riscv: Fix asan-stack clang build

stable inclusion
from stable-5.10.77
commit 6f416815c505ad1e0c2d0f5c7300e18ba16ad281
bugzilla: 185677 https://gitee.com/openeuler/kernel/issues/I4IAP7

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6f416815c505ad1e0c2d0f5c7300e18ba16ad281

--------------------------------

commit 54c5639d upstream.

Nathan reported that because KASAN_SHADOW_OFFSET was not defined in
Kconfig, it prevents asan-stack from getting disabled with clang even
when CONFIG_KASAN_STACK is disabled: fix this by defining the
corresponding config.
Reported-by: NNathan Chancellor <nathan@kernel.org>
Signed-off-by: NAlexandre Ghiti <alexandre.ghiti@canonical.com>
Fixes: 8ad8b727 ("riscv: Add KASAN support")
Cc: stable@vger.kernel.org
Signed-off-by: NPalmer Dabbelt <palmerdabbelt@google.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: NWeilong Chen <chenweilong@huawei.com>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

arch/riscv/Kconfig

@@ -139,6 +139,12 @@ config PAGE_OFFSET
 	default 0xffffffff80000000 if 64BIT && MAXPHYSMEM_2GB
 	default 0xffffffe000000000 if 64BIT && MAXPHYSMEM_128GB
 
+config KASAN_SHADOW_OFFSET
+	hex
+	depends on KASAN_GENERIC
+	default 0xdfffffc800000000 if 64BIT
+	default 0xffffffff if 32BIT
+
 config ARCH_FLATMEM_ENABLE
 	def_bool y
 

arch/riscv/include/asm/kasan.h

@@ -14,8 +14,7 @@
 #define KASAN_SHADOW_START	KERN_VIRT_START /* 2^64 - 2^38 */
 #define KASAN_SHADOW_END	(KASAN_SHADOW_START + KASAN_SHADOW_SIZE)
 
-#define KASAN_SHADOW_OFFSET	(KASAN_SHADOW_END - (1ULL << \
-					(64 - KASAN_SHADOW_SCALE_SHIFT)))
+#define KASAN_SHADOW_OFFSET	_AC(CONFIG_KASAN_SHADOW_OFFSET, UL)
 
 void kasan_init(void);
 asmlinkage void kasan_early_init(void);

arch/riscv/mm/kasan_init.c

@@ -16,6 +16,9 @@ asmlinkage void __init kasan_early_init(void)
 	uintptr_t i;
 	pgd_t *pgd = early_pg_dir + pgd_index(KASAN_SHADOW_START);
 
+	BUILD_BUG_ON(KASAN_SHADOW_OFFSET !=
+		KASAN_SHADOW_END - (1UL << (64 - KASAN_SHADOW_SCALE_SHIFT)));
+
 	for (i = 0; i < PTRS_PER_PTE; ++i)
 		set_pte(kasan_early_shadow_pte + i,
 			mk_pte(virt_to_page(kasan_early_shadow_page),