objtool: Fix reloc generation on big endian cross-compiles

Relocations generated in elf_rebuild_rel[a]_reloc_section() are broken
if objtool is built and run on a big endian system.

The following errors pop up during x86 cross-compilation:

  x86_64-9.1.0-ld: fs/efivarfs/inode.o: bad reloc symbol index (0x2000000 >= 0x22) for offset 0 in section `.orc_unwind_ip'
  x86_64-9.1.0-ld: final link failed: bad value

Convert those functions to use gelf_update_rel[a](), similar to what
elf_write_reloc() does.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Co-developed-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>

tools/objtool/elf.c

@@ -855,25 +855,27 @@ static int elf_rebuild_rel_reloc_section(struct section *sec, int nr)
 {
 	struct reloc *reloc;
 	int idx = 0, size;
-	GElf_Rel *relocs;
+	void *buf;
 
 	/* Allocate a buffer for relocations */
-	size = nr * sizeof(*relocs);
-	relocs = malloc(size);
-	if (!relocs) {
+	size = nr * sizeof(GElf_Rel);
+	buf = malloc(size);
+	if (!buf) {
 		perror("malloc");
 		return -1;
 	}
 
-	sec->data->d_buf = relocs;
+	sec->data->d_buf = buf;
 	sec->data->d_size = size;
+	sec->data->d_type = ELF_T_REL;
 
 	sec->sh.sh_size = size;
 
 	idx = 0;
 	list_for_each_entry(reloc, &sec->reloc_list, list) {
-		relocs[idx].r_offset = reloc->offset;
-		relocs[idx].r_info = GELF_R_INFO(reloc->sym->idx, reloc->type);
+		reloc->rel.r_offset = reloc->offset;
+		reloc->rel.r_info = GELF_R_INFO(reloc->sym->idx, reloc->type);
+		gelf_update_rel(sec->data, idx, &reloc->rel);
 		idx++;
 	}
 
@@ -884,26 +886,28 @@ static int elf_rebuild_rela_reloc_section(struct section *sec, int nr)
 {
 	struct reloc *reloc;
 	int idx = 0, size;
-	GElf_Rela *relocs;
+	void *buf;
 
 	/* Allocate a buffer for relocations with addends */
-	size = nr * sizeof(*relocs);
-	relocs = malloc(size);
-	if (!relocs) {
+	size = nr * sizeof(GElf_Rela);
+	buf = malloc(size);
+	if (!buf) {
 		perror("malloc");
 		return -1;
 	}
 
-	sec->data->d_buf = relocs;
+	sec->data->d_buf = buf;
 	sec->data->d_size = size;
+	sec->data->d_type = ELF_T_RELA;
 
 	sec->sh.sh_size = size;
 
 	idx = 0;
 	list_for_each_entry(reloc, &sec->reloc_list, list) {
-		relocs[idx].r_offset = reloc->offset;
-		relocs[idx].r_addend = reloc->addend;
-		relocs[idx].r_info = GELF_R_INFO(reloc->sym->idx, reloc->type);
+		reloc->rela.r_offset = reloc->offset;
+		reloc->rela.r_addend = reloc->addend;
+		reloc->rela.r_info = GELF_R_INFO(reloc->sym->idx, reloc->type);
+		gelf_update_rela(sec->data, idx, &reloc->rela);
 		idx++;
 	}