[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <d59d33a13c8956d6e2dbd228b247d3d8bc7caf1f.1479742486.git.christophe.leroy@c-s.fr>
Date: Tue, 22 Nov 2016 11:45:51 +0100 (CET)
From: Christophe Leroy <christophe.leroy@....fr>
To: Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Paul Mackerras <paulus@...ba.org>,
Michael Ellerman <mpe@...erman.id.au>,
Scott Wood <oss@...error.net>
Cc: linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
Nicolas Pitre <nicolas.pitre@...aro.org>
Subject: [PATCH v2 2/2] powerpc/32: stack protector: change the canary value
per task
Partially copied from commit df0698be14c66 ("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.
Cc: Nicolas Pitre <nicolas.pitre@...aro.org>
Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
---
arch/powerpc/kernel/asm-offsets.c | 3 +++
arch/powerpc/kernel/entry_32.S | 6 +++++-
2 files changed, 8 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
index caec7bf..5c86030 100644
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -91,6 +91,9 @@ 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
diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index 3841d74..5742dbd 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -674,7 +674,11 @@ 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 */
--
2.10.1
Powered by blists - more mailing lists