This looks to require an acked-by from hpa. On Tue, 15 Jul 2014 06:00:21 +0000 Masami Hiramatsu <[email protected]> wrote:
> Recover original IP register if the pre_handler doesn't change it. > Since current kprobes doesn't expect that another ftrace handler > may change regs->ip, it sets kprobe.addr + MCOUNT_INSN_SIZE to > regs->ip and returns to ftrace. > This seems wrong behavior since kprobes can recover regs->ip > and safely pass it to other handler. s/other/another/ > > This adds a code which recovers original regs->ip passed from "... adds code which recovers the original ..." > ftrace right before returning ftrace, so that another ftrace user "... returning to ftrace, ..." > can change regs->ip. You say BUGFIX in the subject, but as nothing changes the regs->ip currently from ftrace, is this currently a real bug? -- Steve > > Signed-off-by: Masami Hiramatsu <[email protected]> > --- > arch/x86/kernel/kprobes/ftrace.c | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/kernel/kprobes/ftrace.c > b/arch/x86/kernel/kprobes/ftrace.c > index 717b02a..5f8f0b3 100644 > --- a/arch/x86/kernel/kprobes/ftrace.c > +++ b/arch/x86/kernel/kprobes/ftrace.c > @@ -27,7 +27,7 @@ > > static nokprobe_inline > int __skip_singlestep(struct kprobe *p, struct pt_regs *regs, > - struct kprobe_ctlblk *kcb) > + struct kprobe_ctlblk *kcb, unsigned long orig_ip) > { > /* > * Emulate singlestep (and also recover regs->ip) > @@ -39,6 +39,8 @@ int __skip_singlestep(struct kprobe *p, struct pt_regs > *regs, > p->post_handler(p, regs, 0); > } > __this_cpu_write(current_kprobe, NULL); > + if (orig_ip) > + regs->ip = orig_ip; > return 1; > } > > @@ -46,7 +48,7 @@ int skip_singlestep(struct kprobe *p, struct pt_regs *regs, > struct kprobe_ctlblk *kcb) > { > if (kprobe_ftrace(p)) > - return __skip_singlestep(p, regs, kcb); > + return __skip_singlestep(p, regs, kcb, 0); > else > return 0; > } > @@ -71,13 +73,14 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned > long parent_ip, > if (kprobe_running()) { > kprobes_inc_nmissed_count(p); > } else { > + unsigned long orig_ip = regs->ip; > /* Kprobe handler expects regs->ip = ip + 1 as breakpoint hit */ > regs->ip = ip + sizeof(kprobe_opcode_t); > > __this_cpu_write(current_kprobe, p); > kcb->kprobe_status = KPROBE_HIT_ACTIVE; > if (!p->pre_handler || !p->pre_handler(p, regs)) > - __skip_singlestep(p, regs, kcb); > + __skip_singlestep(p, regs, kcb, orig_ip); > /* > * If pre_handler returns !0, it sets regs->ip and > * resets current kprobe. > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
