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Subject[RFC -next] linux/linkage.h: fix symbol prefix handling
Date
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@imgtec.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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