linux-kernel - Re: [PATCH RFC 07/19] perf tools: Workaround missing maps for x86

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Date:   Fri, 11 May 2018 14:15:53 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>, Andi Kleen <ak@...ux.intel.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>, Jiri Olsa <jolsa@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>
Subject: Re: [PATCH RFC 07/19] perf tools: Workaround missing maps for x86_64
 KPTI entry trampolines

On 10/05/18 23:15, Arnaldo Carvalho de Melo wrote:
> Em Thu, May 10, 2018 at 07:08:37PM +0000, Hunter, Adrian escreveu:
>>> -----Original Message-----
>>> From: Arnaldo Carvalho de Melo [mailto:acme@...nel.org]
>>> Sent: Wednesday, May 9, 2018 8:07 PM
>>> To: Hunter, Adrian <adrian.hunter@...el.com>
>>> Cc: Thomas Gleixner <tglx@...utronix.de>; Ingo Molnar
>>> <mingo@...hat.com>; Peter Zijlstra <peterz@...radead.org>; Andy
>>> Lutomirski <luto@...nel.org>; H. Peter Anvin <hpa@...or.com>; Andi Kleen
>>> <ak@...ux.intel.com>; Alexander Shishkin
>>> <alexander.shishkin@...ux.intel.com>; Dave Hansen
>>> <dave.hansen@...ux.intel.com>; Joerg Roedel <joro@...tes.org>; Jiri Olsa
>>> <jolsa@...hat.com>; linux-kernel@...r.kernel.org; x86@...nel.org
>>> Subject: Re: [PATCH RFC 07/19] perf tools: Workaround missing maps for
>>> x86_64 KPTI entry trampolines
>>>
>>> Em Wed, May 09, 2018 at 02:43:36PM +0300, Adrian Hunter escreveu:
>>>> On x86_64 the KPTI entry trampolines are not in the kernel map created
>>>> by perf tools. That results in the addresses having no symbols and
>>>> prevents annotation. It also causes Intel PT to have decoding errors
>>>> at the trampoline addresses. Workaround that by creating maps for the
>>> trampolines.
>>>> At present the kernel does not export information revealing where the
>>>> trampolines are. Until that happens, the addresses are hardcoded.
>>>>
>>>> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
>>>> ---
>>>>  tools/perf/util/machine.c | 104
>>> ++++++++++++++++++++++++++++++++++++++++++++++
>>>>  tools/perf/util/machine.h |   3 ++
>>>>  tools/perf/util/symbol.c  |  12 +++---
>>>>  3 files changed, 114 insertions(+), 5 deletions(-)
>>>>
>>>> diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
>>>> index 22047ff3cf2a..1bf15aa0b099 100644
>>>> --- a/tools/perf/util/machine.c
>>>> +++ b/tools/perf/util/machine.c
>>>> @@ -851,6 +851,110 @@ static int
>>> machine__get_running_kernel_start(struct machine *machine,
>>>>  	return 0;
>>>>  }
>>>>
>>>> +struct special_kernal_map {
>>>
>>> s/kernal/kernel/
>>>
>>> And "special"?
>>
>> I have added comment:
>>
>> /* Kernel-space maps that are not the main kernel map nor a module map */
> 
> Perhaps:
> 
>   /* Kernel-space maps for symbols that are outside the main kernel map and module maps */
> 
>   struct extra_kernel_map;
> 
> What do you think?

I have done the re-naming and comment change and pushed the changes to the
same branch.