From 24851d2447830e6cba4c4b641cb73e713f312373 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Wed, 26 Aug 2009 23:38:30 +0200 Subject: [PATCH] tracing/kprobes: Dump the culprit kprobe in case of kprobe recursion Kprobes can enter into a probing recursion, ie: a kprobe that does an endless loop because one of its core mechanism function used during probing is also probed itself. This patch helps pinpointing the kprobe that raised such recursion by dumping it and raising a BUG instead of a warning (we also disarm the kprobe to try avoiding recursion in BUG itself). Having a BUG instead of a warning stops the stacktrace in the right place and doesn't pollute the logs with hundreds of traces that eventually end up in a stack overflow. Signed-off-by: Frederic Weisbecker Cc: Masami Hiramatsu Cc: Ananth N Mavinakayanahalli --- arch/x86/kernel/kprobes.c | 8 ++++++-- include/linux/kprobes.h | 2 ++ kernel/kprobes.c | 7 +++++++ 3 files changed, 15 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c index 16ae9610f6ff..ecee3d23fef8 100644 --- a/arch/x86/kernel/kprobes.c +++ b/arch/x86/kernel/kprobes.c @@ -490,9 +490,13 @@ static int __kprobes reenter_kprobe(struct kprobe *p, struct pt_regs *regs, /* A probe has been hit in the codepath leading up * to, or just after, single-stepping of a probed * instruction. This entire codepath should strictly - * reside in .kprobes.text section. Raise a warning - * to highlight this peculiar case. + * reside in .kprobes.text section. + * Raise a BUG or we'll continue in an endless + * reentering loop and eventually a stack overflow. */ + arch_disarm_kprobe(p); + dump_kprobe(p); + BUG(); } default: /* impossible cases */ diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h index bcd9c07848be..87eb79c9dd60 100644 --- a/include/linux/kprobes.h +++ b/include/linux/kprobes.h @@ -296,6 +296,8 @@ void recycle_rp_inst(struct kretprobe_instance *ri, struct hlist_head *head); int disable_kprobe(struct kprobe *kp); int enable_kprobe(struct kprobe *kp); +void dump_kprobe(struct kprobe *kp); + #else /* !CONFIG_KPROBES: */ static inline int kprobes_built_in(void) diff --git a/kernel/kprobes.c b/kernel/kprobes.c index ef177d653b2c..f72e96c25a38 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -1141,6 +1141,13 @@ static void __kprobes kill_kprobe(struct kprobe *p) arch_remove_kprobe(p); } +void __kprobes dump_kprobe(struct kprobe *kp) +{ + printk(KERN_WARNING "Dumping kprobe:\n"); + printk(KERN_WARNING "Name: %s\nAddress: %p\nOffset: %x\n", + kp->symbol_name, kp->addr, kp->offset); +} + /* Module notifier call back, checking kprobes on the module */ static int __kprobes kprobes_module_callback(struct notifier_block *nb, unsigned long val, void *data)