Messages in this thread | | | Date | Tue, 19 Oct 2021 10:34:45 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH 2/3] x86/insn-eval: Introduce insn_decode_mmio() |
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On Mon, Oct 18, 2021 at 07:49:41PM +0300, Kirill A. Shutemov wrote: > On Mon, Oct 18, 2021 at 05:53:49PM +0200, Peter Zijlstra wrote: > > On Mon, Oct 18, 2021 at 06:33:32PM +0300, Kirill A. Shutemov wrote: > > > > > diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c > > > index fbaa3fa24bde..2ab29d8d6731 100644 > > > --- a/arch/x86/lib/insn-eval.c > > > +++ b/arch/x86/lib/insn-eval.c > > > @@ -1559,3 +1559,85 @@ bool insn_decode_from_regs(struct insn *insn, struct pt_regs *regs, > > > > > > return true; > > > } > > > + > > > +/** > > > + * insn_decode_mmio() - Decode a MMIO instruction > > > + * @insn: Structure to store decoded instruction > > > + * @bytes: Returns size of memory operand > > > + * > > > + * Decodes instruction that used for Memory-mapped I/O. > > > + * > > > + * Returns: > > > + * > > > + * Type of the instruction. Size of the memory operand is stored in > > > + * @bytes. If decode failed, MMIO_DECODE_FAILED returned. > > > + */ > > > +enum mmio_type insn_decode_mmio(struct insn *insn, int *bytes) > > > +{ > > > + int type = MMIO_DECODE_FAILED; > > > + > > > + *bytes = 0; > > > + > > > + insn_get_opcode(insn); > > > > insn_get_opcode() can fail. Either you assume it's already called and > > don't call it, or you can't assume anything and get to do error > > handling. > > Fair enough. I will return MMIO_DECODE_FAILED if insn_get_opcode() fails. > > BTW, looks like is_string_insn() suffers from the same issue. Not sure how > to fix it though.
AFAICT all callers of insn_get_addr_ref() (which is what is_string_insn() seems to be part of) do a insn_decode_*() call with error checking before.
So it looks like that insn_get_opcode() in there is superfluous. probably same for insn_has_rep_prefix() / get_seg_reg_override_idx() / get_eff_addr_modrm_*(). That all wants cleaning up.
The esaiest way is probably to push those things up the callchains into the !static function and have it fail early there.
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