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

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Date:	Thu, 24 Oct 2013 22:58:56 +0530
From:	Vineet Gupta <vineetg76@...il.com>
To:	Richard Weinberger <richard.weinberger@...il.com>,
	Chen Gang <gang.chen@...anux.com>
CC:	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: Portable assmbler code - newline (was Re: [PATCH] kernel/modsign_certificate.S:
 use real contents instead of macro GLOBAL())

+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.


----------------->
diff --git a/include/linux/linkage.h b/include/linux/linkage.h
index d3e8ad23a8e0..4188c632f2b8 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
@@ -83,7 +87,7 @@

 #ifndef WEAK
 #define WEAK(name)        \
-       .weak name;        \
+       .weak name; __ARCH_NL \
        name:
 #endif

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