linux-kernel - Re: [PATCH v2] perf probe: Fix add event failed when 32-bit perf running in 64-bit kernel

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Date:   Thu, 15 Jul 2021 19:40:57 +0800
From:   Yang Jihong <yangjihong1@...wei.com>
To:     Masami Hiramatsu <mhiramat@...nel.org>
CC:     <peterz@...radead.org>, <mingo@...hat.com>, <acme@...nel.org>,
        <mark.rutland@....com>, <alexander.shishkin@...ux.intel.com>,
        <jolsa@...hat.com>, <namhyung@...nel.org>, <irogers@...gle.com>,
        <fche@...hat.com>, <ravi.bangoria@...ux.ibm.com>,
        <yao.jin@...ux.intel.com>, <srikar@...ux.vnet.ibm.com>,
        <Jianlin.Lv@....com>, <lihuafei1@...wei.com>,
        <linux-perf-users@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] perf probe: Fix add event failed when 32-bit perf
 running in 64-bit kernel

Hello Hiramatsu,

On 2021/7/15 17:05, Masami Hiramatsu wrote:
> On Thu, 15 Jul 2021 14:37:23 +0800
> Yang Jihong <yangjihong1@...wei.com> wrote:
> 
>> The "address" member  of "struct probe_trace_point" uses long data type.
>> If kernel is 64-bit and perf program is 32-bit, size of "address" variable is
>> 32 bits. As a result, upper 32 bits of address read from kernel are truncated,
>> An error occurs during address comparison in kprobe_warn_out_range function.
>>
>> Before:
>>
>>    # perf probe -a schedule
>>    schedule is out of .text, skip it.
>>      Error: Failed to add events.
>>
>> Solution:
>>    Change data type of "address" variable to u64 and change corresponding
>> address printing and value assignment.
>>
>> After:
>>
>>    # perf.new.new probe -a schedule
>>    Added new event:
>>      probe:schedule       (on schedule)
>>
>>    You can now use it in all perf tools, such as:
>>
>>            perf record -e probe:schedule -aR sleep 1
>>
>>    # perf probe -l
>>      probe:schedule       (on schedule@...nel/sched/core.c)
>>    # perf record -e probe:schedule -aR sleep 1
>>    [ perf record: Woken up 1 times to write data ]
>>    [ perf record: Captured and wrote 0.156 MB perf.data (1366 samples) ]
>>    # perf report --stdio
>>    # To display the perf.data header info, please use --header/--header-only options.
>>    #
>>    #
>>    # Total Lost Samples: 0
>>    #
>>    # Samples: 1K of event 'probe:schedule'
>>    # Event count (approx.): 1366
>>    #
>>    # Overhead  Command          Shared Object      Symbol
>>    # ........  ...............  .................  ............
>>    #
>>         6.22%  migration/0      [kernel.kallsyms]  [k] schedule
>>         6.22%  migration/1      [kernel.kallsyms]  [k] schedule
>>         6.22%  migration/2      [kernel.kallsyms]  [k] schedule
>>         6.22%  migration/3      [kernel.kallsyms]  [k] schedule
>>         6.15%  migration/10     [kernel.kallsyms]  [k] schedule
>>         6.15%  migration/11     [kernel.kallsyms]  [k] schedule
>>         6.15%  migration/12     [kernel.kallsyms]  [k] schedule
>>         6.15%  migration/13     [kernel.kallsyms]  [k] schedule
>>         6.15%  migration/14     [kernel.kallsyms]  [k] schedule
>>         6.15%  migration/15     [kernel.kallsyms]  [k] schedule
>>         6.15%  migration/4      [kernel.kallsyms]  [k] schedule
>>         6.15%  migration/5      [kernel.kallsyms]  [k] schedule
>>         6.15%  migration/6      [kernel.kallsyms]  [k] schedule
>>         6.15%  migration/7      [kernel.kallsyms]  [k] schedule
>>         6.15%  migration/8      [kernel.kallsyms]  [k] schedule
>>         6.15%  migration/9      [kernel.kallsyms]  [k] schedule
>>         0.22%  rcu_sched        [kernel.kallsyms]  [k] schedule
>>    ...
>>    #
>>    # (Cannot load tips.txt file, please install perf!)
>>    #
>>
> 
> OK, this looks good to me :)
> 
> Acked-by: Masami Hiramatsu <mhiramat@...nel.org>
> 
Thanks for the Acked :)

Jihong