linux-kernel - Re: [PATCH v4 10/75] x86/insn: Add insn_has_rep

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Date:   Fri, 17 Jul 2020 23:06:22 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Joerg Roedel <joro@...tes.org>
Cc:     x86@...nel.org, Joerg Roedel <jroedel@...e.de>, hpa@...or.com,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Jiri Slaby <jslaby@...e.cz>,
        Dan Williams <dan.j.williams@...el.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Juergen Gross <jgross@...e.com>,
        Kees Cook <keescook@...omium.org>,
        David Rientjes <rientjes@...gle.com>,
        Cfir Cohen <cfir@...gle.com>,
        Erdem Aktas <erdemaktas@...gle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mike Stunes <mstunes@...are.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Martin Radev <martin.b.radev@...il.com>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH v4 10/75] x86/insn: Add insn_has_rep_prefix() helper

On Tue, 14 Jul 2020 14:08:12 +0200
Joerg Roedel <joro@...tes.org> wrote:

> From: Joerg Roedel <jroedel@...e.de>
> 
> Add a function to check whether an instruction has a REP prefix.

This looks good to me.

Reviewed-by: Masami Hiramatsu <mhiramat@...nel.org>
 
Thank you,

> 
> Signed-off-by: Joerg Roedel <jroedel@...e.de>
> ---
>  arch/x86/include/asm/insn-eval.h |  1 +
>  arch/x86/lib/insn-eval.c         | 24 ++++++++++++++++++++++++
>  2 files changed, 25 insertions(+)
> 
> diff --git a/arch/x86/include/asm/insn-eval.h b/arch/x86/include/asm/insn-eval.h
> index f748f57f1491..a0f839aa144d 100644
> --- a/arch/x86/include/asm/insn-eval.h
> +++ b/arch/x86/include/asm/insn-eval.h
> @@ -15,6 +15,7 @@
>  #define INSN_CODE_SEG_OPND_SZ(params) (params & 0xf)
>  #define INSN_CODE_SEG_PARAMS(oper_sz, addr_sz) (oper_sz | (addr_sz << 4))
>  
> +bool insn_has_rep_prefix(struct insn *insn);
>  void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs);
>  int insn_get_modrm_rm_off(struct insn *insn, struct pt_regs *regs);
>  int insn_get_modrm_reg_off(struct insn *insn, struct pt_regs *regs);
> diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c
> index a8ac5c5e94f0..8ed9d645259c 100644
> --- a/arch/x86/lib/insn-eval.c
> +++ b/arch/x86/lib/insn-eval.c
> @@ -53,6 +53,30 @@ static bool is_string_insn(struct insn *insn)
>  	}
>  }
>  
> +/**
> + * insn_has_rep_prefix() - Determine if instruction has a REP prefix
> + * @insn:	Instruction containing the prefix to inspect
> + *
> + * Returns:
> + *
> + * true if the instruction has a REP prefix, false if not.
> + */
> +bool insn_has_rep_prefix(struct insn *insn)
> +{
> +	int i;
> +
> +	insn_get_prefixes(insn);
> +
> +	for (i = 0; i < insn->prefixes.nbytes; i++) {
> +		insn_byte_t p = insn->prefixes.bytes[i];
> +
> +		if (p == 0xf2 || p == 0xf3)
> +			return true;
> +	}
> +
> +	return false;
> +}
> +
>  /**
>   * get_seg_reg_override_idx() - obtain segment register override index
>   * @insn:	Valid instruction with segment override prefixes
> -- 
> 2.27.0
> 


-- 
Masami Hiramatsu <mhiramat@...nel.org>