linux-kernel - Re: [PATCH 13/15] x86/static_call: Add inline static call implementation for x86-64

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: <20190610183357.zj6rwdpgw36anpfc@treble>
Date:   Mon, 10 Jun 2019 13:33:57 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Andy Lutomirski <luto@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Jason Baron <jbaron@...mai.com>, Jiri Kosina <jkosina@...e.cz>,
        David Laight <David.Laight@...LAB.COM>,
        Borislav Petkov <bp@...en8.de>,
        Julia Cartwright <julia@...com>, Jessica Yu <jeyu@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>, Nadav Amit <namit@...are.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Edward Cree <ecree@...arflare.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>
Subject: Re: [PATCH 13/15] x86/static_call: Add inline static call
 implementation for x86-64

On Wed, Jun 05, 2019 at 03:08:06PM +0200, Peter Zijlstra wrote:
> --- a/arch/x86/include/asm/static_call.h
> +++ b/arch/x86/include/asm/static_call.h
> @@ -2,6 +2,20 @@
>  #ifndef _ASM_STATIC_CALL_H
>  #define _ASM_STATIC_CALL_H
>  
> +#include <asm/asm-offsets.h>
> +
> +#ifdef CONFIG_HAVE_STATIC_CALL_INLINE
> +
> +/*
> + * This trampoline is only used during boot / module init, so it's safe to use
> + * the indirect branch without a retpoline.
> + */
> +#define __ARCH_STATIC_CALL_TRAMP_JMP(key, func)				\
> +	ANNOTATE_RETPOLINE_SAFE						\
> +	"jmpq *" __stringify(key) "+" __stringify(SC_KEY_func) "(%rip) \n"
> +
> +#else /* !CONFIG_HAVE_STATIC_CALL_INLINE */

I wonder if we can simplify this (and drop the indirect branch) by
getting rid of the above cruft, and instead just use the out-of-line
trampoline as the default for inline as well.

Then the inline case could fall back to the out-of-line implementation
(by patching the trampoline's jmp dest) before static_call_initialized
is set.

-- 
Josh