[1927] * kern/i386/loader.S (grub_multiboot_backward_relocator): Improve

Revision: 1927
          http://svn.sv.gnu.org/viewvc/?view=rev&root=grub&revision=1927
Author:   robertmh
Date:     2008-11-22 15:00:39 +0000 (Sat, 22 Nov 2008)

Log Message:
-----------
        * kern/i386/loader.S (grub_multiboot_backward_relocator): Improve
        comments.  Avoid copiing one more byte than necessary (just in case).

Modified Paths:
--------------
    trunk/grub2/ChangeLog
    trunk/grub2/kern/i386/loader.S

Modified: trunk/grub2/ChangeLog
===================================================================
--- trunk/grub2/ChangeLog	2008-11-22 14:56:52 UTC (rev 1926)
+++ trunk/grub2/ChangeLog	2008-11-22 15:00:39 UTC (rev 1927)
@@ -5,6 +5,9 @@
 	(grub_vga_text_term): Use grub_vga_text_init_fini() instead of
 	grub_vga_text_cls().
 
+	* kern/i386/loader.S (grub_multiboot_backward_relocator): Improve
+	comments.  Avoid copiing one more byte than necessary (just in case).
+
 2008-11-20  Robert Millan  <[email protected]>
 
 	* kern/i386/coreboot/init.c (grub_time_tics): Remove variable.

Modified: trunk/grub2/kern/i386/loader.S
===================================================================
--- trunk/grub2/kern/i386/loader.S	2008-11-22 14:56:52 UTC (rev 1926)
+++ trunk/grub2/kern/i386/loader.S	2008-11-22 15:00:39 UTC (rev 1927)
@@ -141,24 +141,32 @@
  * edx:	Offset of the entry point (relative to the beginning of the block).
  */
 VARIABLE(grub_multiboot_forward_relocator)
+	/* Add entry offset.  */
+	addl	%edi, %edx
+
+	/* Forward copy.  */
 	cld
-	addl	%edi, %edx
 	rep
 	movsb
+
 	jmp	*%edx
 VARIABLE(grub_multiboot_forward_relocator_end)
 
 VARIABLE(grub_multiboot_backward_relocator)
+	/* Add entry offset (before %edi is mangled).  */
+	addl	%edi, %edx
+
+	/* Backward movsb is implicitly off-by-one.  compensate that.  */
+	decl	%esi
+	decl	%edi
+
+	/* Backward copy.  */
 	std
 	addl	%ecx, %esi
 	addl	%ecx, %edi
-	/* backward movsb is implicitly off-by-one.  compensate that. */
-	incl	%ecx
 	rep
 	movsb
-	/* same problem again. */
-	incl	%edi
-	addl	%edi, %edx
+
 	jmp	*%edx
 VARIABLE(grub_multiboot_backward_relocator_end)