linux-kernel - [tip: objtool/core] objtool: Fix reloc generation on big endian cross-compiles

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Date:   Mon, 18 Jan 2021 10:13:31 -0000
From:   "tip-bot2 for Martin Schwidefsky" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Martin Schwidefsky <schwidefsky@...ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: objtool/core] objtool: Fix reloc generation on big endian
 cross-compiles

The following commit has been merged into the objtool/core branch of tip:

Commit-ID:     a1a664ece586457e9f7652b0bc5b08386259e358
Gitweb:        https://git.kernel.org/tip/a1a664ece586457e9f7652b0bc5b08386259e358
Author:        Martin Schwidefsky <schwidefsky@...ibm.com>
AuthorDate:    Fri, 13 Nov 2020 00:03:26 +01:00
Committer:     Josh Poimboeuf <jpoimboe@...hat.com>
CommitterDate: Wed, 13 Jan 2021 18:13:12 -06:00

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@...ibm.com>
Co-developed-by: Vasily Gorbik <gor@...ux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@...ux.ibm.com>
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Acked-by: Masami Hiramatsu <mhiramat@...nel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
---
 tools/objtool/elf.c | 34 +++++++++++++++++++---------------
 1 file changed, 19 insertions(+), 15 deletions(-)

diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index be89c74..c784122 100644
--- a/tools/objtool/elf.c
+++ b/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++;
 	}