objtool: Create reloc sections implicitly

Have elf_add_reloc() create the relocation section implicitly.

Suggested-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lkml.kernel.org/r/20210326151259.880174448@infradead.org

Author: Peter Zijlstra

tools/objtool/check.c

@@ -459,9 +459,6 @@ static int create_static_call_sections(struct objtool_file *file)
 	if (!sec)
 		return -1;
 
-	if (!elf_create_reloc_section(file->elf, sec, SHT_RELA))
-		return -1;
-
 	idx = 0;
 	list_for_each_entry(insn, &file->static_call_list, static_call_node) {
 
@@ -547,9 +544,6 @@ static int create_mcount_loc_sections(struct objtool_file *file)
 	if (!sec)
 		return -1;
 
-	if (!elf_create_reloc_section(file->elf, sec, SHT_RELA))
-		return -1;
-
 	idx = 0;
 	list_for_each_entry(insn, &file->mcount_loc_list, mcount_loc_node) {
 

tools/objtool/elf.c

@@ -447,11 +447,18 @@ static int read_symbols(struct elf *elf)
 	return -1;
 }
 
+static struct section *elf_create_reloc_section(struct elf *elf,
+						struct section *base,
+						int reltype);
+
 int elf_add_reloc(struct elf *elf, struct section *sec, unsigned long offset,
 		  unsigned int type, struct symbol *sym, int addend)
 {
 	struct reloc *reloc;
 
+	if (!sec->reloc && !elf_create_reloc_section(elf, sec, SHT_RELA))
+		return -1;
+
 	reloc = malloc(sizeof(*reloc));
 	if (!reloc) {
 		perror("malloc");
@@ -829,7 +836,7 @@ static struct section *elf_create_rela_reloc_section(struct elf *elf, struct sec
 	return sec;
 }
 
-struct section *elf_create_reloc_section(struct elf *elf,
+static struct section *elf_create_reloc_section(struct elf *elf,
 					 struct section *base,
 					 int reltype)
 {

tools/objtool/include/objtool/elf.h

@@ -122,7 +122,6 @@ static inline u32 reloc_hash(struct reloc *reloc)
 
 struct elf *elf_open_read(const char *name, int flags);
 struct section *elf_create_section(struct elf *elf, const char *name, unsigned int sh_flags, size_t entsize, int nr);
-struct section *elf_create_reloc_section(struct elf *elf, struct section *base, int reltype);
 
 int elf_add_reloc(struct elf *elf, struct section *sec, unsigned long offset,
 		  unsigned int type, struct symbol *sym, int addend);

tools/objtool/orc_gen.c

@@ -225,8 +225,6 @@ int orc_create(struct objtool_file *file)
 	sec = elf_create_section(file->elf, ".orc_unwind_ip", 0, sizeof(int), nr);
 	if (!sec)
 		return -1;
-	if (!elf_create_reloc_section(file->elf, sec, SHT_RELA))
-		return -1;
 
 	/* Write ORC entries to sections: */
 	list_for_each_entry(entry, &orc_list, list) {