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SubjectRe: [PATCH] ftrace,kcfi: Separate f trace stub() and ftrace stub graph()


On October 18, 2022 6:18:46 AM PDT, Peter Zijlstra <peterz@infradead.org> wrote:
>On Tue, Oct 18, 2022 at 02:35:16PM +0200, Peter Zijlstra wrote:
>> --- a/include/asm-generic/vmlinux.lds.h
>> +++ b/include/asm-generic/vmlinux.lds.h
>> @@ -162,6 +162,16 @@
>> #define PATCHABLE_DISCARDS *(__patchable_function_entries)
>> #endif
>>
>> +#ifndef ARCH_SUPPORTS_CFI_CLANG
>
>#ifndef CONFIG_ARCH_..
>
>works much better as we found.

I nearly did this with an IS_ENABLED() recently. Saved by checkpatch! I wonder if it has similar checks for #ifdefs...

>
>> +/*
>> + * Simply points to ftrace_stub, but with the proper protocol.
>> + * Defined by the linker script in linux/vmlinux.lds.h
>> + */
>> +#define FTRACE_STUB_HACK ftrace_stub_graph = ftrace_stub;
>> +#else
>> +#define FTRACE_STUB_HACK
>> +#endif
>
>Fixed up version available at:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git x86/urgent

Thanks for solving this! Just for future archeology, can you include the splat (I assume you hit a CFI splat) in the commit log, and/or how you triggered the problem? I usually find it helpful in trying to fix similar issues later, etc.

--
Kees Cook

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