Messages in this thread | | | Date | Thu, 11 Mar 2021 00:42:25 +0900 | From | Masami Hiramatsu <> | Subject | Re: [PATCH -tip 3/5] kprobes: treewide: Remove trampoline_address from kretprobe_trampoline_handler() |
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On Wed, 10 Mar 2021 15:21:01 +0100 (CET) Miroslav Benes <mbenes@suse.cz> wrote:
> Hi Masami, > > > --- 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 arch_deref_entry_point() to get real function address. > > s/arch_deref_entry_point/dereference_function_descriptor/ ?
Ah, I missed it. Thanks!
> > > + */ > > +static nokprobe_inline void *kretprobe_trampoline_addr(void) > > +{ > > + return dereference_function_descriptor(kretprobe_trampoline); > > +} > > + > > Would it make sense to use this in s390 and powerpc reliable unwinders? > > Both > > arch/s390/kernel/stacktrace.c:arch_stack_walk_reliable() > arch/powerpc/kernel/stacktrace.c:__save_stack_trace_tsk_reliable() > > have > > if (state.ip == (unsigned long)kretprobe_trampoline) > return -EINVAL; > > which you wanted to hide previously if I am not mistaken.
I think, if "ip" means "instruction pointer", it should point the real instruction address, which is dereferenced from function descriptor. So using kretprobe_trampoline_addr() is good.
But of course, it depends on the architecture. I'm not familiar with the powerpc and s390, I need those maintainer's help...
Thank you,
-- Masami Hiramatsu <mhiramat@kernel.org>
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