Re: [PATCH -tip v7 03/13] kprobes: treewide: Remove trampoline_address from kretprobe_trampoline_han

Masami Hiramatsu
2021-06-15T00:06:26Z

On Mon, 14 Jun 2021 21:16:26 +0530
"Naveen N. Rao" <naveen.n.rao@linux.ibm.com> wrote:

> Hi Masami,
>
> Masami Hiramatsu wrote:
> > Remove trampoline_address from kretprobe_trampoline_handler().
> > Instead of passing the address, kretprobe_trampoline_handler()
> > can use new kretprobe_trampoline_addr().
> >
> > Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
> > Tested-by: Andrii Nakryik <andrii@kernel.org>
> > ---
> > Changes in v3:
> > - Remove wrong kretprobe_trampoline declaration from
> > arch/x86/include/asm/kprobes.h.
> > Changes in v2:
> > - Remove arch_deref_entry_point() from comment.
> > ---
> > arch/arc/kernel/kprobes.c | 2 +-
> > arch/arm/probes/kprobes/core.c | 3 +--
> > arch/arm64/kernel/probes/kprobes.c | 3 +--
> > arch/csky/kernel/probes/kprobes.c | 2 +-
> > arch/ia64/kernel/kprobes.c | 5 ++---
> > arch/mips/kernel/kprobes.c | 3 +--
> > arch/parisc/kernel/kprobes.c | 4 ++--
> > arch/powerpc/kernel/kprobes.c | 2 +-
> > arch/riscv/kernel/probes/kprobes.c | 2 +-
> > arch/s390/kernel/kprobes.c | 2 +-
> > arch/sh/kernel/kprobes.c | 2 +-
> > arch/sparc/kernel/kprobes.c | 2 +-
> > arch/x86/include/asm/kprobes.h | 1 -
> > arch/x86/kernel/kprobes/core.c | 2 +-
> > include/linux/kprobes.h | 18 +++++++++++++-----
> > kernel/kprobes.c | 3 +--
> > 16 files changed, 29 insertions(+), 27 deletions(-)
> >
>
> <snip>
>
> > diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
> > index d65c041b5c22..65dadd4238a2 100644
> > --- a/include/linux/kprobes.h
> > +++ b/include/linux/kprobes.h
> > @@ -205,15 +205,23 @@ extern void arch_prepare_kretprobe(struct kretprobe_instance *ri,
> > struct pt_regs *regs);
> > extern int arch_trampoline_kprobe(struct kprobe *p);
> >
> > +void kretprobe_trampoline(void);
> > +/*
> > + * Since some architecture uses structured function pointer,
> > + * use dereference_function_descriptor() to get real function address.
> > + */
> > +static nokprobe_inline void *kretprobe_trampoline_addr(void)
> > +{
> > + return dereference_function_descriptor(kretprobe_trampoline);
>
> I'm afraid this won't work correctly. For kernel functions, please use
> dereference_kernel_function_descriptor() which checks if the function
> has a descriptor before dereferencing it.

Oops, there is *kernel_function* version, I didn't notice that.
Thank you for reviewing! I'll fix that.

>
>
> Thanks,
> Naveen
>

--
Masami Hiramatsu <mhiramat@kernel.org>