Re: [PATCH gnumach] smp: Remove hardcoded AP_BOOT_ADDR

[Samuel Thibault]

Damien Zammit, le mar. 30 janv. 2024 01:55:32 +0000, a ecrit:
> On 1/29/24 9:20 PM, Samuel Thibault wrote:
> > Damien Zammit, le lun. 29 janv. 2024 10:07:30 +0000, a ecrit:
> >> -  ljmp    $BOOT_CS, $M(0f)
> >> +  xorl    %eax, %eax
> >> +  mov     %cs, %ax
> >> +  shll    $4, %eax
> >> +  addl    $M(0f), %eax
> >> +  movl    %eax, M(ljmp_offset32)
> > This won't work with pipelined processors, which assume a complete
> > separation between code and data, and will thus have already loaded
> > the jmp instruction before your modify it.
> >
> > Rather either perform the relocation from the C code, or use a variable,
> > which you can refer from the ljmp instruction.
> 
> I was unable to make the ljmpl instruction assemble with a memory location
> as the second argument.

(as discussed on IRC, you can as well directly write the absolute
address into the jmp instruction, but perhaps a ljmpl *(%eax) is
possible after all)

Samuel