linux-kernel - Re: [PATCH] perf/x86: Replace strncpy() with memcpy() for vendor string

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Message-ID: <CAPSxiM_X8Ykz-kbBuFmT1vt_V3G4AkA3tE4wwbUniE-edoyJyw@mail.gmail.com>
Date: Fri, 4 Jul 2025 16:01:21 +0530
From: Usman Akinyemi <usmanakinyemi202@...il.com>
To: David Laight <david.laight.linux@...il.com>
Cc: peterz@...radead.org, mingo@...hat.com, acme@...nel.org, 
	namhyung@...nel.org, mark.rutland@....com, alexander.shishkin@...ux.intel.com, 
	jolsa@...nel.org, irogers@...gle.com, adrian.hunter@...el.com, 
	kan.liang@...ux.intel.com, james.clark@...aro.org, 
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org, 
	skhan@...uxfoundation.org, linux-kernel-mentees@...ts.linux.dev
Subject: Re: [PATCH] perf/x86: Replace strncpy() with memcpy() for vendor string

On Fri, Jul 4, 2025 at 2:50 PM David Laight
<david.laight.linux@...il.com> wrote:
>
> On Thu, 19 Jun 2025 03:28:43 +0530
> Usman Akinyemi <usmanakinyemi202@...il.com> wrote:
>
> > strncpy() is unsafe for fixed-size binary data as
> > it may not NUL-terminate and is deprecated for such
> > usage. Since we're copying raw CPUID register values,
> > memcpy() is the correct and safe choice.
> >
> > Signed-off-by: Usman Akinyemi <usmanakinyemi202@...il.com>
> > ---
> >  tools/perf/arch/x86/util/header.c | 6 +++---
> >  1 file changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/tools/perf/arch/x86/util/header.c b/tools/perf/arch/x86/util/header.c
> > index 412977f8aa83..43ba55627817 100644
> > --- a/tools/perf/arch/x86/util/header.c
> > +++ b/tools/perf/arch/x86/util/header.c
> > @@ -16,9 +16,9 @@ void get_cpuid_0(char *vendor, unsigned int *lvl)
> >       unsigned int b, c, d;
> >
> >       cpuid(0, 0, lvl, &b, &c, &d);
> > -     strncpy(&vendor[0], (char *)(&b), 4);
> > -     strncpy(&vendor[4], (char *)(&d), 4);
> > -     strncpy(&vendor[8], (char *)(&c), 4);
> > +     memcpy(&vendor[0], (char *)(&b), 4);
> > +     memcpy(&vendor[4], (char *)(&d), 4);
> > +     memcpy(&vendor[8], (char *)(&c), 4);
>
> Why not:
>         cpuid(0, 0, lvl, (void *)vendor, (void *)(vendor + 8), (void *)(vendor + 4));
Hello David,

This also works well. But, I think the "memcpy" is more clean and
explanatory . I can change it to this if it is prefered.

What do you think ?

Thank you.
>
>
> >       vendor[12] = '\0';
> >  }
> >
>