linux-kernel - Re: [PATCH] perf test: Enable Symbols test to work with a current module dso

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Date: Fri, 16 Feb 2024 11:47:11 +0200
From: Adrian Hunter <adrian.hunter@...el.com>
To: Namhyung Kim <namhyung@...nel.org>,
 Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Jiri Olsa <jolsa@...nel.org>, linux-kernel@...r.kernel.org,
 linux-perf-users@...r.kernel.org, Ian Rogers <irogers@...gle.com>
Subject: Re: [PATCH] perf test: Enable Symbols test to work with a current
 module dso

On 31/01/24 22:58, Ian Rogers wrote:
> On Wed, Jan 31, 2024 at 11:24 AM Adrian Hunter <adrian.hunter@...el.com> wrote:
>>
>> The test needs a struct machine and creates one for the current host,
>> but a side-effect is that struct machine has set up kernel maps
>> including module maps.
>>
>> If the 'Symbols' test --dso option specifies a current kernel module,
>> it will already be present as a kernel dso, and a map with kmaps needs
>> to be used otherwise there will be a segfault - see below.
>>
>> For that case, find the existing map and use that. In that case also,
>> the dso is split by section into multiple dsos, so test those dsos
>> also. That in turn, shows up that those dsos have not had overlapping
>> symbols removed, so the test fails.
>>
>> Example:
>>
>>   Before:
>>
>>     $ perf test -F -v Symbols --dso /lib/modules/$(uname -r)/kernel/arch/x86/kvm/kvm-intel.ko
>>      70: Symbols                                                         :
>>     --- start ---
>>     Testing /lib/modules/6.7.2-local/kernel/arch/x86/kvm/kvm-intel.ko
>>     Segmentation fault (core dumped)
>>
>>   After:
>>
>>     $ perf test -F -v Symbols --dso /lib/modules/$(uname -r)/kernel/arch/x86/kvm/kvm-intel.ko
>>      70: Symbols                                                         :
>>     --- start ---
>>     Testing /lib/modules/6.7.2-local/kernel/arch/x86/kvm/kvm-intel.ko
>>     Overlapping symbols:
>>      41d30-41fbb l vmx_init
>>      41d30-41fbb g init_module
>>     ---- end ----
>>     Symbols: FAILED!
>>
>> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
> 
> Reviewed-by: Ian Rogers <irogers@...gle.com>
> 

Thanks Ian!

This patch is still OK.