linux-kernel - Re: [v3 PATCH 04/10] x86/insn-kernel: Add a function to obtain register offset in ModRM

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Message-Id: <20170126111121.2936732c88f1d60fbdc6835a@kernel.org>
Date:   Thu, 26 Jan 2017 11:11:21 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andy Lutomirski <luto@...nel.org>,
        Borislav Petkov <bp@...e.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Brian Gerst <brgerst@...il.com>,
        Chris Metcalf <cmetcalf@...lanox.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Liang Z Li <liang.z.li@...el.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Huang Rui <ray.huang@....com>, Jiri Slaby <jslaby@...e.cz>,
        Jonathan Corbet <corbet@....net>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Chen Yucong <slaoub@...il.com>,
        Alexandre Julliard <julliard@...ehq.org>,
        Fenghua Yu <fenghua.yu@...el.com>, Stas Sergeev <stsp@...t.ru>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Shuah Khan <shuah@...nel.org>, linux-kernel@...r.kernel.org,
        x86@...nel.org, linux-msdos@...r.kernel.org, wine-devel@...ehq.org,
        Adam Buchbinder <adam.buchbinder@...il.com>,
        Colin Ian King <colin.king@...onical.com>,
        Lorenzo Stoakes <lstoakes@...il.com>,
        Qiaowei Ren <qiaowei.ren@...el.com>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Kees Cook <keescook@...omium.org>,
        Thomas Garnier <thgarnie@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [v3 PATCH 04/10] x86/insn-kernel: Add a function to obtain
 register offset in ModRM

On Wed, 25 Jan 2017 12:23:47 -0800
Ricardo Neri <ricardo.neri-calderon@...ux.intel.com> wrote:

> The function insn_get_reg_offset requires a type to indicate whether
> the returned offset is that given by by the ModRM or the SIB byte.
> Callers of this function would need the definition of the type struct.
> This is not needed. Instead, auxiliary functions can be defined for
> this purpose.
> 
> When the operand is a register, the emulation code for User-Mode
> Instruction Prevention needs to know the offset of the register indicated
> in the r/m part of the ModRM byte. Thus, start by adding an auxiliary
> function for this purpose.

Hmm, why wouldn't you just rename it to insn_get_reg_offset() and export it?

Thank you,

> 
> Cc: Dave Hansen <dave.hansen@...ux.intel.com>
> Cc: Adam Buchbinder <adam.buchbinder@...il.com>
> Cc: Colin Ian King <colin.king@...onical.com>
> Cc: Lorenzo Stoakes <lstoakes@...il.com>
> Cc: Qiaowei Ren <qiaowei.ren@...el.com>
> Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
> Cc: Masami Hiramatsu <mhiramat@...nel.org>
> Cc: Adrian Hunter <adrian.hunter@...el.com>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Thomas Garnier <thgarnie@...gle.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Borislav Petkov <bp@...e.de>
> Cc: Dmitry Vyukov <dvyukov@...gle.com>
> Cc: Ravi V. Shankar <ravi.v.shankar@...el.com>
> Cc: x86@...nel.org
> Signed-off-by: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
> ---
>  arch/x86/include/asm/insn-kernel.h | 1 +
>  arch/x86/lib/insn-kernel.c         | 5 +++++
>  2 files changed, 6 insertions(+)
> 
> diff --git a/arch/x86/include/asm/insn-kernel.h b/arch/x86/include/asm/insn-kernel.h
> index aef416a..3f34649 100644
> --- a/arch/x86/include/asm/insn-kernel.h
> +++ b/arch/x86/include/asm/insn-kernel.h
> @@ -12,5 +12,6 @@
>  #include <asm/ptrace.h>
>  
>  void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs);
> +int insn_get_reg_offset_rm(struct insn *insn, struct pt_regs *regs);
>  
>  #endif /* _ASM_X86_INSN_KERNEL_H */
> diff --git a/arch/x86/lib/insn-kernel.c b/arch/x86/lib/insn-kernel.c
> index 8072abe..267cab4 100644
> --- a/arch/x86/lib/insn-kernel.c
> +++ b/arch/x86/lib/insn-kernel.c
> @@ -95,6 +95,11 @@ static int get_reg_offset(struct insn *insn, struct pt_regs *regs,
>  	return regoff[regno];
>  }
>  
> +int insn_get_reg_offset_rm(struct insn *insn, struct pt_regs *regs)
> +{
> +	return get_reg_offset(insn, regs, REG_TYPE_RM);
> +}
> +
>  /*
>   * return the address being referenced be instruction
>   * for rm=3 returning the content of the rm reg
> -- 
> 2.9.3
> 


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