mbr: save another 5 bytes by terminating error on newline

Save another 5 bytes by making the newline character do double duty as
newline and string terminator.

diff --git a/mbr/mbr.S b/mbr/mbr.S
index 304557b..e0d42d6 100644 (file)
--- a/mbr/mbr.S
+++ b/mbr/mbr.S
@@ -109,7 +109,6 @@ next:
 missing_os:
        call    error
        .ascii  "Missing operating system.\r\n"
-       .byte   0
 
 /*
  * read_sector: read a single sector pointed to by %eax to 0x7c00.
@@ -249,7 +248,6 @@ scan_partition_table:
 too_many_active:
        call    error
        .ascii  "Multiple active partitions.\r\n"
-       .byte   0
 
 /*
  * boot: invoke the actual bootstrap. (%si) points to the partition
@@ -273,7 +271,6 @@ boot:
 disk_error:
        call    error
        .ascii  "Operating system load error.\r\n"
-       .byte   0
 
 /*
  * Print error messages.  This is invoked with "call", with the
@@ -283,14 +280,13 @@ error:
        popw    %si
 2:
        lodsb
-       andb    %al, %al
-       jz      3f
        movb    $0x0e, %ah
        movb    (BIOS_page), %bh
        movb    $0x07, %bl
-       int     $0x10
-       jmp     2b
-3:
+       int     $0x10           /* May destroy %bp */
+       cmpb    $10, %al        /* Newline? */
+       jne     2b
+
        int     $0x18           /* Boot failure */
 die:
        hlt