[PATCH v3 09/16] objtool: Use target file endianness instead of a compiled constant

Sathvika Vasireddy
2022-09-12T08:22:25Z

From: Christophe Leroy <christophe.leroy@csgroup.eu>

Some architectures like powerpc support both endianness, it's
therefore not possible to fix the endianness via arch/endianness.h
because there is no easy way to get the target endianness at
build time.

Use the endianness recorded in the file objtool is working on.

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
.../arch/x86/include/arch/endianness.h | 9 ------
tools/objtool/check.c | 2 +-
tools/objtool/include/objtool/endianness.h | 32 +++++++++----------
tools/objtool/orc_dump.c | 11 +++++--
tools/objtool/orc_gen.c | 4 +--
tools/objtool/special.c | 3 +-
6 files changed, 30 insertions(+), 31 deletions(-)
delete mode 100644 tools/objtool/arch/x86/include/arch/endianness.h

diff --git a/tools/objtool/arch/x86/include/arch/endianness.h b/tools/objtool/arch/x86/include/arch/endianness.h
deleted file mode 100644
index 7c362527da20..000000000000
--- a/tools/objtool/arch/x86/include/arch/endianness.h
+++ /dev/null
@@ -1,9 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0-or-later */
-#ifndef _ARCH_ENDIANNESS_H
-#define _ARCH_ENDIANNESS_H
-
-#include <endian.h>
-
-#define __TARGET_BYTE_ORDER __LITTLE_ENDIAN
-
-#endif /* _ARCH_ENDIANNESS_H */
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index fe935f19447b..c36e7a020d80 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -2077,7 +2077,7 @@ static int read_unwind_hints(struct objtool_file *file)
return -1;
}

- cfi.cfa.offset = bswap_if_needed(hint->sp_offset);
+ cfi.cfa.offset = bswap_if_needed(file->elf, hint->sp_offset);
cfi.type = hint->type;
cfi.end = hint->end;

diff --git a/tools/objtool/include/objtool/endianness.h b/tools/objtool/include/objtool/endianness.h
index 10241341eff3..4d2aa9b0fe2f 100644
--- a/tools/objtool/include/objtool/endianness.h
+++ b/tools/objtool/include/objtool/endianness.h
@@ -2,33 +2,33 @@
#ifndef _OBJTOOL_ENDIANNESS_H
#define _OBJTOOL_ENDIANNESS_H

-#include <arch/endianness.h>
#include <linux/kernel.h>
#include <endian.h>
-
-#ifndef __TARGET_BYTE_ORDER
-#error undefined arch __TARGET_BYTE_ORDER
-#endif
-
-#if __BYTE_ORDER != __TARGET_BYTE_ORDER
-#define __NEED_BSWAP 1
-#else
-#define __NEED_BSWAP 0
-#endif
+#include <objtool/elf.h>

/*
- * Does a byte swap if target endianness doesn't match the host, i.e. cross
+ * Does a byte swap if target file endianness doesn't match the host, i.e. cross
* compilation for little endian on big endian and vice versa.
* To be used for multi-byte values conversion, which are read from / about
* to be written to a target native endianness ELF file.
*/
-#define bswap_if_needed(val) \
+static inline bool need_bswap(struct elf *elf)
+{
+ return (__BYTE_ORDER == __LITTLE_ENDIAN) ^
+ (elf->ehdr.e_ident[EI_DATA] == ELFDATA2LSB);
+}
+
+#define bswap_if_needed(elf, val) \
({ \
__typeof__(val) __ret; \
+ bool __need_bswap = need_bswap(elf); \
switch (sizeof(val)) { \
- case 8: __ret = __NEED_BSWAP ? bswap_64(val) : (val); break; \
- case 4: __ret = __NEED_BSWAP ? bswap_32(val) : (val); break; \
- case 2: __ret = __NEED_BSWAP ? bswap_16(val) : (val); break; \
+ case 8: \
+ __ret = __need_bswap ? bswap_64(val) : (val); break; \
+ case 4: \
+ __ret = __need_bswap ? bswap_32(val) : (val); break; \
+ case 2: \
+ __ret = __need_bswap ? bswap_16(val) : (val); break; \
default: \
BUILD_BUG(); break; \
} \
diff --git a/tools/objtool/orc_dump.c b/tools/objtool/orc_dump.c
index f5a8508c42d6..4f1211fec82c 100644
--- a/tools/objtool/orc_dump.c
+++ b/tools/objtool/orc_dump.c
@@ -76,6 +76,7 @@ int orc_dump(const char *_objname)
GElf_Rela rela;
GElf_Sym sym;
Elf_Data *data, *symtab = NULL, *rela_orc_ip = NULL;
+ struct elf dummy_elf = {};

objname = _objname;
@@ -94,6 +95,12 @@ int orc_dump(const char *_objname)
return -1;
}

+ if (!elf64_getehdr(elf)) {
+ WARN_ELF("elf64_getehdr");
+ return -1;
+ }
+ memcpy(&dummy_elf.ehdr, elf64_getehdr(elf), sizeof(dummy_elf.ehdr));
+
if (elf_getshdrnum(elf, &nr_sections)) {
WARN_ELF("elf_getshdrnum");
return -1;
@@ -198,11 +205,11 @@ int orc_dump(const char *_objname)

printf(" sp:");

- print_reg(orc[i].sp_reg, bswap_if_needed(orc[i].sp_offset));
+ print_reg(orc[i].sp_reg, bswap_if_needed(&dummy_elf, orc[i].sp_offset));

printf(" bp:");

- print_reg(orc[i].bp_reg, bswap_if_needed(orc[i].bp_offset));
+ print_reg(orc[i].bp_reg, bswap_if_needed(&dummy_elf, orc[i].bp_offset));

printf(" type:%s end:%d\n",
orc_type_name(orc[i].type), orc[i].end);
diff --git a/tools/objtool/orc_gen.c b/tools/objtool/orc_gen.c
index dd3c64af9db2..1f22b7ebae58 100644
--- a/tools/objtool/orc_gen.c
+++ b/tools/objtool/orc_gen.c
@@ -97,8 +97,8 @@ static int write_orc_entry(struct elf *elf, struct section *orc_sec,
/* populate ORC data */
orc = (struct orc_entry *)orc_sec->data->d_buf + idx;
memcpy(orc, o, sizeof(*orc));
- orc->sp_offset = bswap_if_needed(orc->sp_offset);
- orc->bp_offset = bswap_if_needed(orc->bp_offset);
+ orc->sp_offset = bswap_if_needed(elf, orc->sp_offset);
+ orc->bp_offset = bswap_if_needed(elf, orc->bp_offset);

/* populate reloc for ip */
if (elf_add_reloc_to_insn(elf, ip_sec, idx * sizeof(int), R_X86_64_PC32,
diff --git a/tools/objtool/special.c b/tools/objtool/special.c
index e2223dd91c37..9c8d827f69af 100644
--- a/tools/objtool/special.c
+++ b/tools/objtool/special.c
@@ -87,7 +87,8 @@ static int get_alt_entry(struct elf *elf, struct special_entry *entry,
if (entry->feature) {
unsigned short feature;

- feature = bswap_if_needed(*(unsigned short *)(sec->data->d_buf +
+ feature = bswap_if_needed(elf,
+ *(unsigned short *)(sec->data->d_buf +
offset +
entry->feature));
arch_handle_alternative(feature, alt);
--
2.31.1