linux-kernel - Re: [PATCH 3/4] x86/ftrace: make ftrace_int3

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Message-ID: <20190429150724.6e501d27@gandalf.local.home>
Date:   Mon, 29 Apr 2019 15:07:24 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Nicolai Stange <nstange@...e.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Jiri Kosina <jikos@...nel.org>,
        Miroslav Benes <mbenes@...e.cz>,
        Petr Mladek <pmladek@...e.com>,
        Joe Lawrence <joe.lawrence@...hat.com>,
        Shuah Khan <shuah@...nel.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        Juergen Gross <jgross@...e.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nayna Jain <nayna@...ux.ibm.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Andy Lutomirski <luto@...nel.org>,
        Joerg Roedel <jroedel@...e.de>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        live-patching@...r.kernel.org,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>
Subject: Re: [PATCH 3/4] x86/ftrace: make ftrace_int3_handler() not to skip
 fops invocation

On Mon, 29 Apr 2019 11:59:04 -0700
Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> I really don't care. Just do what I suggested, and if you have numbers to
> show problems, then maybe I'll care.
> 

Are you suggesting that I rewrite the code to do it one function at a
time? This has always been batch mode. This is not something new. The
function tracer has been around longer than the text poke code.

> Right now you're just making excuses for this. I described the solution
> months ago, now I've written a patch, if that's not good enough then we can
> just skip this all entirely.
> 
> Honestly, if you need to rewrite tens of thousands of calls, maybe you're
> doing something wrong?
> 

 # cd /sys/kernel/debug/tracing
 # cat available_filter_functions | wc -l
 45856
 # cat enabled_functions | wc -l
 0
 # echo function > current_tracer
 # cat enabled_functions | wc -l
 45856

There, I just enabled 45,856 function call sites in one shot!

How else do you want to update them? Every function in the kernel has a
nop, that turns into a call to the ftrace_handler, if I add another
user of that code, it will change each one as well.

-- Steve