[romprefix] Treat 0xffffffff as an error return from PMM

PMM defines the return code 0xffffffff as meaning "unsupported
function".  It's hard to imagine a PMM BIOS that doesn't support
pmmAllocate(), but apparently such things do exist.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

diff --git a/src/arch/i386/prefix/romprefix.S b/src/arch/i386/prefix/romprefix.S
index 950e08452f94c81c5c6f5bd9d9af32bbc2a95788..2719a70aa2c126d600576256a7e3a8122677ac66 100644 (file)
--- a/src/arch/i386/prefix/romprefix.S
+++ b/src/arch/i386/prefix/romprefix.S
@@ -342,7 +342,7 @@ pmm_scan:
        movw    $get_pmm_image_source, %bp
        call    get_pmm
        movl    %esi, image_source
-       jc      1f
+       jz      1f
        /* Copy ROM to image source PMM block */
        pushw   %es
        xorw    %ax, %ax
@@ -448,7 +448,7 @@ no_pmm:
  *  %es:0000 : PMM structure
  * Returns:
  *  %ebx : PMM handle
- *  %esi : allocated block address, or zero (with CF set) if allocation failed
+ *  %esi : allocated block address, or zero (with ZF set) if allocation failed
  */
 get_pmm:
        /* Preserve registers */
@@ -464,7 +464,10 @@ get_pmm_find:
        pushw   %dx
        pushw   %ax
        popl    %esi
-       testl   %esi, %esi
+       /* Treat 0xffffffff (not supported) as 0x00000000 (not found) */
+       incl    %esi
+       jz      get_pmm_allocate
+       decl    %esi
        jz      get_pmm_allocate
        /* Block found - check acceptability */
        call    *%bp
@@ -484,19 +487,20 @@ get_pmm_allocate:
        pushw   %ax
        popl    %esi
        movw    $( '+' ), %di   /* Indicate allocation attempt */
-       testl   %esi, %esi
-       jnz     get_pmm_done
-       stc
 get_pmm_done:
        /* Print block address */
-       pushfw
        movw    %di, %ax
        xorw    %di, %di
        call    print_character
        movl    %esi, %eax
        call    print_hex_dword
-       popfw
-       /* Restore registers and return */
+       /* Treat 0xffffffff (not supported) as 0x00000000 (allocation
+        * failed), and set ZF to indicate a zero result.
+        */
+       incl    %esi
+       jz      1f
+       decl    %esi
+1:     /* Restore registers and return */
        popw    %di
        popl    %eax
        ret