Messages in this thread Patch in this message | | | Date | Wed, 19 Sep 2018 13:58:36 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH v2 1/2] sched: move stack_canary field at the top of task_struct |
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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?
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr> > --- > 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.
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