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Commit 902e06eb authored by Christophe Leroy's avatar Christophe Leroy Committed by Michael Ellerman
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powerpc/32: Change the stack protector canary value per task 



Partially copied from commit df0698be ("ARM: stack protector:
change the canary value per task")

A new random value for the canary is stored in the task struct whenever
a new task is forked.  This is meant to allow for different canary values
per task.  On powerpc, GCC expects the canary value to be found in a global
variable called __stack_chk_guard.  So this variable has to be updated
with the value stored in the task struct whenever a task switch occurs.

Because the variable GCC expects is global, this cannot work on SMP
unfortunately.  So, on SMP, the same initial canary value is kept
throughout, making this feature a bit less effective although it is still
useful.

Signed-off-by: default avatarChristophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent 6533b7c1

arch/powerpc/kernel/asm-offsets.c

+3 −0
Original line number Original line Diff line number Diff line
@@ -91,6 +91,9 @@ int main(void) 
	DEFINE(TI_livepatch_sp, offsetof(struct thread_info, livepatch_sp));

	DEFINE(TI_livepatch_sp, offsetof(struct thread_info, livepatch_sp));

#endif

#endif





#ifdef CONFIG_CC_STACKPROTECTOR

	DEFINE(TSK_STACK_CANARY, offsetof(struct task_struct, stack_canary));

#endif

	DEFINE(KSP, offsetof(struct thread_struct, ksp));

	DEFINE(KSP, offsetof(struct thread_struct, ksp));

	DEFINE(PT_REGS, offsetof(struct thread_struct, regs));

	DEFINE(PT_REGS, offsetof(struct thread_struct, regs));

#ifdef CONFIG_BOOKE

#ifdef CONFIG_BOOKE

arch/powerpc/kernel/entry_32.S

+5 −1
Original line number Original line Diff line number Diff line
@@ -674,7 +674,11 @@ BEGIN_FTR_SECTION 
	mtspr	SPRN_SPEFSCR,r0		/* restore SPEFSCR reg */

	mtspr	SPRN_SPEFSCR,r0		/* restore SPEFSCR reg */

END_FTR_SECTION_IFSET(CPU_FTR_SPE)

END_FTR_SECTION_IFSET(CPU_FTR_SPE)

#endif /* CONFIG_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)

	lwz	r0,_CCR(r1)

	mtcrf	0xFF,r0

	mtcrf	0xFF,r0

	/* r3-r12 are destroyed -- Cort */

	/* r3-r12 are destroyed -- Cort */