[PATCH v8 07/11] powerpc/32: prepare shadow area for KASAN

[Christophe Leroy]

This patch prepares a shadow area for KASAN.

The shadow area will be at the top of the kernel virtual
memory space above the fixmap area and will occupy one
eighth of the total kernel virtual memory space.

Signed-off-by: Christophe Leroy <christophe.leroy at c-s.fr>
---
 arch/powerpc/Kconfig.debug        |  5 +++++
 arch/powerpc/include/asm/fixmap.h |  5 +++++
 arch/powerpc/include/asm/kasan.h  | 16 ++++++++++++++++
 arch/powerpc/mm/mem.c             |  4 ++++
 arch/powerpc/mm/ptdump/ptdump.c   |  8 ++++++++
 5 files changed, 38 insertions(+)

diff --git a/arch/powerpc/Kconfig.debug b/arch/powerpc/Kconfig.debug
index 4e00cb0a5464..61febbbdd02b 100644
--- a/arch/powerpc/Kconfig.debug
+++ b/arch/powerpc/Kconfig.debug
@@ -366,3 +366,8 @@ config PPC_FAST_ENDIAN_SWITCH
         depends on DEBUG_KERNEL && PPC_BOOK3S_64
         help
 	  If you're unsure what this is, say N.
+
+config KASAN_SHADOW_OFFSET
+	hex
+	depends on KASAN
+	default 0xe0000000
diff --git a/arch/powerpc/include/asm/fixmap.h b/arch/powerpc/include/asm/fixmap.h
index b9fbed84ddca..51a1a309c919 100644
--- a/arch/powerpc/include/asm/fixmap.h
+++ b/arch/powerpc/include/asm/fixmap.h
@@ -22,7 +22,12 @@
 #include <asm/kmap_types.h>
 #endif
 
+#ifdef CONFIG_KASAN
+#include <asm/kasan.h>
+#define FIXADDR_TOP	KASAN_SHADOW_START
+#else
 #define FIXADDR_TOP	((unsigned long)(-PAGE_SIZE))
+#endif
 
 /*
  * Here we define all the compile-time 'special' virtual
diff --git a/arch/powerpc/include/asm/kasan.h b/arch/powerpc/include/asm/kasan.h
index c3161b8fc017..8dc1e3819171 100644
--- a/arch/powerpc/include/asm/kasan.h
+++ b/arch/powerpc/include/asm/kasan.h
@@ -12,4 +12,20 @@
 #define EXPORT_SYMBOL_KASAN(fn)	EXPORT_SYMBOL(fn)
 #endif
 
+#ifndef __ASSEMBLY__
+
+#include <asm/page.h>
+
+#define KASAN_SHADOW_SCALE_SHIFT	3
+
+#define KASAN_SHADOW_OFFSET	ASM_CONST(CONFIG_KASAN_SHADOW_OFFSET)
+
+#define KASAN_SHADOW_START	(KASAN_SHADOW_OFFSET + \
+				 (PAGE_OFFSET >> KASAN_SHADOW_SCALE_SHIFT))
+
+#define KASAN_SHADOW_END	0UL
+
+#define KASAN_SHADOW_SIZE	(KASAN_SHADOW_END - KASAN_SHADOW_START)
+
+#endif /* __ASSEMBLY */
 #endif
diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index f6787f90e158..4e7fa4eb2dd3 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -309,6 +309,10 @@ void __init mem_init(void)
 	mem_init_print_info(NULL);
 #ifdef CONFIG_PPC32
 	pr_info("Kernel virtual memory layout:\n");
+#ifdef CONFIG_KASAN
+	pr_info("  * 0x%08lx..0x%08lx  : kasan shadow mem\n",
+		KASAN_SHADOW_START, KASAN_SHADOW_END);
+#endif
 	pr_info("  * 0x%08lx..0x%08lx  : fixmap\n", FIXADDR_START, FIXADDR_TOP);
 #ifdef CONFIG_HIGHMEM
 	pr_info("  * 0x%08lx..0x%08lx  : highmem PTEs\n",
diff --git a/arch/powerpc/mm/ptdump/ptdump.c b/arch/powerpc/mm/ptdump/ptdump.c
index 37138428ab55..812ed680024f 100644
--- a/arch/powerpc/mm/ptdump/ptdump.c
+++ b/arch/powerpc/mm/ptdump/ptdump.c
@@ -101,6 +101,10 @@ static struct addr_marker address_markers[] = {
 	{ 0,	"Fixmap start" },
 	{ 0,	"Fixmap end" },
 #endif
+#ifdef CONFIG_KASAN
+	{ 0,	"kasan shadow mem start" },
+	{ 0,	"kasan shadow mem end" },
+#endif
 	{ -1,	NULL },
 };
 
@@ -322,6 +326,10 @@ static void populate_markers(void)
 #endif
 	address_markers[i++].start_address = FIXADDR_START;
 	address_markers[i++].start_address = FIXADDR_TOP;
+#ifdef CONFIG_KASAN
+	address_markers[i++].start_address = KASAN_SHADOW_START;
+	address_markers[i++].start_address = KASAN_SHADOW_END;
+#endif
 #endif /* CONFIG_PPC64 */
 }
 
-- 
2.13.3