x86/cpu: Add 'unsafe_fsgsbase' to enable CR4.FSGSBASE (dd649bd0) · Commits · 戴 / test

Documentation/admin-guide/kernel-parameters.txt

+3 −0

Original line number	Diff line number	Diff line
		@@ -3079,6 +3079,9 @@
		no5lvl [X86-64] Disable 5-level paging mode. Forces
		kernel to use 4-level paging instead.

		unsafe_fsgsbase [X86] Allow FSGSBASE instructions. This will be
		replaced with a nofsgsbase flag.

		no_console_suspend
		[HW] Never suspend the console
		Disable suspending of consoles during suspend and

+24 −0

Original line number	Diff line number	Diff line
		@@ -441,6 +441,22 @@ static void __init setup_cr_pinning(void)
		static_key_enable(&cr_pinning.key);
		}

		/*
		* Temporary hack: FSGSBASE is unsafe until a few kernel code paths are
		* updated. This allows us to get the kernel ready incrementally.
		*
		* Once all the pieces are in place, these will go away and be replaced with
		* a nofsgsbase chicken flag.
		*/
		static bool unsafe_fsgsbase;

		static __init int setup_unsafe_fsgsbase(char *arg)
		{
		unsafe_fsgsbase = true;
		return 1;
		}
		__setup("unsafe_fsgsbase", setup_unsafe_fsgsbase);

		/*
		* Protection Keys are not available in 32-bit mode.
		*/
		@@ -1495,6 +1511,14 @@ static void identify_cpu(struct cpuinfo_x86 *c)
		setup_smap(c);
		setup_umip(c);

		/* Enable FSGSBASE instructions if available. */
		if (cpu_has(c, X86_FEATURE_FSGSBASE)) {
		if (unsafe_fsgsbase)
		cr4_set_bits(X86_CR4_FSGSBASE);
		else
		clear_cpu_cap(c, X86_FEATURE_FSGSBASE);
		}

		/*
		* The vendor-specific functions might have changed features.
		* Now we do "generic changes."