H. Peter Anvin wrote:
startup_32:
cld
/* test KEEP_SEGMENTS flag to see if the bootloader is asking
* us to not reload segments */
testb $(1<<6), BP_loadflags(%esi)
jnz 1f
cli
movl $(__BOOT_DS),%eax
movl %eax,%ds
movl %eax,%es
movl %eax,%fs
movl %eax,%gs
movl %eax,%ss
1:
On this general subject... I keep thinking that it would be better to have this as:
movl %cs, %eax
addl $8, %eax
movl %eax, %cs
... instead of a hard-coded constant. That actually removes all hard-coded uses of BOOT_CS/BOOT_DS until we eventually load the kernel's own boot GDT at head_32.S:94.
Does anyone see any problem with that? As far as I can tell, we're requiring %cs == BOOT_CS for the current code anyway (unless KEEP_SEGMENTS), but %ds == %cs + 8 seems like a more sensible requirement.