linux-kernel - Re: [PATCH v2 08/59] x86/build: Ensure proper function alignment

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAHk-=whdvPcHmH5eG+FUrbQw1e-05n__EWobMqbxcCTP7dtZAg@mail.gmail.com>
Date:   Fri, 2 Sep 2022 09:51:17 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org,
        x86@...nel.org, Tim Chen <tim.c.chen@...ux.intel.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Andrew Cooper <Andrew.Cooper3@...rix.com>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Johannes Wikner <kwikner@...z.ch>,
        Alyssa Milburn <alyssa.milburn@...ux.intel.com>,
        Jann Horn <jannh@...gle.com>, "H.J. Lu" <hjl.tools@...il.com>,
        Joao Moreira <joao.moreira@...el.com>,
        Joseph Nuzman <joseph.nuzman@...el.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Juergen Gross <jgross@...e.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        K Prateek Nayak <kprateek.nayak@....com>,
        Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH v2 08/59] x86/build: Ensure proper function alignment

On Fri, Sep 2, 2022 at 6:55 AM Peter Zijlstra <peterz@...radead.org> wrote:
>
> --- a/arch/x86/include/asm/linkage.h
> +++ b/arch/x86/include/asm/linkage.h
> @@ -14,9 +14,10 @@
>
>  #ifdef __ASSEMBLY__
>
> -#if defined(CONFIG_X86_64) || defined(CONFIG_X86_ALIGNMENT_16)
> -#define __ALIGN                .p2align 4, 0x90
> -#define __ALIGN_STR    __stringify(__ALIGN)
> +#if CONFIG_FUNCTION_ALIGNMENT == 16
> +#define __ALIGN                        .p2align 4, 0x90
> +#define __ALIGN_STR            __stringify(__ALIGN)
> +#define FUNCTION_ALIGNMENT     16
>  #endif

Ugh.

Why is this conditional on that alignment being 16?

Is it purely because the CONFIG variable was mis-designed, and is the
number of bytes, instead of being the shift? If so, just fix that, and
then do an unconditional

  #define __ALIGN                        .p2align
CONFIG_FUNCTION_ALIGNMENT_SHIFT, 0x90
  #define __ALIGN_STR            __stringify(__ALIGN)

(leave the asm-generic one conditional, since then the condition makes
sense - it's arch-specific).

           Linus