linux-kernel - [RFC -next] linux/linkage.h: fix symbol prefix handling

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Date:	Thu, 7 Mar 2013 11:44:02 +0000
From:	James Hogan <james.hogan@...tec.com>
To:	Al Viro <viro@...iv.linux.org.uk>
CC:	Michal Marek <mmarek@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Guenter Roeck <linux@...ck-us.net>,
	Jean Delvare <khali@...ux-fr.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	<linux-kbuild@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	Mike Frysinger <vapier@...too.org>,
	<uclinux-dist-devel@...ckfin.uclinux.org>,
	<linux-next@...r.kernel.org>, James Hogan <james.hogan@...tec.com>
Subject: [RFC -next] linux/linkage.h: fix symbol prefix handling

The commit "consolidate cond_syscall and SYSCALL_ALIAS declarations"
broke the build on blackfin and metag due to the following code:

  #ifndef SYMBOL_NAME
  #ifdef CONFIG_SYMBOL_PREFIX
  #define SYMBOL_NAME(x) CONFIG_SYMBOL_PREFIX ## x
  #else
  #define SYMBOL_NAME(x) x
  #endif
  #endif
  #define __SYMBOL_NAME(x) __stringify(SYMBOL_NAME(x))

__stringify literally stringifies CONFIG_SYMBOL_PREFIX ##x, so you get
lines like this in the assembly output:

  .weak CONFIG_SYMBOL_PREFIXsys_quotactl
  .set
  CONFIG_SYMBOL_PREFIXsys_quotactl,CONFIG_SYMBOL_PREFIXsys_ni_syscall

This is fixed by defining SYMBOL_PREFIX from the command line for c
files in addition to assembly for architectures that set
CONFIG_SYMBOL_PREFIX (scripts/Makefile.lib), and defining __SYMBOL_NAME
as:

  #define __SYMBOL_NAME(x) __stringify(SYMBOL_PREFIX) #x

We first have to ensure SYMBOL_PREFIX is defined (which avoids polluting
the command lines for architectures that don't use symbol prefixes).
Also the definition of SYMBOL_PREFIX in <linux/kernel.h> is removed as
it conflicts, isn't used anywhere, and is defined as a string so differs
from the assembly definition.

Signed-off-by: James Hogan <james.hogan@...tec.com>
---
This is just one possible way of fixing it. It felt the cleanest out of
the ways I tried, but feel free to suggest something better!

 include/linux/kernel.h  |  7 -------
 include/linux/linkage.h | 12 +++++-------
 scripts/Makefile.lib    |  1 +
 3 files changed, 6 insertions(+), 14 deletions(-)

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 80d3687..e13e992 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -723,13 +723,6 @@ static inline void ftrace_dump(enum ftrace_dump_mode oops_dump_mode) { }
 /* Trap pasters of __FUNCTION__ at compile-time */
 #define __FUNCTION__ (__func__)
 
-/* This helps us to avoid #ifdef CONFIG_SYMBOL_PREFIX */
-#ifdef CONFIG_SYMBOL_PREFIX
-#define SYMBOL_PREFIX CONFIG_SYMBOL_PREFIX
-#else
-#define SYMBOL_PREFIX ""
-#endif
-
 /* Rebuild everything on CONFIG_FTRACE_MCOUNT_RECORD */
 #ifdef CONFIG_FTRACE_MCOUNT_RECORD
 # define REBUILD_DUE_TO_FTRACE_MCOUNT_RECORD
diff --git a/include/linux/linkage.h b/include/linux/linkage.h
index 829d66c..acb869b 100644
--- a/include/linux/linkage.h
+++ b/include/linux/linkage.h
@@ -15,14 +15,12 @@
 #define asmlinkage CPP_ASMLINKAGE
 #endif
 
-#ifndef SYMBOL_NAME
-#ifdef CONFIG_SYMBOL_PREFIX
-#define SYMBOL_NAME(x) CONFIG_SYMBOL_PREFIX ## x
-#else
-#define SYMBOL_NAME(x) x
-#endif
+/* This helps us to avoid #ifdef SYMBOL_PREFIX */
+#ifndef SYMBOL_PREFIX
+#define SYMBOL_PREFIX
 #endif
-#define __SYMBOL_NAME(x) __stringify(SYMBOL_NAME(x))
+
+#define __SYMBOL_NAME(x) __stringify(SYMBOL_PREFIX) #x
 
 #ifndef cond_syscall
 #define cond_syscall(x) asm(".weak\t" __SYMBOL_NAME(x) \
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 07125e6..f1cce6a 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -123,6 +123,7 @@ ifdef CONFIG_SYMBOL_PREFIX
 _sym_flags = -DSYMBOL_PREFIX=$(patsubst "%",%,$(CONFIG_SYMBOL_PREFIX))
 _cpp_flags += $(_sym_flags)
 _a_flags += $(_sym_flags)
+_c_flags += $(_sym_flags)
 endif
 
 
-- 
1.8.1.2


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