linux-kernel - Re: [PATCH 2/4] kfence: add function to mask address bits

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Message-ID: <YQJdarx6XSUQ1tFZ@elver.google.com>
Date:   Thu, 29 Jul 2021 09:48:58 +0200
From:   Marco Elver <elver@...gle.com>
To:     Heiko Carstens <hca@...ux.ibm.com>
Cc:     Alexander Potapenko <glider@...gle.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        kasan-dev@...glegroups.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org
Subject: Re: [PATCH 2/4] kfence: add function to mask address bits

On Wed, Jul 28, 2021 at 09:02PM +0200, Heiko Carstens wrote:
> From: Sven Schnelle <svens@...ux.ibm.com>
> 
> s390 only reports the page address during a translation fault.
> To make the kfence unit tests pass, add a function that might
> be implemented by architectures to mask out address bits.
> 
> Signed-off-by: Sven Schnelle <svens@...ux.ibm.com>
> Signed-off-by: Heiko Carstens <hca@...ux.ibm.com>

I noticed this breaks on x86 if CONFIG_KFENCE_KUNIT_TEST=m, because x86
conditionally declares some asm functions if !MODULE.

I think the below is the simplest to fix, and if you agree, please carry
it as a patch in this series before this patch.

With the below, you can add to this patch:

	Reviewed-by: Marco Elver <elver@...gle.com>

Thanks,
-- Marco

------ >8 ------

From: Marco Elver <elver@...gle.com>
Date: Wed, 28 Jul 2021 21:57:41 +0200
Subject: [PATCH] kfence, x86: only define helpers if !MODULE

x86's <asm/tlbflush.h> only declares non-module accessible functions
(such as flush_tlb_one_kernel) if !MODULE.

In preparation of including <asm/kfence.h> from the KFENCE test module,
only define the helpers if !MODULE to avoid breaking the build with
CONFIG_KFENCE_KUNIT_TEST=m.

Signed-off-by: Marco Elver <elver@...gle.com>
---
 arch/x86/include/asm/kfence.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/include/asm/kfence.h b/arch/x86/include/asm/kfence.h
index 05b48b33baf0..ff5c7134a37a 100644
--- a/arch/x86/include/asm/kfence.h
+++ b/arch/x86/include/asm/kfence.h
@@ -8,6 +8,8 @@
 #ifndef _ASM_X86_KFENCE_H
 #define _ASM_X86_KFENCE_H
 
+#ifndef MODULE
+
 #include <linux/bug.h>
 #include <linux/kfence.h>
 
@@ -66,4 +68,6 @@ static inline bool kfence_protect_page(unsigned long addr, bool protect)
 	return true;
 }
 
+#endif /* !MODULE */
+
 #endif /* _ASM_X86_KFENCE_H */
-- 
2.32.0.554.ge1b32706d8-goog