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Subject: Re: [PATCH V6 08/15] ftrace: Add perf text poke events for ftrace
 trampolines
To:     Arnaldo Carvalho de Melo <acme@kernel.org>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Borislav Petkov <bp@alien8.de>,
        "H . Peter Anvin" <hpa@zytor.com>, x86@kernel.org,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Mathieu Poirier <mathieu.poirier@linaro.org>,
        Leo Yan <leo.yan@linaro.org>, Jiri Olsa <jolsa@redhat.com>,
        linux-kernel@vger.kernel.org
References: <20200405201327.7332-1-adrian.hunter@intel.com>
 <20200405201327.7332-9-adrian.hunter@intel.com>
 <20200421134504.GQ20730@hirez.programming.kicks-ass.net>
 <ce16611a-8b6c-765d-c254-5bb98493b082@intel.com>
 <20200422114659.GE20730@hirez.programming.kicks-ass.net>
From:   Adrian Hunter <adrian.hunter@intel.com>
Organization: Intel Finland Oy, Registered Address: PL 281, 00181 Helsinki,
 Business Identity Code: 0357606 - 4, Domiciled in Helsinki
Message-ID: <76de871f-fb0a-6918-68a9-94aa7b049d6b@intel.com>
Date:   Mon, 27 Apr 2020 10:23:05 +0300
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On 22/04/20 2:46 pm, Peter Zijlstra wrote:
> On Wed, Apr 22, 2020 at 10:39:06AM +0300, Adrian Hunter wrote:
>> On 21/04/20 4:45 pm, Peter Zijlstra wrote:
>>> On Sun, Apr 05, 2020 at 11:13:20PM +0300, Adrian Hunter wrote:
>>>> Add perf text poke events for ftrace trampolines when created and when
>>>> freed.
>>>
>>> Maybe also put in a little more detail on the various events. Because
>>> arch_ftrace_update_trampoline() can also generate text_poke_bp() events,
>>> to update an existing trampoline.
>>>
>>> A diagram, like with the kprobes thing perhaps.
>>
>> How about adding this:
>>
>> There can be 3 text_poke events for ftrace trampolines:
>>
>> 1. NULL -> trampoline
>>    By ftrace_update_trampoline() when !ops->trampoline
>>    Trampoline created
>>
>> 2. [e.g. on x86] CALL rel32 -> CALL rel32
>>    By arch_ftrace_update_trampoline() when ops->trampoline and
>>                         ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP
>>    [e.g. on x86] via text_poke_bp() which generates text poke events
>>    Trampoline-called function target updated
>>
>> 3. trampoline -> NULL
>>    By ftrace_trampoline_free() when ops->trampoline and
>>                  ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP
>>    Trampoline freed
> 
> Yes, very nice. Thanks!

Arnaldo, do you have this patchset on your radar?