CONFIG_SYMBOL_PREFIX: cleanup.

We have CONFIG_SYMBOL_PREFIX, which three archs define to the string
"_".  But Al Viro broke this in "consolidate cond_syscall and
SYSCALL_ALIAS declarations" (in linux-next), and he's not the first to
do so.

Using CONFIG_SYMBOL_PREFIX is awkward, since we usually just want to
prefix it so something.  So various places define helpers which are
defined to nothing if CONFIG_SYMBOL_PREFIX isn't set:

1) include/asm-generic/unistd.h defines __SYMBOL_PREFIX.
2) include/asm-generic/vmlinux.lds.h defines VMLINUX_SYMBOL(sym)
3) include/linux/export.h defines MODULE_SYMBOL_PREFIX.
4) include/linux/kernel.h defines SYMBOL_PREFIX (which differs from #7)
5) kernel/modsign_certificate.S defines ASM_SYMBOL(sym)
6) scripts/modpost.c defines MODULE_SYMBOL_PREFIX
7) scripts/Makefile.lib defines SYMBOL_PREFIX on the commandline if
   CONFIG_SYMBOL_PREFIX is set, so that we have a non-string version
   for pasting.

(arch/h8300/include/asm/linkage.h defines SYMBOL_NAME(), too).

Let's solve this properly:
1) No more generic prefix, just CONFIG_HAVE_UNDERSCORE_SYMBOL_PREFIX.
2) Make linux/export.h usable from asm.
3) Define VMLINUX_SYMBOL() and VMLINUX_SYMBOL_STR().
4) Make everyone use them.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Reviewed-by: James Hogan <james.hogan@imgtec.com>
Tested-by: James Hogan <james.hogan@imgtec.com> (metag)

3 files changed, 17 insertions, 31 deletions

diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 07125e697d7a..a373a1f66023 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -119,13 +119,6 @@ _c_flags += $(if $(patsubst n%,, \
                 $(CFLAGS_GCOV))
 endif
 
-ifdef CONFIG_SYMBOL_PREFIX
-_sym_flags = -DSYMBOL_PREFIX=$(patsubst "%",%,$(CONFIG_SYMBOL_PREFIX))
-_cpp_flags += $(_sym_flags)
-_a_flags += $(_sym_flags)
-endif
-
-
 # If building the kernel in a separate objtree expand all occurrences
 # of -Idir to -I$(srctree)/dir except for absolute paths (starting with '/').
 
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index 3d569d6022c2..014994936b1c 100644
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -74,9 +74,8 @@ kallsyms()
         info KSYM ${2}
         local kallsymopt;
 
-        if [ -n "${CONFIG_SYMBOL_PREFIX}" ]; then
-                kallsymopt="${kallsymopt} \
-                            --symbol-prefix=${CONFIG_SYMBOL_PREFIX}"
+        if [ -n "${CONFIG_HAVE_UNDERSCORE_SYMBOL_PREFIX}" ]; then
+                kallsymopt="${kallsymopt} --symbol-prefix=_"
         fi
 
         if [ -n "${CONFIG_KALLSYMS_ALL}" ]; then
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 78b30c1548e9..282decfa29ae 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -18,14 +18,7 @@
 #include "modpost.h"
 #include "../../include/generated/autoconf.h"
 #include "../../include/linux/license.h"
-
-/* Some toolchains use a `_' prefix for all user symbols. */
-#ifdef CONFIG_SYMBOL_PREFIX
-#define MODULE_SYMBOL_PREFIX CONFIG_SYMBOL_PREFIX
-#else
-#define MODULE_SYMBOL_PREFIX ""
-#endif
-
+#include "../../include/linux/export.h"
 
 /* Are we using CONFIG_MODVERSIONS? */
 int modversions = 0;
@@ -562,7 +555,7 @@ static void parse_elf_finish(struct elf_info *info)
 static int ignore_undef_symbol(struct elf_info *info, const char *symname)
 {
         /* ignore __this_module, it will be resolved shortly */
-        if (strcmp(symname, MODULE_SYMBOL_PREFIX "__this_module") == 0)
+        if (strcmp(symname, VMLINUX_SYMBOL_STR(__this_module)) == 0)
                 return 1;
         /* ignore global offset table */
         if (strcmp(symname, "_GLOBAL_OFFSET_TABLE_") == 0)
@@ -583,8 +576,8 @@ static int ignore_undef_symbol(struct elf_info *info, const char *symname)
         return 0;
 }
 
-#define CRC_PFX     MODULE_SYMBOL_PREFIX "__crc_"
-#define KSYMTAB_PFX MODULE_SYMBOL_PREFIX "__ksymtab_"
+#define CRC_PFX     VMLINUX_SYMBOL_STR(__crc_)
+#define KSYMTAB_PFX VMLINUX_SYMBOL_STR(__ksymtab_)
 
 static void handle_modversions(struct module *mod, struct elf_info *info,
                                Elf_Sym *sym, const char *symname)
@@ -637,14 +630,15 @@ static void handle_modversions(struct module *mod, struct elf_info *info,
                 }
 #endif
 
-                if (memcmp(symname, MODULE_SYMBOL_PREFIX,
-                           strlen(MODULE_SYMBOL_PREFIX)) == 0) {
-                        mod->unres =
-                          alloc_symbol(symname +
-                                       strlen(MODULE_SYMBOL_PREFIX),
-                                       ELF_ST_BIND(sym->st_info) == STB_WEAK,
-                                       mod->unres);
-                }
+#ifdef CONFIG_HAVE_UNDERSCORE_SYMBOL_PREFIX
+                if (symname[0] != '_')
+                        break;
+                else
+                        symname++;
+#endif
+                mod->unres = alloc_symbol(symname,
+                                          ELF_ST_BIND(sym->st_info) == STB_WEAK,
+                                          mod->unres);
                 break;
         default:
                 /* All exported symbols */
@@ -652,9 +646,9 @@ static void handle_modversions(struct module *mod, struct elf_info *info,
                         sym_add_exported(symname + strlen(KSYMTAB_PFX), mod,
                                         export);
                 }
-                if (strcmp(symname, MODULE_SYMBOL_PREFIX "init_module") == 0)
+                if (strcmp(symname, VMLINUX_SYMBOL_STR(init_module)) == 0)
                         mod->has_init = 1;
-                if (strcmp(symname, MODULE_SYMBOL_PREFIX "cleanup_module") == 0)
+                if (strcmp(symname, VMLINUX_SYMBOL_STR(cleanup_module)) == 0)
                         mod->has_cleanup = 1;
                 break;
         }