This is a note to let you know that I've just added the patch titled
powerpc: do_notify_resume can be called with bad thread_info flags argument
to the 3.17-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
powerpc-do_notify_resume-can-be-called-with-bad-thread_info-flags-argument.patch
and it can be found in the queue-3.17 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 808be31426af57af22268ef0fcb42617beb3d15b Mon Sep 17 00:00:00 2001
From: Anton Blanchard <[email protected]>
Date: Fri, 31 Oct 2014 16:50:57 +1100
Subject: powerpc: do_notify_resume can be called with bad thread_info flags
argument
From: Anton Blanchard <[email protected]>
commit 808be31426af57af22268ef0fcb42617beb3d15b upstream.
Back in 7230c5644188 ("powerpc: Rework lazy-interrupt handling") we
added a call out to restore_interrupts() (written in c) before calling
do_notify_resume:
bl restore_interrupts
addi r3,r1,STACK_FRAME_OVERHEAD
bl do_notify_resume
Unfortunately do_notify_resume takes two arguments, the second one
being the thread_info flags:
void do_notify_resume(struct pt_regs *regs, unsigned long thread_info_flags)
We do populate r4 (the second argument) earlier, but
restore_interrupts() is free to muck it up all it wants. My guess is
the gcc compiler gods shone down on us and its register allocator
never used r4. Sometimes, rarely, luck is on our side.
LLVM on the other hand did trample r4.
Signed-off-by: Anton Blanchard <[email protected]>
Signed-off-by: Michael Ellerman <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
arch/powerpc/kernel/entry_64.S | 6 ++++++
1 file changed, 6 insertions(+)
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -659,7 +659,13 @@ _GLOBAL(ret_from_except_lite)
3:
#endif
bl save_nvgprs
+ /*
+ * Use a non volatile GPR to save and restore our thread_info flags
+ * across the call to restore_interrupts.
+ */
+ mr r30,r4
bl restore_interrupts
+ mr r4,r30
addi r3,r1,STACK_FRAME_OVERHEAD
bl do_notify_resume
b ret_from_except
Patches currently in stable-queue which might be from [email protected] are
queue-3.17/powerpc-do_notify_resume-can-be-called-with-bad-thread_info-flags-argument.patch
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