsigned comparisons, so that we sort into unsigned numeric order.
Within groups with the same address, sort by name. */
static int
compare_minimal_symbols (const void *fn1p, const void *fn2p)
{
const struct minimal_symbol *fn1;
const struct minimal_symbol *fn2;
fn1 = (const struct minimal_symbol *) fn1p;
fn2 = (const struct minimal_symbol *) fn2p;
if (SYMBOL_VALUE_ADDRESS (fn1) < SYMBOL_VALUE_ADDRESS (fn2))
{
return (-1); /* addr 1 is less than addr 2 */
}
else if (SYMBOL_VALUE_ADDRESS (fn1) > SYMBOL_VALUE_ADDRESS (fn2))
{
return (1); /* addr 1 is greater than addr 2 */
}
else
/* addrs are equal: sort by name */
{
char *name1 = SYMBOL_LINKAGE_NAME (fn1);
char *name2 = SYMBOL_LINKAGE_NAME (fn2);
if (name1 && name2) /* both have names */
return strcmp (name1, name2);
else if (name2)
return 1; /* fn1 has no name, so it is "less" */
else if (name1) /* fn2 has no name, so it is "less" */
return -1;
else
return (0); /* neither has a name, so they're equal. */
}
}
/* 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? */
static void
do_discard_minimal_symbols_cleanup (void *arg)
{
struct msym_bunch *next;
while (msym_bunch != NULL)
{
next = msym_bunch->next;
xfree (msym_bunch);
msym_bunch = next;
}
}
struct cleanup *
make_cleanup_discard_minimal_symbols (void)
{
return make_cleanup (do_discard_minimal_symbols_cleanup, 0);
}
/* Compact duplicate entries out of a minimal symbol table by walking
through the table and compacting out entries with duplicate addresses
and matching names. Return the number of entries remaining.
On entry, the table resides between msymbol[0] and msymbol[mcount].
On exit, it resides between msymbol[0] and msymbol[result_count].
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 we
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 objfile_obstack, and will get automatically freed when the symbol
table is freed. The caller can free up the unused minimal symbols at
the end of the compacted region if their allocation strategy allows it.
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 (struct minimal_symbol *msymbol, int mcount,
struct objfile *objfile)
{
struct minimal_symbol *copyfrom;
struct minimal_symbol *copyto;
if (mcount > 0)
{
copyfrom = copyto = msymbol;
while (copyfrom < msymbol + mcount - 1)
{
if (SYMBOL_VALUE_ADDRESS (copyfrom)
== SYMBOL_VALUE_ADDRESS ((copyfrom + 1))
&& strcmp (SYMBOL_LINKAGE_NAME (copyfrom),
SYMBOL_LINKAGE_NAME ((copyfrom + 1))) == 0)
{
if (MSYMBOL_TYPE ((copyfrom + 1)) == mst_unknown)
{
MSYMBOL_TYPE ((copyfrom + 1)) = MSYMBOL_TYPE (copyfrom);
}
copyfrom++;
}
else
*copyto++ = *copyfrom++;
}
*copyto++ = *copyfrom++;
mcount = copyto - msymbol;
}
return (mcount);
}
/* Build (or rebuild) the minimal symbol hash tables. This is necessary
after compacting or sorting the table since the entries move around
thus causing the internal minimal_symbol pointers to become jumbled. */
static void
build_minimal_symbol_hash_tables (struct objfile *objfile)
{
int i;
struct minimal_symbol *msym;
/* Clear the hash tables. */
for (i = 0; i < MINIMAL_SYMBOL_HASH_SIZE; i++)
{
objfile->msymbol_hash[i] = 0;
objfile->msymbol_demangled_hash[i] = 0;
}
/* Now, (re)insert the actual entries. */
for (i = objfile->minimal_symbol_count, msym = objfile->msymbols;
i > 0;
i--, msym++)
{
msym->hash_next = 0;
add_minsym_to_hash_table (msym, objfile->msymbol_hash);
msym->demangled_hash_next = 0;
if (SYMBOL_SEARCH_NAME (msym) != SYMBOL_LINKAGE_NAME (msym))
add_minsym_to_demangled_hash_table (msym,
objfile->msymbol_demangled_hash);
}
}
/* Add the minimal symbols in the existing bunches to the objfile's official
minimal symbol table. In most cases there is no minimal symbol table yet
for this objfile, and the existing bunches are used to create one. Once
in a while (for shared libraries for example), we add symbols (e.g. common
symbols) to an existing objfile.
Because of the way minimal symbols are collected, we generally have no way
of knowing what source language applies to any particular minimal symbol.
Specifically, we have no way of knowing if the minimal symbol comes from a
C++ compilation unit or not. So for the sake of supporting cached
demangled C++ names, we have no choice but to try and demangle each new one
that comes in. If the demangling succeeds, then we assume it is a C++
symbol and set the symbol's language and demangled name fields
appropriately. Note that in order to avoid unnecessary demanglings, and
allocating obstack space that subsequently can't be freed for the demangled
names, we mark all newly added symbols with language_auto. After
compaction of the minimal symbols, we go back and scan the entire minimal
symbol table looking for these new symbols. For each new symbol we attempt
to demangle it, and if successful, record it as a language_cplus symbol
and cache the demangled form on the symbol obstack. Symbols which don't
demangle are marked as language_unknown symbols, which inhibits future
attempts to demangle them if we later add more minimal symbols. */
void
install_minimal_symbols (struct objfile *objfile)
{
int bindex;
int mcount;
struct msym_bunch *bunch;
struct minimal_symbol *msymbols;
int alloc_count;
if (msym_count > 0)
{
/* Allocate enough space in the obstack, into which we will gather the
bunches of new and existing minimal symbols, sort them, and then
compact out the duplicate entries. Once we have a final table,
we will give back the excess space. */
alloc_count = msym_count + objfile->minimal_symbol_count + 1;
obstack_blank (&objfile->objfile_obstack,
alloc_count * sizeof (struct minimal_symbol));
msymbols = (struct minimal_symbol *)
obstack_base (&objfile->objfile_obstack);
/* Copy in the existing minimal symbols, if there are any. */
if (objfile->minimal_symbol_count)
memcpy ((char *) msymbols, (char *) objfile->msymbols,
objfile->minimal_symbol_count * sizeof (struct minimal_symbol));
/* 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. */
mcount = objfile->minimal_symbol_count;
for (bunch = msym_bunch; bunch != NULL; bunch = bunch->next)
{
for (bindex = 0; bindex < msym_bunch_index; bindex++, mcount++)
msymbols[mcount] = bunch->contents[bindex];
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, and free up whatever space we are
no longer using. */
mcount = compact_minimal_symbols (msymbols, mcount, objfile);
obstack_blank (&objfile->objfile_obstack,
(mcount + 1 - alloc_count) * sizeof (struct minimal_symbol));
msymbols = (struct minimal_symbol *)
obstack_finish (&objfile->objfile_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. 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. */
SYMBOL_LINKAGE_NAME (&msymbols[mcount]) = NULL;
SYMBOL_VALUE_ADDRESS (&msymbols[mcount]) = 0;
MSYMBOL_INFO (&msymbols[mcount]) = NULL;
MSYMBOL_SIZE (&msymbols[mcount]) = 0;
MSYMBOL_TYPE (&msymbols[mcount]) = mst_unknown;
SYMBOL_INIT_LANGUAGE_SPECIFIC (&msymbols[mcount], language_unknown);
/* Attach the minimal symbol table to the specified objfile.
The strings themselves are also located in the objfile_obstack
of this objfile. */
objfile->minimal_symbol_count = mcount;
objfile->msymbols = msymbols;
/* Try to guess the appropriate C++ ABI by looking at the names
of the minimal symbols in the table. */
{
int i;
for (i = 0; i < mcount; i++)
{
/* If a symbol's name starts with _Z and was successfully
demangled, then we can assume we've found a GNU v3 symbol.
For now we set the C++ ABI globally; if the user is
mixing ABIs then the user will need to "set cp-abi"
manually. */
const char *name = SYMBOL_LINKAGE_NAME (&objfile->msymbols[i]);
if (name[0] == '_' && name[1] == 'Z'
&& SYMBOL_DEMANGLED_NAME (&objfile->msymbols[i]) != NULL)
{
set_cp_abi_as_auto_default ("gnu-v3");
break;
}
}
}
/* Now build the hash tables; we can't do this incrementally
at an earlier point since we weren't finished with the obstack
yet. (And if the msymbol obstack gets moved, all the internal
pointers to other msymbols need to be adjusted.) */
build_minimal_symbol_hash_tables (objfile);
}
}
/* Sort all the minimal symbols in OBJFILE. */
void
msymbols_sort (struct objfile *objfile)
{
qsort (objfile->msymbols, objfile->minimal_symbol_count,
sizeof (struct minimal_symbol), compare_minimal_symbols);
build_minimal_symbol_hash_tables (objfile);
}
/* Check if PC is in a shared library trampoline code stub.
Return minimal symbol for the trampoline entry or NULL if PC is not
in a trampoline code stub. */
struct minimal_symbol *
lookup_solib_trampoline_symbol_by_pc (CORE_ADDR pc)
{
struct minimal_symbol *msymbol = lookup_minimal_symbol_by_pc (pc);
if (msymbol != NULL && MSYMBOL_TYPE (msymbol) == mst_solib_trampoline)
return msymbol;
return NULL;
}
/* If PC is in a shared library trampoline code stub, return the
address of the `real' function belonging to the stub.
Return 0 if PC is not in a trampoline code stub or if the real
function is not found in the minimal symbol table.
We may fail to find the right function if a function with the
same name is defined in more than one shared library, but this
is considered bad programming style. We could return 0 if we find
a duplicate function in case this matters someday. */
CORE_ADDR
find_solib_trampoline_target (struct frame_info *frame, CORE_ADDR pc)
{
struct objfile *objfile;
struct minimal_symbol *msymbol;
struct minimal_symbol *tsymbol = lookup_solib_trampoline_symbol_by_pc (pc);
if (tsymbol != NULL)
{
ALL_MSYMBOLS (objfile, msymbol)
{
if (MSYMBOL_TYPE (msymbol) == mst_text
&& strcmp (SYMBOL_LINKAGE_NAME (msymbol),
SYMBOL_LINKAGE_NAME (tsymbol)) == 0)
return SYMBOL_VALUE_ADDRESS (msymbol);
}
}
return 0;
}
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