linux-kernel - Re: Portable assmbler code - newline (was Re: [PATCH] kernel/modsign_certificate.S: use real contents instead of macro GLOBAL())

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Message-ID: <5269FD53.6040903@synopsys.com>
Date:	Fri, 25 Oct 2013 10:40:43 +0530
From:	Vineet Gupta <vineetg76@...il.com>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
CC:	Richard Weinberger <richard.weinberger@...il.com>,
	Chen Gang <gang.chen@...anux.com>,
	Joern Rennecke <joern.rennecke@...ecosm.com>,
	James Hogan <james.hogan@...tec.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Takashi Iwai <tiwai@...e.de>,
	Vineet Gupta <Vineet.Gupta1@...opsys.com>,
	"jeremy.bennett@...ecosm.com" <jeremy.bennett@...ecosm.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Claudiu Zissulescu <Claudiu.Zissulescu@...opsys.com>,
	Francois Bedard <Francois.Bedard@...opsys.com>,
	Sam Ravnborg <sam@...nborg.org>, Joe Perches <joe@...ches.com>,
	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>
Subject: Re: Portable assmbler code - newline (was Re: [PATCH] kernel/modsign_certificate.S:
 use real contents instead of macro GLOBAL())

On 10/25/2013 01:11 AM, Geert Uytterhoeven wrote:
> On Thu, Oct 24, 2013 at 7:28 PM, Vineet Gupta <vineetg76@...il.com> wrote:
>> > +CC linux-arch
>> >
>> > On 10/24/2013 11:33 AM, Richard Weinberger wrote:
>>> >> On Thu, Oct 24, 2013 at 7:31 AM, Chen Gang <gang.chen@...anux.com> wrote:
>>>>> >>> > For some architectures, tool chain is not smart enough to recognize the
>>>>> >>> > macro with multiple lines (e.g. arc tool chain), and for common ".S"
>>>>> >>> > file, this kind of macro is also rarely used.
>>> >> Does not "not smart enough" mean than the said toolchain is broken/buggy
>>> >> or is the kernel using an unsupported notation?
>>> >>
>> >
>> > IMHO this is not broken - rather the code is not fully portable - given that gas
>> > ports of arches have differnet notions of what to treat as comment and what newline.
>> >
>> > Looking as binutils/gas/config, I can see that avr, cris,...are likely broken in
>> > the same way as ARC is.
>> >
>> > Historically ARC has had ';' as comment char, which Joern relatively recently
>> > augmented to have '#' as well. However there's legacy codebase which relies on ';'
>> > being a comment and we can't change that fact.
>> >
>> > So can we introduce an ARCH over-ridable newline annotation in linkage.h and other
>> > places after auditing. Since asm/linkage.h preempts linux/linkage.h by way of
>> > #include it shd be pretty strightforward.
>> >
>> > Something like below. I can send the formal patch if people think the approach is OK.
> By what are you gonna override __ARCH_NL on ARC?
> I'm afraid cpp will still turn it into a single line.
> 

Eh ! My untested patch was broken but not because of what you mentioned.

For ARC, the ; negating the newline annotation. So the following works (backquote
is new line for ARC)

diff --git a/arch/arc/include/asm/linkage.h b/arch/arc/include/asm/linkage.h
index 0283e9e44e0d..b3eea2999322 100644
--- a/arch/arc/include/asm/linkage.h
+++ b/arch/arc/include/asm/linkage.h
@@ -9,6 +9,8 @@
 #ifndef __ASM_LINKAGE_H
 #define __ASM_LINKAGE_H

+#define __ARCH_NL      `
+
 #ifdef __ASSEMBLY__


diff --git a/include/linux/linkage.h b/include/linux/linkage.h
index d3e8ad23a8e0..969e70ad231a 100644
--- a/include/linux/linkage.h
+++ b/include/linux/linkage.h
@@ -6,6 +6,10 @@
 #include <linux/export.h>
 #include <asm/linkage.h>

+#ifndef __ARCH_NL
+#define __ARCH_NL      ;
+#endif
+
 #ifdef __cplusplus
 #define CPP_ASMLINKAGE extern "C"
 #else
@@ -75,7 +79,7 @@

 #ifndef ENTRY
 #define ENTRY(name) \
-  .globl name; \
+  .globl name __ARCH_NL \
   ALIGN; \
   name:
 #endif


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