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From: Ilya Leoshkevich <iii@linux.ibm.com>
To: Alexander Gordeev <agordeev@linux.ibm.com>,
        Alexander Potapenko <glider@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Christoph Lameter <cl@linux.com>, David Rientjes <rientjes@google.com>,
        Heiko Carstens <hca@linux.ibm.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>, Marco Elver <elver@google.com>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Pekka Enberg <penberg@kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Vasily Gorbik <gor@linux.ibm.com>, Vlastimil Babka <vbabka@suse.cz>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Hyeonggon Yoo <42.hyeyoo@gmail.com>, kasan-dev@googlegroups.com,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        linux-s390@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
        Mark Rutland <mark.rutland@arm.com>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        Sven Schnelle <svens@linux.ibm.com>,
        Ilya Leoshkevich <iii@linux.ibm.com>
Subject: [PATCH v4 29/35] s390/mm: Define KMSAN metadata for vmalloc and modules
Date: Thu, 13 Jun 2024 17:34:31 +0200
Message-ID: <20240613153924.961511-30-iii@linux.ibm.com>
In-Reply-To: <20240613153924.961511-1-iii@linux.ibm.com>
References: <20240613153924.961511-1-iii@linux.ibm.com>
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The pages for the KMSAN metadata associated with most kernel mappings
are taken from memblock by the common code. However, vmalloc and module
metadata needs to be defined by the architectures.

Be a little bit more careful than x86: allocate exactly MODULES_LEN
for the module shadow and origins, and then take 2/3 of vmalloc for
the vmalloc shadow and origins. This ensures that users passing small
vmalloc= values on the command line do not cause module metadata
collisions.

Reviewed-by: Alexander Potapenko <glider@google.com>
Acked-by: Alexander Gordeev <agordeev@linux.ibm.com>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 arch/s390/boot/startup.c        | 7 +++++++
 arch/s390/include/asm/pgtable.h | 8 ++++++++
 2 files changed, 15 insertions(+)

diff --git a/arch/s390/boot/startup.c b/arch/s390/boot/startup.c
index 182aac6a0f77..93775142322d 100644
--- a/arch/s390/boot/startup.c
+++ b/arch/s390/boot/startup.c
@@ -301,11 +301,18 @@ static unsigned long setup_kernel_memory_layout(unsigned long kernel_size)
 	MODULES_END = round_down(kernel_start, _SEGMENT_SIZE);
 	MODULES_VADDR = MODULES_END - MODULES_LEN;
 	VMALLOC_END = MODULES_VADDR;
+	if (IS_ENABLED(CONFIG_KMSAN))
+		VMALLOC_END -= MODULES_LEN * 2;
 
 	/* allow vmalloc area to occupy up to about 1/2 of the rest virtual space left */
 	vsize = (VMALLOC_END - FIXMAP_SIZE) / 2;
 	vsize = round_down(vsize, _SEGMENT_SIZE);
 	vmalloc_size = min(vmalloc_size, vsize);
+	if (IS_ENABLED(CONFIG_KMSAN)) {
+		/* take 2/3 of vmalloc area for KMSAN shadow and origins */
+		vmalloc_size = round_down(vmalloc_size / 3, _SEGMENT_SIZE);
+		VMALLOC_END -= vmalloc_size * 2;
+	}
 	VMALLOC_START = VMALLOC_END - vmalloc_size;
 
 	__memcpy_real_area = round_down(VMALLOC_START - MEMCPY_REAL_SIZE, PAGE_SIZE);
diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index 70b6ee557eb2..2f44c23efec0 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -107,6 +107,14 @@ static inline int is_module_addr(void *addr)
 	return 1;
 }
 
+#ifdef CONFIG_KMSAN
+#define KMSAN_VMALLOC_SIZE (VMALLOC_END - VMALLOC_START)
+#define KMSAN_VMALLOC_SHADOW_START VMALLOC_END
+#define KMSAN_VMALLOC_ORIGIN_START (KMSAN_VMALLOC_SHADOW_START + KMSAN_VMALLOC_SIZE)
+#define KMSAN_MODULES_SHADOW_START (KMSAN_VMALLOC_ORIGIN_START + KMSAN_VMALLOC_SIZE)
+#define KMSAN_MODULES_ORIGIN_START (KMSAN_MODULES_SHADOW_START + MODULES_LEN)
+#endif
+
 #ifdef CONFIG_RANDOMIZE_BASE
 #define KASLR_LEN	(1UL << 31)
 #else
-- 
2.45.1