linux-kernel - Re: [PATCH v3 1/7] perf tools: Set vdso name to vdso[64,32] depending on platform

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Date:	Thu, 12 May 2016 13:06:50 +0300
From:	Adrian Hunter <adrian.hunter@...el.com>
To:	He Kuang <hekuang@...wei.com>, peterz@...radead.org,
	mingo@...hat.com, acme@...nel.org,
	alexander.shishkin@...ux.intel.com, jolsa@...hat.com,
	wangnan0@...wei.com, jpoimboe@...hat.com, ak@...ux.intel.com,
	eranian@...gle.com, namhyung@...nel.org,
	sukadev@...ux.vnet.ibm.com, masami.hiramatsu.pt@...achi.com,
	tumanova@...ux.vnet.ibm.com, kan.liang@...el.com,
	penberg@...nel.org, dsahern@...il.com
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/7] perf tools: Set vdso name to vdso[64,32] depending
 on platform

On 12/05/16 11:43, He Kuang wrote:
> This is a preparation for cross-platform vdso lookup.
> 
> There is a naming confusion about vdso name, vdso buildid generated by
> a 32-bit machine stores it with the name 'vdso', but when processing
> buildid on a 64-bit machine with the same 'perf.data', perf will
> search for vdso named as 'vdso32' and get failed.
> 
> This patch uses different names when storing the buildid, i.e. vdso64
> for 64-bit machine and vdso32 for 32-bit machine, and eliminates this
> naming confusion.

That looks like it will break existing perf.data files because they will
have a different name recorded in the buildid section.

Also it doesn't look like it would work the other way around i.e. recording
on a 64-bit machine and processing on a 32-bit machine.

> 
> Signed-off-by: He Kuang <hekuang@...wei.com>
> ---
>  tools/perf/util/vdso.h | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/perf/util/vdso.h b/tools/perf/util/vdso.h
> index cdc4fab..45e9ef4 100644
> --- a/tools/perf/util/vdso.h
> +++ b/tools/perf/util/vdso.h
> @@ -4,10 +4,15 @@
>  #include <linux/types.h>
>  #include <string.h>
>  #include <stdbool.h>
> +#include "util.h"
>  
>  #define VDSO__MAP_NAME "[vdso]"
>  
> -#define DSO__NAME_VDSO    "[vdso]"
> +#if BITS_PER_LONG == 64
> +#define DSO__NAME_VDSO    "[vdso64]"
> +#else
> +#define DSO__NAME_VDSO    "[vdso32]"
> +#endif
>  #define DSO__NAME_VDSO32  "[vdso32]"
>  #define DSO__NAME_VDSOX32 "[vdsox32]"
>  
>