Messages in this thread | | | From | Denys Vlasenko <> | Date | Fri, 11 Apr 2014 14:23:27 +0200 | Subject | Re: Re: [RFC PATCH 4/6] uprobes/x86: Emulate rip-relative call's |
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On Fri, Apr 11, 2014 at 5:03 AM, Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> wrote: > At least, if we can trust Intel SDM, it says that depends > on the operand-size (insn->opnd_bytes) and stack segment > descriptor. Please check the SDM vol.1 6.2.2 Stack Alignment > and vol.2a, 3.2 Instructions (A-M), CALL--Call Procedure. > But we'd better check it on x86-32.
I am past trusting CPU manuals on this one:
By now I verified on the real hardware that AMD and Intel CPUs handle this insn differently in 64-bit mode: Intel ignores 0x66 prefix. AMD treats this insn the same as in 32-bit mode: as 16-bit insn.
(Should I submit a patch adding comment about it in x86-opcode-map.txt?)
So there is no universally "correct" way to emulate it.
We, theoretically, can decode it differently *depending on actual CPU(s) on the system*... do we really want to go *that* far? I guess not.
-- vda
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