From: Prasanna S Panchamukhi In situations where a kprobes handler calls a routine which has a probe on it, then kprobes_handler() disarms the new probe forever. This patch removes the above limitation by temporarily disarming the new probe. When the another probe hits while handling the old probe, the kprobes_handler() saves previous kprobes state and handles the new probe without calling the new kprobes registered handlers. kprobe_post_handler() restores back the previous kprobes state and the normal execution continues. However on x86_64 architecture, re-rentrancy is provided only through pre_handler(). If a routine having probe is referenced through post_handler(), then the probes on that routine are disarmed forever, since the exception stack is gets changed after the processor single steps the instruction of the new probe. This patch includes generic changes to support temporary disarming on reentrancy of probes. Signed-of-by: Prasanna S Panchamukhi Signed-off-by: Andrew Morton --- include/linux/kprobes.h | 9 +++++++++ kernel/kprobes.c | 1 + 2 files changed, 10 insertions(+) diff -puN include/linux/kprobes.h~kprobes-temporary-disarming-of-reentrant-probe include/linux/kprobes.h --- 25/include/linux/kprobes.h~kprobes-temporary-disarming-of-reentrant-probe 2005-05-24 23:59:14.000000000 -0700 +++ 25-akpm/include/linux/kprobes.h 2005-05-24 23:59:14.000000000 -0700 @@ -36,6 +36,12 @@ #include +/* kprobe_status settings */ +#define KPROBE_HIT_ACTIVE 0x00000001 +#define KPROBE_HIT_SS 0x00000002 +#define KPROBE_REENTER 0x00000004 +#define KPROBE_HIT_SSDONE 0x00000008 + struct kprobe; struct pt_regs; struct kretprobe; @@ -55,6 +61,9 @@ struct kprobe { /* list of kprobes for multi-handler support */ struct list_head list; + /*count the number of times this probe was temporarily disarmed */ + unsigned long nmissed; + /* location of the probe point */ kprobe_opcode_t *addr; diff -puN kernel/kprobes.c~kprobes-temporary-disarming-of-reentrant-probe kernel/kprobes.c --- 25/kernel/kprobes.c~kprobes-temporary-disarming-of-reentrant-probe 2005-05-24 23:59:14.000000000 -0700 +++ 25-akpm/kernel/kprobes.c 2005-05-24 23:59:14.000000000 -0700 @@ -334,6 +334,7 @@ int register_kprobe(struct kprobe *p) } spin_lock_irqsave(&kprobe_lock, flags); old_p = get_kprobe(p->addr); + p->nmissed = 0; if (old_p) { ret = register_aggr_kprobe(old_p, p); goto out; _