linux-kernel - Re: [PATCH v2 08/39] x86/linkage: Add ENDBR to SYM_FUNC

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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <202202241643.1258DB72D8@keescook>
Date:   Thu, 24 Feb 2022 16:45:05 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     x86@...nel.org, joao@...rdrivepizza.com, hjl.tools@...il.com,
        jpoimboe@...hat.com, andrew.cooper3@...rix.com,
        linux-kernel@...r.kernel.org, ndesaulniers@...gle.com,
        samitolvanen@...gle.com, mark.rutland@....com,
        alyssa.milburn@...el.com, mbenes@...e.cz, rostedt@...dmis.org,
        mhiramat@...nel.org, alexei.starovoitov@...il.com
Subject: Re: [PATCH v2 08/39] x86/linkage: Add ENDBR to SYM_FUNC_START*()

On Thu, Feb 24, 2022 at 03:51:46PM +0100, Peter Zijlstra wrote:
> Ensure the ASM functions have ENDBR on for IBT builds, this follows
> the ARM64 example. Unlike ARM64, we'll likely end up overwriting them
> with poison.
> 
> Suggested-by: Mark Rutland <mark.rutland@....com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> ---
>  arch/x86/include/asm/linkage.h |   39 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 39 insertions(+)
> 
> --- a/arch/x86/include/asm/linkage.h
> +++ b/arch/x86/include/asm/linkage.h
> @@ -3,6 +3,7 @@
>  #define _ASM_X86_LINKAGE_H
>  
>  #include <linux/stringify.h>
> +#include <asm/ibt.h>
>  
>  #undef notrace
>  #define notrace __attribute__((no_instrument_function))
> @@ -34,5 +35,43 @@
>  
>  #endif /* __ASSEMBLY__ */
>  
> +/*
> + * compressed and purgatory define this to disable EXPORT,
> + * hijack this same to also not emit ENDBR.
> + */
> +#ifndef __DISABLE_EXPORTS

It's certainly cleaner to avoid increasing boot stub image size, but
there's no _harm_ in including them, yes?

Reviewed-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook