On 07/27/2015 06:59 PM, Catalin Marinas wrote:

On Fri, Jul 24, 2015 at 07:41:57PM +0300, Andrey Ryabinin wrote:

quoted

diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index 4d2a925..2cacf55 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile

@@ -40,6 +40,12 @@ else
 TEXT_OFFSET := 0x00080000
 endif
 
+# KASAN_SHADOW_OFFSET = VA_START + (1 << (VA_BITS - 3)) - (1 << 61)
+KASAN_SHADOW_OFFSET := $(shell printf "0x%x\n" $$(( \
+			(-1 << $(CONFIG_ARM64_VA_BITS)) \
+			+ (1 << ($(CONFIG_ARM64_VA_BITS) - 3)) \
+			- (1 << (64 - 3)) )) )

Does this work with any POSIX shell? Do we always have a 64-bit type?
As I wasn't sure about this, I suggested awk (or perl).

Ok, It will be safer to use 32-bit arithmetic.
I've checked this on 32-bit bash, however this doesn't guarantee that it works with
any other version of bash or another shell.

quoted

+static void __init clear_pgds(unsigned long start,
+			unsigned long end)
+{
+	/*
+	 * Remove references to kasan page tables from
+	 * swapper_pg_dir. pgd_clear() can't be used
+	 * here because it's nop on 2,3-level pagetable setups
+	 */
+	for (; start && start < end; start += PGDIR_SIZE)
+		set_pgd(pgd_offset_k(start), __pgd(0));
+}

I don't think we need the "start" check, just "start < end". Do you
expect a start == 0 (or overflow)?

Right, we don't need this.