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glibc/elf/get-dynamic-info.h

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/* Read the dynamic section at DYN and fill in INFO with indices DT_*.
Copyright (C) 2012-2025 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/>. */
/* Populate dynamic tags in l_info. */
#ifndef _GET_DYNAMIC_INFO_H
#define _GET_DYNAMIC_INFO_H
#include <assert.h>
#include <dl-machine-rel.h>
#include <libc-diag.h>
static inline void __attribute__ ((unused, always_inline))
elf_get_dynamic_info (struct link_map *l, bool bootstrap,
bool static_pie_bootstrap)
{
#if __ELF_NATIVE_CLASS == 32
typedef Elf32_Word d_tag_utype;
#elif __ELF_NATIVE_CLASS == 64
typedef Elf64_Xword d_tag_utype;
#endif
#ifndef STATIC_PIE_BOOTSTRAP
if (!bootstrap && l->l_ld == NULL)
return;
#endif
ElfW(Dyn) **info = l->l_info;
for (ElfW(Dyn) *dyn = l->l_ld; dyn->d_tag != DT_NULL; dyn++)
{
d_tag_utype i;
if ((d_tag_utype) dyn->d_tag < DT_NUM)
i = dyn->d_tag;
else if (dyn->d_tag >= DT_LOPROC
&& dyn->d_tag < DT_LOPROC + DT_THISPROCNUM)
i = dyn->d_tag - DT_LOPROC + DT_NUM;
else if ((d_tag_utype) DT_VERSIONTAGIDX (dyn->d_tag) < DT_VERSIONTAGNUM)
i = VERSYMIDX (dyn->d_tag);
else if ((d_tag_utype) DT_EXTRATAGIDX (dyn->d_tag) < DT_EXTRANUM)
i = DT_EXTRATAGIDX (dyn->d_tag) + DT_NUM + DT_THISPROCNUM
+ DT_VERSIONTAGNUM;
else if ((d_tag_utype) DT_VALTAGIDX (dyn->d_tag) < DT_VALNUM)
i = DT_VALTAGIDX (dyn->d_tag) + DT_NUM + DT_THISPROCNUM
+ DT_VERSIONTAGNUM + DT_EXTRANUM;
else if ((d_tag_utype) DT_ADDRTAGIDX (dyn->d_tag) < DT_ADDRNUM)
i = DT_ADDRTAGIDX (dyn->d_tag) + DT_NUM + DT_THISPROCNUM
+ DT_VERSIONTAGNUM + DT_EXTRANUM + DT_VALNUM;
else
continue;
info[i] = dyn;
}
/* Don't adjust .dynamic unnecessarily. */
if (l->l_addr != 0 && dl_relocate_ld (l))
{
ElfW(Addr) l_addr = l->l_addr;
# define ADJUST_DYN_INFO(tag) \
do \
{ \
if (info[tag] != NULL) \
info[tag]->d_un.d_ptr += l_addr; \
} \
while (0)
ADJUST_DYN_INFO (DT_HASH);
ADJUST_DYN_INFO (DT_PLTGOT);
ADJUST_DYN_INFO (DT_STRTAB);
ADJUST_DYN_INFO (DT_SYMTAB);
ADJUST_DYN_INFO (DT_RELR);
ADJUST_DYN_INFO (DT_JMPREL);
ADJUST_DYN_INFO (VERSYMIDX (DT_VERSYM));
ADJUST_DYN_INFO (ADDRIDX (DT_GNU_HASH));
# undef ADJUST_DYN_INFO
/* DT_RELA/DT_REL are mandatory. But they may have zero value if
there is DT_RELR. Don't relocate them if they are zero. */
# define ADJUST_DYN_INFO(tag) \
do \
if (info[tag] != NULL && info[tag]->d_un.d_ptr != 0) \
info[tag]->d_un.d_ptr += l_addr; \
while (0)
# if ! ELF_MACHINE_NO_RELA
ADJUST_DYN_INFO (DT_RELA);
# endif
# if ! ELF_MACHINE_NO_REL
ADJUST_DYN_INFO (DT_REL);
# endif
# undef ADJUST_DYN_INFO
}
if (info[DT_PLTREL] != NULL)
{
#if ELF_MACHINE_NO_RELA
assert (info[DT_PLTREL]->d_un.d_val == DT_REL);
#elif ELF_MACHINE_NO_REL
assert (info[DT_PLTREL]->d_un.d_val == DT_RELA);
#else
assert (info[DT_PLTREL]->d_un.d_val == DT_REL
|| info[DT_PLTREL]->d_un.d_val == DT_RELA);
#endif
}
#if ! ELF_MACHINE_NO_RELA
if (info[DT_RELA] != NULL)
assert (info[DT_RELAENT]->d_un.d_val == sizeof (ElfW(Rela)));
# endif
# if ! ELF_MACHINE_NO_REL
if (info[DT_REL] != NULL)
assert (info[DT_RELENT]->d_un.d_val == sizeof (ElfW(Rel)));
#endif
if (info[DT_RELR] != NULL)
assert (info[DT_RELRENT]->d_un.d_val == sizeof (ElfW(Relr)));
if (bootstrap || static_pie_bootstrap)
{
assert (info[DT_RUNPATH] == NULL);
assert (info[DT_RPATH] == NULL);
}
if (bootstrap)
{
/* Only the bind now flags are allowed. */
assert (info[VERSYMIDX (DT_FLAGS_1)] == NULL
|| (info[VERSYMIDX (DT_FLAGS_1)]->d_un.d_val & ~DF_1_NOW) == 0);
/* Flags must not be set for ld.so. */
assert (info[DT_FLAGS] == NULL
|| (info[DT_FLAGS]->d_un.d_val & ~DF_BIND_NOW) == 0);
}
else
{
if (info[DT_FLAGS] != NULL)
{
/* Flags are used. Translate to the old form where available.
Since these l_info entries are only tested for NULL pointers it
is ok if they point to the DT_FLAGS entry. */
l->l_flags = info[DT_FLAGS]->d_un.d_val;
if (l->l_flags & DF_SYMBOLIC)
info[DT_SYMBOLIC] = info[DT_FLAGS];
if (l->l_flags & DF_TEXTREL)
info[DT_TEXTREL] = info[DT_FLAGS];
if (l->l_flags & DF_BIND_NOW)
info[DT_BIND_NOW] = info[DT_FLAGS];
}
if (info[VERSYMIDX (DT_FLAGS_1)] != NULL)
{
l->l_flags_1 = info[VERSYMIDX (DT_FLAGS_1)]->d_un.d_val;
if (l->l_flags_1 & DF_1_NODELETE)
l->l_nodelete_pending = true;
/* Only DT_1_SUPPORTED_MASK bits are supported, and we would like
to assert this, but we can't. Users have been setting
unsupported DF_1_* flags for a long time and glibc has ignored
them. Therefore to avoid breaking existing applications the
best we can do is add a warning during debugging with the
intent of notifying the user of the problem. */
if (__builtin_expect (GLRO(dl_debug_mask) & DL_DEBUG_FILES, 0)
&& l->l_flags_1 & ~DT_1_SUPPORTED_MASK)
_dl_debug_printf ("\nWARNING: Unsupported flag value(s) of 0x%x "
"in DT_FLAGS_1.\n",
l->l_flags_1 & ~DT_1_SUPPORTED_MASK);
if (l->l_flags_1 & DF_1_NOW)
info[DT_BIND_NOW] = info[VERSYMIDX (DT_FLAGS_1)];
}
if (info[DT_RUNPATH] != NULL)
/* If both RUNPATH and RPATH are given, the latter is ignored. */
info[DT_RPATH] = NULL;
}
}
#endif
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