Date: Wed, 13 Aug 2008 21:07:07 +0200 (MEST)
Message-Id: <200808131907.m7DJ77Pp013757@harpo.it.uu.se>
From: Mikael Pettersson <mikpe@it.uu.se>
To: mingo@redhat.com
Subject: [RESEND][PATCH 2.6.27-rc3] x86: fix readb() et al compile error with gcc-3.2.3
Cc: hpa@zytor.com, linux-kernel@vger.kernel.org, tglx@linutronix.de
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 3804
Lines: 85

Building 2.6.27-rc1 on x86 with gcc-3.2.3 fails with:

In file included from include/asm/dma.h:12,
                 from include/linux/bootmem.h:8,
                 from init/main.c:26:
include/asm/io.h: In function `readb':
include/asm/io.h:32: syntax error before string constant
include/asm/io.h: In function `readw':
include/asm/io.h:33: syntax error before string constant
include/asm/io.h: In function `readl':
include/asm/io.h:34: syntax error before string constant
include/asm/io.h: In function `__readb':
include/asm/io.h:36: syntax error before string constant
include/asm/io.h: In function `__readw':
include/asm/io.h:37: syntax error before string constant
include/asm/io.h: In function `__readl':
include/asm/io.h:38: syntax error before string constant
make[1]: *** [init/main.o] Error 1
make: *** [init] Error 2

Starting with 2.6.27-rc1 readb() et al are generated by a
build_mmio_read() macro, which generates asm() statements with
output register constraints like "=" "q", i.e. as two adjacent
string literals. This doesn't work with gcc-3.2.3.

Fixed by moving the "=" part into the callers' reg parameter
(as suggested by Ingo).

Build and boot-tested with gcc-3.2.3 on 32 and 64-bit x86.

Fixes <http://bugzilla.kernel.org/show_bug.cgi?id=11205>.

Signed-off-by: Mikael Pettersson <mikpe@it.uu.se>
---
First posted 2008-07-30. The bug is still present in 2.6.27-rc3.

diff -rupN linux-2.6.27-rc3/include/asm-x86/io.h linux-2.6.27-rc3.x86-build_mmio_read-gcc323-fix/include/asm-x86/io.h
--- linux-2.6.27-rc3/include/asm-x86/io.h	2008-08-13 18:19:57.000000000 +0200
+++ linux-2.6.27-rc3.x86-build_mmio_read-gcc323-fix/include/asm-x86/io.h	2008-08-13 19:07:51.000000000 +0200
@@ -21,7 +21,7 @@ extern void __iomem *fix_ioremap(unsigne
 
 #define build_mmio_read(name, size, type, reg, barrier) \
 static inline type name(const volatile void __iomem *addr) \
-{ type ret; asm volatile("mov" size " %1,%0":"=" reg (ret) \
+{ type ret; asm volatile("mov" size " %1,%0":reg (ret) \
 :"m" (*(volatile type __force *)addr) barrier); return ret; }
 
 #define build_mmio_write(name, size, type, reg, barrier) \
@@ -29,13 +29,13 @@ static inline void name(type val, volati
 { asm volatile("mov" size " %0,%1": :reg (val), \
 "m" (*(volatile type __force *)addr) barrier); }
 
-build_mmio_read(readb, "b", unsigned char, "q", :"memory")
-build_mmio_read(readw, "w", unsigned short, "r", :"memory")
-build_mmio_read(readl, "l", unsigned int, "r", :"memory")
-
-build_mmio_read(__readb, "b", unsigned char, "q", )
-build_mmio_read(__readw, "w", unsigned short, "r", )
-build_mmio_read(__readl, "l", unsigned int, "r", )
+build_mmio_read(readb, "b", unsigned char, "=q", :"memory")
+build_mmio_read(readw, "w", unsigned short, "=r", :"memory")
+build_mmio_read(readl, "l", unsigned int, "=r", :"memory")
+
+build_mmio_read(__readb, "b", unsigned char, "=q", )
+build_mmio_read(__readw, "w", unsigned short, "=r", )
+build_mmio_read(__readl, "l", unsigned int, "=r", )
 
 build_mmio_write(writeb, "b", unsigned char, "q", :"memory")
 build_mmio_write(writew, "w", unsigned short, "r", :"memory")
@@ -59,8 +59,8 @@ build_mmio_write(__writel, "l", unsigned
 #define mmiowb() barrier()
 
 #ifdef CONFIG_X86_64
-build_mmio_read(readq, "q", unsigned long, "r", :"memory")
-build_mmio_read(__readq, "q", unsigned long, "r", )
+build_mmio_read(readq, "q", unsigned long, "=r", :"memory")
+build_mmio_read(__readq, "q", unsigned long, "=r", )
 build_mmio_write(writeq, "q", unsigned long, "r", :"memory")
 build_mmio_write(__writeq, "q", unsigned long, "r", )
 
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