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SubjectRe: [RFC PATCH kernel] trace: Make FTRACE_MCOUNT_USE_RECORDMCOUNT configurable
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On 2/15/22 03:10, Sami Tolvanen wrote:
> On Fri, Feb 11, 2022 at 4:11 PM Nick Desaulniers
> <ndesaulniers@google.com> wrote:
>>
>> + Sami, Kees
>>
>> Do you guys remember why we don't support
>> FTRACE_MCOUNT_USE_RECORDMCOUNT with LTO?
>
> It's because recordmcount cannot distinguish between calls and other
> references to mcount/fentry, which is a problem with LTO where we have
> to process the entire vmlinux.o and cannot ignore individual
> translation units. Instead of resorting to workarounds, Peter was kind
> enough to implement a smarter mcount pass in objtool, which we now use
> on x86_64 with LTO.


So can x86_64 have both FTRACE_MCOUNT_USE_RECORDMCOUNT and LTO?

> Alexey, which architecture are you trying to fix here?


powerpc64le.

>
> Sami

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