On Wed, 15 Feb 2017 23:47:52 +0530
"Naveen N. Rao" <naveen.n....@linux.vnet.ibm.com> wrote:
> kretprobes can be registered by specifying an absolute address or by
> specifying offset to a symbol. However, we need to ensure this falls at
> function entry so as to be able to determine the return address.
>
> Validate the same during kretprobe registration. By default, there
> should not be any offset from a function entry, as determined through a
> kallsyms_lookup(). Introduce arch_function_offset_within_entry() as a
> way for architectures to override this.
>
Looks good to me.
Acked-by: Masami Hiramatsu <mhira...@kernel.org>
Thanks!
> Signed-off-by: Naveen N. Rao <naveen.n....@linux.vnet.ibm.com>
> ---
> powerpc64 ABIv2 will need to use the over-ride as we want to use the
> local entry point which will be at an offset of 8 bytes from the
> (global) entry point. I have a patch that I will post separately.
>
> Thanks,
> Naveen
>
> include/linux/kprobes.h | 1 +
> kernel/kprobes.c | 13 +++++++++++++
> 2 files changed, 14 insertions(+)
>
> diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
> index 8f6849084248..0c2489435117 100644
> --- a/include/linux/kprobes.h
> +++ b/include/linux/kprobes.h
> @@ -266,6 +266,7 @@ extern int arch_init_kprobes(void);
> extern void show_registers(struct pt_regs *regs);
> extern void kprobes_inc_nmissed_count(struct kprobe *p);
> extern bool arch_within_kprobe_blacklist(unsigned long addr);
> +extern bool arch_function_offset_within_entry(unsigned long offset);
>
> extern bool within_kprobe_blacklist(unsigned long addr);
>
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index 43460104f119..72ecbf5a6312 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -1834,12 +1834,25 @@ static int pre_handler_kretprobe(struct kprobe *p,
> struct pt_regs *regs)
> }
> NOKPROBE_SYMBOL(pre_handler_kretprobe);
>
> +bool __weak arch_function_offset_within_entry(unsigned long offset)
> +{
> + return !offset;
> +}
> +
> int register_kretprobe(struct kretprobe *rp)
> {
> int ret = 0;
> struct kretprobe_instance *inst;
> int i;
> void *addr;
> + unsigned long offset;
> +
> + addr = kprobe_addr(&rp->kp);
> + if (!kallsyms_lookup_size_offset((unsigned long)addr, NULL, &offset))
> + return -EINVAL;
> +
> + if (!arch_function_offset_within_entry(offset))
> + return -EINVAL;
>
> if (kretprobe_blacklist_size) {
> addr = kprobe_addr(&rp->kp);
> --
> 2.11.0
>
--
Masami Hiramatsu <mhira...@kernel.org>
