On Thu, Mar 03, 2016 at 07:26:06AM -0800, H. Peter Anvin wrote:
> Why -8?
GLOBAL(stack_start)
.quad init_thread_union+THREAD_SIZE-8
^^^
But I don't see why it needed the -8 then. It came with a conglomerate
dump in 2002:
commit af53c7a2c81399b805b6d4eff887401a5e50feef
Author: Andi Kleen <a...@muc.de>
Date: Fri Apr 19 20:23:17 2002 -0700
[PATCH] x86-64 architecture specific sync for 2.5.8
- /* Setup the first kernel stack (this instruction is modified by
smpboot) */
- .byte 0x48, 0xb8 /* movq *init_rsp,%rax */
-init_rsp:
- .quad init_thread_union+THREAD_SIZE
- movq %rax, %rsp
...
-
- /* SMP bootup changes this */
+ /* SMP bootup changes these two */
.globl initial_code
initial_code:
.quad x86_64_start_kernel
+ .globl init_rsp
+init_rsp:
+ .quad init_thread_union+THREAD_SIZE-8
+
---
But since we decrement first and then copy to stack ptr when we push, I
don't see why we need the -8.
Do you have a better clue?
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
