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#define CBFS_HEADER_PTR 0xfffffffc
#define CBFS_HEADER_MAGIC 0
#define CBFS_HEADER_VERSION (CBFS_HEADER_MAGIC + 4)
#define CBFS_HEADER_ROMSIZE (CBFS_HEADER_VERSION + 4)
#define CBFS_HEADER_BOOTBLOCKSIZE (CBFS_HEADER_ROMSIZE + 4)
#define CBFS_HEADER_ALIGN (CBFS_HEADER_BOOTBLOCKSIZE + 4)
#define CBFS_HEADER_OFFSET (CBFS_HEADER_ALIGN + 4)
#define CBFS_FILE_MAGIC 0
#define CBFS_FILE_LEN (CBFS_FILE_MAGIC + 8)
#define CBFS_FILE_TYPE (CBFS_FILE_LEN + 4)
#define CBFS_FILE_CHECKSUM (CBFS_FILE_TYPE + 4)
#define CBFS_FILE_OFFSET (CBFS_FILE_CHECKSUM + 4)
#define CBFS_FILE_STRUCTSIZE (CBFS_FILE_OFFSET + 4)
#define CBFS_STAGE_COMPRESSION 0
#define CBFS_STAGE_ENTRY (CBFS_STAGE_COMPRESSION + 4)
#define CBFS_STAGE_LOAD (CBFS_STAGE_ENTRY + 8)
#define CBFS_STAGE_LEN (CBFS_STAGE_LOAD + 8)
#define CBFS_STAGE_MEMLEN (CBFS_STAGE_LEN + 4)
/*
input %esi: filename
input %esp: return address (not pointer to return address!)
output %eax: entry point
clobbers %ebx, %ecx, %edx, %edi, %ebp
*/
walkcbfs:
mov %esi, %ebp /* stash away filename pointer */
mov $0, %edx
1:
cmpb $0, (%edx,%esi)
jz 2f
add $1, %edx
jmp 1b
2:
add $1, %edx
mov CBFS_HEADER_PTR, %eax
mov CBFS_HEADER_ROMSIZE(%eax), %ecx
bswap %ecx
mov $0, %ebx
sub %ecx, %ebx
mov CBFS_HEADER_OFFSET(%eax), %ecx
bswap %ecx
add %ecx, %ebx
mov CBFS_HEADER_ALIGN(%eax), %eax
bswap %eax
sub $1, %eax
walker:
mov %ebp, %esi
mov %ebx, %edi
add $CBFS_FILE_STRUCTSIZE, %edi /* edi = address of first byte after struct cbfs_file */
mov %edx, %ecx
repe cmpsb
# zero flag set if strings are equal
jnz tryharder
# we found it!
mov CBFS_FILE_OFFSET(%ebx), %eax
bswap %eax
add %ebx, %eax
add $CBFS_STAGE_ENTRY, %eax /* eax = ((cbfs_stage* (cbfs_file* ebx)->offset)->entry) */
mov 0(%eax), %eax
jmp *%esp
tryharder:
mov CBFS_FILE_OFFSET(%ebx), %ecx
bswap %ecx
add %ebx, %ecx
mov CBFS_FILE_LEN(%ebx), %edi
bswap %edi
add %edi, %ecx
add %eax, %ecx
mov %eax, %edi
not %edi
and %edi, %ecx
mov %ecx, %ebx
/* look if we should exit */
mov CBFS_HEADER_PTR, %esi
mov CBFS_HEADER_ROMSIZE(%esi), %ecx
bswap %ecx
not %ecx
add $1, %ecx
cmp %ebx, %ecx
/* if we're still inside the ROM area, jump back */
jbe walker
mov $0, %eax
jmp *%esp
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