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powerpc: Revert the initial stack protector support

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Unfortunately the stack protector support we merged recently only works
on some toolchains. If the toolchain is built without glibc support
everything works fine, but if glibc is built then it leads to a panic
at boot.

The solution is not rc5 material, so revert the support for now. This
reverts commits:

6533b7c16e ("powerpc: Initial stack protector (-fstack-protector) support")
902e06eb86 ("powerpc/32: Change the stack protector canary value per task")

Fixes: 6533b7c16e ("powerpc: Initial stack protector (-fstack-protector) support")
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Michael Ellerman 2017-01-24 21:37:20 +11:00
parent f05fea5b35
commit f2574030b0
6 changed files with 1 additions and 59 deletions
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1
arch/powerpc/Kconfig
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@ -164,7 +164,6 @@ config PPC
select ARCH_HAS_SCALED_CPUTIME if VIRT_CPU_ACCOUNTING_NATIVE
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
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@ -1,40 +0,0 @@
/*
* 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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@ -19,10 +19,6 @@ 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)

3
arch/powerpc/kernel/asm-offsets.c
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@ -91,9 +91,6 @@ int main(void)
DEFINE(TI_livepatch_sp, offsetof(struct thread_info, livepatch_sp));
#endif
#ifdef CONFIG_CC_STACKPROTECTOR
DEFINE(TSK_STACK_CANARY, offsetof(struct task_struct, stack_canary));
#endif
DEFINE(KSP, offsetof(struct thread_struct, ksp));
DEFINE(PT_REGS, offsetof(struct thread_struct, regs));
#ifdef CONFIG_BOOKE

6
arch/powerpc/kernel/entry_32.S
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@ -674,11 +674,7 @@ BEGIN_FTR_SECTION
mtspr SPRN_SPEFSCR,r0 /* restore SPEFSCR reg */
END_FTR_SECTION_IFSET(CPU_FTR_SPE)
#endif /* CONFIG_SPE */
#if defined(CONFIG_CC_STACKPROTECTOR) && !defined(CONFIG_SMP)
lwz r0,TSK_STACK_CANARY(r2)
lis r4,__stack_chk_guard@ha
stw r0,__stack_chk_guard@l(r4)
#endif
lwz r0,_CCR(r1)
mtcrf 0xFF,r0
/* r3-r12 are destroyed -- Cort */

6
arch/powerpc/kernel/process.c
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@ -64,12 +64,6 @@
#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)