/*
下面是glibc-2.3.5/sysdeps/i386/i686/memcmp.S的完整代码，在编译的过程中报错。具体的错误信息俺找着麻烦就不贴了，大致意思就是说：“.rodata”和“memcmp”这两个不同字段之间不能相减。哪位大牛给看看，是不是代码有问题？如果有，怎么改？

*/

#include <sysdep.h>
#include "asm-syntax.h"
#include "bp-sym.h"
#include "bp-asm.h"

#define PARMS LINKAGE+4 /* Preserve EBX. */
#define BLK1 PARMS
#define BLK2 BLK1+PTR_SIZE
#define LEN BLK2+PTR_SIZE
#define ENTRANCE pushl %ebx; ENTER
#define RETURN popl %ebx; LEAVE; ret

/* Load an entry in a jump table into EBX. TABLE is a jump table
with relative offsets. INDEX is a register contains the index
into the jump table. */
#define LOAD_JUMP_TABLE_ENTRY(TABLE, INDEX) \
/* We first load PC into EBX. */ \
call __i686.get_pc_thunk.bx; \
/* Get the address of the jump table. */ \
addl $(TABLE - .), %ebx; \
/* Get the entry and convert the relative offset to the \
absolute address. */ \
addl (%ebx,INDEX,4), %ebx

#ifdef HAVE_HIDDEN
.section .gnu.linkonce.t.__i686.get_pc_thunk.bx,"ax",@progbits
.globl __i686.get_pc_thunk.bx
.hidden __i686.get_pc_thunk.bx
#else
.text
#endif
ALIGN (4)
.type __i686.get_pc_thunk.bx,@function
__i686.get_pc_thunk.bx:
movl (%esp), %ebx
ret

.text
ALIGN (4)
ENTRY (BP_SYM (memcmp))
ENTRANCE

movl BLK1(%esp), %eax
movl BLK2(%esp), %edx
movl LEN(%esp), %ecx

cmpl $1, %ecx
jne L(not_1)
movzbl (%eax), %ecx /* LEN == 1 */
cmpb (%edx), %cl
jne L(neq)
L(bye):
xorl %eax, %eax
RETURN

L(neq):
sbbl %eax, %eax
sbbl $-1, %eax
RETURN

L(not_1):
jl L(bye) /* LEN == 0 */

pushl %esi
movl %eax, %esi
cmpl $32, %ecx;
jge L(32bytesormore) /* LEN => 32 */

LOAD_JUMP_TABLE_ENTRY (L(table_32bytes), %ecx)
addl %ecx, %edx
addl %ecx, %esi
jmp *%ebx

ALIGN (4)
L(28bytes):
movl -28(%esi), %eax
movl -28(%edx), %ecx
cmpl %ecx, %eax
jne L(find_diff)
L(24bytes):
movl -24(%esi), %eax
movl -24(%edx), %ecx
cmpl %ecx, %eax
jne L(find_diff)
L(20bytes):
movl -20(%esi), %eax
movl -20(%edx), %ecx
cmpl %ecx, %eax
jne L(find_diff)
L(16bytes):
movl -16(%esi), %eax
movl -16(%edx), %ecx
cmpl %ecx, %eax
jne L(find_diff)
L(12bytes):
movl -12(%esi), %eax
movl -12(%edx), %ecx
cmpl %ecx, %eax
jne L(find_diff)
L(8bytes):
movl -8(%esi), %eax
movl -8(%edx), %ecx
cmpl %ecx, %eax
jne L(find_diff)
L(4bytes):
movl -4(%esi), %eax
movl -4(%edx), %ecx
cmpl %ecx, %eax
jne L(find_diff)
L(0bytes):
popl %esi
xorl %eax, %eax
RETURN

L(29bytes):
movl -29(%esi), %eax
movl -29(%edx), %ecx
cmpl %ecx, %eax
jne L(find_diff)
L(25bytes):
movl -25(%esi), %eax
movl -25(%edx), %ecx
cmpl %ecx, %eax
jne L(find_diff)
L(21bytes):
movl -21(%esi), %eax
movl -21(%edx), %ecx
cmpl %ecx, %eax
jne L(find_diff)
L(17bytes):
movl -17(%esi), %eax
movl -17(%edx), %ecx
cmpl %ecx, %eax
jne L(find_diff)
L(13bytes):
movl -13(%esi), %eax
movl -13(%edx), %ecx
cmpl %ecx, %eax
jne L(find_diff)
L(9bytes):
movl -9(%esi), %eax
movl -9(%edx), %ecx
cmpl %ecx, %eax
jne L(find_diff)
L(5bytes):
movl -5(%esi), %eax
movl -5(%edx), %ecx
cmpl %ecx, %eax
jne L(find_diff)
L(1bytes):
movzbl -1(%esi), %eax
cmpb -1(%edx), %al
jne L(set)
popl %esi
xorl %eax, %eax
RETURN

L(30bytes):
movl -30(%esi), %eax
movl -30(%edx), %ecx
cmpl %ecx, %eax
jne L(find_diff)
L(26bytes):
movl -26(%esi), %eax
movl -26(%edx), %ecx
cmpl %ecx, %eax
jne L(find_diff)
L(22bytes):
movl -22(%esi), %eax
movl -22(%edx), %ecx
cmpl %ecx, %eax
jne L(find_diff)
L(18bytes):
movl -18(%esi), %eax
movl -18(%edx), %ecx
cmpl %ecx, %eax
jne L(find_diff)
L(14bytes):
movl -14(%esi), %eax
movl -14(%edx), %ecx
cmpl %ecx, %eax
jne L(find_diff)
L(10bytes):
movl -10(%esi), %eax
movl -10(%edx), %ecx
cmpl %ecx, %eax
jne L(find_diff)
L(6bytes):
movl -6(%esi), %eax
movl -6(%edx), %ecx
cmpl %ecx, %eax
jne L(find_diff)
L(2bytes):
movzwl -2(%esi), %eax
movzwl -2(%edx), %ecx
cmpb %cl, %al
jne L(set)
cmpl %ecx, %eax
jne L(set)
popl %esi
xorl %eax, %eax
RETURN

L(31bytes):
movl -31(%esi), %eax
movl -31(%edx), %ecx
cmpl %ecx, %eax
jne L(find_diff)
L(27bytes):
movl -27(%esi), %eax
movl -27(%edx), %ecx
cmpl %ecx, %eax
jne L(find_diff)
L(23bytes):
movl -23(%esi), %eax
movl -23(%edx), %ecx
cmpl %ecx, %eax
jne L(find_diff)
L(19bytes):
movl -19(%esi), %eax
movl -19(%edx), %ecx
cmpl %ecx, %eax
jne L(find_diff)
L(15bytes):
movl -15(%esi), %eax
movl -15(%edx), %ecx
cmpl %ecx, %eax
jne L(find_diff)
L(11bytes):
movl -11(%esi), %eax
movl -11(%edx), %ecx
cmpl %ecx, %eax
jne L(find_diff)
L(7bytes):
movl -7(%esi), %eax
movl -7(%edx), %ecx
cmpl %ecx, %eax
jne L(find_diff)
L(3bytes):
movzwl -3(%esi), %eax
movzwl -3(%edx), %ecx
cmpb %cl, %al
jne L(set)
cmpl %ecx, %eax
jne L(set)
movzbl -1(%esi), %eax
cmpb -1(%edx), %al
jne L(set)
popl %esi
xorl %eax, %eax
RETURN

ALIGN (4)
/* ECX >= 32. */
L(32bytesormore):
subl $32, %ecx

movl (%esi), %eax
cmpl (%edx), %eax
jne L(load_ecx)

movl 4(%esi), %eax
cmpl 4(%edx), %eax
jne L(load_ecx_4)

movl 8(%esi), %eax
cmpl 8(%edx), %eax
jne L(load_ecx_8)

movl 12(%esi), %eax
cmpl 12(%edx), %eax
jne L(load_ecx_12)

movl 16(%esi), %eax
cmpl 16(%edx), %eax
jne L(load_ecx_16)

movl 20(%esi), %eax
cmpl 20(%edx), %eax
jne L(load_ecx_20)

movl 24(%esi), %eax
cmpl 24(%edx), %eax
jne L(load_ecx_24)

movl 28(%esi), %eax
cmpl 28(%edx), %eax
jne L(load_ecx_28)

addl $32, %esi
addl $32, %edx
cmpl $32, %ecx
jge L(32bytesormore)

LOAD_JUMP_TABLE_ENTRY (L(table_32bytes), %ecx)
addl %ecx, %edx
addl %ecx, %esi
jmp *%ebx

L(load_ecx_28):
addl $0x4, %edx
L(load_ecx_24):
addl $0x4, %edx
L(load_ecx_20):
addl $0x4, %edx
L(load_ecx_16):
addl $0x4, %edx
L(load_ecx_12):
addl $0x4, %edx
L(load_ecx_8):
addl $0x4, %edx
L(load_ecx_4):
addl $0x4, %edx
L(load_ecx):
movl (%edx), %ecx

L(find_diff):
cmpb %cl, %al
jne L(set)
cmpb %ch, %ah
jne L(set)
shrl $16,%eax
shrl $16,%ecx
cmpb %cl, %al
jne L(set)
/* We get there only if we already know there is a
difference. */
cmpl %ecx, %eax
L(set):
sbbl %eax, %eax
sbbl $-1, %eax
popl %esi
RETURN

.section .rodata
ALIGN (2)
L(table_32bytes) :
.long L(0bytes) - . + 0x0
.long L(1bytes) - . + 0x4
.long L(2bytes) - . + 0x8
.long L(3bytes) - . + 0xc
.long L(4bytes) - . + 0x10
.long L(5bytes) - . + 0x14
.long L(6bytes) - . + 0x18
.long L(7bytes) - . + 0x1c
.long L(8bytes) - . + 0x20
.long L(9bytes) - . + 0x24
.long L(10bytes) - . + 0x28
.long L(11bytes) - . + 0x2c
.long L(12bytes) - . + 0x30
.long L(13bytes) - . + 0x34
.long L(14bytes) - . + 0x38
.long L(15bytes) - . + 0x3c
.long L(16bytes) - . + 0x40
.long L(17bytes) - . + 0x44
.long L(18bytes) - . + 0x48
.long L(19bytes) - . + 0x4c
.long L(20bytes) - . + 0x50
.long L(21bytes) - . + 0x54
.long L(22bytes) - . + 0x58
.long L(23bytes) - . + 0x5c
.long L(24bytes) - . + 0x60
.long L(25bytes) - . + 0x64
.long L(26bytes) - . + 0x68
.long L(27bytes) - . + 0x6c
.long L(28bytes) - . + 0x70
.long L(29bytes) - . + 0x74
.long L(30bytes) - . + 0x78
.long L(31bytes) - . + 0x7c

END (BP_SYM (memcmp))

#undef bcmp
weak_alias (BP_SYM (memcmp), BP_SYM (bcmp))
libc_hidden_builtin_def (BP_SYM (memcmp))