Messages in this thread | | | Date | Wed, 25 Nov 2020 17:03:10 +0900 | From | Masami Hiramatsu <> | Subject | Re: [RFC PATCH v0 00/19] x86/insn: Add an insn_decode() API |
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On Tue, 24 Nov 2020 18:46:47 +0100 Borislav Petkov <bp@alien8.de> wrote:
> On Tue, Nov 24, 2020 at 11:19:33AM +0100, Borislav Petkov wrote: > > In any case, at least the case where I give it > > > > 0x48 0xcf 0x48 0x83 > > > > and say that buf size is 4, should return an error because the second > > insn is incomplete. So I need to go look at that now. > > Ok, got it: > > ./arch/x86/tools/insn_sanity: Success: decoded and checked 10000 random instructions with 0 errors (seed:0x826fdf9c) > insn buffer: > 0x48 0xcf 0x48 0x83 0x90 0x90 0x90 0x90 0x90 0x90 0x90 0x90 0x90 0x90 0x90 > supplied buf size: 15, ret 0 > supplied buf size: 2, ret 0 > supplied buf size: 3, ret 0 > supplied buf size: 4, ret 0 > supplied buf size: 1, ret -22 > > the current decoder simply decodes the *first* insn in the buffer it > encounters and that's it.
Yes, currently the buf_size is only for checking the maximum length of the buffer, because we expect the user doesn't know the actual length of the instruction before calling insn_get_length(). But yes, for the insn_sanity.c, the return length should be compared.
Thank you,
> > When you give it a buffer of size smaller than the first instruction: > > supplied buf size: 1, ret -22 > > while the first insn is 2 bytes long: > > 0x48 0xcf (IRETQ) > > then it signals an error. > > Andy, does that work for your use cases? > > -- > Regards/Gruss, > Boris. > > https://people.kernel.org/tglx/notes-about-netiquette
-- Masami Hiramatsu <mhiramat@kernel.org>
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