kpatch-build: do symbol/section bundling in create-diff-object

kpatch-build/create-diff-object.c

@@ -81,6 +81,102 @@ struct special_section {
  * Functions
  * **********/
 
+static int is_bundleable(struct symbol *sym)
+{
+	if (sym->type == STT_FUNC &&
+	    !strncmp(sym->sec->name, ".text.",6) &&
+	    !strcmp(sym->sec->name + 6, sym->name))
+		return 1;
+
+	if (sym->type == STT_FUNC &&
+	    !strncmp(sym->sec->name, ".text.unlikely.",15) &&
+	    !strcmp(sym->sec->name + 15, sym->name))
+		return 1;
+
+	if (sym->type == STT_OBJECT &&
+	   !strncmp(sym->sec->name, ".data.",6) &&
+	   !strcmp(sym->sec->name + 6, sym->name))
+		return 1;
+
+	if (sym->type == STT_OBJECT &&
+	   !strncmp(sym->sec->name, ".rodata.",8) &&
+	   !strcmp(sym->sec->name + 8, sym->name))
+		return 1;
+
+	if (sym->type == STT_OBJECT &&
+	   !strncmp(sym->sec->name, ".bss.",5) &&
+	   !strcmp(sym->sec->name + 5, sym->name))
+		return 1;
+
+	return 0;
+}
+
+#ifdef __powerpc__
+/* Symbol st_others value for powerpc */
+#define STO_PPC64_LOCAL_BIT     5
+#define STO_PPC64_LOCAL_MASK    (7 << STO_PPC64_LOCAL_BIT)
+#define PPC64_LOCAL_ENTRY_OFFSET(other)                                 \
+	        (((1 << (((other) & STO_PPC64_LOCAL_MASK) >> STO_PPC64_LOCAL_BIT)) >> 2) << 2)
+
+/*
+ * On ppc64le, the function prologue generated by GCC 6+ has the sequence:
+ *
+ *	.globl my_func
+ *	.type my_func, @function
+ *	.quad .TOC.-my_func
+ * my_func:
+ *	.reloc ., R_PPC64_ENTRY ; optional
+ *	ld r2,-8(r12)
+ *	add r2,r2,r12
+ *	.localentry my_func, .-my_func
+ *
+ * my_func is the global entry point, which, when called, sets up the TOC.
+ * .localentry is the local entry point, for calls to the function from within
+ * the object file.  The local entry point is 8 bytes after the global entry
+ * point.
+ */
+static int is_localentry_sym(struct symbol *sym)
+{
+	if (sym->type != STT_FUNC || sym->sym.st_shndx == SHN_UNDEF)
+		return 0;
+
+	if (sym->sym.st_value != 0x8)
+		return 0;
+
+	if (!PPC64_LOCAL_ENTRY_OFFSET(sym->sym.st_other))
+		return 0;
+
+	return 1;
+}
+#else
+static int is_localentry_sym(struct symbol *sym)
+{
+	return 0;
+}
+#endif
+
+/*
+ * When compiling with -ffunction-sections and -fdata-sections, almost every
+ * symbol gets its own dedicated section.  We call such symbols "bundled"
+ * symbols.  They're indicated by "sym->sec->sym == sym".
+ */
+static void kpatch_bundle_symbols(struct kpatch_elf *kelf)
+{
+	struct symbol *sym;
+
+	list_for_each_entry(sym, &kelf->symbols, list) {
+		if (is_bundleable(sym)) {
+			if (sym->sym.st_value != 0 && !is_localentry_sym(sym)) {
+				ERROR("symbol %s at offset %lu within section %s, expected 0",
+				      sym->name, sym->sym.st_value,
+				      sym->sec->name);
+			}
+
+			sym->sec->sym = sym;
+		}
+	}
+}
+
 /*
  * This function detects whether the given symbol is a "special" static local
  * variable (for lack of a better term).
@@ -2713,6 +2809,9 @@ int main(int argc, char *argv[])
 	kelf_base = kpatch_elf_open(arguments.args[0]);
 	kelf_patched = kpatch_elf_open(arguments.args[1]);
 
+	kpatch_bundle_symbols(kelf_base);
+	kpatch_bundle_symbols(kelf_patched);
+
 	kpatch_compare_elf_headers(kelf_base->elf, kelf_patched->elf);
 	kpatch_check_program_headers(kelf_base->elf);
 	kpatch_check_program_headers(kelf_patched->elf);

kpatch-build/create-klp-module.c

@@ -155,9 +155,9 @@ static struct section *find_or_add_klp_relasec(struct kpatch_elf *kelf,
 static void create_klp_relasecs_and_syms(struct kpatch_elf *kelf, struct section *krelasec,
 					 struct section *ksymsec, char *strings)
 {
-	struct section *base, *klp_relasec;
+	struct section *klp_relasec;
 	struct kpatch_relocation *krelas;
-	struct symbol *sym;
+	struct symbol *sym, *dest;
 	struct rela *rela;
 	char *objname;
 	int nr, index, offset, toc_offset;
@@ -207,9 +207,7 @@ static void create_klp_relasecs_and_syms(struct kpatch_elf *kelf, struct section
 		 */
 		toc_offset = rela->addend;
 
-		base = rela->sym->sec;
-		if (!base)
-			ERROR("base sec of krela not found");
+		dest = rela->sym;
 
 		/* Get the name of the object the rela belongs to */
 		rela = find_rela_by_offset(krelasec->rela,
@@ -232,19 +230,19 @@ static void create_klp_relasecs_and_syms(struct kpatch_elf *kelf, struct section
 		if (!sym)
 			ERROR("error finding or adding ksym to symtab");
 
-		/* Create (or find) the .klp.rela. section for this base sec and object */
-		klp_relasec = find_or_add_klp_relasec(kelf, base, objname);
+		/* Create (or find) the .klp.rela. section for this dest sec and object */
+		klp_relasec = find_or_add_klp_relasec(kelf, dest->sec, objname);
 		if (!klp_relasec)
 			ERROR("error finding or adding klp relasec");
 
 		/* Add the rela to the .klp.rela. section */
 		ALLOC_LINK(rela, &klp_relasec->relas);
 		rela->sym = sym;
 		rela->type = krelas[index].type;
-		if (!strcmp(base->name, ".toc"))
+		if (!strcmp(dest->sec->name, ".toc"))
 			rela->offset = toc_offset;
 		else
-			rela->offset = krelas[index].offset;
+			rela->offset = krelas[index].offset + dest->sym.st_value;
 
 		/*
 		 * GCC 6+ adds 0x8 to the offset of every local function entry
@@ -253,7 +251,7 @@ static void create_klp_relasecs_and_syms(struct kpatch_elf *kelf, struct section
 		 * local function becomes global, we don't want to skip the
 		 * .toc setup anymore.
 		 */
-		if (!strcmp(base->name, ".toc") &&
+		if (!strcmp(dest->sec->name, ".toc") &&
 			rela->sym->type == STT_FUNC && rela->sym->bind == STB_LOCAL) {
 				rela->addend = 0;
 		} else {

kpatch-build/create-kpatch-module.c

@@ -43,7 +43,8 @@ static void create_dynamic_rela_sections(struct kpatch_elf *kelf, struct section
 	struct kpatch_patch_dynrela *dynrelas;
 	struct kpatch_relocation *krelas;
 	struct kpatch_symbol *ksym, *ksyms;
-	struct section *base, *dynsec;
+	struct section *dynsec;
+	struct symbol *sym;
 	struct rela *rela;
 	int index, nr, offset, dest_offset, objname_offset, name_offset;
 
@@ -58,19 +59,16 @@ static void create_dynamic_rela_sections(struct kpatch_elf *kelf, struct section
 		offset = index * sizeof(*krelas);
 
 		/*
-		 * To fill in each dynrela entry, find base section (dest),
+		 * To fill in each dynrela entry, find dest location,
 		 * objname offset, ksym, and symbol name offset
 		 */
 
-		/* Get base section */
+		/* Get dest location */
 		rela = find_rela_by_offset(krelasec->rela,
 					   offset + offsetof(struct kpatch_relocation, dest));
 		if (!rela)
 			ERROR("find_rela_by_offset");
-
-		base = rela->sym->sec;
-		if (!base)
-			ERROR("base sec of krela not found");
+		sym = rela->sym;
 		dest_offset = rela->addend;
 
 		/* Get objname offset */
@@ -103,7 +101,7 @@ static void create_dynamic_rela_sections(struct kpatch_elf *kelf, struct section
 
 		/* dest */
 		ALLOC_LINK(rela, &dynsec->rela->relas);
-		rela->sym = base->sym ? base->sym : base->secsym;
+		rela->sym = sym;
 		rela->type = R_X86_64_64;
 		rela->addend = dest_offset;
 		rela->offset = index * sizeof(*dynrelas);

kpatch-build/kpatch-elf.c

@@ -76,46 +76,6 @@ int is_debug_section(struct section *sec)
 	       !strncmp(name, ".eh_frame", 9);
 }
 
-#ifdef __powerpc__
-
-/* Symbol st_others value for powerpc */
-#define STO_PPC64_LOCAL_BIT     5
-#define STO_PPC64_LOCAL_MASK    (7 << STO_PPC64_LOCAL_BIT)
-#define PPC64_LOCAL_ENTRY_OFFSET(other)                                 \
-	        (((1 << (((other) & STO_PPC64_LOCAL_MASK) >> STO_PPC64_LOCAL_BIT)) >> 2) << 2)
-
-/*
- * On ppc64le, the function prologue generated by GCC 6+ has the sequence:
- *
- *	.globl my_func
- *	.type my_func, @function
- *	.quad .TOC.-my_func
- * my_func:
- *	.reloc ., R_PPC64_ENTRY ; optional
- *	ld r2,-8(r12)
- *	add r2,r2,r12
- *	.localentry my_func, .-my_func
- *
- * my_func is the global entry point, which, when called, sets up the TOC.
- * .localentry is the local entry point, for calls to the function from within
- * the object file.  The local entry point is 8 bytes after the global entry
- * point.
- */
-static int is_localentry_sym(struct symbol *sym)
-{
-	if (sym->type != STT_FUNC || sym->sym.st_shndx == SHN_UNDEF)
-		return 0;
-
-	if (sym->sym.st_value != 0x8)
-		return 0;
-
-	if (!PPC64_LOCAL_ENTRY_OFFSET(sym->sym.st_other))
-		return 0;
-
-	return 1;
-}
-#endif
-
 struct section *find_section_by_index(struct list_head *list, unsigned int index)
 {
 	struct section *sec;
@@ -299,36 +259,6 @@ void kpatch_create_section_list(struct kpatch_elf *kelf)
 		ERROR("expected NULL");
 }
 
-static int is_bundleable(struct symbol *sym)
-{
-	if (sym->type == STT_FUNC &&
-	    !strncmp(sym->sec->name, ".text.",6) &&
-	    !strcmp(sym->sec->name + 6, sym->name))
-		return 1;
-
-	if (sym->type == STT_FUNC &&
-	    !strncmp(sym->sec->name, ".text.unlikely.",15) &&
-	    !strcmp(sym->sec->name + 15, sym->name))
-		return 1;
-
-	if (sym->type == STT_OBJECT &&
-	   !strncmp(sym->sec->name, ".data.",6) &&
-	   !strcmp(sym->sec->name + 6, sym->name))
-		return 1;
-
-	if (sym->type == STT_OBJECT &&
-	   !strncmp(sym->sec->name, ".rodata.",8) &&
-	   !strcmp(sym->sec->name + 8, sym->name))
-		return 1;
-
-	if (sym->type == STT_OBJECT &&
-	   !strncmp(sym->sec->name, ".bss.",5) &&
-	   !strcmp(sym->sec->name + 5, sym->name))
-		return 1;
-
-	return 0;
-}
-
 void kpatch_create_symbol_list(struct kpatch_elf *kelf)
 {
 	struct section *symtab;
@@ -367,18 +297,7 @@ void kpatch_create_symbol_list(struct kpatch_elf *kelf)
 				ERROR("couldn't find section for symbol %s\n",
 					sym->name);
 
-			if (is_bundleable(sym)) {
-				if (sym->sym.st_value != 0) {
-#ifdef __powerpc__
-					if (!is_localentry_sym(sym))
-#endif
-					ERROR("symbol %s at offset %lu within section %s, expected 0",
-						sym->name, sym->sym.st_value, sym->sec->name);
-				}
-
-				sym->sec->sym = sym;
-
-			} else if (sym->type == STT_SECTION) {
+			if (sym->type == STT_SECTION) {
 				sym->sec->secsym = sym;
 				/* use the section name as the symbol name */
 				sym->name = sym->sec->name;