Miscellaneous efficiency improvements, and extend read_sectors to

handle multiple sectors.

diff --git a/src/arch/i386/prefix/bootpart.S b/src/arch/i386/prefix/bootpart.S
index 87104f5..22ad3e3 100644 (file)
--- a/src/arch/i386/prefix/bootpart.S
+++ b/src/arch/i386/prefix/bootpart.S
@@ -20,6 +20,7 @@ find_active_partition:
        movw    $STACK_SEG, %ax
        movw    %ax, %ss
        movw    $STACK_SIZE, %sp
+
        /* Relocate self to EXEC_SEG */
        pushw   $BOOT_SEG
        popw    %ds
@@ -34,12 +35,24 @@ find_active_partition:
        popw    %es
        pushw   %cs
        popw    %ds
+
+       /* Check for LBA extensions */
+       movb    $0x41, %ah
+       movw    $0x55aa, %bx
+       stc
+       int     $0x13
+       jc      1f
+       cmpw    $0xaa55, %bx
+       jne     1f
+       movw    $read_lba, read_sector
+1:     
        /* Read and process root partition table */
        xorb    %dh, %dh
        movw    $0x0001, %cx
        xorl    %esi, %esi
        xorl    %edi, %edi
        call    process_table
+
        /* Print failure message */
        movw    $10f, %si
        movw    $(20f-10f), %cx
@@ -48,6 +61,7 @@ find_active_partition:
        lodsb
        int     $0x10
        loop    1b
+
        /* Boot next device */
        int     $0x18
 10:    .ascii  "Could not locate active partition\r\n"
@@ -69,10 +83,10 @@ find_active_partition:
  */
 process_table:
        pushal
-       movw    $446, %bx
-1:     call    read_sector
+       call    read_boot_sector
        jc      99f
-       call    process_partition
+       movw    $446, %bx
+1:     call    process_partition
        addw    $16, %bx
        cmpw    $510, %bx
        jne     1b
@@ -102,7 +116,7 @@ process_partition:
        /* Check active flag */
        testb   $0x80, %es:(%bx)
        jz      1f
-       call    read_sector
+       call    read_boot_sector
        jc      99f
        jmp     *%bp
 1:     /* Check for extended partition */
@@ -115,10 +129,12 @@ process_partition:
        jne     99f
 2:     call    process_table
 99:    popal
+       /* Reload original partition table */
+       call    read_boot_sector
        ret
 
 /*
- * Read single sector to 0000:7c00 and verify 0x55aa signature
+ * Read single sector to %es:0000 and verify 0x55aa signature
  *
  * Parameters:
  *   %dl       : BIOS drive number
@@ -130,32 +146,56 @@ process_partition:
  * Returns:
  *   CF set on error
  */
-read_sector:
-       pushal
-       /* Check for LBA extensions */
-       call    check_lba
-       jnc     read_lba
+read_boot_sector:
+       pushw   %ax
+       movw    $1, %ax
+       call    *read_sector
+       jc      99f
+       cmpw    $0xaa55, %es:(510)
+       je      99f
+       stc     
+99:    popw    %ax
+       ret
+       
+/*
+ * Read single sector to %es:0000 and verify 0x55aa signature
+ *
+ * Parameters:
+ *   %dl       : BIOS drive number
+ *   %dh       : Head
+ *   %cl       : Sector (bits 0-5), high two bits of cylinder (bits 6-7)
+ *   %ch       : Low eight bits of cylinder
+ *   %esi:%edi : LBA address
+ *   %ax       : Number of sectors (max 127)
+ *
+ * Returns:
+ *   CF set on error
+ */
+read_sector:   .word   read_chs
+
 read_chs:
-       /* Read sector using C/H/S address */
-       movw    $0x0201, %ax
+       /* Read sectors using C/H/S address */
+       pushal
        xorw    %bx, %bx
+       movb    $0x02, %ah
        stc
        int     $0x13
        sti
-       jmp     99f
+       popal
+       ret
+
 read_lba:
-       /* Read sector using LBA address */
-       movb    $0x42, %ah
-       movl    %esi, (lba_desc + 12)
+       /* Read sectors using LBA address */
+       pushal
+       movw    %ax, (lba_desc + 2)
+       pushw   %es
+       popw    (lba_desc + 6)
        movl    %edi, (lba_desc + 8)
+       movl    %esi, (lba_desc + 12)
        movw    $lba_desc, %si
+       movb    $0x42, %ah
        int     $0x13
-99:    /* Check for 55aa signature */
-       jc      99f
-       cmpw    $0xaa55, %es:(510)
-       je      99f
-       stc
-99:    popal
+       popal
        ret
 
 lba_desc:
@@ -163,27 +203,5 @@ lba_desc:
        .byte   0
        .word   1
        .word   0x0000
-       .word   0x07c0
+       .word   0x0000
        .long   0, 0
-
-/*
- * Check for LBA extensions
- *     
- * Parameters:
- *   %dl       : BIOS drive number
- *
- * Returns:
- *   CF clear if LBA extensions supported
- */
-check_lba:
-       pushal
-       movb    $0x41, %ah
-       movw    $0x55aa, %bx
-       stc
-       int     $0x13
-       jc      99f
-       cmpw    $0xaa55, %bx
-       je      99f
-       stc
-99:    popal
-       ret