linux-kernel - Re: [PATCH 2/4] x86/insn: perf tools: Pedantically tweak opcode map for MPX instructions

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Date:	Mon, 31 Aug 2015 11:48:39 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Adrian Hunter <adrian.hunter@...el.com>
Cc:	linux-kernel@...r.kernel.org, Jiri Olsa <jolsa@...hat.com>,
	Andy Lutomirski <luto@...capital.net>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Qiaowei Ren <qiaowei.ren@...el.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 2/4] x86/insn: perf tools: Pedantically tweak opcode map
 for MPX instructions

Em Mon, Aug 31, 2015 at 04:58:40PM +0300, Adrian Hunter escreveu:
> The MPX instructions are presently not described in the SDM
> opcode maps, and there are not encoding characters for bnd
> registers, address method or operand type.  So the kernel
> opcode map is using 'Gv' for bnd registers and 'Ev' for
> everything else.  That is fine because the instruction
> decoder does not use that information anyway, except as
> an indication that there is a ModR/M byte.
> 
> Nevertheless, in some cases the 'Gv' and 'Ev' are the wrong
> way around, BNDLDX and BNDSTX have 2 operands not 3, and it
> wouldn't hurt to identify the mandatory prefixes.
> 
> This has no effect on the decoding of valid instructions,
> but the addition of the mandatory prefixes will cause some
> invalid instructions to error out that wouldn't have
> previously.
> 
> Note that perf tools has a copy of the instruction decoder
> and provides a test for new instructions which includes MPX
> instructions e.g.
> 
> 	$ perf test list 2>&1 | grep "x86 ins"
> 	39: Test x86 instruction decoder - new instructions
> 	$ perf test 39
> 	39: Test x86 instruction decoder - new instructions          : Ok
> 
> Or to see the details:
> 
> 	$ perf test -v 39

this is a handy shortcut, but I think that sometimes showing that one
can also do it using the test description is handy, i.e. I forgot the
number of it was reordered, doing it like:

[root@zoo linux]# perf test syscall
 2: detect openat syscall event                              : Ok
 3: detect openat syscall event on all cpus                  : Ok
14: Generate and check syscalls:sys_enter_openat event fields: Ok
[root@zoo linux]#

Also works, which, for your case would be 'perf test x86', oops, that
would also catch:

[root@zoo linux]# perf test x86
 6: x86 rdpmc test                                           : Ok
[root@zoo linux]#

:-)

- Arnaldo
 
> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
> ---
>  arch/x86/lib/x86-opcode-map.txt                     | 8 ++++++--
>  tools/perf/util/intel-pt-decoder/x86-opcode-map.txt | 8 ++++++--
>  2 files changed, 12 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/lib/x86-opcode-map.txt b/arch/x86/lib/x86-opcode-map.txt
> index 816488c0b97e..a02a195d219c 100644
> --- a/arch/x86/lib/x86-opcode-map.txt
> +++ b/arch/x86/lib/x86-opcode-map.txt
> @@ -353,8 +353,12 @@ AVXcode: 1
>  17: vmovhps Mq,Vq (v1) | vmovhpd Mq,Vq (66),(v1)
>  18: Grp16 (1A)
>  19:
> -1a: BNDCL Ev,Gv | BNDCU Ev,Gv | BNDMOV Gv,Ev | BNDLDX Gv,Ev,Gv
> -1b: BNDCN Ev,Gv | BNDMOV Ev,Gv | BNDMK Gv,Ev | BNDSTX Ev,GV,Gv
> +# Intel SDM opcode map does not list MPX instructions. For now using Gv for
> +# bnd registers and Ev for everything else is OK because the instruction
> +# decoder does not use the information except as an indication that there is
> +# a ModR/M byte.
> +1a: BNDCL Gv,Ev (F3) | BNDCU Gv,Ev (F2) | BNDMOV Gv,Ev (66) | BNDLDX Gv,Ev
> +1b: BNDCN Gv,Ev (F2) | BNDMOV Ev,Gv (66) | BNDMK Gv,Ev (F3) | BNDSTX Ev,Gv
>  1c:
>  1d:
>  1e:
> diff --git a/tools/perf/util/intel-pt-decoder/x86-opcode-map.txt b/tools/perf/util/intel-pt-decoder/x86-opcode-map.txt
> index 816488c0b97e..a02a195d219c 100644
> --- a/tools/perf/util/intel-pt-decoder/x86-opcode-map.txt
> +++ b/tools/perf/util/intel-pt-decoder/x86-opcode-map.txt
> @@ -353,8 +353,12 @@ AVXcode: 1
>  17: vmovhps Mq,Vq (v1) | vmovhpd Mq,Vq (66),(v1)
>  18: Grp16 (1A)
>  19:
> -1a: BNDCL Ev,Gv | BNDCU Ev,Gv | BNDMOV Gv,Ev | BNDLDX Gv,Ev,Gv
> -1b: BNDCN Ev,Gv | BNDMOV Ev,Gv | BNDMK Gv,Ev | BNDSTX Ev,GV,Gv
> +# Intel SDM opcode map does not list MPX instructions. For now using Gv for
> +# bnd registers and Ev for everything else is OK because the instruction
> +# decoder does not use the information except as an indication that there is
> +# a ModR/M byte.
> +1a: BNDCL Gv,Ev (F3) | BNDCU Gv,Ev (F2) | BNDMOV Gv,Ev (66) | BNDLDX Gv,Ev
> +1b: BNDCN Gv,Ev (F2) | BNDMOV Ev,Gv (66) | BNDMK Gv,Ev (F3) | BNDSTX Ev,Gv
>  1c:
>  1d:
>  1e:
> -- 
> 1.9.1
--
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