Commit-ID: 6c0aca288e726405b01dacb12cac556454d34b2a Gitweb: http://git.kernel.org/tip/6c0aca288e726405b01dacb12cac556454d34b2a Author: Frederic Weisbecker <fweisbec@xxxxxxxxx> AuthorDate: Thu, 11 Nov 2010 21:18:43 +0100 Committer: Frederic Weisbecker <fweisbec@xxxxxxxxx> CommitDate: Fri, 12 Nov 2010 14:51:01 +0100 x86: Ignore trap bits on single step exceptions When a single step exception fires, the trap bits, used to signal hardware breakpoints, are in a random state. These trap bits might be set if another exception will follow, like a breakpoint in the next instruction, or a watchpoint in the previous one. Or there can be any junk there. So if we handle these trap bits during the single step exception, we are going to handle an exception twice, or we are going to handle junk. Just ignore them in this case. This fixes https://bugzilla.kernel.org/show_bug.cgi?id=21332 Reported-by: Michael Stefaniuc <mstefani@xxxxxxxxxx> Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx> Cc: Rafael J. Wysocki <rjw@xxxxxxx> Cc: Maciej Rutecki <maciej.rutecki@xxxxxxxxx> Cc: Alexandre Julliard <julliard@xxxxxxxxxx> Cc: Jason Wessel <jason.wessel@xxxxxxxxxxxxx> Cc: All since 2.6.33.x <stable@xxxxxxxxxx> --- arch/x86/kernel/hw_breakpoint.c | 4 ++++ 1 files changed, 4 insertions(+), 0 deletions(-) diff --git a/arch/x86/kernel/hw_breakpoint.c b/arch/x86/kernel/hw_breakpoint.c index ff15c9d..42c5942 100644 --- a/arch/x86/kernel/hw_breakpoint.c +++ b/arch/x86/kernel/hw_breakpoint.c @@ -433,6 +433,10 @@ static int __kprobes hw_breakpoint_handler(struct die_args *args) dr6_p = (unsigned long *)ERR_PTR(args->err); dr6 = *dr6_p; + /* If it's a single step, TRAP bits are random */ + if (dr6 & DR_STEP) + return NOTIFY_DONE; + /* Do an early return if no trap bits are set in DR6 */ if ((dr6 & DR_TRAP_BITS) == 0) return NOTIFY_DONE; -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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