Messages in this thread | | | Date | Fri, 07 Sep 2012 17:44:23 +0900 | From | Masami Hiramatsu <> | Subject | Re: [PATCH -tip 4/4] [BUGFIX] kprobes/x86: Fix to support jprobes on ftrace-based kprobe |
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(2012/09/05 23:31), Masami Hiramatsu wrote: > 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). > > Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Ingo Molnar <mingo@redhat.com> > Cc: "H. Peter Anvin" <hpa@zytor.com> > Cc: Steven Rostedt <rostedt@goodmis.org>
This should have a below line...
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Thanks!
> --- > > 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; >
-- Masami HIRAMATSU Software Platform Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@hitachi.com
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