linux-kernel - Re: [bug report][stable] perf probe: failed to add events

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Message-ID: <fea29ce5-b410-27cc-045e-feeecbc4a7f5@intel.com>
Date:   Thu, 28 Feb 2019 09:19:08 +0200
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Joseph Qi <joseph.qi@...ux.alibaba.com>,
        Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
Cc:     Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        luto@...nel.org, Jiufei Xue <jiufei.xue@...ux.alibaba.com>,
        Xu Yu <xuyu@...ux.alibaba.com>, peterz@...radead.org,
        mingo@...hat.com
Subject: Re: [bug report][stable] perf probe: failed to add events

On 28/02/19 4:07 AM, Joseph Qi wrote:
> Hi Adrian,
> 
> On 19/2/27 20:39, Adrian Hunter wrote:
>> Seems to be fixed by this:
>>
>> From: Adrian Hunter <adrian.hunter@...el.com>
>> Date: Wed, 27 Feb 2019 05:35:25 +0200
>> Subject: [PATCH] perf probe: Fix getting the kernel map
>>
>> Since commit 4d99e4136580 ("perf machine: Workaround missing maps for x86
>> PTI entry trampolines"), perf tools has been creating more than one kernel
>> map, however 'perf probe' assumed there could be only one.
>>
>> Fix by using machine__kernel_map() to get the main kernel map.
>>
>> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
>> Fixes: 4d99e4136580 ("perf machine: Workaround missing maps for x86 PTI entry trampolines")
> 
> Below is my investigation result before, FYI.
> the first bad commit (v4.18 ~ v4.19):
> d83212d5dd67 kallsyms, x86: Export addresses of PTI entry trampolines

Yes we should add a fixes tag for that also.

> revert this commit on 4.19.0, it works.
> the first good commit again (v4.19 ~ v4.20):
> bf904d2762ee x86/pti/64: Remove the SYSCALL64 entry trampoline
> backported this commit as well as the related commit 98f05b5138f0 on
> v4.19.24, it works.
> 
> And I've tested your fix on v4.19.24, it also works.
> Tested-by: Joseph Qi <joseph.qi@...ux.alibaba.com>
>