ARM: 9017/2: Enable KASan for ARM

This patch enables the kernel address sanitizer for ARM. XIP_KERNEL
has not been tested and is therefore not allowed for now.

Cc: Andrey Ryabinin <[e-mail]>
Cc: Alexander Potapenko <[e-mail]>
Cc: Dmitry Vyukov <[e-mail]>
Cc: [e-mail]
Acked-by: Dmitry Vyukov <[e-mail]>
Reviewed-by: Ard Biesheuvel <[e-mail]>
Tested-by: Ard Biesheuvel <[e-mail]> # QEMU/KVM/mach-virt/LPAE/8G
Tested-by: Florian Fainelli <[e-mail]> # Brahma SoCs
Tested-by: Ahmad Fatoum <[e-mail]> # i.MX6Q
Signed-off-by: Abbott Liu <[e-mail]>
Signed-off-by: Florian Fainelli <[e-mail]>
Signed-off-by: Linus Walleij <[e-mail]>
Signed-off-by: Russell King <[e-mail]>

Documentation/dev-tools/kasan.rst

···
 
 Tag-based KASAN is only supported in Clang.
 
-Currently generic KASAN is supported for the x86_64, arm64, xtensa, s390 and
-riscv architectures, and tag-based KASAN is supported only for arm64.
+Currently generic KASAN is supported for the x86_64, arm, arm64, xtensa, s390
+and riscv architectures, and tag-based KASAN is supported only for arm64.
 
 Usage
 -----

Documentation/features/debug/KASAN/arch-support.txt

···
     -----------------------
     |       alpha: | TODO |
     |         arc: | TODO |
-    |         arm: | TODO |
+    |         arm: |  ok  |
     |       arm64: |  ok  |
     |         c6x: | TODO |
     |        csky: | TODO |

arch/arm/Kconfig

···
 	select HAVE_ARCH_BITREVERSE if (CPU_32v7M || CPU_32v7) && !CPU_32v6
 	select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL && !CPU_ENDIAN_BE32 && MMU
 	select HAVE_ARCH_KGDB if !CPU_ENDIAN_BE32 && MMU
+	select HAVE_ARCH_KASAN if MMU && !XIP_KERNEL
 	select HAVE_ARCH_MMAP_RND_BITS if MMU
 	select HAVE_ARCH_SECCOMP
 	select HAVE_ARCH_SECCOMP_FILTER if AEABI && !OABI_COMPAT