linux-kernel - Re: [RFC][PATCH 1.5/2] x86: Add int3_emulate

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Date:   Fri, 3 May 2019 14:46:33 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.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>,
        Joerg Roedel <jroedel@...e.de>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>, stable <stable@...r.kernel.org>
Subject: Re: [RFC][PATCH 1.5/2] x86: Add int3_emulate_call() selftest

On Fri, 3 May 2019 12:22:47 +0200
Peter Zijlstra <peterz@...radead.org> wrote:

> Given that the entry_*.S changes for this functionality are somewhat
> tricky, make sure the paths are tested every boot, instead of on the
> rare occasion when we trip an INT3 while rewriting text.
> 
> Getting the INT3 frame setup even slightly wrong will make this come
> unstuck something spectacular.
> 
> Requested-by: Andy Lutomirski <luto@...nel.org>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> ---
>  arch/x86/kernel/alternative.c | 81 ++++++++++++++++++++++++++++++++++++++++---
>  1 file changed, 77 insertions(+), 4 deletions(-)

I'll add this to my queue, as I tested this on x86_32 and 64. I also
put in a printk("HERE in int3_magic\n") to make sure it really did get
there (although, the BUG_ON should be good enough).

The printk will be removed from the official commit. It was just for my
peace of mind.

-- Steve