kprobes/x86: Fix to support jprobes on ftrace-based kprobe
Fix kprobes/x86 to support jprobes on ftrace-based kprobes.
Because of -mfentry support of ftrace, ftrace is now put
on the beginning of function where jprobes are put.
Originally ftrace-based kprobes doesn't support jprobe
because it will change regs->ip and ftrace doesn't support
changing IP and ftrace itself doesn't conflict jprobe.
However, ftrace -mfentry support moves mcount call on the
top of functions where jprobes are put. This means that
jprobe always conflicts with ftrace-based kprobe and fails.
This patch allows ftrace-based kprobes to support jprobes
by allowing to modify regs->ip and kprobes breakpoint
handler also allows to skip singlestepping because there
is a ftrace call (not an original instruction).
Link: http://lkml.kernel.org/r/20120905143125.10329.90836.stgit@localhost.localdomain
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c
index f49f60c..b7c2a85 100644
--- a/arch/x86/kernel/kprobes.c
+++ b/arch/x86/kernel/kprobes.c
@@ -541,6 +541,8 @@
return 1;
}
+static void __kprobes skip_singlestep(struct kprobe *p, struct pt_regs *regs,
+ struct kprobe_ctlblk *kcb);
/*
* Interrupts are disabled on entry as trap3 is an interrupt gate and they
* remain disabled throughout this function.
@@ -599,6 +601,12 @@
} else if (kprobe_running()) {
p = __this_cpu_read(current_kprobe);
if (p->break_handler && p->break_handler(p, regs)) {
+#ifdef KPROBES_CAN_USE_FTRACE
+ if (kprobe_ftrace(p)) {
+ skip_singlestep(p, regs, kcb);
+ return 1;
+ }
+#endif
setup_singlestep(p, regs, kcb, 0);
return 1;
}
@@ -1053,6 +1061,21 @@
}
#ifdef KPROBES_CAN_USE_FTRACE
+static void __kprobes skip_singlestep(struct kprobe *p, struct pt_regs *regs,
+ struct kprobe_ctlblk *kcb)
+{
+ /*
+ * Emulate singlestep (and also recover regs->ip)
+ * as if there is a 5byte nop
+ */
+ regs->ip = (unsigned long)p->addr + MCOUNT_INSN_SIZE;
+ if (unlikely(p->post_handler)) {
+ kcb->kprobe_status = KPROBE_HIT_SSDONE;
+ p->post_handler(p, regs, 0);
+ }
+ __this_cpu_write(current_kprobe, NULL);
+}
+
/* Ftrace callback handler for kprobes */
void __kprobes kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
struct ftrace_ops *ops, struct pt_regs *regs)
@@ -1077,19 +1100,12 @@
__this_cpu_write(current_kprobe, p);
kcb->kprobe_status = KPROBE_HIT_ACTIVE;
- if (p->pre_handler)
- p->pre_handler(p, regs);
-
- if (unlikely(p->post_handler)) {
- /*
- * Emulate singlestep (and also recover regs->ip)
- * as if there is a 5byte nop
- */
- regs->ip = ip + MCOUNT_INSN_SIZE;
- kcb->kprobe_status = KPROBE_HIT_SSDONE;
- p->post_handler(p, regs, 0);
- }
- __this_cpu_write(current_kprobe, NULL);
+ if (!p->pre_handler || !p->pre_handler(p, regs))
+ skip_singlestep(p, regs, kcb);
+ /*
+ * If pre_handler returns !0, it sets regs->ip and
+ * resets current kprobe.
+ */
}
end:
local_irq_restore(flags);