Re: [PATCH v2 1/2] sched: move stack_canary field at the top of task_struct
From: Peter Zijlstra <peterz@infradead.org>
Date: 2018-09-19 11:58:53
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On Wed, Sep 19, 2018 at 11:14:43AM +0000, Christophe Leroy wrote:
In order to allow the use of non global stack protector canary, the stack canary needs to be located at a know offset defined in Makefile via -mstack-protector-guard-offset. On powerpc/32, register r2 points to current task_struct at all time, the stack_canary located inside task_struct can be used directly if it is located in a known place. In order to allow that, this patch moves the stack_canary field out of the randomized area of task_struct.
And you cannot use something like asm-offsets to extract this?
quoted hunk ↗ jump to hunk
Signed-off-by: Christophe Leroy <redacted> --- include/linux/sched.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)diff --git a/include/linux/sched.h b/include/linux/sched.h index 977cb57d7bc9..1d977b8a4bac 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h@@ -601,6 +601,10 @@ struct task_struct { /* -1 unrunnable, 0 runnable, >0 stopped: */ volatile long state; +#ifdef CONFIG_STACKPROTECTOR + /* Canary value for the -fstack-protector GCC feature: */ + unsigned long stack_canary; +#endif /* * This begins the randomizable portion of task_struct. Only * scheduling-critical items should be added above here.
Might as well put it before state, right after the task_info thing.