Commit e6da8bb6 authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

x86/speculation: Split out TIF update 



The update of the TIF_SSBD flag and the conditional speculation control MSR
update is done in the ssb_prctl_set() function directly. The upcoming prctl
support for controlling indirect branch speculation via STIBP needs the
same mechanism.

Split the code out and make it reusable. Reword the comment about updates
for other tasks.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarIngo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Woodhouse <dwmw@amazon.co.uk>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Casey Schaufler <casey.schaufler@intel.com>
Cc: Asit Mallick <asit.k.mallick@intel.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Jon Masters <jcm@redhat.com>
Cc: Waiman Long <longman9394@gmail.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Dave Stewart <david.c.stewart@intel.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20181125185005.652305076@linutronix.de
parent 46f7ecb1

arch/x86/kernel/cpu/bugs.c

+23 −12
Original line number Diff line number Diff line
@@ -702,10 +702,29 @@ static void ssb_select_mitigation(void) 
#undef pr_fmt

#define pr_fmt(fmt)     "Speculation prctl: " fmt



static int ssb_prctl_set(struct task_struct *task, unsigned long ctrl)

static void task_update_spec_tif(struct task_struct *tsk, int tifbit, bool on)

{

	bool update;



	if (on)

		update = !test_and_set_tsk_thread_flag(tsk, tifbit);

	else

		update = test_and_clear_tsk_thread_flag(tsk, tifbit);



	/*

	 * Immediately update the speculation control MSRs for the current

	 * task, but for a non-current task delay setting the CPU

	 * mitigation until it is scheduled next.

	 *

	 * This can only happen for SECCOMP mitigation. For PRCTL it's

	 * always the current task.

	 */

	if (tsk == current && update)

		speculation_ctrl_update_current();

}



static int ssb_prctl_set(struct task_struct *task, unsigned long ctrl)

{

	if (ssb_mode != SPEC_STORE_BYPASS_PRCTL &&

	    ssb_mode != SPEC_STORE_BYPASS_SECCOMP)

		return -ENXIO;
@@ -716,28 +735,20 @@ static int ssb_prctl_set(struct task_struct *task, unsigned long ctrl) 
		if (task_spec_ssb_force_disable(task))

			return -EPERM;

		task_clear_spec_ssb_disable(task);

		update = test_and_clear_tsk_thread_flag(task, TIF_SSBD);

		task_update_spec_tif(task, TIF_SSBD, false);

		break;

	case PR_SPEC_DISABLE:

		task_set_spec_ssb_disable(task);

		update = !test_and_set_tsk_thread_flag(task, TIF_SSBD);

		task_update_spec_tif(task, TIF_SSBD, true);

		break;

	case PR_SPEC_FORCE_DISABLE:

		task_set_spec_ssb_disable(task);

		task_set_spec_ssb_force_disable(task);

		update = !test_and_set_tsk_thread_flag(task, TIF_SSBD);

		task_update_spec_tif(task, TIF_SSBD, true);

		break;

	default:

		return -ERANGE;

	}



	/*

	 * If being set on non-current task, delay setting the CPU

	 * mitigation until it is next scheduled.

	 */

	if (task == current && update)

		speculation_ctrl_update_current();



	return 0;

}

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