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authorFrederic Weisbecker <fweisbec@gmail.com>2013-02-24 01:19:14 +0100
committerFrederic Weisbecker <fweisbec@gmail.com>2013-03-07 17:10:11 +0100
commit6c1e0256fad84a843d915414e4b5973b7443d48d (patch)
treed93a2f27817f05c67840d947e0f9eb7f31fd24aa /arch/x86/mm/fault.c
parent56dd9470d7c8734f055da2a6bac553caf4a468eb (diff)
downloadlinaro-lsk-6c1e0256fad84a843d915414e4b5973b7443d48d.tar.gz
context_tracking: Restore correct previous context state on exception exit
On exception exit, we restore the previous context tracking state based on the regs of the interrupted frame. Iff that frame is in user mode as stated by user_mode() helper, we restore the context tracking user mode. However there is a tiny chunck of low level arch code after we pass through user_enter() and until the CPU eventually resumes userspace. If an exception happens in this tiny area, exception_enter() correctly exits the context tracking user mode but exception_exit() won't restore it because of the value returned by user_mode(regs). As a result we may return to userspace with the wrong context tracking state. To fix this, change exception_enter() to return the context tracking state prior to its call and pass this saved state to exception_exit(). This restores the real context tracking state of the interrupted frame. (May be this patch was suggested to me, I don't recall exactly. If so, sorry for the missing credit). Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Cc: Kevin Hilman <khilman@linaro.org> Cc: Mats Liljegren <mats.liljegren@enea.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@kernel.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Namhyung Kim <namhyung.kim@lge.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'arch/x86/mm/fault.c')
-rw-r--r--arch/x86/mm/fault.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index f946e6ce331..fa8c02de0d2 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -1222,7 +1222,9 @@ good_area:
dotraplinkage void __kprobes
do_page_fault(struct pt_regs *regs, unsigned long error_code)
{
- exception_enter(regs);
+ enum ctx_state prev_state;
+
+ prev_state = exception_enter();
__do_page_fault(regs, error_code);
- exception_exit(regs);
+ exception_exit(prev_state);
}