kbuild: add symbol prefix arg to kallsyms

Commit 1f2bfbd00e466ff3489b2ca5cc75b1cccd14c123 ("kbuild: link of
vmlinux moved to a script") introduced in v3.5-rc1 broke kallsyms on
architectures which have symbol prefixes.

The --symbol-prefix argument used to be added to the KALLSYMS command
line from the architecture Makefile, however this isn't picked up by the
new scripts/link-vmlinux.sh. This resulted in symbols like
kallsyms_addresses being added which weren't correctly overriding the
weak symbols such as _kallsyms_addresses. These could then trigger
BUG_ONs in kallsyms code.

This is fixed by removing the KALLSYMS addition from the architecture
Makefile, and using CONFIG_SYMBOL_PREFIX in the link-vmlinux.sh script
to determine whether to add the --symbol-prefix argument.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Signed-off-by: Bob Liu <lliubbo@gmail.com>

arch/blackfin/Makefile

@@ -20,7 +20,6 @@ endif
 KBUILD_AFLAGS           += $(call cc-option,-mno-fdpic)
 KBUILD_CFLAGS_MODULE    += -mlong-calls
 LDFLAGS                 += -m elf32bfin
-KALLSYMS         += --symbol-prefix=_
 
 KBUILD_DEFCONFIG := BF537-STAMP_defconfig
 

scripts/link-vmlinux.sh

@@ -74,8 +74,13 @@ kallsyms()
 	info KSYM ${2}
 	local kallsymopt;
 
+	if [ -n "${CONFIG_SYMBOL_PREFIX}" ]; then
+		kallsymopt="${kallsymopt} \
+			    --symbol-prefix=${CONFIG_SYMBOL_PREFIX}"
+	fi
+
 	if [ -n "${CONFIG_KALLSYMS_ALL}" ]; then
-		kallsymopt=--all-symbols
+		kallsymopt="${kallsymopt} --all-symbols"
 	fi
 
 	local aflags="${KBUILD_AFLAGS} ${KBUILD_AFLAGS_KERNEL}               \