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powerpc/perf: Ensure all EBB register state is cleared on fork()

Message ID 1402382781-17618-1-git-send-email-mpe@ellerman.id.au (mailing list archive)
State Accepted
Commit 3df48c981d5a9610e02e9270b1bc4274fb536710
Headers show

Commit Message

Michael Ellerman June 10, 2014, 6:46 a.m. UTC 
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>
Cc: stable@vger.kernel.org
---
 arch/powerpc/include/asm/switch_to.h | 2 ++
 1 file changed, 2 insertions(+)
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Patch

diff --git a/arch/powerpc/include/asm/switch_to.h b/arch/powerpc/include/asm/switch_to.h
index 0e83e7d..b5fad8a 100644
--- a/arch/powerpc/include/asm/switch_to.h
+++ b/arch/powerpc/include/asm/switch_to.h
@@ -84,6 +84,8 @@  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;