linux-kernel - Re: [PATCH v6 02/10] x86/retpoline/crypto: Convert crypto assembler indirect jumps

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Date:   Mon, 8 Jan 2018 07:49:23 -0600
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     David Woodhouse <dwmw@...zon.co.uk>
Cc:     Andi Kleen <ak@...ux.intel.com>, Paul Turner <pjt@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...ux-foundation.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>, tglx@...utronix.de,
        Kees Cook <keescook@...gle.com>,
        Rik van Riel <riel@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...capital.net>,
        Jiri Kosina <jikos@...nel.org>, gnomes@...rguk.ukuu.org.uk
Subject: Re: [PATCH v6 02/10] x86/retpoline/crypto: Convert crypto assembler
 indirect jumps

On Sun, Jan 07, 2018 at 10:11:17PM +0000, David Woodhouse wrote:
> Convert all indirect jumps in crypto assembler code to use non-speculative
> sequences when CONFIG_RETPOLINE is enabled.
> 
> Signed-off-by: David Woodhouse <dwmw@...zon.co.uk>
> Acked-By: Arjan van de Ven <arjan@...ux.intel.com>
> ---
>  arch/x86/crypto/aesni-intel_asm.S            | 5 +++--
>  arch/x86/crypto/camellia-aesni-avx-asm_64.S  | 3 ++-
>  arch/x86/crypto/camellia-aesni-avx2-asm_64.S | 3 ++-
>  arch/x86/crypto/crc32c-pcl-intel-asm_64.S    | 3 ++-
>  4 files changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/crypto/aesni-intel_asm.S b/arch/x86/crypto/aesni-intel_asm.S
> index 16627fe..f128680 100644
> --- a/arch/x86/crypto/aesni-intel_asm.S
> +++ b/arch/x86/crypto/aesni-intel_asm.S
> @@ -32,6 +32,7 @@
>  #include <linux/linkage.h>
>  #include <asm/inst.h>
>  #include <asm/frame.h>
> +#include <asm/nospec-branch.h>
>  
>  /*
>   * The following macros are used to move an (un)aligned 16 byte value to/from
> @@ -2884,7 +2885,7 @@ ENTRY(aesni_xts_crypt8)
>  	pxor INC, STATE4
>  	movdqu IV, 0x30(OUTP)
>  
> -	call *%r11
> +	NOSPEC_CALL %r11

Personally I find

	CALL_NOSPEC %r11

to be more readable.  The call is the action and the nospec is a detail.

And similarly for NOSPEC_JMP -> JMP_NOSPEC.

-- 
Josh