riscv: define ILLEGAL_POINTER_VALUE for 64bit

This is used in poison.h for poison pointer offset. Based on current
SV39, SV48 and SV57 vm layout, 0xdead000000000000 is a proper value
that is not mappable, this can avoid potentially turning an oops to
an expolit.

Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Fixes: fbe934d69eb7 ("RISC-V: Build Infrastructure")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20240705170210.3236-1-jszhang@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 4871220061c45c36bd82f73f4e03bc2475e4de00..31d94179236978bb2ed91e9b3ea7d20fda604419 100644 (file)
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -320,6 +320,11 @@ config GENERIC_HWEIGHT
 config FIX_EARLYCON_MEM
        def_bool MMU
 
+config ILLEGAL_POINTER_VALUE
+       hex
+       default 0 if 32BIT
+       default 0xdead000000000000 if 64BIT
+
 config PGTABLE_LEVELS
        int
        default 5 if 64BIT