linux-kernel - Re: [PATCH] perf tools: fix endian conversion reading event attr from header

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Message-ID: <4E205D36.3010707@gmail.com>
Date:	Fri, 15 Jul 2011 09:31:02 -0600
From:	David Ahern <dsahern@...il.com>
To:	mingo@...e.hu, fweisbec@...il.com
CC:	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	acme@...stprotocols.net, peterz@...radead.org, paulus@...ba.org
Subject: Re: [PATCH] perf tools: fix endian conversion reading event attr
 from header



On 07/12/2011 09:19 AM, David Ahern wrote:
> The perf_event_attr struct has 2 __u32's at the top and need to
> be swapped individually. With this change I was able to analyze
> a perf.data collected in a 32-bit PPC VM on an x86 system. I
> tested both 32-bit and 64-bit binaries for the Intel analysis
> side; both read the PPC perf.data file correctly.

Similarly with this one. It replaces a call to perf_header__getbuffer64
with what it does inline -- only doing the swap of the attr struct after
the initial 2 u32's. I spent 2 days tracking this down and would hate to
lose it waiting for Arnaldo's return.

David

> 
> Signed-off-by: David Ahern <dsahern@...il.com>
> ---
>  tools/perf/util/header.c |    9 ++++++++-
>  1 files changed, 8 insertions(+), 1 deletions(-)
> 
> diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
> index afb0849..8044c6f 100644
> --- a/tools/perf/util/header.c
> +++ b/tools/perf/util/header.c
> @@ -877,9 +877,16 @@ int perf_session__read_header(struct perf_session *session, int fd)
>  		struct perf_evsel *evsel;
>  		off_t tmp;
>  
> -		if (perf_header__getbuffer64(header, fd, &f_attr, sizeof(f_attr)))
> +		if (readn(fd, &f_attr, sizeof(f_attr)) <= 0)
>  			goto out_errno;
>  
> +		if (header->needs_swap) {
> +			f_attr.attr.type = bswap_32(f_attr.attr.type);
> +			f_attr.attr.size = bswap_32(f_attr.attr.size);
> +			mem_bswap_64(&f_attr.attr.config,
> +				     sizeof(struct perf_event_attr) - 8);
> +		}
> +
>  		tmp = lseek(fd, 0, SEEK_CUR);
>  		evsel = perf_evsel__new(&f_attr.attr, i);
>  
--
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