| From | Luis Henriques <> | Subject | [PATCH 3.11 122/198] powerpc/perf: Ensure all EBB register state is cleared on fork() | Date | Thu, 3 Jul 2014 10:19:25 +0100 |
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3.11.10.13 -stable review patch. If anyone has any objections, please let me know.
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From: Michael Ellerman <mpe@ellerman.id.au>
commit 3df48c981d5a9610e02e9270b1bc4274fb536710 upstream.
In commit 330a1eb "Core EBB support for 64-bit book3s" I messed up clear_task_ebb(). It clears some but not all of the task's Event Based Branch (EBB) registers when we duplicate a task struct.
That allows a child task to observe the EBBHR & EBBRR of its parent, which it should not be able to do.
Fix it by clearing EBBHR & EBBRR.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by: Luis Henriques <luis.henriques@canonical.com> --- arch/powerpc/include/asm/switch_to.h | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/arch/powerpc/include/asm/switch_to.h b/arch/powerpc/include/asm/switch_to.h index 671c58f4eb44..64ff06b14630 100644 --- a/arch/powerpc/include/asm/switch_to.h +++ b/arch/powerpc/include/asm/switch_to.h @@ -82,6 +82,8 @@ static inline void clear_task_ebb(struct task_struct *t) { #ifdef CONFIG_PPC_BOOK3S_64 /* EBB perf events are not inherited, so clear all EBB state. */ + t->thread.ebbrr = 0; + t->thread.ebbhr = 0; t->thread.bescr = 0; t->thread.mmcr2 = 0; t->thread.mmcr0 = 0; -- 1.9.1
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