BOOT_CS

H. Peter Anvin
2004-02-21T05:47:36Z

Anyone happen to know of any legitimate reason not to reload %cs in
head.S? I think the following would be a lot cleaner, as well as a
lot safer (the jump and indirect branch aren't guaranteed to have the
proper effects, although technically neither should be required due to
the %cr0 write):

@@ -117,10 +147,7 @@
movl %cr0,%eax
orl $0x80000000,%eax
movl %eax,%cr0 /* ..and set paging (PG) bit */
- jmp 1f /* flush the prefetch-queue */
-1:
- movl $1f,%eax
- jmp *%eax /* make sure eip is relocated */
+ ljmp $__BOOT_CS,$1f /* Clear prefetch and normalize %eip
*/
1:
/* Set up the stack pointer */
lss stack_start,%esp

I've been doing some cleanups in head.S after making the early page
tables dynamic.

-hpa