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Initialize the stack guard earlier when linking statically [BZ #7065]

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The address of the stack canary is stored in a per-thread variable,
which means that we must ensure that the TLS area is intialized before
calling any -fstack-protector'ed functions.  For dynamically linked
applications, we ensure this (in a later patch) by disabling
-fstack-protector for the whole dynamic linker, but for static
applications, the AT_ENTRY address is called directly by the kernel, so
we must deal with the problem differently.

In static appliations, __libc_setup_tls performs the TCB setup and TLS
initialization, so this commit arranges for it to be called early and
unconditionally.  The call (and the stack guard initialization) is
before the DL_SYSDEP_OSCHECK hook, which if set will probably call
functions which are stack-protected (it does on Linux and NaCL too).  We
also move apply_irel up, so that we can still safely call functions that
require ifuncs while in __libc_setup_tls (though if stack-protection is
enabled we still have to avoid calling functions that are not
stack-protected at this stage).
This commit is contained in:
Nick Alcock
2016-12-26 10:08:34 +01:00
committed by Florian Weimer
parent 03baef1c9c
commit 003a27e819
5 changed files with 51 additions and 45 deletions
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33
csu/libc-start.c
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@@ -29,7 +29,6 @@ extern int __libc_multiple_libcs;
#include <tls.h>
#ifndef SHARED
# include <dl-osinfo.h>
extern void __pthread_initialize_minimal (void);
# ifndef THREAD_SET_STACK_GUARD
/* Only exported for architectures that don't store the stack guard canary
in thread local area. */
@@ -175,6 +174,20 @@ LIBC_START_MAIN (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
}
}
/* Perform IREL{,A} relocations. */
apply_irel ();
/* The stack guard goes into the TCB, so initialize it early. */
__libc_setup_tls ();
/* Set up the stack checker's canary. */
uintptr_t stack_chk_guard = _dl_setup_stack_chk_guard (_dl_random);
# ifdef THREAD_SET_STACK_GUARD
THREAD_SET_STACK_GUARD (stack_chk_guard);
# else
__stack_chk_guard = stack_chk_guard;
# endif
# ifdef DL_SYSDEP_OSCHECK
if (!__libc_multiple_libcs)
{
@@ -184,21 +197,9 @@ LIBC_START_MAIN (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
}
# endif
/* Perform IREL{,A} relocations. */
apply_irel ();
/* Initialize the thread library at least a bit since the libgcc
functions are using thread functions if these are available and
we need to setup errno. */
__pthread_initialize_minimal ();
/* Set up the stack checker's canary. */
uintptr_t stack_chk_guard = _dl_setup_stack_chk_guard (_dl_random);
# ifdef THREAD_SET_STACK_GUARD
THREAD_SET_STACK_GUARD (stack_chk_guard);
# else
__stack_chk_guard = stack_chk_guard;
# endif
/* Initialize libpthread if linked in. */
if (__pthread_initialize_minimal != NULL)
__pthread_initialize_minimal ();
/* Set up the pointer guard value. */
uintptr_t pointer_chk_guard = _dl_setup_pointer_guard (_dl_random,