A while back, I was looking for eight extra bytes in boot.img so that I
could put a keyboard modifier check in there, allowing me to avoid
printing "GRUB loading" by default, which my boss^3 has been asking me
for, without crippling debugging in the process. I knew I could find a
few by shortening error messages (e.g. "Hard Disk" -> "HD"), but I asked
Colin King, one of our kernel hackers, if he could find a nicer
approach. He came up with a patch which I massaged a bit into this.
What do people think?
It seems as if it might be generally useful to have a bit of spare space
in here, although I would certainly appreciate it if people didn't use
it all at once. ;-)
2010-02-10 Colin King <colin.k...@ubuntu.com>
2010-02-10 Colin Watson <cjwat...@ubuntu.com>
Shrink the pre-partition-table part of boot.img by eight bytes.
* boot/i386/pc/boot.S (ERR): New macro.
(chs_mode): Use ERR.
(geometry_error): Likewise.
(hd_probe_error): Remove. This is only used once, so we wrwite
it inline instead.
(read_error): Instead of printing read_error_string, just set up
%si and fall through to ...
(error_message): ... this new function, also used by ERR.
=== modified file 'boot/i386/pc/boot.S'
--- boot/i386/pc/boot.S 2010-01-03 22:05:07 +0000
+++ boot/i386/pc/boot.S 2010-02-10 11:32:08 +0000
@@ -27,6 +27,7 @@
/* Print message string */
#define MSG(x) movw $x, %si; call LOCAL(message)
+#define ERR(x) movw $x, %si; jmp LOCAL(error_message)
.file "boot.S"
@@ -233,7 +234,7 @@ LOCAL(chs_mode):
jz LOCAL(floppy_probe)
/* Nope, we definitely have a hard disk, and we're screwed. */
- jmp LOCAL(hd_probe_error)
+ ERR(hd_probe_error_string)
LOCAL(final_init):
/* set the mode to zero */
@@ -360,22 +361,15 @@ LOCAL(copy_buffer):
* BIOS Geometry translation error (past the end of the disk geometry!).
*/
LOCAL(geometry_error):
- MSG(geometry_error_string)
- jmp LOCAL(general_error)
-
-/*
- * Disk probe failure.
- */
-LOCAL(hd_probe_error):
- MSG(hd_probe_error_string)
- jmp LOCAL(general_error)
+ ERR(geometry_error_string)
/*
* Read error on the disk.
*/
LOCAL(read_error):
- MSG(read_error_string)
-
+ movw $read_error_string, %si
+LOCAL(error_message):
+ call LOCAL(message)
LOCAL(general_error):
MSG(general_error_string)
Thanks,
--
Colin Watson [cjwat...@ubuntu.com]
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