linux-kernel - Re: [lkp-robot] [x86/asm] 51bad67ffb: int3:#[##]

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Message-ID: <20180515214337.GA18021@avx2>
Date:   Wed, 16 May 2018 00:43:37 +0300
From:   Alexey Dobriyan <adobriyan@...il.com>
To:     "Anvin, H Peter" <h.peter.anvin@...el.com>
Cc:     "Ye, Xiaolong" <xiaolong.ye@...el.com>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andy Lutomirski <luto@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        Brian Gerst <brgerst@...il.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        "tipbuild@...or.com" <tipbuild@...or.com>,
        "lkp@...org" <lkp@...org>
Subject: Re: [lkp-robot] [x86/asm]  51bad67ffb: int3:#[##]

On Tue, May 15, 2018 at 09:25:53PM +0000, Anvin, H Peter wrote:
> Why is that a problem?
> Code: 00 00 00 eb e6 cc cc cc cc cc cc cc cc cc cc cc cc cc fa 8d b6 00 00 00 00 e8 5d e8 8f ff 8b 44 24 34 83 e0 03 83 f8 03 72 28 cc &lt;cc&gt; cc cc cc cc cc cc fa 8d b6 00 00 00 00 e8 3d e8 8f ff 89 e0
> 
> EIP: ret_from_intr+0xd/0x14 SS:ESP: 0068:8603bfb4
> 
> INT3 slipped through M586 =&gt; X86_ALIGNMENT_16 :-\

I could make the patch x86_64 only, but!

It crashed into the middle of the padding.

796ef8fc <ret_from_intr>:
796ef8fc:       8b 44 24 34             mov    eax,DWORD PTR [esp+0x34]
796ef900:       83 e0 03                and    eax,0x3
796ef903:       83 f8 03                cmp    eax,0x3
796ef906:       72 28                   jb     796ef930 <resume_kernel>
796ef908:       cc                      int3
796ef909:       cc       <========>     int3
796ef90a:       cc                      int3
796ef90b:       cc                      int3
796ef90c:       cc                      int3
796ef90d:       cc                      int3
796ef90e:       cc                      int3
796ef90f:       cc                      int3