linux-kernel - Re: [PATCH v3 04/22] x86/doublefault: Make memmove() notrace/NOKPROBE

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Date:   Wed, 19 Feb 2020 10:36:14 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        mingo@...nel.org, joel@...lfernandes.org,
        gregkh@...uxfoundation.org, gustavo@...eddedor.com,
        tglx@...utronix.de, paulmck@...nel.org, josh@...htriplett.org,
        mathieu.desnoyers@...icios.com, jiangshanlai@...il.com,
        luto@...nel.org, tony.luck@...el.com, frederic@...nel.org,
        dan.carpenter@...cle.com, mhiramat@...nel.org
Subject: Re: [PATCH v3 04/22] x86/doublefault: Make memmove()
 notrace/NOKPROBE

On Wed, 19 Feb 2020 15:47:28 +0100
Peter Zijlstra <peterz@...radead.org> wrote:

> --- a/arch/x86/lib/memcpy_32.c
> +++ b/arch/x86/lib/memcpy_32.c
> @@ -21,7 +21,7 @@ __visible void *memset(void *s, int c, s
>  }
>  EXPORT_SYMBOL(memset);
>  
> -__visible void *memmove(void *dest, const void *src, size_t n)
> +__visible notrace void *memmove(void *dest, const void *src, size_t n)
>  {
>  	int d0,d1,d2,d3,d4,d5;
>  	char *ret = dest;
> @@ -207,3 +207,8 @@ __visible void *memmove(void *dest, cons
>  
>  }
>  EXPORT_SYMBOL(memmove);

Hmm, for things like this, which is adding notrace because of a single
instance of it (although it is fine to trace in any other instance), it
would be nice to have a gcc helper that could call "memmove+5" which
would skip the tracing portion.

-- Steve