mirror of
https://github.com/grub4dos/ntloader.git
synced 2025-05-09 04:01:08 +08:00
102 lines
2.5 KiB
C
102 lines
2.5 KiB
C
/*
|
|
* Copyright (C) 2021 Michael Brown <mbrown@fensystems.co.uk>.
|
|
*
|
|
* This program is free software; you can redistribute it and/or
|
|
* modify it under the terms of the GNU General Public License as
|
|
* published by the Free Software Foundation; either version 2 of the
|
|
* License, or (at your option) any later version.
|
|
*
|
|
* This program 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
|
|
* General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU General Public License
|
|
* along with this program; if not, write to the Free Software
|
|
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
|
|
* 02110-1301, USA.
|
|
*/
|
|
|
|
/**
|
|
* @file
|
|
*
|
|
* Stack cookie
|
|
*
|
|
*/
|
|
|
|
#include "ntloader.h"
|
|
|
|
/** Stack cookie */
|
|
unsigned long __stack_chk_guard;
|
|
|
|
/**
|
|
* Construct stack cookie value
|
|
*
|
|
*/
|
|
static __attribute__ ((noinline)) unsigned long make_cookie (void)
|
|
{
|
|
union
|
|
{
|
|
struct
|
|
{
|
|
uint32_t eax;
|
|
uint32_t edx;
|
|
} __attribute__ ((packed));
|
|
uint64_t raw;
|
|
} u;
|
|
unsigned long cookie;
|
|
|
|
/* We have no viable source of entropy. Use the CPU timestamp
|
|
* counter, which will have at least some minimal randomness
|
|
* in the low bits by the time we are invoked.
|
|
*/
|
|
#if defined(__i386__) || defined(__x86_64__)
|
|
__asm__ ("rdtsc" : "=a" (u.eax), "=d" (u.edx));
|
|
#elif defined(__aarch64__)
|
|
__asm__ ("mrs %0, CNTVCT_EL0\n\t" : "=r" (u.raw));
|
|
#endif
|
|
cookie = u.raw;
|
|
|
|
/* Ensure that the value contains a NUL byte, to act as a
|
|
* runaway string terminator. Construct the NUL using a shift
|
|
* rather than a mask, to avoid losing valuable entropy in the
|
|
* lower-order bits.
|
|
*/
|
|
cookie <<= 8;
|
|
|
|
return cookie;
|
|
}
|
|
|
|
/**
|
|
* Initialise stack cookie
|
|
*
|
|
* This function must not itself use stack guard
|
|
*/
|
|
void init_cookie (void)
|
|
{
|
|
|
|
/* Set stack cookie value
|
|
*
|
|
* This function must not itself use stack protection, since
|
|
* the change in the stack guard value would trigger a false
|
|
* positive.
|
|
*
|
|
* There is unfortunately no way to annotate a function to
|
|
* exclude the use of stack protection. We must therefore
|
|
* rely on correctly anticipating the compiler's decision on
|
|
* the use of stack protection.
|
|
*/
|
|
__stack_chk_guard = make_cookie();
|
|
}
|
|
|
|
/**
|
|
* Abort on stack check failure
|
|
*
|
|
*/
|
|
void __stack_chk_fail (void)
|
|
{
|
|
|
|
/* Abort program */
|
|
die ("Stack check failed\n");
|
|
}
|