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add some comments to walkcbfs.S 

Signed-off-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Acked-by: Stefan Reinauer <stefan.reinauer@coreboot.org>



git-svn-id: svn://svn.coreboot.org/coreboot/trunk@6498 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1
This commit is contained in:
Stefan Reinauer 2011-04-14 20:33:53 +00:00 committed by Stefan Reinauer
parent 31853d8976
commit 1fdfed1798
1 changed files with 11 additions and 10 deletions
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21
src/arch/x86/lib/walkcbfs.S
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@ -16,11 +16,11 @@
#define CBFS_FILE_STRUCTSIZE (CBFS_FILE_OFFSET + 4)
/*
input %esi: filename
input %esp: return address (not pointer to return address!)
output %eax: entry point
clobbers %ebx, %ecx, %edi
*/
* input %esi: filename
* input %esp: return address (not pointer to return address!)
* output %eax: entry point
* clobbers %ebx, %ecx, %edi
*/
walkcbfs_asm:
cld
@ -28,10 +28,10 @@ walkcbfs_asm:
mov CBFS_HEADER_ROMSIZE(%eax), %ecx
bswap %ecx
mov $0, %ebx
sub %ecx, %ebx
sub %ecx, %ebx /* rom base address in ebx */
mov CBFS_HEADER_OFFSET(%eax), %ecx
bswap %ecx
add %ecx, %ebx
add %ecx, %ebx /* address where we start looking for LARCHIVEs */
/* determine filename length */
mov $0, %eax
@ -43,21 +43,22 @@ walkcbfs_asm:
2:
add $1, %eax
walker:
mov 0(%ebx), %edi
mov 0(%ebx), %edi /* Check for LARCHIVE header */
cmp %edi, filemagic
jne searchfile
mov 4(%ebx), %edi
cmp %edi, filemagic+4
jne searchfile
/* LARCHIVE header found */
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
/* zero flag set if strings are equal */
jnz tryharder
# we found it!
/* we found it! */
mov CBFS_FILE_OFFSET(%ebx), %eax
bswap %eax
add %ebx, %eax