On 2017/02/16 08:39AM, Masami Hiramatsu wrote:
> 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, Masami! I am cc'ing linux-arch in case any other architectures
need to override the arch-specific helper with a custom offset.
- Naveen
>
> 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>
>
