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Re: [PATCH 2/6] x86/MPX: fix address size handling
- From: "H.J. Lu" <hjl dot tools at gmail dot com>
- To: Jan Beulich <JBeulich at suse dot com>
- Cc: kirill dot yukhin at intel dot com, Binutils <binutils at sourceware dot org>
- Date: Tue, 8 Oct 2013 08:15:33 -0700
- Subject: Re: [PATCH 2/6] x86/MPX: fix address size handling
- Authentication-results: sourceware.org; auth=none
- References: <5254349502000078000F9A3D at nat28 dot tlf dot novell dot com> <525435BC02000078000F9A51 at nat28 dot tlf dot novell dot com>
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.