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glibc/elf/rtld_static_init.c

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elf: Partially initialize ld.so after static dlopen (bug 20802) After static dlopen, a copy of ld.so is loaded into the inner namespace, but that copy is not initialized at all. Some architectures run into serious problems as result, which is why the _dl_var_init mechanism was invented. With libpthread moving into libc and parts into ld.so, more architectures impacted, so it makes sense to switch to a generic mechanism which performs the partial initialization. As a result, getauxval now works after static dlopen (bug 20802). Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
2021-05-17 07:59:14 +00:00
/* Partial initialization of ld.so loaded via static dlopen.
Copyright (C) 2021 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/>. */
#include <assert.h>
/* Very special case: This object is built into the static libc, but
must know the layout of _rtld_global_ro. */
#define SHARED
#include <ldsodefs.h>
#include <rtld_static_init.h>
dlfcn: Rework static dlopen hooks Consolidate all hooks structures into a single one. There are no static dlopen ABI concerns because glibc 2.34 already comes with substantial ABI-incompatible changes in this area. (Static dlopen requires the exact same dynamic glibc version that was used for static linking.) The new approach uses a pointer to the hooks structure into _rtld_global_ro and initalizes it in __rtld_static_init. This avoids a back-and-forth with various callback functions. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
2021-06-03 06:26:04 +00:00
static const struct dlfcn_hook _dlfcn_hook =
{
.dlopen = __dlopen,
.dlclose = __dlclose,
.dlsym = __dlsym,
.dlvsym = __dlvsym,
.dlerror = __dlerror,
.dladdr = __dladdr,
.dladdr1 = __dladdr1,
.dlinfo = __dlinfo,
.dlmopen = __dlmopen,
.libc_dlopen_mode = __libc_dlopen_mode,
.libc_dlsym = __libc_dlsym,
.libc_dlvsym = __libc_dlvsym,
.libc_dlclose = __libc_dlclose,
};
elf: Partially initialize ld.so after static dlopen (bug 20802) After static dlopen, a copy of ld.so is loaded into the inner namespace, but that copy is not initialized at all. Some architectures run into serious problems as result, which is why the _dl_var_init mechanism was invented. With libpthread moving into libc and parts into ld.so, more architectures impacted, so it makes sense to switch to a generic mechanism which performs the partial initialization. As a result, getauxval now works after static dlopen (bug 20802). Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
2021-05-17 07:59:14 +00:00
void
__rtld_static_init (struct link_map *map)
{
const ElfW(Sym) *sym
= _dl_lookup_direct (map, "_rtld_global_ro",
0x9f28436a, /* dl_new_hash output. */
"GLIBC_PRIVATE",
0x0963cf85); /* _dl_elf_hash output. */
assert (sym != NULL);
struct rtld_global_ro *dl = DL_SYMBOL_ADDRESS (map, sym);
/* Perform partial initialization here. Note that this runs before
ld.so is relocated, so only members initialized without
relocations can be written here. */
#ifdef HAVE_AUX_VECTOR
extern __typeof (dl->_dl_auxv) _dl_auxv attribute_hidden;
dl->_dl_auxv = _dl_auxv;
extern __typeof (dl->_dl_clktck) _dl_clktck attribute_hidden;
dl->_dl_clktck = _dl_clktck;
#endif
dlfcn: Rework static dlopen hooks Consolidate all hooks structures into a single one. There are no static dlopen ABI concerns because glibc 2.34 already comes with substantial ABI-incompatible changes in this area. (Static dlopen requires the exact same dynamic glibc version that was used for static linking.) The new approach uses a pointer to the hooks structure into _rtld_global_ro and initalizes it in __rtld_static_init. This avoids a back-and-forth with various callback functions. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
2021-06-03 06:26:04 +00:00
dl->_dl_dlfcn_hook = &_dlfcn_hook;
elf: Partially initialize ld.so after static dlopen (bug 20802) After static dlopen, a copy of ld.so is loaded into the inner namespace, but that copy is not initialized at all. Some architectures run into serious problems as result, which is why the _dl_var_init mechanism was invented. With libpthread moving into libc and parts into ld.so, more architectures impacted, so it makes sense to switch to a generic mechanism which performs the partial initialization. As a result, getauxval now works after static dlopen (bug 20802). Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
2021-05-17 07:59:14 +00:00
extern __typeof (dl->_dl_hwcap) _dl_hwcap attribute_hidden;
dl->_dl_hwcap = _dl_hwcap;
extern __typeof (dl->_dl_hwcap2) _dl_hwcap2 attribute_hidden;
dl->_dl_hwcap2 = _dl_hwcap2;
elf: Initialize GLRO (dl_minsigstacksize) after static dlopen This is another field of _rtld_global_ro that benefits from initialization in __rtld_static_init. Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
2021-05-20 16:55:26 +00:00
extern __typeof (dl->_dl_minsigstacksize) _dl_minsigstacksize
attribute_hidden;
dl->_dl_minsigstacksize = _dl_minsigstacksize;
elf: Partially initialize ld.so after static dlopen (bug 20802) After static dlopen, a copy of ld.so is loaded into the inner namespace, but that copy is not initialized at all. Some architectures run into serious problems as result, which is why the _dl_var_init mechanism was invented. With libpthread moving into libc and parts into ld.so, more architectures impacted, so it makes sense to switch to a generic mechanism which performs the partial initialization. As a result, getauxval now works after static dlopen (bug 20802). Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
2021-05-17 07:59:14 +00:00
extern __typeof (dl->_dl_pagesize) _dl_pagesize attribute_hidden;
dl->_dl_pagesize = _dl_pagesize;
elf: Move static TLS size and alignment into _rtld_global_ro This helps to clarify that the caching of these fields in libpthread (in __static_tls_size, __static_tls_align_m1) is unnecessary. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
2021-05-17 07:59:14 +00:00
extern __typeof (dl->_dl_tls_static_align) _dl_tls_static_align
attribute_hidden;
dl->_dl_tls_static_align = _dl_tls_static_align;
extern __typeof (dl->_dl_tls_static_size) _dl_tls_static_size
attribute_hidden;
dl->_dl_tls_static_size = _dl_tls_static_size;
elf: Add _dl_find_object function It can be used to speed up the libgcc unwinder, and the internal _dl_find_dso_for_object function (which is used for caller identification in dlopen and related functions, and in dladdr). _dl_find_object is in the internal namespace due to bug 28503. If libgcc switches to _dl_find_object, this namespace issue will be fixed. It is located in libc for two reasons: it is necessary to forward the call to the static libc after static dlopen, and there is a link ordering issue with -static-libgcc and libgcc_eh.a because libc.so is not a linker script that includes ld.so in the glibc build tree (so that GCC's internal -lc after libgcc_eh.a does not pick up ld.so). It is necessary to do the i386 customization in the sysdeps/x86/bits/dl_find_object.h header shared with x86-64 because otherwise, multilib installations are broken. The implementation uses software transactional memory, as suggested by Torvald Riegel. Two copies of the supporting data structures are used, also achieving full async-signal-safety. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
2021-12-28 21:52:56 +00:00
dl->_dl_find_object = _dl_find_object;
elf: Partially initialize ld.so after static dlopen (bug 20802) After static dlopen, a copy of ld.so is loaded into the inner namespace, but that copy is not initialized at all. Some architectures run into serious problems as result, which is why the _dl_var_init mechanism was invented. With libpthread moving into libc and parts into ld.so, more architectures impacted, so it makes sense to switch to a generic mechanism which performs the partial initialization. As a result, getauxval now works after static dlopen (bug 20802). Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
2021-05-17 07:59:14 +00:00
__rtld_static_init_arch (map, dl);
}
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