Messages in this thread | | | Date | Thu, 3 Mar 2016 17:29:52 +0100 | From | Borislav Petkov <> | Subject | Re: [RFC PATCH] x86: Make sure verify_cpu has a good stack |
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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 <ak@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.
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