From aa9887608e77b835d51f05a54940380391cd4e21 Mon Sep 17 00:00:00 2001 From: Anup Patel Date: Sun, 27 Sep 2020 11:09:16 +0530 Subject: RISC-V: Check clint_time_val before use The NoMMU kernel is broken for QEMU virt machine from Linux-5.9-rc6 because clint_time_val is used even before CLINT driver is probed at following places: 1. rand_initialize() calls get_cycles() which in-turn uses clint_time_val 2. boot_init_stack_canary() calls get_cycles() which in-turn uses clint_time_val The issue#1 (above) is fixed by providing custom random_get_entropy() for RISC-V NoMMU kernel. For issue#2 (above), we remove dependency of boot_init_stack_canary() on get_cycles() and this is aligned with the boot_init_stack_canary() implementations of ARM, ARM64 and MIPS kernel. Fixes: d5be89a8d118 ("RISC-V: Resurrect the MMIO timer implementation for M-mode systems") Signed-off-by: Anup Patel Tested-by: Damien Le Moal Signed-off-by: Palmer Dabbelt --- arch/riscv/include/asm/stackprotector.h | 4 ---- arch/riscv/include/asm/timex.h | 13 +++++++++++++ 2 files changed, 13 insertions(+), 4 deletions(-) (limited to 'arch') diff --git a/arch/riscv/include/asm/stackprotector.h b/arch/riscv/include/asm/stackprotector.h index d95f7b2a7f37..5962f8891f06 100644 --- a/arch/riscv/include/asm/stackprotector.h +++ b/arch/riscv/include/asm/stackprotector.h @@ -5,7 +5,6 @@ #include #include -#include extern unsigned long __stack_chk_guard; @@ -18,12 +17,9 @@ extern unsigned long __stack_chk_guard; static __always_inline void boot_init_stack_canary(void) { unsigned long canary; - unsigned long tsc; /* Try to get a semi random initial value. */ get_random_bytes(&canary, sizeof(canary)); - tsc = get_cycles(); - canary += tsc + (tsc << BITS_PER_LONG/2); canary ^= LINUX_VERSION_CODE; canary &= CANARY_MASK; diff --git a/arch/riscv/include/asm/timex.h b/arch/riscv/include/asm/timex.h index 7f659dda0032..ab104905d4db 100644 --- a/arch/riscv/include/asm/timex.h +++ b/arch/riscv/include/asm/timex.h @@ -33,6 +33,19 @@ static inline u32 get_cycles_hi(void) #define get_cycles_hi get_cycles_hi #endif /* CONFIG_64BIT */ +/* + * Much like MIPS, we may not have a viable counter to use at an early point + * in the boot process. Unfortunately we don't have a fallback, so instead + * we just return 0. + */ +static inline unsigned long random_get_entropy(void) +{ + if (unlikely(clint_time_val == NULL)) + return 0; + return get_cycles(); +} +#define random_get_entropy() random_get_entropy() + #else /* CONFIG_RISCV_M_MODE */ static inline cycles_t get_cycles(void) -- cgit v1.2.3