Messages in this thread Patch in this message | | | Subject | Re: [PATCH 0/5 v2] [GIT PULL] x86/jump label: Paranoid checks and 2 or 5 byte nops | From | Steven Rostedt <> | Date | Thu, 02 Feb 2012 17:04:40 -0500 |
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On Thu, 2012-02-02 at 09:31 -0500, Steven Rostedt wrote:
> This code died on "enabling" the nop. I think the code now enables some > nops by default on boot up, which doesn't expect to see the > "default_nop". >
Ah, we do have jump labels that are default on. I'm still not triggering these, I'm not sure why. Perhaps a command line difference?
Anyway, this should fix the bug:
-- Steve
Ingo,
Please pull the latest tip/perf/jump-label-4 tree, which can be found at:
git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git tip/perf/jump-label-4
Head SHA1: 7bbd9688727dd30cd44b90b3c9c35f0f66af77ff
Steven Rostedt (1): x86/jump labels: Handle initialization of enabled nops
---- arch/x86/kernel/jump_label.c | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-) --------------------------- commit 7bbd9688727dd30cd44b90b3c9c35f0f66af77ff Author: Steven Rostedt <srostedt@redhat.com> Date: Thu Feb 2 16:55:43 2012 -0500
x86/jump labels: Handle initialization of enabled nops When jump labels are initialized at boot up, they are compared to the default_nop before switching to the ideal nop. But if a jump label is enabled by default on start up, the enabled code does not test against the default nop, only the ideal nop. But as this jump label has not been converted to the ideal nop, it fails the check, and will crash the box. The enabled path needs to be aware of initialization too. Reported-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c index 2839524..d560c80 100644 --- a/arch/x86/kernel/jump_label.c +++ b/arch/x86/kernel/jump_label.c @@ -66,7 +66,8 @@ static void __jump_label_transform(struct jump_entry *entry, code.jump_short = 0xeb; code.offset = entry->target - (entry->code + 2); /* Check for overflow ? */ - } else if (memcmp(ip, ideal_nop, 5) == 0) { + } else if ((!init && memcmp(ip, ideal_nop, 5) == 0) || + (init && memcmp(ip, default_nop, 5) == 0)) { size = JUMP_LABEL_NOP_SIZE; code.jump = 0xe9; code.offset = entry->target - (entry->code + size); [unhandled content-type:application/pgp-signature] | |