[stable-only] Revert "powerpc: Simplify module TOC handling"

This reverts commit 504017f7.

Breaks ppc64 builds on hosts which don't include the kmod patch:
  "depmod: Ignore PowerPC64 ABIv2 .TOC. symbol"
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

arch/powerpc/kernel/misc_64.S

@@ -634,3 +634,31 @@ _GLOBAL(kexec_sequence)
 	li	r5,0
 	blr	/* image->start(physid, image->start, 0); */
 #endif /* CONFIG_KEXEC */
+
+#ifdef CONFIG_MODULES
+#if defined(_CALL_ELF) && _CALL_ELF == 2
+
+#ifdef CONFIG_MODVERSIONS
+.weak __crc_TOC.
+.section "___kcrctab+TOC.","a"
+.globl __kcrctab_TOC.
+__kcrctab_TOC.:
+	.llong	__crc_TOC.
+#endif
+
+/*
+ * Export a fake .TOC. since both modpost and depmod will complain otherwise.
+ * Both modpost and depmod strip the leading . so we do the same here.
+ */
+.section "__ksymtab_strings","a"
+__kstrtab_TOC.:
+	.asciz "TOC."
+
+.section "___ksymtab+TOC.","a"
+/* This symbol name is important: it's used by modpost to find exported syms */
+.globl __ksymtab_TOC.
+__ksymtab_TOC.:
+	.llong 0 /* .value */
+	.llong __kstrtab_TOC.
+#endif /* ELFv2 */
+#endif /* MODULES */

arch/powerpc/kernel/module_64.c

@@ -326,10 +326,7 @@ static void dedotify_versions(struct modversion_info *vers,
 		}
 }
 
-/*
- * Undefined symbols which refer to .funcname, hack to funcname. Make .TOC.
- * seem to be defined (value set later).
- */
+/* Undefined symbols which refer to .funcname, hack to funcname (or .TOC.) */
 static void dedotify(Elf64_Sym *syms, unsigned int numsyms, char *strtab)
 {
 	unsigned int i;
@@ -337,11 +334,8 @@ static void dedotify(Elf64_Sym *syms, unsigned int numsyms, char *strtab)
 	for (i = 1; i < numsyms; i++) {
 		if (syms[i].st_shndx == SHN_UNDEF) {
 			char *name = strtab + syms[i].st_name;
-			if (name[0] == '.') {
-				if (strcmp(name+1, "TOC.") == 0)
-					syms[i].st_shndx = SHN_ABS;
+			if (name[0] == '.')
 				memmove(name, name+1, strlen(name));
-			}
 		}
 	}
 }
@@ -357,7 +351,7 @@ static Elf64_Sym *find_dot_toc(Elf64_Shdr *sechdrs,
 	numsyms = sechdrs[symindex].sh_size / sizeof(Elf64_Sym);
 
 	for (i = 1; i < numsyms; i++) {
-		if (syms[i].st_shndx == SHN_ABS
+		if (syms[i].st_shndx == SHN_UNDEF
 		    && strcmp(strtab + syms[i].st_name, "TOC.") == 0)
 			return &syms[i];
 	}

scripts/mod/modpost.c

@@ -593,8 +593,7 @@ static int ignore_undef_symbol(struct elf_info *info, const char *symname)
 		if (strncmp(symname, "_restgpr0_", sizeof("_restgpr0_") - 1) == 0 ||
 		    strncmp(symname, "_savegpr0_", sizeof("_savegpr0_") - 1) == 0 ||
 		    strncmp(symname, "_restvr_", sizeof("_restvr_") - 1) == 0 ||
-		    strncmp(symname, "_savevr_", sizeof("_savevr_") - 1) == 0 ||
-		    strcmp(symname, ".TOC.") == 0)
+		    strncmp(symname, "_savevr_", sizeof("_savevr_") - 1) == 0)
 			return 1;
 	/* Do not ignore this symbol */
 	return 0;