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Date: Tue, 08 Oct 2013 15:15:00 -0000
Message-ID: <CAMe9rOrZuQRgcaUNgex=MDFjKYxsJimK1aCMqzEyM2XbZXCo4w@mail.gmail.com>
Subject: Re: [PATCH 2/6] x86/MPX: fix address size handling
From: "H.J. Lu" <hjl.tools@gmail.com>
To: Jan Beulich <JBeulich@suse.com>
Cc: kirill.yukhin@intel.com, Binutils <binutils@sourceware.org>
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On Tue, Oct 8, 2013 at 7:41 AM, Jan Beulich <JBeulich@suse.com> wrote:
> While address overrides are ignored in 64-bit mode (and hence shouldn't
> result in an error), trying to use 16-bit addressing is documented to
> result in #UD, and hence the assembler should reject the attempt.
>
> gas/
> 2013-10-08  Jan Beulich <jbeulich@suse.com>
>
>         * tc-i386.c (md_assemble): Alter address size checking for MPX
>         instructions.
>
> --- 2013-10-07/gas/config/tc-i386.c
> +++ 2013-10-07/gas/config/tc-i386.c
> @@ -3549,10 +3549,15 @@ md_assemble (char *line)
>    if (i.bnd_prefix && !i.tm.opcode_modifier.bndprefixok)
>      as_bad (_("expecting valid branch instruction after `bnd'"));
>
> -  if (i.tm.cpu_flags.bitfield.cpumpx
> -      && flag_code == CODE_64BIT
> -      && i.prefix[ADDR_PREFIX])
> -    as_bad (_("32-bit address isn't allowed in 64-bit MPX instructions."));

It is done on purpose.  When 32-bit address prefix in 64-bit is ignored,
MPX doesn't work correctly for x32.

> +  if (i.tm.cpu_flags.bitfield.cpumpx)
> +    {
> +      if (flag_code == CODE_64BIT && i.prefix[ADDR_PREFIX])
> +       as_warn (_("32-bit addressing is ignored in 64-bit MPX instructions"));
> +      else if (flag_code != CODE_16BIT
> +              ? i.prefix[ADDR_PREFIX]
> +              : i.mem_operands && !i.prefix[ADDR_PREFIX])
> +       as_bad (_("16-bit addressing isn't allowed in MPX instructions"));
> +    }
>
>    /* Insert BND prefix.  */
>    if (add_bnd_prefix
>
>
>



-- 
H.J.