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elf: Extract _dl_sym_post, _dl_sym_find_caller_map from elf/dl-sym.c

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The definitions are moved into a new file, elf/dl-sym-post.h, so that
this code can be used by the dynamic loader as well.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
This commit is contained in:
Florian Weimer 2020-02-08 15:00:28 +01:00
parent abcc039d2e
commit c76147afe9
2 changed files with 110 additions and 82 deletions
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106
elf/dl-sym-post.h Normal file
View File

@ -0,0 +1,106 @@
/* Post-processing of a symbol produced by dlsym, dlvsym.
Copyright (C) 1999-2020 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
/* Return the link map containing the caller address. */
static struct link_map *
_dl_sym_find_caller_link_map (ElfW(Addr) caller)
{
struct link_map *l = _dl_find_dso_for_object (caller);
if (l != NULL)
return l;
else
/* If the address is not recognized the call comes from the main
program (we hope). */
return GL(dl_ns)[LM_ID_BASE]._ns_loaded;
}
/* Translates RESULT, *REF, VALUE into a symbol address from the point
of view of MATCH. Performs IFUNC resolution and auditing if
necessary. If MATCH is NULL, CALLER is used to determine it. */
static void *
_dl_sym_post (lookup_t result, const ElfW(Sym) *ref, void *value,
ElfW(Addr) caller, struct link_map *match)
{
/* Resolve indirect function address. */
if (__glibc_unlikely (ELFW(ST_TYPE) (ref->st_info) == STT_GNU_IFUNC))
{
DL_FIXUP_VALUE_TYPE fixup
= DL_FIXUP_MAKE_VALUE (result, (ElfW(Addr)) value);
fixup = elf_ifunc_invoke (DL_FIXUP_VALUE_ADDR (fixup));
value = (void *) DL_FIXUP_VALUE_CODE_ADDR (fixup);
}
#ifdef SHARED
/* Auditing checkpoint: we have a new binding. Provide the
auditing libraries the possibility to change the value and
tell us whether further auditing is wanted. */
if (__glibc_unlikely (GLRO(dl_naudit) > 0))
{
const char *strtab = (const char *) D_PTR (result,
l_info[DT_STRTAB]);
/* Compute index of the symbol entry in the symbol table of
the DSO with the definition. */
unsigned int ndx = (ref - (ElfW(Sym) *) D_PTR (result,
l_info[DT_SYMTAB]));
if (match == NULL)
match = _dl_sym_find_caller_link_map (caller);
if ((match->l_audit_any_plt | result->l_audit_any_plt) != 0)
{
unsigned int altvalue = 0;
struct audit_ifaces *afct = GLRO(dl_audit);
/* Synthesize a symbol record where the st_value field is
the result. */
ElfW(Sym) sym = *ref;
sym.st_value = (ElfW(Addr)) value;
for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
{
struct auditstate *match_audit
= link_map_audit_state (match, cnt);
struct auditstate *result_audit
= link_map_audit_state (result, cnt);
if (afct->symbind != NULL
&& ((match_audit->bindflags & LA_FLG_BINDFROM) != 0
|| ((result_audit->bindflags & LA_FLG_BINDTO)
!= 0)))
{
unsigned int flags = altvalue | LA_SYMB_DLSYM;
uintptr_t new_value
= afct->symbind (&sym, ndx,
&match_audit->cookie,
&result_audit->cookie,
&flags, strtab + ref->st_name);
if (new_value != (uintptr_t) sym.st_value)
{
altvalue = LA_SYMB_ALTVALUE;
sym.st_value = new_value;
}
}
afct = afct->next;
}
value = (void *) sym.st_value;
}
}
#endif
return value;
}

86
elf/dl-sym.c
View File

@ -28,6 +28,7 @@
#include <sysdep-cancel.h>
#include <dl-tls.h>
#include <dl-irel.h>
#include <dl-sym-post.h>
#ifdef SHARED
@ -80,19 +81,6 @@ call_dl_lookup (void *ptr)
args->flags, NULL);
}
/* Return the link map containing the caller address. */
static inline struct link_map *
find_caller_link_map (ElfW(Addr) caller)
{
struct link_map *l = _dl_find_dso_for_object (caller);
if (l != NULL)
return l;
else
/* If the address is not recognized the call comes from the main
program (we hope). */
return GL(dl_ns)[LM_ID_BASE]._ns_loaded;
}
static void *
do_sym (void *handle, const char *name, void *who,
struct r_found_version *vers, int flags)
@ -106,7 +94,7 @@ do_sym (void *handle, const char *name, void *who,
if (handle == RTLD_DEFAULT)
{
match = find_caller_link_map (caller);
match = _dl_sym_find_caller_link_map (caller);
/* Search the global scope. We have the simple case where
we look up in the scope of an object which was part of
@ -140,7 +128,7 @@ do_sym (void *handle, const char *name, void *who,
}
else if (handle == RTLD_NEXT)
{
match = find_caller_link_map (caller);
match = _dl_sym_find_caller_link_map (caller);
if (__glibc_unlikely (match == GL(dl_ns)[LM_ID_BASE]._ns_loaded))
{
@ -179,73 +167,7 @@ RTLD_NEXT used in code not dynamically loaded"));
#endif
value = DL_SYMBOL_ADDRESS (result, ref);
/* Resolve indirect function address. */
if (__glibc_unlikely (ELFW(ST_TYPE) (ref->st_info) == STT_GNU_IFUNC))
{
DL_FIXUP_VALUE_TYPE fixup
= DL_FIXUP_MAKE_VALUE (result, (ElfW(Addr)) value);
fixup = elf_ifunc_invoke (DL_FIXUP_VALUE_ADDR (fixup));
value = (void *) DL_FIXUP_VALUE_CODE_ADDR (fixup);
}
#ifdef SHARED
/* Auditing checkpoint: we have a new binding. Provide the
auditing libraries the possibility to change the value and
tell us whether further auditing is wanted. */
if (__glibc_unlikely (GLRO(dl_naudit) > 0))
{
const char *strtab = (const char *) D_PTR (result,
l_info[DT_STRTAB]);
/* Compute index of the symbol entry in the symbol table of
the DSO with the definition. */
unsigned int ndx = (ref - (ElfW(Sym) *) D_PTR (result,
l_info[DT_SYMTAB]));
if (match == NULL)
match = find_caller_link_map (caller);
if ((match->l_audit_any_plt | result->l_audit_any_plt) != 0)
{
unsigned int altvalue = 0;
struct audit_ifaces *afct = GLRO(dl_audit);
/* Synthesize a symbol record where the st_value field is
the result. */
ElfW(Sym) sym = *ref;
sym.st_value = (ElfW(Addr)) value;
for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
{
struct auditstate *match_audit
= link_map_audit_state (match, cnt);
struct auditstate *result_audit
= link_map_audit_state (result, cnt);
if (afct->symbind != NULL
&& ((match_audit->bindflags & LA_FLG_BINDFROM) != 0
|| ((result_audit->bindflags & LA_FLG_BINDTO)
!= 0)))
{
unsigned int flags = altvalue | LA_SYMB_DLSYM;
uintptr_t new_value
= afct->symbind (&sym, ndx,
&match_audit->cookie,
&result_audit->cookie,
&flags, strtab + ref->st_name);
if (new_value != (uintptr_t) sym.st_value)
{
altvalue = LA_SYMB_ALTVALUE;
sym.st_value = new_value;
}
}
afct = afct->next;
}
value = (void *) sym.st_value;
}
}
#endif
return value;
return _dl_sym_post (result, ref, value, caller, match);
}
return NULL;