[zbin] Allow decompressor to generate debug output via BIOS console

The 0xe9 debug port exists only on virtual machines.  Provide an
option to print debug output on the BIOS console, to allow for
debugging on real hardware.

Note that this option can be used only if the decompressor is called
in flat real mode; the easiest way to achieve this is to build with
DEBUG=libprefix.

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

diff --git a/src/arch/i386/prefix/unlzma.S b/src/arch/i386/prefix/unlzma.S
index b0588fdacfbe26b0794b487a45169978049e12c5..f4cbcdac5b67a514a6a6c52c1d3520d8a05acacc 100644 (file)
--- a/src/arch/i386/prefix/unlzma.S
+++ b/src/arch/i386/prefix/unlzma.S
@@ -55,25 +55,58 @@ FILE_LICENCE ( GPL2_OR_LATER );
 #endif /* CODE16 */
 
 /****************************************************************************
- * Debugging (via 0xe9 debug port)
+ * Debugging
  ****************************************************************************
+ *
+ * This code will usually run in 16-bit protected mode, in which case
+ * only the 0xe9 debug port (present on some virtual machines) can be
+ * used.
+ *
+ * To debug on real hardware, build with DEBUG=libprefix.  This will
+ * cause this code to be called in flat real mode, and so DEBUG_INT10
+ * may be used.
  */
 
-#define DEBUG 0
+/* Enable debugging via 0xe9 debug port */
+#define DEBUG_E9 0
 
-#if DEBUG
-       .macro  print_character, char
+/* Enable debugging via BIOS INT 10 (works only when in flat real mode) */
+#define DEBUG_INT10 0
+
+#if ( DEBUG_E9 || DEBUG_INT10 )
+       .macro  print_character, reg
+       pushfl
        pushw   %ax
-       movb    $\char, %al
+       pushw   %bx
+       pushw   %bp
+       movb    \reg, %al
+       movw    $0x0007, %bx
+       movb    $0x0e, %ah
+#if DEBUG_E9
        outb    %al, $0xe9
+#endif
+#if DEBUG_INT10
+       cmpb    $('\n'), %al
+       jne     L\@
+       int     $0x10
+       movb    $('\r'), %al
+L\@:   int     $0x10
+#endif
+       popw    %bp
+       popw    %bx
        popw    %ax
+       popfl
        .endm
 
        .macro  print_hex_nibble
+       pushfl
+       pushw   %ax
        cmpb    $10, %al
        sbb     $0x69, %al
        das
-       outb    %al, $0xe9
+       print_character %al
+       popw    %ax
+       popfl
        .endm
 
        .macro  print_hex_byte, reg
@@ -205,8 +238,6 @@ literal:    .rept   ( ( 1 << LZMA_LC ) * 0x300 )
  * Returns:
  *   %ds:%esi : compressed input data pointer (possibly updated)
  *   %eax : current range
- * Corrupts:
- *   %eax
  *****************************************************************************
  */
 rc_normalise:
@@ -476,7 +507,7 @@ lzma_literal:
        /* Store output byte */
        ADDR32 stosb
        print_hex_byte %al
-       print_character ' '
+       print_character $(' ')
        /* Update LZMA state */
        subb    $3, %dl
        jns     1f
@@ -562,14 +593,14 @@ lzma_len:
  *****************************************************************************
  */
 match: /* Update repeated match list */
-       print_character '['
+       print_character $('[')
        movl    $3, %ecx
        jmp     1f
 match_rep:
-       print_character '['
-       print_character 'R'
+       print_character $('[')
+       print_character $('R')
        print_hex_byte %cl
-       print_character '='
+       print_character $('=')
        movzbl  %cl, %ecx
        movl    reps(%ebp,%ecx,4), %eax
        jcxz    2f
@@ -582,10 +613,10 @@ match_rep:
        /* Get stored match length */
        movzwl  len(%ebp), %ecx
        print_hex_dword %eax
-       print_character '+'
+       print_character $('+')
        print_hex_word %cx
-       print_character ']'
-       print_character ' '
+       print_character $(']')
+       print_character $(' ')
        /* Abort with CF set if match distance is out of range */
        movl    out_start(%ebp), %esi
        negl    %esi
@@ -872,13 +903,13 @@ decompress:
        /* Initialise remaining parameters */
        movl    %esi, in_start(%ebp)
        movl    %edi, out_start(%ebp)
-       print_character '\n'
+       print_character $('\n')
        ADDR32 lodsb    /* discard initial byte */
        print_hex_byte %al
        ADDR32 lodsl
        bswapl  %eax
        print_hex_dword %eax
-       print_character '\n'
+       print_character $('\n')
        movl    %eax, rc_code(%ebp)
        decl    rc_range(%ebp)
        movl    $STATE_LIT_LIT, %edx
@@ -886,7 +917,7 @@ decompress:
        call    lzma_decode
        jnc     1b
        call    rc_normalise
-       print_character '\n'
+       print_character $('\n')
        /* Undo BCJ filter */
        pushl   %esi
        movl    out_start(%ebp), %esi