mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-21 12:30:06 +00:00
elf: Fix GL(dl_phdr) and GL(dl_phnum) for static builds [BZ #29864]
The 73fc4e28b9
refactor did not add the GL(dl_phdr) and
GL(dl_phnum) for static build, relying on the __ehdr_start symbol,
which is always added by the static linker, to get the correct values.
This is problematic in some ways:
- The segment may see its in-memory size differ from its in-file
size (or the binary may have holes). The Linux has fixed is to
provide concise values for both AT_PHDR and AT_PHNUM (commit
0da1d5002745c - "fs/binfmt_elf: Fix AT_PHDR for unusual ELF files")
- Some archs (alpha for instance) the hidden weak reference is not
correctly pulled by the static linker and __ehdr_start address
end up being 0, which makes GL(dl_phdr) and GL(dl_phnum) have both
invalid values (and triggering a segfault later on libc.so while
accessing TLS variables).
The safer fix is to just restore the previous behavior to setup
GL(dl_phdr) and GL(dl_phnum) for static based on kernel auxv. The
__ehdr_start fallback can also be simplified by not assuming weak
linkage (as for PIE).
The libc-static.c auxv init logic is moved to dl-support.c, since
the later is build without SHARED and then GLRO macro is defined
to access the variables directly.
The _dl_phdr is also assumed to be always non NULL, since an invalid
NULL values does not trigger TLS initialization (which is used in
various libc systems).
Checked on aarch64-linux-gnu, x86_64-linux-gnu, and i686-linux-gnu.
Reviewed-by: Florian Weimer <fweimer@redhat.com>
This commit is contained in:
parent
402853be1d
commit
7e31d16651
@ -262,28 +262,7 @@ LIBC_START_MAIN (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
|
||||
}
|
||||
# endif
|
||||
_dl_aux_init (auxvec);
|
||||
if (GL(dl_phdr) == NULL)
|
||||
# endif
|
||||
{
|
||||
/* Starting from binutils-2.23, the linker will define the
|
||||
magic symbol __ehdr_start to point to our own ELF header
|
||||
if it is visible in a segment that also includes the phdrs.
|
||||
So we can set up _dl_phdr and _dl_phnum even without any
|
||||
information from auxv. */
|
||||
|
||||
extern const ElfW(Ehdr) __ehdr_start
|
||||
# if BUILD_PIE_DEFAULT
|
||||
__attribute__ ((visibility ("hidden")));
|
||||
# else
|
||||
__attribute__ ((weak, visibility ("hidden")));
|
||||
if (&__ehdr_start != NULL)
|
||||
# endif
|
||||
{
|
||||
assert (__ehdr_start.e_phentsize == sizeof *GL(dl_phdr));
|
||||
GL(dl_phdr) = (const void *) &__ehdr_start + __ehdr_start.e_phoff;
|
||||
GL(dl_phnum) = __ehdr_start.e_phnum;
|
||||
}
|
||||
}
|
||||
|
||||
__tunables_init (__environ);
|
||||
|
||||
|
@ -119,19 +119,18 @@ __libc_setup_tls (void)
|
||||
__tls_pre_init_tp ();
|
||||
|
||||
/* Look through the TLS segment if there is any. */
|
||||
if (_dl_phdr != NULL)
|
||||
for (phdr = _dl_phdr; phdr < &_dl_phdr[_dl_phnum]; ++phdr)
|
||||
if (phdr->p_type == PT_TLS)
|
||||
{
|
||||
/* Remember the values we need. */
|
||||
memsz = phdr->p_memsz;
|
||||
filesz = phdr->p_filesz;
|
||||
initimage = (void *) phdr->p_vaddr + main_map->l_addr;
|
||||
align = phdr->p_align;
|
||||
if (phdr->p_align > max_align)
|
||||
max_align = phdr->p_align;
|
||||
break;
|
||||
}
|
||||
for (phdr = _dl_phdr; phdr < &_dl_phdr[_dl_phnum]; ++phdr)
|
||||
if (phdr->p_type == PT_TLS)
|
||||
{
|
||||
/* Remember the values we need. */
|
||||
memsz = phdr->p_memsz;
|
||||
filesz = phdr->p_filesz;
|
||||
initimage = (void *) phdr->p_vaddr + main_map->l_addr;
|
||||
align = phdr->p_align;
|
||||
if (phdr->p_align > max_align)
|
||||
max_align = phdr->p_align;
|
||||
break;
|
||||
}
|
||||
|
||||
/* Calculate the size of the static TLS surplus, with 0 auditors. */
|
||||
_dl_tls_static_surplus_init (0);
|
||||
|
@ -256,6 +256,25 @@ _dl_aux_init (ElfW(auxv_t) *av)
|
||||
for (int i = 0; i < array_length (auxv_values); ++i)
|
||||
auxv_values[i] = 0;
|
||||
_dl_parse_auxv (av, auxv_values);
|
||||
|
||||
_dl_phdr = (void*) auxv_values[AT_PHDR];
|
||||
_dl_phnum = auxv_values[AT_PHNUM];
|
||||
|
||||
if (_dl_phdr == NULL)
|
||||
{
|
||||
/* Starting from binutils-2.23, the linker will define the
|
||||
magic symbol __ehdr_start to point to our own ELF header
|
||||
if it is visible in a segment that also includes the phdrs.
|
||||
So we can set up _dl_phdr and _dl_phnum even without any
|
||||
information from auxv. */
|
||||
|
||||
extern const ElfW(Ehdr) __ehdr_start attribute_hidden;
|
||||
assert (__ehdr_start.e_phentsize == sizeof *GL(dl_phdr));
|
||||
_dl_phdr = (const void *) &__ehdr_start + __ehdr_start.e_phoff;
|
||||
_dl_phnum = __ehdr_start.e_phnum;
|
||||
}
|
||||
|
||||
assert (_dl_phdr != NULL);
|
||||
}
|
||||
#endif
|
||||
|
||||
@ -324,20 +343,19 @@ _dl_non_dynamic_init (void)
|
||||
if (_dl_platform != NULL)
|
||||
_dl_platformlen = strlen (_dl_platform);
|
||||
|
||||
if (_dl_phdr != NULL)
|
||||
for (const ElfW(Phdr) *ph = _dl_phdr; ph < &_dl_phdr[_dl_phnum]; ++ph)
|
||||
switch (ph->p_type)
|
||||
{
|
||||
/* Check if the stack is nonexecutable. */
|
||||
case PT_GNU_STACK:
|
||||
_dl_stack_flags = ph->p_flags;
|
||||
break;
|
||||
for (const ElfW(Phdr) *ph = _dl_phdr; ph < &_dl_phdr[_dl_phnum]; ++ph)
|
||||
switch (ph->p_type)
|
||||
{
|
||||
/* Check if the stack is nonexecutable. */
|
||||
case PT_GNU_STACK:
|
||||
_dl_stack_flags = ph->p_flags;
|
||||
break;
|
||||
|
||||
case PT_GNU_RELRO:
|
||||
_dl_main_map.l_relro_addr = ph->p_vaddr;
|
||||
_dl_main_map.l_relro_size = ph->p_memsz;
|
||||
break;
|
||||
}
|
||||
case PT_GNU_RELRO:
|
||||
_dl_main_map.l_relro_addr = ph->p_vaddr;
|
||||
_dl_main_map.l_relro_size = ph->p_memsz;
|
||||
break;
|
||||
}
|
||||
|
||||
call_function_static_weak (_dl_find_object_init);
|
||||
|
||||
|
Loading…
Reference in New Issue
Block a user