On Tue, 28 Feb 2017 01:14:38 +0900
Masami Hiramatsu <mhira...@kernel.org> wrote:
> Exit single-stepping out of line and get back regs->ip to original
> (probed) address before trying fixup_exception() if the exception
> happened on the singlestep buffer, since the fixup_exception()
> depends on regs->ip to search an entry on __ex_table.
>
> Signed-off-by: Masami Hiramatsu <mhira...@kernel.org>
> ---
> arch/x86/include/asm/kprobes.h | 1
> arch/x86/kernel/kprobes/core.c | 83
> +++++++++++++++++++++++++---------------
> arch/x86/kernel/traps.c | 19 +++++++++
> 3 files changed, 71 insertions(+), 32 deletions(-)
>
> diff --git a/arch/x86/include/asm/kprobes.h b/arch/x86/include/asm/kprobes.h
> index d1d1e50..79e121a 100644
> --- a/arch/x86/include/asm/kprobes.h
> +++ b/arch/x86/include/asm/kprobes.h
> @@ -111,6 +111,7 @@ struct kprobe_ctlblk {
> struct prev_kprobe prev_kprobe;
> };
>
> +extern int kprobe_exit_singlestep(struct pt_regs *regs);
> extern int kprobe_fault_handler(struct pt_regs *regs, int trapnr);
> extern int kprobe_exceptions_notify(struct notifier_block *self,
> unsigned long val, void *data);
> diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
> index 34d3a52..f2a3f3b 100644
> --- a/arch/x86/kernel/kprobes/core.c
> +++ b/arch/x86/kernel/kprobes/core.c
> @@ -949,43 +949,62 @@ int kprobe_debug_handler(struct pt_regs *regs)
> }
> NOKPROBE_SYMBOL(kprobe_debug_handler);
>
> -int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
> +/* Fixup current ip register and reset current kprobe, if needed. */
> +int kprobe_exit_singlestep(struct pt_regs *regs)
> {
> - struct kprobe *cur = kprobe_running();
> struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
> + struct kprobe *cur = kprobe_running();
>
> - if (unlikely(regs->ip == (unsigned long)cur->ainsn.insn)) {
> - /* This must happen on single-stepping */
> - WARN_ON(kcb->kprobe_status != KPROBE_HIT_SS &&
> - kcb->kprobe_status != KPROBE_REENTER);
> - /*
> - * We are here because the instruction being single
> - * stepped caused a page fault. We reset the current
> - * kprobe and the ip points back to the probe address
> - * and allow the page fault handler to continue as a
> - * normal page fault.
> - */
> - regs->ip = (unsigned long)cur->addr;
> - /*
> - * Trap flag (TF) has been set here because this fault
> - * happened where the single stepping will be done.
> - * So clear it by resetting the current kprobe:
> - */
> - regs->flags &= ~X86_EFLAGS_TF;
> + if (unlikely(regs->ip != (unsigned long)cur->ainsn.insn))
Oops, this is not unlikely, this is likely case (since I inverted the
condition).
Thanks,
--
Masami Hiramatsu <mhira...@kernel.org>
