From: Masami Hiramatsu 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 Cc: Peter Zijlstra Cc: Frederic Weisbecker Cc: Thomas Gleixner Cc: "H. Peter Anvin" Signed-off-by: Masami Hiramatsu Signed-off-by: Steven Rostedt --- arch/x86/kernel/kprobes.c | 42 +++++++++++++++++++++++++++++------------- kernel/kprobes.c | 3 --- 2 files changed, 29 insertions(+), 16 deletions(-) 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 @@ reenter_kprobe(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb 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 @@ static int __kprobes kprobe_handler(struct pt_regs *regs) } 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 @@ int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs) } #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 @@ void __kprobes kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip, __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); diff --git a/kernel/kprobes.c b/kernel/kprobes.c index 35b4315..098f396 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -1418,9 +1418,6 @@ static __kprobes int check_kprobe_address_safe(struct kprobe *p, /* Given address is not on the instruction boundary */ if ((unsigned long)p->addr != ftrace_addr) return -EILSEQ; - /* break_handler (jprobe) can not work with ftrace */ - if (p->break_handler) - return -EINVAL; p->flags |= KPROBE_FLAG_FTRACE; #else /* !KPROBES_CAN_USE_FTRACE */ return -EINVAL; -- 1.7.10.4