Re: [RFC][PATCH 07/11] perf: Provide PERF_SAMPLE_REGS

From: Stephane Eranian
Date: Wed Mar 03 2010 - 13:18:50 EST

On Wed, Mar 3, 2010 at 9:55 AM, David Miller <davem@xxxxxxxxxxxxx> wrote:
> From: Stephane Eranian <eranian@xxxxxxxxxx>
> Date: Wed, 3 Mar 2010 09:49:33 -0800
>> On Wed, Mar 3, 2010 at 9:39 AM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
>>> On Wed, 2010-03-03 at 09:30 -0800, Stephane Eranian wrote:
>>>> This assumes struct pt_regs is somehow exported to userland.
>>>> Is that the case?
>>> I seems to have understood they were, and asm/ptrace.h seems to agree
>>> with that, it has !__KERNEL__ definitions for struct pt_regs.
>> Seems to be the case, indeed.
> BTW, how are you going to cope with compat systems?
> If I build 'perf' on a sparc64 kernel build, it's going to get the
> 64-bit pt_regs. ÂSo I can't then use that binary on a sparc box
> running a 32-bit kernel.
> And vice versa.
That was going to be my next question. The pt_regs you return
depends on the binary you are monitoring (32 vs. 64) if interrupt
occurred in userland. But what about if it happens in kernel mode?

> And more generally aren't we supposed to be able to eventually analyze
> perf dumps on any platform not just the one 'perf' was built under?
> We'll need to do something about the encoding of pt_regs, therefore.

Stephane Eranian | EMEA Software Engineering
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