Re: [tip:x86/asm] x86/entry/vsyscall: Add CONFIG to control default

[Borislav Petkov <bp@alien8.de>]

On Sun, Sep 20, 2015 at 04:29:18AM -0700, tip-bot for Kees Cook wrote:
> Commit-ID:  3dc33bd30f3e1c1bcaaafa3482737694debf0f0b
> Gitweb:     http://git.kernel.org/tip/3dc33bd30f3e1c1bcaaafa3482737694debf0f0b
> Author:     Kees Cook <keescook@chromium.org>
> AuthorDate: Wed, 12 Aug 2015 17:55:19 -0700
> Committer:  Ingo Molnar <mingo@kernel.org>
> CommitDate: Sun, 20 Sep 2015 10:31:06 +0200
> 
> x86/entry/vsyscall: Add CONFIG to control default
> 
> Most modern systems can run with vsyscall=none. In an effort to
> provide a way for build-time defaults to lack legacy settings,
> this adds a new CONFIG to select the type of vsyscall mapping to
> use, similar to the existing "vsyscall" command line parameter.
> 
> Signed-off-by: Kees Cook <keescook@chromium.org>
> Acked-by: Andy Lutomirski <luto@amacapital.net>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: Brian Gerst <brgerst@gmail.com>
> Cc: Denys Vlasenko <dvlasenk@redhat.com>
> Cc: H. Peter Anvin <hpa@zytor.com>
> Cc: Josh Triplett <josh@joshtriplett.org>
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Link: http://lkml.kernel.org/r/20150813005519.GA11696@www.outflux.net
> Signed-off-by: Ingo Molnar <mingo@kernel.org>
> ---
>  arch/x86/Kconfig                      | 49 +++++++++++++++++++++++++++++++++++
>  arch/x86/entry/vsyscall/vsyscall_64.c |  9 ++++++-
>  2 files changed, 57 insertions(+), 1 deletion(-)

...

> diff --git a/arch/x86/entry/vsyscall/vsyscall_64.c b/arch/x86/entry/vsyscall/vsyscall_64.c
> index b160c0c..76e0fd3 100644
> --- a/arch/x86/entry/vsyscall/vsyscall_64.c
> +++ b/arch/x86/entry/vsyscall/vsyscall_64.c
> @@ -38,7 +38,14 @@
>  #define CREATE_TRACE_POINTS
>  #include "vsyscall_trace.h"
>  
> -static enum { EMULATE, NATIVE, NONE } vsyscall_mode = EMULATE;
> +static enum { EMULATE, NATIVE, NONE } vsyscall_mode =
> +#ifdef CONFIG_LEGACY_VSYSCALL_NATIVE
> +	NATIVE;
> +#elif CONFIG_LEGACY_VSYSCALL_NONE

My gcc complains about this. If it hasn't been fixed yet, here's a fix:

---
From: Borislav Petkov <bp@suse.de>
Date: Mon, 21 Sep 2015 09:34:23 +0200
Subject: [PATCH] x86/entry/vsyscall: Fix undefined symbol warning

3dc33bd30f3e1 ("x86/entry/vsyscall: Add CONFIG to control default") did
the ifdef/elif thing but gcc doesn't like that:

  arch/x86/entry/vsyscall/vsyscall_64.c:44:7: warning: "CONFIG_LEGACY_VSYSCALL_NONE" is not defined [-Wundef]
   #elif CONFIG_LEGACY_VSYSCALL_NONE
         ^

Use defined() instead.

Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Kees Cook <keescook@chromium.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20150813005519.GA11696@www.outflux.net
Signed-off-by: Borislav Petkov <bp@suse.de>
---
 arch/x86/entry/vsyscall/vsyscall_64.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/entry/vsyscall/vsyscall_64.c b/arch/x86/entry/vsyscall/vsyscall_64.c
index 76e0fd3ea1fb..174c2549939d 100644
--- a/arch/x86/entry/vsyscall/vsyscall_64.c
+++ b/arch/x86/entry/vsyscall/vsyscall_64.c
@@ -39,9 +39,9 @@
 #include "vsyscall_trace.h"
 
 static enum { EMULATE, NATIVE, NONE } vsyscall_mode =
-#ifdef CONFIG_LEGACY_VSYSCALL_NATIVE
+#if defined(CONFIG_LEGACY_VSYSCALL_NATIVE)
 	NATIVE;
-#elif CONFIG_LEGACY_VSYSCALL_NONE
+#elif defined(CONFIG_LEGACY_VSYSCALL_NONE)
 	NONE;
 #else
 	EMULATE;
-- 
2.1.4

-- 
Regards/Gruss,
    Boris.

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