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| author |   Andy Lutomirski <luto@kernel.org> | 2016-03-09 19:00:28 -0800 |
|---|---|---|
| committer |   Ingo Molnar <mingo@kernel.org> | 2016-03-10 09:48:13 +0100 |
| commit | 81edd9f69a6fd214fdbe66b43de6aa1610c84c63 (patch) | |
| tree | c93d1ac792c7864ff0836b159e69f30c5032bf17 /arch | |
| parent | x86/entry/32: Restore FLAGS on SYSEXIT (diff) | |
| download | linux-dev-81edd9f69a6fd214fdbe66b43de6aa1610c84c63.tar.xz linux-dev-81edd9f69a6fd214fdbe66b43de6aa1610c84c63.zip | |
x86/entry/traps: Clear TIF_BLOCKSTEP on all debug exceptions
The SDM says that debug exceptions clear BTF, and we need to keep
TIF_BLOCKSTEP in sync with BTF. Clear it unconditionally and improve
the comment.
I suspect that the fact that kmemcheck could cause TIF_BLOCKSTEP not
to be cleared was just an oversight.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/fa86e55d196e6dde5b38839595bde2a292c52fdc.1457578375.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/kernel/traps.c | 12 |
1 files changed, 7 insertions, 5 deletions
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 410e8e2700c5..1af56217fb5d 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -598,6 +598,13 @@ dotraplinkage void do_debug(struct pt_regs *regs, long error_code) dr6 &= ~DR6_RESERVED; /* + * The SDM says "The processor clears the BTF flag when it + * generates a debug exception." Clear TIF_BLOCKSTEP to keep + * TIF_BLOCKSTEP in sync with the hardware BTF flag. + */ + clear_tsk_thread_flag(tsk, TIF_BLOCKSTEP); + + /* * If dr6 has no reason to give us about the origin of this trap, * then it's very likely the result of an icebp/int01 trap. * User wants a sigtrap for that. @@ -612,11 +619,6 @@ dotraplinkage void do_debug(struct pt_regs *regs, long error_code) /* DR6 may or may not be cleared by the CPU */ set_debugreg(0, 6); - /* - * The processor cleared BTF, so don't mark that we need it set. - */ - clear_tsk_thread_flag(tsk, TIF_BLOCKSTEP); - /* Store the virtualized DR6 value */ tsk->thread.debugreg6 = dr6; |