linux-kernel - Re: [PATCH] x86/asm/entry/64: Clean up entry

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Message-ID: <CALCETrUNurOoDE7TXb3-Xnw-gx559c_q-Fe3qY6KyMCfdL2UDA@mail.gmail.com>
Date:	Mon, 6 Jul 2015 10:20:22 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Sasha Levin <sasha.levin@...cle.com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Brian Gerst <brgerst@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Borislav Petkov <bp@...en8.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] x86/asm/entry/64: Clean up entry_64.S

On Mon, Jul 6, 2015 at 8:00 AM, Sasha Levin <sasha.levin@...cle.com> wrote:
>
> --- entry.before.o.cmd  2015-07-06 10:48:32.110189938 -0400
> +++ entry.after.o.cmd   2015-07-06 10:48:23.509645442 -0400
> @@ -1,5 +1,5 @@
>
> -entry.before.o:     file format elf64-x86-64
> +entry.after.o:     file format elf64-x86-64
>
>
>  Disassembly of section .entry.text:
> @@ -3961,8 +3961,8 @@
>    3b:  09 02                   or     %eax,(%rdx)
>         ...
>                         3d: R_X86_64_64 .entry.text
> -  45:  03 3a                   add    (%rdx),%edi
> -  47:  01 3d 03 d6 00 c8       add    %edi,-0x37ff29fd(%rip)        # ffffffffc800d650 <ignore_sysret+0xffffffffc800b1f0>
> +  45:  03 33                   add    (%rbx),%esi
> +  47:  01 3d 03 d5 00 c8       add    %edi,-0x37ff2afd(%rip)        # ffffffffc800d550 <ignore_sysret+0xffffffffc800b0f0>

What exactly are you doing to generate this diff?  This all looks really weird.

>    4d:  44 91                   rex.R xchg %eax,%ecx
>    4f:  93                      xchg   %eax,%ebx
>    50:  2f                      (bad)

For example: what on earth is the asm above?

--Andy
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