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Subject[RFC PATCH v4 4/4] objtool: fix x86 orc generation on big endian cross compiles
Correct objtool orc generation endianness problems to enable fully
functional x86 cross compiles on big endian hardware.

Introduces bswap_if_needed macro which does a byte swap if target
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.

Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

diff --git a/arch/x86/include/asm/orc_types.h b/arch/x86/include/asm/orc_types.h
index fdbffec4cfde..5a2baf28a1dc 100644
--- a/arch/x86/include/asm/orc_types.h
+++ b/arch/x86/include/asm/orc_types.h
@@ -40,6 +40,8 @@
#define ORC_REG_MAX 15

#ifndef __ASSEMBLY__
+#include <asm/byteorder.h>
+
/*
* This struct is more or less a vastly simplified version of the DWARF Call
* Frame Information standard. It contains only the necessary parts of DWARF
@@ -51,10 +53,18 @@
struct orc_entry {
s16 sp_offset;
s16 bp_offset;
+#if defined(__LITTLE_ENDIAN_BITFIELD)
unsigned sp_reg:4;
unsigned bp_reg:4;
unsigned type:2;
unsigned end:1;
+#elif defined(__BIG_ENDIAN_BITFIELD)
+ unsigned bp_reg:4;
+ unsigned sp_reg:4;
+ unsigned unused:5;
+ unsigned end:1;
+ unsigned type:2;
+#endif
} __packed;

#endif /* __ASSEMBLY__ */
diff --git a/tools/arch/x86/include/asm/orc_types.h b/tools/arch/x86/include/asm/orc_types.h
index fdbffec4cfde..5a2baf28a1dc 100644
--- a/tools/arch/x86/include/asm/orc_types.h
+++ b/tools/arch/x86/include/asm/orc_types.h
@@ -40,6 +40,8 @@
#define ORC_REG_MAX 15

#ifndef __ASSEMBLY__
+#include <asm/byteorder.h>
+
/*
* This struct is more or less a vastly simplified version of the DWARF Call
* Frame Information standard. It contains only the necessary parts of DWARF
@@ -51,10 +53,18 @@
struct orc_entry {
s16 sp_offset;
s16 bp_offset;
+#if defined(__LITTLE_ENDIAN_BITFIELD)
unsigned sp_reg:4;
unsigned bp_reg:4;
unsigned type:2;
unsigned end:1;
+#elif defined(__BIG_ENDIAN_BITFIELD)
+ unsigned bp_reg:4;
+ unsigned sp_reg:4;
+ unsigned unused:5;
+ unsigned end:1;
+ unsigned type:2;
+#endif
} __packed;

#endif /* __ASSEMBLY__ */
diff --git a/tools/objtool/arch/x86/include/arch_endianness.h b/tools/objtool/arch/x86/include/arch_endianness.h
new file mode 100644
index 000000000000..7c362527da20
--- /dev/null
+++ b/tools/objtool/arch/x86/include/arch_endianness.h
@@ -0,0 +1,9 @@
+/* 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 2df9f769412e..fd892b77e98f 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -13,6 +13,7 @@
#include "special.h"
#include "warn.h"
#include "arch_elf.h"
+#include "endianness.h"

#include <linux/objtool.h>
#include <linux/hashtable.h>
@@ -1370,7 +1371,7 @@ static int read_unwind_hints(struct objtool_file *file)
cfa = &insn->cfi.cfa;

if (hint->type == UNWIND_HINT_TYPE_RET_OFFSET) {
- insn->ret_offset = hint->sp_offset;
+ insn->ret_offset = bswap_if_needed(hint->sp_offset);
continue;
}

@@ -1382,7 +1383,7 @@ static int read_unwind_hints(struct objtool_file *file)
return -1;
}

- cfa->offset = hint->sp_offset;
+ cfa->offset = bswap_if_needed(hint->sp_offset);
insn->cfi.type = hint->type;
insn->cfi.end = hint->end;
}
diff --git a/tools/objtool/endianness.h b/tools/objtool/endianness.h
new file mode 100644
index 000000000000..ebece3191b58
--- /dev/null
+++ b/tools/objtool/endianness.h
@@ -0,0 +1,38 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef _OBJTOOL_ENDIANNESS_H
+#define _OBJTOOL_ENDIANNESS_H
+
+#include <linux/kernel.h>
+#include <endian.h>
+#include "arch_endianness.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
+
+/*
+ * Does a byte swap if target 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) \
+({ \
+ __typeof__(val) __ret; \
+ 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; \
+ default: \
+ BUILD_BUG(); break; \
+ } \
+ __ret; \
+})
+
+#endif /* _OBJTOOL_ENDIANNESS_H */
diff --git a/tools/objtool/orc_dump.c b/tools/objtool/orc_dump.c
index 5e6a95368d35..4e818a22e44b 100644
--- a/tools/objtool/orc_dump.c
+++ b/tools/objtool/orc_dump.c
@@ -8,6 +8,7 @@
#include <asm/orc_types.h>
#include "objtool.h"
#include "warn.h"
+#include "endianness.h"

static const char *reg_name(unsigned int reg)
{
@@ -197,11 +198,11 @@ int orc_dump(const char *_objname)

printf(" sp:");

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

printf(" bp:");

- print_reg(orc[i].bp_reg, orc[i].bp_offset);
+ print_reg(orc[i].bp_reg, bswap_if_needed(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 235663b96adc..134d7863093d 100644
--- a/tools/objtool/orc_gen.c
+++ b/tools/objtool/orc_gen.c
@@ -11,6 +11,7 @@

#include "check.h"
#include "warn.h"
+#include "endianness.h"

int create_orc(struct objtool_file *file)
{
@@ -96,6 +97,8 @@ static int create_orc_entry(struct elf *elf, struct section *u_sec, struct secti
/* populate ORC data */
orc = (struct orc_entry *)u_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);

/* populate reloc for ip */
reloc = malloc(sizeof(*reloc));
diff --git a/tools/objtool/special.c b/tools/objtool/special.c
index 1a2420febd08..ab7cb1e13411 100644
--- a/tools/objtool/special.c
+++ b/tools/objtool/special.c
@@ -15,6 +15,7 @@
#include "special.h"
#include "warn.h"
#include "arch_special.h"
+#include "endianness.h"

struct special_entry {
const char *sec;
@@ -77,8 +78,9 @@ static int get_alt_entry(struct elf *elf, struct special_entry *entry,
if (entry->feature) {
unsigned short feature;

- feature = *(unsigned short *)(sec->data->d_buf + offset +
- entry->feature);
+ feature = bswap_if_needed(*(unsigned short *)(sec->data->d_buf +
+ offset +
+ entry->feature));
arch_handle_alternative(feature, alt);
}
---
arch/x86/include/asm/orc_types.h | 10 +++++
tools/arch/x86/include/asm/orc_types.h | 10 +++++
.../arch/x86/include/arch_endianness.h | 9 +++++
tools/objtool/check.c | 5 ++-
tools/objtool/endianness.h | 38 +++++++++++++++++++
tools/objtool/orc_dump.c | 5 ++-
tools/objtool/orc_gen.c | 3 ++
tools/objtool/special.c | 6 ++-
8 files changed, 80 insertions(+), 6 deletions(-)
create mode 100644 tools/objtool/arch/x86/include/arch_endianness.h
create mode 100644 tools/objtool/endianness.h
diff --git a/arch/x86/include/asm/orc_types.h b/arch/x86/include/asm/orc_types.h
index fdbffec4cfde..5a2baf28a1dc 100644
--- a/arch/x86/include/asm/orc_types.h
+++ b/arch/x86/include/asm/orc_types.h
@@ -40,6 +40,8 @@
#define ORC_REG_MAX 15

#ifndef __ASSEMBLY__
+#include <asm/byteorder.h>
+
/*
* This struct is more or less a vastly simplified version of the DWARF Call
* Frame Information standard. It contains only the necessary parts of DWARF
@@ -51,10 +53,18 @@
struct orc_entry {
s16 sp_offset;
s16 bp_offset;
+#if defined(__LITTLE_ENDIAN_BITFIELD)
unsigned sp_reg:4;
unsigned bp_reg:4;
unsigned type:2;
unsigned end:1;
+#elif defined(__BIG_ENDIAN_BITFIELD)
+ unsigned bp_reg:4;
+ unsigned sp_reg:4;
+ unsigned unused:5;
+ unsigned end:1;
+ unsigned type:2;
+#endif
} __packed;

#endif /* __ASSEMBLY__ */
diff --git a/tools/arch/x86/include/asm/orc_types.h b/tools/arch/x86/include/asm/orc_types.h
index fdbffec4cfde..5a2baf28a1dc 100644
--- a/tools/arch/x86/include/asm/orc_types.h
+++ b/tools/arch/x86/include/asm/orc_types.h
@@ -40,6 +40,8 @@
#define ORC_REG_MAX 15

#ifndef __ASSEMBLY__
+#include <asm/byteorder.h>
+
/*
* This struct is more or less a vastly simplified version of the DWARF Call
* Frame Information standard. It contains only the necessary parts of DWARF
@@ -51,10 +53,18 @@
struct orc_entry {
s16 sp_offset;
s16 bp_offset;
+#if defined(__LITTLE_ENDIAN_BITFIELD)
unsigned sp_reg:4;
unsigned bp_reg:4;
unsigned type:2;
unsigned end:1;
+#elif defined(__BIG_ENDIAN_BITFIELD)
+ unsigned bp_reg:4;
+ unsigned sp_reg:4;
+ unsigned unused:5;
+ unsigned end:1;
+ unsigned type:2;
+#endif
} __packed;

#endif /* __ASSEMBLY__ */
diff --git a/tools/objtool/arch/x86/include/arch_endianness.h b/tools/objtool/arch/x86/include/arch_endianness.h
new file mode 100644
index 000000000000..7c362527da20
--- /dev/null
+++ b/tools/objtool/arch/x86/include/arch_endianness.h
@@ -0,0 +1,9 @@
+/* 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 2df9f769412e..fd892b77e98f 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -13,6 +13,7 @@
#include "special.h"
#include "warn.h"
#include "arch_elf.h"
+#include "endianness.h"

#include <linux/objtool.h>
#include <linux/hashtable.h>
@@ -1370,7 +1371,7 @@ static int read_unwind_hints(struct objtool_file *file)
cfa = &insn->cfi.cfa;

if (hint->type == UNWIND_HINT_TYPE_RET_OFFSET) {
- insn->ret_offset = hint->sp_offset;
+ insn->ret_offset = bswap_if_needed(hint->sp_offset);
continue;
}

@@ -1382,7 +1383,7 @@ static int read_unwind_hints(struct objtool_file *file)
return -1;
}

- cfa->offset = hint->sp_offset;
+ cfa->offset = bswap_if_needed(hint->sp_offset);
insn->cfi.type = hint->type;
insn->cfi.end = hint->end;
}
diff --git a/tools/objtool/endianness.h b/tools/objtool/endianness.h
new file mode 100644
index 000000000000..ebece3191b58
--- /dev/null
+++ b/tools/objtool/endianness.h
@@ -0,0 +1,38 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef _OBJTOOL_ENDIANNESS_H
+#define _OBJTOOL_ENDIANNESS_H
+
+#include <linux/kernel.h>
+#include <endian.h>
+#include "arch_endianness.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
+
+/*
+ * Does a byte swap if target 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) \
+({ \
+ __typeof__(val) __ret; \
+ 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; \
+ default: \
+ BUILD_BUG(); break; \
+ } \
+ __ret; \
+})
+
+#endif /* _OBJTOOL_ENDIANNESS_H */
diff --git a/tools/objtool/orc_dump.c b/tools/objtool/orc_dump.c
index 5e6a95368d35..4e818a22e44b 100644
--- a/tools/objtool/orc_dump.c
+++ b/tools/objtool/orc_dump.c
@@ -8,6 +8,7 @@
#include <asm/orc_types.h>
#include "objtool.h"
#include "warn.h"
+#include "endianness.h"

static const char *reg_name(unsigned int reg)
{
@@ -197,11 +198,11 @@ int orc_dump(const char *_objname)

printf(" sp:");

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

printf(" bp:");

- print_reg(orc[i].bp_reg, orc[i].bp_offset);
+ print_reg(orc[i].bp_reg, bswap_if_needed(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 235663b96adc..134d7863093d 100644
--- a/tools/objtool/orc_gen.c
+++ b/tools/objtool/orc_gen.c
@@ -11,6 +11,7 @@

#include "check.h"
#include "warn.h"
+#include "endianness.h"

int create_orc(struct objtool_file *file)
{
@@ -96,6 +97,8 @@ static int create_orc_entry(struct elf *elf, struct section *u_sec, struct secti
/* populate ORC data */
orc = (struct orc_entry *)u_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);

/* populate reloc for ip */
reloc = malloc(sizeof(*reloc));
diff --git a/tools/objtool/special.c b/tools/objtool/special.c
index 1a2420febd08..ab7cb1e13411 100644
--- a/tools/objtool/special.c
+++ b/tools/objtool/special.c
@@ -15,6 +15,7 @@
#include "special.h"
#include "warn.h"
#include "arch_special.h"
+#include "endianness.h"

struct special_entry {
const char *sec;
@@ -77,8 +78,9 @@ static int get_alt_entry(struct elf *elf, struct special_entry *entry,
if (entry->feature) {
unsigned short feature;

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

--
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