Commit 3df48c98 authored Jun 10, 2014 by Michael Ellerman Committed by Benjamin Herrenschmidt Jun 11, 2014

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



In commit 330a1eb7 "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 [v3.11+]
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

parent caf69ba6

arch/powerpc/include/asm/switch_to.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -86,6 +86,8 @@ 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;