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ssp: add APIs for Stack Smashing Protection 

Compiling with any of the -fstack-protector* flags requires the
__stack_chk_guard data import (which needs to be initialized) and the
__stack_chk_fail{,_local} functions.  While GCC's own libssp can provide
these, it is better that we provide these ourselves.  The implementation
is custom due to being OS-specific.

Signed-off-by: Yaakov Selkowitz <yselkowi@redhat.com>
This commit is contained in:
Yaakov Selkowitz 2017-11-27 23:04:09 -06:00
parent 1bbdb3c953
commit 0a5dfdbd1b
1 changed files with 45 additions and 0 deletions
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45
newlib/libc/ssp/stack_protector.c Normal file
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#include <sys/cdefs.h>
#include <sys/param.h>
#include <signal.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
uintptr_t __stack_chk_guard = 0;
void
__attribute__((__constructor__))
__stack_chk_init (void)
{
if (__stack_chk_guard != 0)
return;
#if defined(__CYGWIN__) || defined(__rtems__)
arc4random_buf(&__stack_chk_guard, sizeof(__stack_chk_guard));
#else
/* If getentropy is not available, use the "terminator canary". */
((unsigned char *)&__stack_chk_guard)[0] = 0;
((unsigned char *)&__stack_chk_guard)[1] = 0;
((unsigned char *)&__stack_chk_guard)[2] = '\n';
((unsigned char *)&__stack_chk_guard)[3] = 255;
#endif
}
void
__attribute__((__noreturn__))
__stack_chk_fail (void)
{
char msg[] = "*** stack smashing detected ***: terminated\n";
write (2, msg, strlen (msg));
raise (SIGABRT);
_exit (127);
}
#ifdef __ELF__
void
__attribute__((visibility ("hidden")))
__stack_chk_fail_local (void)
{
__stack_chk_fail();
}
#endif