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authorAnup Patel <anup.patel@wdc.com>2020-09-27 11:09:16 +0530
committerPalmer Dabbelt <palmerdabbelt@google.com>2020-09-30 11:05:14 -0700
commitaa9887608e77b835d51f05a54940380391cd4e21 (patch)
tree82f0d59e8e554944c3941d2197f58789e1e71c8c
parentc14decfca23cfbeb423ad8be3961a58a31a5473c (diff)
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>
-rw-r--r--arch/riscv/include/asm/stackprotector.h4
-rw-r--r--arch/riscv/include/asm/timex.h13
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)