romcc:

[coreboot.git] / src / arch / i386 / lib / walkcbfs.S

diff --git a/src/arch/i386/lib/walkcbfs.S b/src/arch/i386/lib/walkcbfs.S
index aba0453d1f46e69d278ecc42085cf715b079aa86..d043af5690e73e0b40445bc38c2248e0c85e69b2 100644 (file)
--- a/src/arch/i386/lib/walkcbfs.S
+++ b/src/arch/i386/lib/walkcbfs.S
@@ -25,18 +25,9 @@
   input %esi: filename
   input %esp: return address (not pointer to return address!)
   output %eax: entry point
-  clobbers %ebx, %ecx, %edx, %edi, %ebp
+  clobbers %ebx, %ecx, %edi
 */
 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
@@ -45,15 +36,20 @@ walkcbfs:
        mov CBFS_HEADER_OFFSET(%eax), %ecx
        bswap %ecx
        add %ecx, %ebx
-       mov CBFS_HEADER_ALIGN(%eax), %eax
-       bswap %eax
-       sub $1, %eax
 
+       /* determine filename length */
+       mov $0, %eax
+1:
+       cmpb $0, (%eax,%esi)
+       jz 2f
+       add $1, %eax
+       jmp 1b
+2:
+       add $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
+       mov %eax, %ecx
        repe cmpsb
        # zero flag set if strings are equal
        jnz tryharder
@@ -67,21 +63,29 @@ walker:
        jmp *%esp
 
 tryharder:
+       sub %ebx, %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
-       add %eax, %ecx
-       mov %eax, %edi
+       mov CBFS_HEADER_PTR, %ebx
+       mov CBFS_HEADER_ALIGN(%ebx), %ebx
+       bswap %ebx
+       sub $1, %ebx
+       add %ebx, %ecx
+       mov %ebx, %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
+       mov CBFS_HEADER_PTR, %ecx
+       mov CBFS_HEADER_ROMSIZE(%ecx), %ecx
        bswap %ecx
        not %ecx
        add $1, %ecx