linux-kernel - Re: [PATCH 2/3] x86/insn-eval: Introduce insn_decode

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Message-ID: <YW2YjRjUg8MzV0rJ@hirez.programming.kicks-ass.net>
Date:   Mon, 18 Oct 2021 17:53:49 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Tom Lendacky <thomas.lendacky@....com>,
        Joerg Roedel <jroedel@...e.de>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Sean Christopherson <seanjc@...gle.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Tony Luck <tony.luck@...el.com>
Subject: Re: [PATCH 2/3] x86/insn-eval: Introduce insn_decode_mmio()

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.

> +	switch (insn->opcode.bytes[0]) {
...
> +	}
> +
> +	return type;
> +}
> -- 
> 2.32.0
>