diff options
| author | Anup Patel <anup.patel@wdc.com> | 2020-09-27 07:39:16 +0200 |
|---|---|---|
| committer | Palmer Dabbelt <palmerdabbelt@google.com> | 2020-09-30 20:05:14 +0200 |
| commit | aa9887608e77b835d51f05a54940380391cd4e21 (patch) | |
| tree | 82f0d59e8e554944c3941d2197f58789e1e71c8c /arch/riscv | |
| parent | clocksource: clint: Export clint_time_val for modules (diff) | |
| download | linux-aa9887608e77b835d51f05a54940380391cd4e21.tar.xz linux-aa9887608e77b835d51f05a54940380391cd4e21.zip | |
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 <anup.patel@wdc.com>
Tested-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
Diffstat (limited to 'arch/riscv')
| -rw-r--r-- | arch/riscv/include/asm/stackprotector.h | 4 | ||||
| -rw-r--r-- | arch/riscv/include/asm/timex.h | 13 |
2 files changed, 13 insertions, 4 deletions
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 <linux/random.h> #include <linux/version.h> -#include <asm/timex.h> 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) |