linux-kernel - Re: [PATCH v2] X86: Makefile: Replace -pg with CC_FLAGS

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Message-ID: <87pmytuc46.ffs@nanos.tec.linutronix.de>
Date:   Fri, 16 Apr 2021 23:56:57 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     zhaoxiao <zhaoxiao@...ontech.com>
Cc:     mingo@...hat.com, bp@...en8.de, x86@...nel.org, hpa@...or.com,
        nivedita@...m.mit.edu, clin@...e.com,
        andriy.shevchenko@...ux.intel.com, ndesaulniers@...gle.com,
        dan.j.williams@...el.com, masahiroy@...nel.org,
        linux-kernel@...r.kernel.org, jroedel@...e.de,
        peterz@...radead.org, jpoimboe@...hat.com,
        zhaoxiao <zhaoxiao@...ontech.com>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH v2] X86: Makefile: Replace -pg with CC_FLAGS_FTRACE

On Fri, Apr 16 2021 at 13:39, zhaoxiao wrote:
> In preparation for x86 supporting ftrace built on other compiler
> options, let's have the x86 Makefiles remove the $(CC_FLAGS_FTRACE)
> flags, whatever these may be, rather than assuming '-pg'.

s/let's have the/make the/

> There should be no functional change as a result of this patch.

Should be? Either you know that there is no functional change or not. If
you're unsure why are you posting it at all?

So this wants to be:

   No functional change.

Other than that and the fact that this is incomplete as it fails to
catch _all_ instances of -pg in arch/x86 and also leaves stale comments
around I'm ok with the intent.

# git grep '\-pg' arch/x86/
arch/x86/entry/vdso/Makefile:# vDSO code runs in userspace and -pg doesn't help with profiling anyway.
arch/x86/kernel/ftrace_64.S: * gcc -pg option adds a call to 'mcount' in most functions.
arch/x86/purgatory/Makefile:# Default KBUILD_CFLAGS can have -pg option set when FTRACE is enabled. That
arch/x86/um/vdso/Makefile:# vDSO code runs in userspace and -pg doesn't help with profiling anyway.
arch/x86/um/vdso/Makefile:CFLAGS_REMOVE_vdso-note.o = -pg -fprofile-arcs -ftest-coverage
arch/x86/um/vdso/Makefile:CFLAGS_REMOVE_um_vdso.o = -pg -fprofile-arcs -ftest-coverage

grep is not rocket science ...

Thanks,

        tglx