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authorKeshavamurthy Anil S <anil.s.keshavamurthy@intel.com>2006-01-11 15:17:42 -0500
committerLinus Torvalds <torvalds@g5.osdl.org>2006-01-11 21:42:12 -0500
commiteb3a72921c8276bf2cd028a458bb83435f16c91c (patch)
tree634eff43e1926bdb400d038eb08115193b6a7506 /arch/i386/kernel/kprobes.c
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/kernel/kprobes.c')
-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 2f372dbd34fd..6483eeb1a4e8 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)
188 kcb->kprobe_status = KPROBE_REENTER; 188 kcb->kprobe_status = KPROBE_REENTER;
189 return 1; 189 return 1;
190 } else { 190 } else {
191 if (regs->eflags & VM_MASK) {
192 /* We are in virtual-8086 mode. Return 0 */
193 goto no_kprobe;
194 }
195 if (*addr != BREAKPOINT_INSTRUCTION) {
196 /* The breakpoint instruction was removed by
197 * another cpu right after we hit, no further
198 * handling of this interrupt is appropriate
199 */
200 regs->eip -= sizeof(kprobe_opcode_t);
201 ret = 1;
202 goto no_kprobe;
203 }
191 p = __get_cpu_var(current_kprobe); 204 p = __get_cpu_var(current_kprobe);
192 if (p->break_handler && p->break_handler(p, regs)) { 205 if (p->break_handler && p->break_handler(p, regs)) {
193 goto ss_probe; 206 goto ss_probe;