RISC-V: Check clint_time_val before use (aa988760) · Commits · 戴 / test

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: ("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>

arch/riscv/include/asm/stackprotector.h

+0 −4

Original line number	Diff line number	Diff line
		@@ -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;

arch/riscv/include/asm/timex.h

+13 −0

Original line number	Diff line number	Diff line
		@@ -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)

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