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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.

Introduce 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.  The macro is used for conversion
of multi-byte values which are read from / about to be written to a
target native endianness ELF file.

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>
This commit is contained in:
Vasily Gorbik 2020-11-13 00:03:29 +01:00 committed by Josh Poimboeuf
parent a1a664ece5
commit 8bfe273238
8 changed files with 80 additions and 6 deletions
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10
arch/x86/include/asm/orc_types.h
View File

@ -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__ */

10
tools/arch/x86/include/asm/orc_types.h
View File

@ -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__ */

9
tools/objtool/arch/x86/include/arch_endianness.h Normal file
View File

@ -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 */

5
tools/objtool/check.c
View File

@ -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>
@ -1435,7 +1436,7 @@ 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;
}
@ -1447,7 +1448,7 @@ 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;
}

38
tools/objtool/endianness.h Normal file
View File

@ -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 */

5
tools/objtool/orc_dump.c
View File

@ -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);

3
tools/objtool/orc_gen.c
View File

@ -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));

6
tools/objtool/special.c
View File

@ -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);
}