linux-kernel - [PATCH v4 45/45] x86: kmsan: enable KMSAN builds for x86

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Date:   Fri,  1 Jul 2022 16:23:10 +0200
From:   Alexander Potapenko <glider@...gle.com>
To:     glider@...gle.com
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        Alexei Starovoitov <ast@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
        Christoph Hellwig <hch@....de>,
        Christoph Lameter <cl@...ux.com>,
        David Rientjes <rientjes@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Ilya Leoshkevich <iii@...ux.ibm.com>,
        Ingo Molnar <mingo@...hat.com>, Jens Axboe <axboe@...nel.dk>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Kees Cook <keescook@...omium.org>,
        Marco Elver <elver@...gle.com>,
        Mark Rutland <mark.rutland@....com>,
        Matthew Wilcox <willy@...radead.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Pekka Enberg <penberg@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Vegard Nossum <vegard.nossum@...cle.com>,
        Vlastimil Babka <vbabka@...e.cz>, kasan-dev@...glegroups.com,
        linux-mm@...ck.org, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v4 45/45] x86: kmsan: enable KMSAN builds for x86

Make KMSAN usable by adding the necessary Kconfig bits.

Also declare x86-specific functions checking address validity
in arch/x86/include/asm/kmsan.h.

Signed-off-by: Alexander Potapenko <glider@...gle.com>
---
v4:
 -- per Marco Elver's request, create arch/x86/include/asm/kmsan.h
    and move arch-specific inline functions there.

Link: https://linux-review.googlesource.com/id/I1d295ce8159ce15faa496d20089d953a919c125e
---
 arch/x86/Kconfig             |  1 +
 arch/x86/include/asm/kmsan.h | 55 ++++++++++++++++++++++++++++++++++++
 2 files changed, 56 insertions(+)
 create mode 100644 arch/x86/include/asm/kmsan.h

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index aadbb16a59f01..d1a601111b277 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -169,6 +169,7 @@ config X86
 	select HAVE_ARCH_KASAN			if X86_64
 	select HAVE_ARCH_KASAN_VMALLOC		if X86_64
 	select HAVE_ARCH_KFENCE
+	select HAVE_ARCH_KMSAN			if X86_64
 	select HAVE_ARCH_KGDB
 	select HAVE_ARCH_MMAP_RND_BITS		if MMU
 	select HAVE_ARCH_MMAP_RND_COMPAT_BITS	if MMU && COMPAT
diff --git a/arch/x86/include/asm/kmsan.h b/arch/x86/include/asm/kmsan.h
new file mode 100644
index 0000000000000..a790b865d0a68
--- /dev/null
+++ b/arch/x86/include/asm/kmsan.h
@@ -0,0 +1,55 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * x86 KMSAN support.
+ *
+ * Copyright (C) 2022, Google LLC
+ * Author: Alexander Potapenko <glider@...gle.com>
+ */
+
+#ifndef _ASM_X86_KMSAN_H
+#define _ASM_X86_KMSAN_H
+
+#ifndef MODULE
+
+#include <asm/processor.h>
+#include <linux/mmzone.h>
+
+/*
+ * Taken from arch/x86/mm/physaddr.h to avoid using an instrumented version.
+ */
+static inline bool kmsan_phys_addr_valid(unsigned long addr)
+{
+	if (IS_ENABLED(CONFIG_PHYS_ADDR_T_64BIT))
+		return !(addr >> boot_cpu_data.x86_phys_bits);
+	else
+		return true;
+}
+
+/*
+ * Taken from arch/x86/mm/physaddr.c to avoid using an instrumented version.
+ */
+static inline bool kmsan_virt_addr_valid(void *addr)
+{
+	unsigned long x = (unsigned long)addr;
+	unsigned long y = x - __START_KERNEL_map;
+
+	/* use the carry flag to determine if x was < __START_KERNEL_map */
+	if (unlikely(x > y)) {
+		x = y + phys_base;
+
+		if (y >= KERNEL_IMAGE_SIZE)
+			return false;
+	} else {
+		x = y + (__START_KERNEL_map - PAGE_OFFSET);
+
+		/* carry flag will be set if starting x was >= PAGE_OFFSET */
+		if ((x > y) || !kmsan_phys_addr_valid(x))
+			return false;
+	}
+
+	return pfn_valid(x >> PAGE_SHIFT);
+}
+
+#endif /* !MODULE */
+
+#endif /* _ASM_X86_KMSAN_H */
-- 
2.37.0.rc0.161.g10f37bed90-goog