Re: [RFC] [PATCH 1/7] User Space Breakpoint Assistance Layer (UBP)

From: Masami Hiramatsu
Date: Mon Jan 18 2010 - 16:23:17 EST

Jim Keniston wrote:
> On Mon, 2010-01-18 at 10:58 -0500, Masami Hiramatsu wrote:
>> Jim Keniston wrote:
>>> Not really. For #3 (boosting), you need to know everything for #2,
>>> plus be able to compute the length of each instruction -- which we can
>>> now do for x86. To emulate an instruction (#4), you need to replicate
>>> what it does, side-effects and all. The x86 instruction set seems to
>>> be adding new floating-point instructions all the time, and I bet even
>>> Masami doesn't know what they all do, but so far, they all seem to
>>> adhere to the instruction-length rules encoded in Masami's instruction
>>> decoder.
>> Actually, current x86 decoder doesn't support FP(x87) instructions.(even
>> it already supported AVX) But I think it's not so hard to add it.
> At one point I verified that it worked for all the x87 instructions in
> libm:
> I'm pretty sure I tested mmx instructions as well. But I guess this was
> before you rearranged the opcode tables.
> Yeah, it wouldn't be hard to add back in, at least for purposes of
> computing instruction lengths.

objdump -d /lib/ | awk -f arch/x86/tools/distill.awk | ./test_get_len
Succeed: decoded and checked 37198 instructions

Hmm, yeah, that's already supported :-D.

Thank you,

Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division

e-mail: mhiramat@xxxxxxxxxx

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