linux-kernel - Re: [PATCH] tools, perf: Add asprintf replacement

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Message-ID: <20140318142632.GB6482@ghostprotocols.net>
Date:	Tue, 18 Mar 2014 11:26:32 -0300
From:	Arnaldo Carvalho de Melo <acme@...radead.org>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	mingo@...nel.org, linux-kernel@...r.kernel.org,
	peterz@...radead.org, eranian@...gle.com, namhyung@...nel.org,
	jolsa@...hat.com, Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH] tools, perf: Add asprintf replacement

Em Mon, Mar 10, 2014 at 11:43:24PM -0700, Andi Kleen escreveu:
> From: Andi Kleen <ak@...ux.intel.com>
> 
> asprintf corrupts memory on some older glibc versions.
> Provide a replacement. This fixes various segfaults
> with --branch-history on older Fedoras.

Humm, this unconditionally replaces it with an alternative that limits
the buffer to a fixed size :-\

Do you recall at least one of those old glibc version/release number?

A reproducer? So that I can try to reproduce it here and try to polish
this a bit more...

- Arnaldo
 
> Signed-off-by: Andi Kleen <ak@...ux.intel.com>
> ---
>  tools/perf/Makefile.perf   |  1 +
>  tools/perf/util/asprintf.c | 28 ++++++++++++++++++++++++++++
>  2 files changed, 29 insertions(+)
>  create mode 100644 tools/perf/util/asprintf.c
> 
> diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
> index 1f7ec48..5174fb9 100644
> --- a/tools/perf/Makefile.perf
> +++ b/tools/perf/Makefile.perf
> @@ -373,6 +373,7 @@ LIB_OBJS += $(OUTPUT)util/vdso.o
>  LIB_OBJS += $(OUTPUT)util/stat.o
>  LIB_OBJS += $(OUTPUT)util/record.o
>  LIB_OBJS += $(OUTPUT)util/srcline.o
> +LIB_OBJS += $(OUTPUT)util/asprintf.o
>  LIB_OBJS += $(OUTPUT)util/data.o
>  
>  LIB_OBJS += $(OUTPUT)ui/setup.o
> diff --git a/tools/perf/util/asprintf.c b/tools/perf/util/asprintf.c
> new file mode 100644
> index 0000000..9aafaca
> --- /dev/null
> +++ b/tools/perf/util/asprintf.c
> @@ -0,0 +1,28 @@
> +/* Replacement for asprintf as it's buggy in older glibc versions */
> +#include <stdio.h>
> +#include <stdarg.h>
> +#include <stdlib.h>
> +#include <string.h>
> +
> +int vasprintf(char **str, const char *fmt, va_list ap)
> +{
> +	char buf[1024];
> +	int len = vsnprintf(buf, sizeof buf, fmt, ap);
> +
> +	*str = malloc(len + 1);
> +	if (!*str)
> +		return -1;
> +	strcpy(*str, buf);
> +	return len;
> +}
> +
> +int asprintf(char **str, const char *fmt, ...)
> +{
> +	va_list ap;
> +	int ret;
> +
> +	va_start(ap, fmt);
> +	ret = vasprintf(str, fmt, ap);
> +	va_end(ap);
> +	return ret;
> +}
> -- 
> 1.8.5.3
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