Commit 75581a20 authored by Borislav Petkov's avatar Borislav Petkov
Browse files

x86/mce: Move the tainting outside of the noinstr region 



add_taint() is yet another external facility which the #MC handler
calls. Move that tainting call into the instrumentation-allowed part of
the handler.

Fixes

  vmlinux.o: warning: objtool: do_machine_check()+0x617: call to add_taint() leaves .noinstr.text section

While at it, allow instrumentation around the mce_log() call.

Fixes

  vmlinux.o: warning: objtool: do_machine_check()+0x690: call to mce_log() leaves .noinstr.text section

Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20211208111343.8130-11-bp@alien8.de
parent db6c996d

arch/x86/kernel/cpu/mce/core.c

+26 −15
Original line number Diff line number Diff line
@@ -1180,13 +1180,14 @@ static noinstr bool mce_check_crashing_cpu(void) 
	return false;

}



static void __mc_scan_banks(struct mce *m, struct pt_regs *regs, struct mce *final,

			    unsigned long *toclear, unsigned long *valid_banks,

			    int no_way_out, int *worst)

static __always_inline int

__mc_scan_banks(struct mce *m, struct pt_regs *regs, struct mce *final,

		unsigned long *toclear, unsigned long *valid_banks, int no_way_out,

		int *worst)

{

	struct mce_bank *mce_banks = this_cpu_ptr(mce_banks_array);

	struct mca_config *cfg = &mca_cfg;

	int severity, i;

	int severity, i, taint = 0;



	for (i = 0; i < this_cpu_read(mce_num_banks); i++) {

		__clear_bit(i, toclear);
@@ -1213,7 +1214,7 @@ static void __mc_scan_banks(struct mce *m, struct pt_regs *regs, struct mce *fin 
			continue;



		/* Set taint even when machine check was not enabled. */

		add_taint(TAINT_MACHINE_CHECK, LOCKDEP_NOW_UNRELIABLE);

		taint++;



		severity = mce_severity(m, regs, cfg->tolerant, NULL, true);
@@ -1236,7 +1237,13 @@ static void __mc_scan_banks(struct mce *m, struct pt_regs *regs, struct mce *fin 
		/* assuming valid severity level != 0 */

		m->severity = severity;



		/*

		 * Enable instrumentation around the mce_log() call which is

		 * done in #MC context, where instrumentation is disabled.

		 */

		instrumentation_begin();

		mce_log(m);

		instrumentation_end();



		if (severity > *worst) {

			*final = *m;
@@ -1246,6 +1253,8 @@ static void __mc_scan_banks(struct mce *m, struct pt_regs *regs, struct mce *fin 


	/* mce_clear_state will clear *final, save locally for use later */

	*m = *final;



	return taint;

}



static void kill_me_now(struct callback_head *ch)
@@ -1362,7 +1371,7 @@ static noinstr void unexpected_machine_check(struct pt_regs *regs) 
 */

noinstr void do_machine_check(struct pt_regs *regs)

{

	int worst = 0, order, no_way_out, kill_current_task, lmce;

	int worst = 0, order, no_way_out, kill_current_task, lmce, taint = 0;

	DECLARE_BITMAP(valid_banks, MAX_NR_BANKS) = { 0 };

	DECLARE_BITMAP(toclear, MAX_NR_BANKS) = { 0 };

	struct mca_config *cfg = &mca_cfg;
@@ -1441,7 +1450,7 @@ noinstr void do_machine_check(struct pt_regs *regs) 
		order = mce_start(&no_way_out);

	}



	__mc_scan_banks(&m, regs, final, toclear, valid_banks, no_way_out, &worst);

	taint = __mc_scan_banks(&m, regs, final, toclear, valid_banks, no_way_out, &worst);



	if (!no_way_out)

		mce_clear_state(toclear);
@@ -1473,17 +1482,19 @@ noinstr void do_machine_check(struct pt_regs *regs) 
		}

	}



	if (worst != MCE_AR_SEVERITY && !kill_current_task)

		goto out;



	/*

	 * Enable instrumentation around the external facilities like

	 * task_work_add() (via queue_task_work()), fixup_exception() etc.

	 * For now, that is. Fixing this properly would need a lot more involved

	 * reorganization.

	 * Enable instrumentation around the external facilities like task_work_add()

	 * (via queue_task_work()), fixup_exception() etc. For now, that is. Fixing this

	 * properly would need a lot more involved reorganization.

	 */

	instrumentation_begin();



	if (taint)

		add_taint(TAINT_MACHINE_CHECK, LOCKDEP_NOW_UNRELIABLE);



	if (worst != MCE_AR_SEVERITY && !kill_current_task)

		goto out;



	/* Fault was in user mode and we need to take some action */

	if ((m.cs & 3) == 3) {

		/* If this triggers there is no way to recover. Die hard. */
@@ -1513,9 +1524,9 @@ noinstr void do_machine_check(struct pt_regs *regs) 
			queue_task_work(&m, msg, kill_me_never);

	}



out:

	instrumentation_end();



out:

	mce_wrmsrl(MSR_IA32_MCG_STATUS, 0);

}

EXPORT_SYMBOL_GPL(do_machine_check);