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 15:21:00 -0000 [thread overview]
Message-ID: <CAMe9rOrwY-MmZcPPxEo7NsO1O6yR4K6rO08j-SvmivOYXGuNag@mail.gmail.com> (raw)
In-Reply-To: <alpine.LSU.2.20.1505121713290.4883@wotan.suse.de>
On Tue, May 12, 2015 at 8:14 AM, Michael Matz <matz@suse.de> wrote:
> Hi,
>
> On Tue, 12 May 2015, H.J. Lu wrote:
>
>> >> 2. Can you speculate what
>> >>
>> >> " jmpw 4"
>> >>
>> >> does?
>> >
>> > It should do a jump to $nextip+offset, of course, just like a 32bit
>> > jump. The disassembly is correct, because with a zero offset, that's
>> > indeed '4'.
>>
>> I thought it did jump to "(nextip + offset) & 0xffff" on AMD. Can you
>> verify if it is true?
>
> Sorry, yes, this is true, the 16bit operand size prefix truncates RIP to
> 16 bit. Nevertheless it's a valid instruction and works as documented.
It doesn't work on Intel processors. Can you show me a real usage
for this?
--
H.J.
next prev parent reply other threads:[~2015-05-12 15:21 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 [this message]
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
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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