add can driver

hc

2023-12-02 57e32c52610e6a560beda60bf33c48f9f42306d5

 kernel/arch/x86/include/asm/stackprotector.h
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@@ -65,7 +65,7 @@
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  */
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 static __always_inline void boot_init_stack_canary(void)
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 {
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-	u64 canary;
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+	u64 uninitialized_var(canary);
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 	u64 tsc;
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 #ifdef CONFIG_X86_64
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@@ -76,8 +76,14 @@
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 	 * of randomness. The TSC only matters for very early init,
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 	 * there it already has some randomness on most systems. Later
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 	 * on during the bootup the random pool has true entropy too.
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+	 * For preempt-rt we need to weaken the randomness a bit, as
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+	 * we can't call into the random generator from atomic context
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+	 * due to locking constraints. We just leave canary
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+	 * uninitialized and use the TSC based randomness on top of it.
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 	 */
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+#ifndef CONFIG_PREEMPT_RT_FULL
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 	get_random_bytes(&canary, sizeof(canary));
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+#endif
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 	tsc = rdtsc();
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 	canary += tsc + (tsc << 32UL);
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 	canary &= CANARY_MASK;