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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, %edi
*/
walkcbfs:
cld
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
/* determine filename length */
mov $0, %eax
1:
cmpb $0, (%eax,%esi)
jz 2f
add $1, %eax
jmp 1b
2:
add $1, %eax
walker:
mov 0(%ebx), %edi
cmp %edi, filemagic
jne searchfile
mov 4(%ebx), %edi
cmp %edi, filemagic+4
jne searchfile
mov %ebx, %edi
add $CBFS_FILE_STRUCTSIZE, %edi /* edi = address of first byte after struct cbfs_file */
mov %eax, %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:
sub %ebx, %edi
sub $CBFS_FILE_STRUCTSIZE, %edi /* edi = # of walked bytes */
sub %edi, %esi /* esi = start of filename */
/* ebx = ecx = (current+offset+len+ALIGN-1) & ~(ALIGN-1) */
mov CBFS_FILE_OFFSET(%ebx), %ecx
bswap %ecx
add %ebx, %ecx
mov CBFS_FILE_LEN(%ebx), %edi
bswap %edi
add %edi, %ecx
mov CBFS_HEADER_PTR, %edi
mov CBFS_HEADER_ALIGN(%edi), %edi
bswap %edi
sub $1, %edi
add %edi, %ecx
not %edi
and %edi, %ecx
/* if oldaddr >= addr, leave */
cmp %ebx, %ecx
jbe out
mov %ecx, %ebx
check_for_exit:
/* look if we should exit: did we pass into the bootblock already? */
mov CBFS_HEADER_PTR, %ecx
mov CBFS_HEADER_BOOTBLOCKSIZE(%ecx), %ecx
bswap %ecx
not %ecx
add $1, %ecx
cmp %ecx, %ebx
/* if bootblockstart >= addr (==we're still in the data area) , jump back */
jbe walker
out:
mov $0, %eax
jmp *%esp
searchfile:
/* if filemagic isn't found, move forward cbfs_header->align bytes */
mov CBFS_HEADER_PTR, %edi
mov CBFS_HEADER_ALIGN(%edi), %edi
bswap %edi
add %edi, %ebx
jmp check_for_exit
filemagic:
.ascii "LARCHIVE"
|
