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Commit b2f9d678 authored by Tony Luck's avatar Tony Luck Committed by Ingo Molnar
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x86/mce: Check for faults tagged in EXTABLE_CLASS_FAULT exception table entries 



Extend the severity checking code to add a new context IN_KERN_RECOV
which is used to indicate that the machine check was triggered by code
in the kernel tagged with _ASM_EXTABLE_FAULT() so that the ex_handler_fault()
handler will provide the fixup code with the trap number.

Major re-work to the tail code in do_machine_check() to make all this
readable/maintainable. One functional change is that tolerant=3 no longer
stops recovery actions. Revert to only skipping sending SIGBUS to the
current process.

Signed-off-by: default avatarTony Luck <tony.luck@intel.com>
Reviewed-by: default avatarBorislav Petkov <bp@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/89d243d05a7943bb187d1074bb30d9c4f482d5f5.1455732970.git.tony.luck@intel.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 548acf19

arch/x86/kernel/cpu/mcheck/mce-severity.c

+20 −2
Original line number Diff line number Diff line
@@ -14,6 +14,7 @@ 
#include <linux/init.h>

#include <linux/debugfs.h>

#include <asm/mce.h>

#include <asm/uaccess.h>



#include "mce-internal.h"
@@ -29,7 +30,7 @@ 
 * panic situations)

 */



enum context { IN_KERNEL = 1, IN_USER = 2 };

enum context { IN_KERNEL = 1, IN_USER = 2, IN_KERNEL_RECOV = 3 };

enum ser { SER_REQUIRED = 1, NO_SER = 2 };

enum exception { EXCP_CONTEXT = 1, NO_EXCP = 2 };
@@ -48,6 +49,7 @@ static struct severity { 
#define MCESEV(s, m, c...) { .sev = MCE_ ## s ## _SEVERITY, .msg = m, ## c }

#define  KERNEL		.context = IN_KERNEL

#define  USER		.context = IN_USER

#define  KERNEL_RECOV	.context = IN_KERNEL_RECOV

#define  SER		.ser = SER_REQUIRED

#define  NOSER		.ser = NO_SER

#define  EXCP		.excp = EXCP_CONTEXT
@@ -86,6 +88,10 @@ static struct severity { 
		PANIC, "In kernel and no restart IP",

		EXCP, KERNEL, MCGMASK(MCG_STATUS_RIPV, 0)

		),

	MCESEV(

		PANIC, "In kernel and no restart IP",

		EXCP, KERNEL_RECOV, MCGMASK(MCG_STATUS_RIPV, 0)

		),

	MCESEV(

		DEFERRED, "Deferred error",

		NOSER, MASK(MCI_STATUS_UC|MCI_STATUS_DEFERRED|MCI_STATUS_POISON, MCI_STATUS_DEFERRED)
@@ -122,6 +128,11 @@ static struct severity { 
		SER, MASK(MCI_STATUS_OVER|MCI_UC_SAR|MCI_ADDR, MCI_UC_SAR|MCI_ADDR),

		MCGMASK(MCG_STATUS_RIPV|MCG_STATUS_EIPV, MCG_STATUS_RIPV)

		),

	MCESEV(

		AR, "Action required: data load in error recoverable area of kernel",

		SER, MASK(MCI_STATUS_OVER|MCI_UC_SAR|MCI_ADDR|MCACOD, MCI_UC_SAR|MCI_ADDR|MCACOD_DATA),

		KERNEL_RECOV

		),

	MCESEV(

		AR, "Action required: data load error in a user process",

		SER, MASK(MCI_STATUS_OVER|MCI_UC_SAR|MCI_ADDR|MCACOD, MCI_UC_SAR|MCI_ADDR|MCACOD_DATA),
@@ -170,6 +181,9 @@ static struct severity { 
		)	/* always matches. keep at end */

};



#define mc_recoverable(mcg) (((mcg) & (MCG_STATUS_RIPV|MCG_STATUS_EIPV)) == \

				(MCG_STATUS_RIPV|MCG_STATUS_EIPV))



/*

 * If mcgstatus indicated that ip/cs on the stack were

 * no good, then "m->cs" will be zero and we will have
@@ -183,7 +197,11 @@ static struct severity { 
 */

static int error_context(struct mce *m)

{

	return ((m->cs & 3) == 3) ? IN_USER : IN_KERNEL;

	if ((m->cs & 3) == 3)

		return IN_USER;

	if (mc_recoverable(m->mcgstatus) && ex_has_fault_handler(m->ip))

		return IN_KERNEL_RECOV;

	return IN_KERNEL;

}



/*

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

+36 −34
Original line number Diff line number Diff line
@@ -961,6 +961,20 @@ static void mce_clear_state(unsigned long *toclear) 
	}

}



static int do_memory_failure(struct mce *m)

{

	int flags = MF_ACTION_REQUIRED;

	int ret;



	pr_err("Uncorrected hardware memory error in user-access at %llx", m->addr);

	if (!(m->mcgstatus & MCG_STATUS_RIPV))

		flags |= MF_MUST_KILL;

	ret = memory_failure(m->addr >> PAGE_SHIFT, MCE_VECTOR, flags);

	if (ret)

		pr_err("Memory error not recovered");

	return ret;

}



/*

 * The actual machine check handler. This only handles real

 * exceptions when something got corrupted coming in through int 18.
@@ -998,8 +1012,6 @@ void do_machine_check(struct pt_regs *regs, long error_code) 
	DECLARE_BITMAP(toclear, MAX_NR_BANKS);

	DECLARE_BITMAP(valid_banks, MAX_NR_BANKS);

	char *msg = "Unknown";

	u64 recover_paddr = ~0ull;

	int flags = MF_ACTION_REQUIRED;

	int lmce = 0;



	/* If this CPU is offline, just bail out. */
@@ -1136,22 +1148,13 @@ void do_machine_check(struct pt_regs *regs, long error_code) 
	}



	/*

	 * At insane "tolerant" levels we take no action. Otherwise

	 * we only die if we have no other choice. For less serious

	 * issues we try to recover, or limit damage to the current

	 * process.

	 * If tolerant is at an insane level we drop requests to kill

	 * processes and continue even when there is no way out.

	 */

	if (cfg->tolerant < 3) {

		if (no_way_out)

	if (cfg->tolerant == 3)

		kill_it = 0;

	else if (no_way_out)

		mce_panic("Fatal machine check on current CPU", &m, msg);

		if (worst == MCE_AR_SEVERITY) {

			recover_paddr = m.addr;

			if (!(m.mcgstatus & MCG_STATUS_RIPV))

				flags |= MF_MUST_KILL;

		} else if (kill_it) {

			force_sig(SIGBUS, current);

		}

	}



	if (worst > 0)

		mce_report_event(regs);
@@ -1159,25 +1162,24 @@ void do_machine_check(struct pt_regs *regs, long error_code) 
out:

	sync_core();



	if (recover_paddr == ~0ull)

		goto done;

	if (worst != MCE_AR_SEVERITY && !kill_it)

		goto out_ist;



	pr_err("Uncorrected hardware memory error in user-access at %llx",

		 recover_paddr);

	/*

	 * We must call memory_failure() here even if the current process is

	 * doomed. We still need to mark the page as poisoned and alert any

	 * other users of the page.

	 */

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

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

		ist_begin_non_atomic(regs);

		local_irq_enable();

	if (memory_failure(recover_paddr >> PAGE_SHIFT, MCE_VECTOR, flags) < 0) {

		pr_err("Memory error not recovered");



		if (kill_it || do_memory_failure(&m))

			force_sig(SIGBUS, current);

	}

		local_irq_disable();

		ist_end_non_atomic();

done:

	} else {

		if (!fixup_exception(regs, X86_TRAP_MC))

			mce_panic("Failed kernel mode recovery", &m, NULL);

	}



out_ist:

	ist_exit(regs);

}

EXPORT_SYMBOL_GPL(do_machine_check);