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Re: [PATCH gnumach] smp: Remove hardcoded AP_BOOT_ADDR
From: |
Samuel Thibault |
Subject: |
Re: [PATCH gnumach] smp: Remove hardcoded AP_BOOT_ADDR |
Date: |
Tue, 30 Jan 2024 19:18:15 +0100 |
User-agent: |
NeoMutt/20170609 (1.8.3) |
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