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fork in libpthread cannot use IFUNC resolver [BZ #19861]

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This commit only addresses the fork case, the vfork case has to be a
tail call, which is why the generic code needs an IFUNC resolver
there.
This commit is contained in:
Florian Weimer 2016-06-01 07:14:42 +02:00
parent 7838d298d8
commit f06f3f05b4
2 changed files with 19 additions and 33 deletions
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9
ChangeLog
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@ -1,3 +1,12 @@
2016-06-01 Florian Weimer <fweimer@redhat.com>
[BZ #19861]
Do not use IFUNC resolver with potentially unrelocated symbol.
* nptl/pt-fork.c [HAVE_IFUNC]: Remove.
(DEFINE_FORK): Remove macro and inline definition.
(fork_alias): Renamed from fork_ifunc.
(__fork_alias): Renamed from __fork_ifunc.
2016-05-30 Paul Pluzhnikov <ppluzhnikov@google.com>
[BZ 19653]

43
nptl/pt-fork.c
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@ -25,48 +25,25 @@
the historical ABI requires it. For static linking, there is no need to
provide anything here--the libc version will be linked in. For shared
library ABI compatibility, there must be __fork and fork symbols in
libpthread.so; so we define them using IFUNC to redirect to the libc
function. */
libpthread.so.
With an IFUNC resolver, it would be possible to avoid the
indirection, but the IFUNC resolver might run before the
__libc_fork symbol has been relocated, in which case the IFUNC
resolver would not be able to provide the correct address. */
#if SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_22)
# if HAVE_IFUNC
static __typeof (fork) *
__attribute__ ((used))
fork_resolve (void)
{
return &__libc_fork;
}
# ifdef HAVE_ASM_SET_DIRECTIVE
# define DEFINE_FORK(name) \
asm (".set " #name ", fork_resolve\n" \
".globl " #name "\n" \
".type " #name ", %gnu_indirect_function");
# else
# define DEFINE_FORK(name) \
asm (#name " = fork_resolve\n" \
".globl " #name "\n" \
".type " #name ", %gnu_indirect_function");
# endif
# else /* !HAVE_IFUNC */
static pid_t __attribute__ ((used))
fork_compat (void)
{
return __libc_fork ();
}
# define DEFINE_FORK(name) strong_alias (fork_compat, name)
strong_alias (fork_compat, fork_alias)
compat_symbol (libpthread, fork_alias, fork, GLIBC_2_0);
# endif /* HAVE_IFUNC */
DEFINE_FORK (fork_ifunc)
compat_symbol (libpthread, fork_ifunc, fork, GLIBC_2_0);
DEFINE_FORK (__fork_ifunc)
compat_symbol (libpthread, __fork_ifunc, __fork, GLIBC_2_0);
strong_alias (fork_compat, __fork_alias)
compat_symbol (libpthread, __fork_alias, __fork, GLIBC_2_0);
#endif