From: "H.J. Lu" <hjl.tools@gmail.com>
To: Michael Matz <matz@suse.de>
Cc: Jan Beulich <JBeulich@suse.com>, Binutils <binutils@sourceware.org>
Subject: Re: [committed, PATCH] Remove Disp16|Disp32 from 64-bit direct branches
Date: Tue, 12 May 2015 15:43:00 -0000 [thread overview]
Message-ID: <CAMe9rOo76QirYvEH=tX7BDBws3z=g0O8c+A1wSp+19yaNXUk1w@mail.gmail.com> (raw)
In-Reply-To: <alpine.LSU.2.20.1505121736050.4883@wotan.suse.de>
On Tue, May 12, 2015 at 8:37 AM, Michael Matz <matz@suse.de> wrote:
> Hi,
>
> On Tue, 12 May 2015, Jan Beulich wrote:
>
>> I don't think so - this looks quite okay. It would become more of an
>> issue when looking at other than relocatable object files (namely when
>> their image base is non-zero), or ones with .text exceeding 32k.
>
> Actually also that one is correctly printed I think (from a hello world
> main, where I added a jmprel16 +0):
>
> 000000000040055c <main>:
> 40055c: 55 push %rbp
> 40055d: 48 89 e5 mov %rsp,%rbp
> 400560: 48 83 ec 30 sub $0x30,%rsp
> 400564: c6 45 d1 00 movb $0x0,-0x2f(%rbp)
> 400568: c6 45 d0 61 movb $0x61,-0x30(%rbp)
> 40056c: 48 8d 45 d0 lea -0x30(%rbp),%rax
> 400570: 48 89 c2 mov %rax,%rdx
> 400573: be 44 06 40 00 mov $0x400644,%esi
> 400578: 66 e9 00 00 jmpw 57c <_init-0x3ffe8c>
>
> 000000000040057c <next>:
> 40057c: bf 52 06 40 00 mov $0x400652,%edi
> ...
>
> It shows that rip is going to be truncated.
>
This is the same issue as
https://sourceware.org/bugzilla/show_bug.cgi?id=18386
On Intel processors, 0x66 prefix before direct 32-bit unconditional
call/jmp is ignored. Whatever we do is wrong on AMD or Intel
processors.
--
H.J.
next prev parent reply other threads:[~2015-05-12 15:43 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-11 21:23 H.J. Lu
2015-05-12 10:41 ` Jan Beulich
2015-05-12 11:54 ` H.J. Lu
2015-05-12 12:20 ` Jan Beulich
2015-05-12 12:37 ` H.J. Lu
2015-05-12 13:03 ` Jan Beulich
2015-05-12 13:37 ` H.J. Lu
2015-05-12 13:49 ` Michael Matz
2015-05-12 13:57 ` H.J. Lu
2015-05-12 14:31 ` Michael Matz
2015-05-12 14:49 ` H.J. Lu
2015-05-12 15:14 ` Michael Matz
2015-05-12 15:21 ` H.J. Lu
2015-05-12 15:32 ` Michael Matz
2015-05-12 14:59 ` Jan Beulich
2015-05-12 15:03 ` H.J. Lu
2015-05-12 15:09 ` Jan Beulich
2015-05-12 15:11 ` H.J. Lu
2015-05-12 15:17 ` Jan Beulich
2015-05-12 15:37 ` Michael Matz
2015-05-12 15:43 ` H.J. Lu [this message]
2015-05-12 15:47 ` Michael Matz
2015-05-12 16:00 ` H.J. Lu
2015-05-12 16:03 ` Michael Matz
2015-05-12 16:08 ` H.J. Lu
2015-05-13 6:18 ` Jan Beulich
2015-05-13 11:35 ` H.J. Lu
2015-05-13 12:27 ` Jan Beulich
2015-05-13 13:15 ` H.J. Lu
2015-05-13 12:34 ` Michael Matz
2015-05-13 13:32 ` H.J. Lu
2015-05-13 16:50 ` Maciej W. Rozycki
2015-05-13 16:53 ` H.J. Lu
2015-05-15 6:39 ` Jan Beulich
2015-05-15 16:52 ` H.J. Lu
2015-05-18 7:05 ` Jan Beulich
2015-05-18 11:22 ` H.J. Lu
2015-05-18 11:48 ` Jan Beulich
2015-05-18 12:18 ` H.J. Lu
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