linux-kernel - Re: [PATCH v2] tools/perf: Fix the mask in regs_dump_

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Date:	Mon, 20 Jun 2016 11:18:18 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>
Cc:	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	Yury Norov <ynorov@...iumnetworks.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Kan Liang <kan.liang@...el.com>,
	Wang Nan <wangnan0@...wei.com>,
	Michael Ellerman <mpe@...erman.id.au>
Subject: Re: [PATCH v2] tools/perf: Fix the mask in regs_dump__printf and

On Mon, Jun 20, 2016 at 02:14:01PM +0530, Madhavan Srinivasan wrote:
> When decoding the perf_regs mask in regs_dump__printf(),
> we loop through the mask using find_first_bit and find_next_bit functions.
> "mask" is of type "u64", but sent as a "unsigned long *" to
> lib functions along with sizeof(). While the exisitng code works fine in
> most of the case, the logic is broken when using a 32bit perf on a
> 64bit kernel (Big Endian). We end up reading the wrong word of the u64
> first in the lib functions.

hum, I still don't see why this happens.. why do we read the
wrong word in this case?

thanks,
jirka

> first in the lib functions. Proposed fix is to swap the words of the
> u64 to handle this case. This is not endianess swap.
> 

SNIP