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powerpc: Initial stack protector (-fstack-protector) support

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Partialy copied from commit c743f38013 ("ARM: initial stack protector
(-fstack-protector) support")

This is the very basic stuff without the changing canary upon
task switch yet.  Just the Kconfig option and a constant canary
value initialized at boot time.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Christophe Leroy 2016-11-22 11:49:30 +01:00 committed by Michael Ellerman
parent d0563a1297
commit 6533b7c16e
4 changed files with 51 additions and 0 deletions
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1
arch/powerpc/Kconfig
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@ -163,6 +163,7 @@ config PPC
select HAVE_VIRT_CPU_ACCOUNTING
select HAVE_ARCH_HARDENED_USERCOPY
select HAVE_KERNEL_GZIP
select HAVE_CC_STACKPROTECTOR
config GENERIC_CSUM
def_bool CPU_LITTLE_ENDIAN

40
arch/powerpc/include/asm/stackprotector.h Normal file
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@ -0,0 +1,40 @@
/*
* GCC stack protector support.
*
* Stack protector works by putting predefined pattern at the start of
* the stack frame and verifying that it hasn't been overwritten when
* returning from the function. The pattern is called stack canary
* and gcc expects it to be defined by a global variable called
* "__stack_chk_guard" on PPC. This unfortunately means that on SMP
* we cannot have a different canary value per task.
*/
#ifndef _ASM_STACKPROTECTOR_H
#define _ASM_STACKPROTECTOR_H
#include <linux/random.h>
#include <linux/version.h>
#include <asm/reg.h>
extern unsigned long __stack_chk_guard;
/*
* Initialize the stackprotector canary value.
*
* NOTE: this must only be called from functions that never return,
* and it must always be inlined.
*/
static __always_inline void boot_init_stack_canary(void)
{
unsigned long canary;
/* Try to get a semi random initial value. */
get_random_bytes(&canary, sizeof(canary));
canary ^= mftb();
canary ^= LINUX_VERSION_CODE;
current->stack_canary = canary;
__stack_chk_guard = current->stack_canary;
}
#endif /* _ASM_STACKPROTECTOR_H */

4
arch/powerpc/kernel/Makefile
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@ -19,6 +19,10 @@ CFLAGS_init.o += $(DISABLE_LATENT_ENTROPY_PLUGIN)
CFLAGS_btext.o += $(DISABLE_LATENT_ENTROPY_PLUGIN)
CFLAGS_prom.o += $(DISABLE_LATENT_ENTROPY_PLUGIN)
# -fstack-protector triggers protection checks in this code,
# but it is being used too early to link to meaningful stack_chk logic.
CFLAGS_prom_init.o += $(call cc-option, -fno-stack-protector)
ifdef CONFIG_FUNCTION_TRACER
# Do not trace early boot code
CFLAGS_REMOVE_cputable.o = -mno-sched-epilog $(CC_FLAGS_FTRACE)

6
arch/powerpc/kernel/process.c
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@ -64,6 +64,12 @@
#include <linux/kprobes.h>
#include <linux/kdebug.h>
#ifdef CONFIG_CC_STACKPROTECTOR
#include <linux/stackprotector.h>
unsigned long __stack_chk_guard __read_mostly;
EXPORT_SYMBOL(__stack_chk_guard);
#endif
/* Transactional Memory debug */
#ifdef TM_DEBUG_SW
#define TM_DEBUG(x...) printk(KERN_INFO x)