Re: [PATCH RFC 07/19] perf tools: Workaround missing maps for x86_64 KPTI entry trampolines

[Adrian Hunter]

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@xxxxxxxxxx]
>>> Sent: Wednesday, May 9, 2018 8:07 PM
>>> To: Hunter, Adrian <adrian.hunter@xxxxxxxxx>
>>> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>; Ingo Molnar
>>> <mingo@xxxxxxxxxx>; Peter Zijlstra <peterz@xxxxxxxxxxxxx>; Andy
>>> Lutomirski <luto@xxxxxxxxxx>; H. Peter Anvin <hpa@xxxxxxxxx>; Andi Kleen
>>> <ak@xxxxxxxxxxxxxxx>; Alexander Shishkin
>>> <alexander.shishkin@xxxxxxxxxxxxxxx>; Dave Hansen
>>> <dave.hansen@xxxxxxxxxxxxxxx>; Joerg Roedel <joro@xxxxxxxxxx>; Jiri Olsa
>>> <jolsa@xxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; x86@xxxxxxxxxx
>>> 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@xxxxxxxxx>
>>>> ---
>>>>  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.