s390/kasan: add option for 4-level paging support

By default 3-level paging is used when the kernel is compiled with kasan support. Add 4-level paging option to support systems with more then 3TB of physical memory and to cover 4-level paging specific code with kasan as well. Reviewed-by: Martin Schwidefsky <[email protected]> Signed-off-by: Vasily Gorbik <[email protected]> Signed-off-by: Martin Schwidefsky <[email protected]>
niw · Oct 9, 2018 · 5dff038 · 5dff038
1 parent 135ff16
commit 5dff038
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Showing 5 changed files with 35 additions and 7 deletions.
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
@@ -59,6 +59,7 @@ config ARCH_SUPPORTS_UPROBES
 config KASAN_SHADOW_OFFSET
 	hex
 	depends on KASAN
+	default 0x18000000000000 if KASAN_S390_4_LEVEL_PAGING
 	default 0x30000000000
 
 config S390

diff --git a/arch/s390/include/asm/kasan.h b/arch/s390/include/asm/kasan.h
@@ -7,8 +7,13 @@
 #ifdef CONFIG_KASAN
 
 #define KASAN_SHADOW_SCALE_SHIFT 3
+#ifdef CONFIG_KASAN_S390_4_LEVEL_PAGING
+#define KASAN_SHADOW_SIZE						       \
+	(_AC(1, UL) << (_REGION1_SHIFT - KASAN_SHADOW_SCALE_SHIFT))
+#else
 #define KASAN_SHADOW_SIZE						       \
 	(_AC(1, UL) << (_REGION2_SHIFT - KASAN_SHADOW_SCALE_SHIFT))
+#endif
 #define KASAN_SHADOW_OFFSET	_AC(CONFIG_KASAN_SHADOW_OFFSET, UL)
 #define KASAN_SHADOW_START	KASAN_SHADOW_OFFSET
 #define KASAN_SHADOW_END	(KASAN_SHADOW_START + KASAN_SHADOW_SIZE)

diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c
@@ -535,7 +535,9 @@ static void __init setup_memory_end(void)
 	/* Choose kernel address space layout: 3 or 4 levels. */
 	vmalloc_size = VMALLOC_END ?: (128UL << 30) - MODULES_LEN;
 	if (IS_ENABLED(CONFIG_KASAN)) {
-		vmax = _REGION2_SIZE; /* 3-level kernel page table */
+		vmax = IS_ENABLED(CONFIG_KASAN_S390_4_LEVEL_PAGING)
+			   ? _REGION1_SIZE
+			   : _REGION2_SIZE;
 	} else {
 		tmp = (memory_end ?: max_physmem_end) / PAGE_SIZE;
 		tmp = tmp * (sizeof(struct page) + PAGE_SIZE);

diff --git a/arch/s390/mm/kasan_init.c b/arch/s390/mm/kasan_init.c
@@ -252,12 +252,23 @@ void __init kasan_early_init(void)
 		pgt_prot &= ~_PAGE_NOEXEC;
 	pte_z = __pte(__pa(kasan_zero_page) | pgt_prot);
 
-	/* 3 level paging */
-	BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_START, PUD_SIZE));
-	BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_END, PUD_SIZE));
-	crst_table_init((unsigned long *)early_pg_dir, _REGION3_ENTRY_EMPTY);
-	untracked_mem_end = vmax = _REGION2_SIZE;
-	asce_type = _ASCE_TYPE_REGION3;
+	if (IS_ENABLED(CONFIG_KASAN_S390_4_LEVEL_PAGING)) {
+		/* 4 level paging */
+		BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_START, P4D_SIZE));
+		BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_END, P4D_SIZE));
+		crst_table_init((unsigned long *)early_pg_dir,
+				_REGION2_ENTRY_EMPTY);
+		untracked_mem_end = vmax = _REGION1_SIZE;
+		asce_type = _ASCE_TYPE_REGION2;
+	} else {
+		/* 3 level paging */
+		BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_START, PUD_SIZE));
+		BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_END, PUD_SIZE));
+		crst_table_init((unsigned long *)early_pg_dir,
+				_REGION3_ENTRY_EMPTY);
+		untracked_mem_end = vmax = _REGION2_SIZE;
+		asce_type = _ASCE_TYPE_REGION3;
+	}
 
 	/* init kasan zero shadow */
 	crst_table_init((unsigned long *)kasan_zero_p4d, p4d_val(p4d_z));

diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
@@ -57,6 +57,15 @@ config KASAN_INLINE
 
 endchoice
 
+config KASAN_S390_4_LEVEL_PAGING
+	bool "KASan: use 4-level paging"
+	depends on KASAN && S390
+	help
+	  Compiling the kernel with KASan disables automatic 3-level vs
+	  4-level paging selection. 3-level paging is used by default (up
+	  to 3TB of RAM with KASan enabled). This options allows to force
+	  4-level paging instead.
+
 config TEST_KASAN
 	tristate "Module for testing kasan for bug detection"
 	depends on m && KASAN