From: "Jan Beulich" <JBeulich@suse.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Xen-devel <xen-devel@lists.xen.org>,
"Wei Liu" <wei.liu2@citrix.com>,
"Roger Pau Monné" <roger.pau@citrix.com>
Subject: Re: [PATCH 3/7] x86/alt: Clean up the assembly used to generate alternatives
Date: Fri, 23 Feb 2018 10:28:49 -0700 [thread overview]
Message-ID: <5A905D6102000078001AB18A@prv-mh.provo.novell.com> (raw)
In-Reply-To: <193ccb3c-d4bb-5939-90a1-1a781adcb587@citrix.com>
>>> On 23.02.18 at 17:24, <andrew.cooper3@citrix.com> wrote:
> On 23/02/18 15:12, Jan Beulich wrote:
>>>>> On 23.02.18 at 15:03, <andrew.cooper3@citrix.com> wrote:
>>> On 13/02/18 14:37, Jan Beulich wrote:
>>>> >>> On 12.02.18 at 12:23, <andrew.cooper3@citrix.com> wrote:
>>>>> --- a/xen/include/asm-x86/alternative-asm.h
>>>>> +++ b/xen/include/asm-x86/alternative-asm.h
>>>>> @@ -9,60 +9,67 @@
>>>>> * enough information for the alternatives patching code to patch an
>>>>> * instruction. See apply_alternatives().
>>>>> */
>>>>> -.macro altinstruction_entry orig alt feature orig_len alt_len
>>>>> +.macro altinstruction_entry orig repl feature orig_len repl_len
>>>>> .long \orig - .
>>>>> - .long \alt - .
>>>>> + .long \repl - .
>>>>> .word \feature
>>>>> .byte \orig_len
>>>>> - .byte \alt_len
>>>>> + .byte \repl_len
>>>>> .endm
>>>>>
>>>>> +#define orig_len (.L\@_orig_e - .L\@_orig_s)
>>>>> +#define repl_len(nr) (.L\@_repl_e\()nr - .L\@_repl_s\()nr)
>>>>> +#define decl_repl(insn, nr) .L\@_repl_s\()nr: insn; .L\@_repl_e\()nr:
>>>> Wouldn't it work equally well but look slightly less odd if you used
>>>> \(nr) instead of \()nr?
>>> How would that work? \() is the token separator.
>> When there's nothing inside the parentheses, this construct
>> can be used as a token separator, but that's not its main
>> purpose. Instead \(<text>) means to take <text> literally,
>> without e.g. expanding macro arguments inside it.
>
> I've never come across it before, and I still can't find reference to it
> in the as manual.
>
> As for why not to use it, Clang has no idea what \(nr) means, meaning
> that it doesn't expand the construct in the way you describe. (Although
> I see that GCC/AS do behave as you describe).
Oh, if clang can't cope, then leave it as is.
Jan
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next prev parent reply other threads:[~2018-02-23 17:28 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-12 11:23 [PATCH 0/7] x86/alternatives: Support for automatic padding calculations Andrew Cooper
2018-02-12 11:23 ` [PATCH 1/7] x86/alt: Drop unused alternative infrastructure Andrew Cooper
2018-02-12 12:30 ` Wei Liu
2018-02-12 15:56 ` Roger Pau Monné
2018-02-12 15:58 ` Andrew Cooper
2018-02-13 14:22 ` Jan Beulich
2018-02-13 14:41 ` Andrew Cooper
2018-02-13 15:33 ` Jan Beulich
2018-02-14 10:02 ` Jan Beulich
2018-02-12 11:23 ` [PATCH 2/7] x86/alt: Clean up struct alt_instr and its users Andrew Cooper
2018-02-12 12:30 ` Wei Liu
2018-02-12 16:52 ` Roger Pau Monné
2018-02-12 17:18 ` Wei Liu
2018-02-12 17:53 ` Andrew Cooper
2018-02-13 14:26 ` Jan Beulich
2018-02-21 21:22 ` Konrad Rzeszutek Wilk
2018-02-12 11:23 ` [PATCH 3/7] x86/alt: Clean up the assembly used to generate alternatives Andrew Cooper
2018-02-12 12:30 ` Wei Liu
2018-02-12 17:26 ` Roger Pau Monné
2018-02-12 17:54 ` Andrew Cooper
2018-02-13 14:37 ` Jan Beulich
2018-02-23 14:03 ` Andrew Cooper
2018-02-23 15:12 ` Jan Beulich
2018-02-23 16:24 ` Andrew Cooper
2018-02-23 17:28 ` Jan Beulich [this message]
2018-02-12 11:23 ` [PATCH 4/7] x86/asm: Remove opencoded uses of altinstruction_entry Andrew Cooper
2018-02-12 12:30 ` Wei Liu
2018-02-12 12:34 ` Andrew Cooper
2018-02-13 9:56 ` Jan Beulich
2018-02-13 10:07 ` Andrew Cooper
2018-02-13 11:10 ` Jan Beulich
2018-02-12 12:52 ` Wei Liu
2018-02-12 17:46 ` Roger Pau Monné
2018-02-12 17:59 ` Andrew Cooper
2018-02-14 9:53 ` Jan Beulich
2018-02-12 11:23 ` [PATCH 5/7] x86/alt: Support for automatic padding calculations Andrew Cooper
2018-02-12 14:39 ` Wei Liu
2018-02-12 15:04 ` Andrew Cooper
2018-02-12 18:41 ` Roger Pau Monné
2018-02-12 18:45 ` Andrew Cooper
2018-02-12 18:09 ` Roger Pau Monné
2018-02-13 9:45 ` Roger Pau Monné
2018-02-13 10:09 ` Andrew Cooper
2018-02-13 10:26 ` Roger Pau Monné
2018-02-14 9:46 ` Jan Beulich
2018-02-12 11:23 ` [PATCH 6/7] x86/alt: Drop explicit padding of origin sites Andrew Cooper
2018-02-12 14:39 ` Wei Liu
2018-02-12 18:12 ` Roger Pau Monné
2018-02-14 9:53 ` Jan Beulich
2018-02-12 11:23 ` [PATCH 7/7] x86/build: Use new .nop directive when available Andrew Cooper
2018-02-12 14:40 ` Wei Liu
2018-02-13 11:08 ` Roger Pau Monné
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