On Mon, 15 May 2017 23:35:04 +0530
"Naveen N. Rao" <naveen.n....@linux.vnet.ibm.com> wrote:
> Fix a circa 2005 FIXME by implementing a check to ensure that we
> actually got into the jprobe break handler() due to the trap in
> jprobe_return().
>
> Signed-off-by: Naveen N. Rao <naveen.n....@linux.vnet.ibm.com>
> ---
> arch/powerpc/kernel/kprobes.c | 20 +++++++++-----------
> 1 file changed, 9 insertions(+), 11 deletions(-)
>
> diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
> index 19b053475758..1ebeb8c482db 100644
> --- a/arch/powerpc/kernel/kprobes.c
> +++ b/arch/powerpc/kernel/kprobes.c
> @@ -627,25 +627,23 @@ NOKPROBE_SYMBOL(setjmp_pre_handler);
>
> void __used jprobe_return(void)
> {
> - asm volatile("trap" ::: "memory");
> + asm volatile("jprobe_return_trap:\n"
> + "trap\n"
> + ::: "memory");
> }
> NOKPROBE_SYMBOL(jprobe_return);
>
> -static void __used jprobe_return_end(void)
> -{
> -}
> -NOKPROBE_SYMBOL(jprobe_return_end);
> -
> int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
> {
> struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
> unsigned long sp;
>
> - /*
> - * FIXME - we should ideally be validating that we got here 'cos
> - * of the "trap" in jprobe_return() above, before restoring the
> - * saved regs...
> - */
> + if (regs->nip != ppc_kallsyms_lookup_name("jprobe_return_trap")) {
> + WARN(1, "longjmp_break_handler NIP (0x%lx) does not match
> jprobe_return_trap (0x%lx)\n",
> + regs->nip,
> ppc_kallsyms_lookup_name("jprobe_return_trap"));
> + return 0;
If you don't handle this break, you shouldn't warn it, because
program_check_exception() will continue to find how to handle it
by notify_die(). IOW, please return silently, or just add a
debug message.
Thank you,
> + }
> +
> memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
> sp = kernel_stack_pointer(regs);
> memcpy((void *)sp, &kcb->jprobes_stack, MIN_STACK_SIZE(sp));
> --
> 2.12.2
>
--
Masami Hiramatsu <mhira...@kernel.org>
