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authorKeshavamurthy Anil S <anil.s.keshavamurthy@intel.com>2006-01-11 12:17:42 -0800
committerLinus Torvalds <torvalds@g5.osdl.org>2006-01-11 18:42:12 -0800
commiteb3a72921c8276bf2cd028a458bb83435f16c91c (patch)
tree634eff43e1926bdb400d038eb08115193b6a7506 /arch/i386
parentdf019b1d8b893d0f0ee5a9b0f71486f0892561ae (diff)
[PATCH] kprobes: fix race in recovery of reentrant probe
There is a window where a probe gets removed right after the probe is hit on some different cpu. In this case probe handlers can't find a matching probe instance related to break address. In this case we need to read the original instruction at break address to see if that is not a break/int3 instruction and recover safely. Previous code had a bug where we were not checking for the above race in case of reentrant probes and the below patch fixes this race. Tested on IA64, Powerpc, x86_64. Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'arch/i386')
-rw-r--r--arch/i386/kernel/kprobes.c13
1 files changed, 13 insertions, 0 deletions
diff --git a/arch/i386/kernel/kprobes.c b/arch/i386/kernel/kprobes.c
index 2f372dbd34f..6483eeb1a4e 100644
--- a/arch/i386/kernel/kprobes.c
+++ b/arch/i386/kernel/kprobes.c
@@ -188,6 +188,19 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
kcb->kprobe_status = KPROBE_REENTER;
return 1;
} else {
+ if (regs->eflags & VM_MASK) {
+ /* We are in virtual-8086 mode. Return 0 */
+ goto no_kprobe;
+ }
+ if (*addr != BREAKPOINT_INSTRUCTION) {
+ /* The breakpoint instruction was removed by
+ * another cpu right after we hit, no further
+ * handling of this interrupt is appropriate
+ */
+ regs->eip -= sizeof(kprobe_opcode_t);
+ ret = 1;
+ goto no_kprobe;
+ }
p = __get_cpu_var(current_kprobe);
if (p->break_handler && p->break_handler(p, regs)) {
goto ss_probe;