Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit d4812e16 authored by Tony Luck's avatar Tony Luck Committed by Andy Lutomirski
Browse files

x86, mce: Get rid of TIF_MCE_NOTIFY and associated mce tricks 



We now switch to the kernel stack when a machine check interrupts
during user mode.  This means that we can perform recovery actions
in the tail of do_machine_check()

Acked-by: default avatarBorislav Petkov <bp@suse.de>
Signed-off-by: default avatarTony Luck <tony.luck@intel.com>
Signed-off-by: default avatarAndy Lutomirski <luto@amacapital.net>
parent bced35b6

arch/x86/include/asm/mce.h

+0 −1
Original line number Diff line number Diff line
@@ -190,7 +190,6 @@ enum mcp_flags { 
void machine_check_poll(enum mcp_flags flags, mce_banks_t *b);



int mce_notify_irq(void);

void mce_notify_process(void);



DECLARE_PER_CPU(struct mce, injectm);

arch/x86/include/asm/thread_info.h

+1 −3
Original line number Diff line number Diff line
@@ -75,7 +75,6 @@ struct thread_info { 
#define TIF_SYSCALL_EMU		6	/* syscall emulation active */

#define TIF_SYSCALL_AUDIT	7	/* syscall auditing active */

#define TIF_SECCOMP		8	/* secure computing */

#define TIF_MCE_NOTIFY		10	/* notify userspace of an MCE */

#define TIF_USER_RETURN_NOTIFY	11	/* notify kernel of userspace return */

#define TIF_UPROBE		12	/* breakpointed or singlestepping */

#define TIF_NOTSC		16	/* TSC is not accessible in userland */
@@ -100,7 +99,6 @@ struct thread_info { 
#define _TIF_SYSCALL_EMU	(1 << TIF_SYSCALL_EMU)

#define _TIF_SYSCALL_AUDIT	(1 << TIF_SYSCALL_AUDIT)

#define _TIF_SECCOMP		(1 << TIF_SECCOMP)

#define _TIF_MCE_NOTIFY		(1 << TIF_MCE_NOTIFY)

#define _TIF_USER_RETURN_NOTIFY	(1 << TIF_USER_RETURN_NOTIFY)

#define _TIF_UPROBE		(1 << TIF_UPROBE)

#define _TIF_NOTSC		(1 << TIF_NOTSC)
@@ -140,7 +138,7 @@ struct thread_info { 


/* Only used for 64 bit */

#define _TIF_DO_NOTIFY_MASK						\

	(_TIF_SIGPENDING | _TIF_MCE_NOTIFY | _TIF_NOTIFY_RESUME |	\

	(_TIF_SIGPENDING | _TIF_NOTIFY_RESUME |				\

	 _TIF_USER_RETURN_NOTIFY | _TIF_UPROBE)



/* flags to check in __switch_to() */

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

+25 −84
Original line number Diff line number Diff line
@@ -1003,51 +1003,6 @@ static void mce_clear_state(unsigned long *toclear) 
	}

}



/*

 * Need to save faulting physical address associated with a process

 * in the machine check handler some place where we can grab it back

 * later in mce_notify_process()

 */

#define	MCE_INFO_MAX	16



struct mce_info {

	atomic_t		inuse;

	struct task_struct	*t;

	__u64			paddr;

	int			restartable;

} mce_info[MCE_INFO_MAX];



static void mce_save_info(__u64 addr, int c)

{

	struct mce_info *mi;



	for (mi = mce_info; mi < &mce_info[MCE_INFO_MAX]; mi++) {

		if (atomic_cmpxchg(&mi->inuse, 0, 1) == 0) {

			mi->t = current;

			mi->paddr = addr;

			mi->restartable = c;

			return;

		}

	}



	mce_panic("Too many concurrent recoverable errors", NULL, NULL);

}



static struct mce_info *mce_find_info(void)

{

	struct mce_info *mi;



	for (mi = mce_info; mi < &mce_info[MCE_INFO_MAX]; mi++)

		if (atomic_read(&mi->inuse) && mi->t == current)

			return mi;

	return NULL;

}



static void mce_clear_info(struct mce_info *mi)

{

	atomic_set(&mi->inuse, 0);

}



/*

 * The actual machine check handler. This only handles real

 * exceptions when something got corrupted coming in through int 18.
@@ -1086,6 +1041,8 @@ 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;



	prev_state = ist_enter(regs);
@@ -1207,9 +1164,9 @@ void do_machine_check(struct pt_regs *regs, long error_code) 
		if (no_way_out)

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

		if (worst == MCE_AR_SEVERITY) {

			/* schedule action before return to userland */

			mce_save_info(m.addr, m.mcgstatus & MCG_STATUS_RIPV);

			set_thread_flag(TIF_MCE_NOTIFY);

			recover_paddr = m.addr;

			if (!(m.mcgstatus & MCG_STATUS_RIPV))

				flags |= MF_MUST_KILL;

		} else if (kill_it) {

			force_sig(SIGBUS, current);

		}
@@ -1220,6 +1177,26 @@ void do_machine_check(struct pt_regs *regs, long error_code) 
	mce_wrmsrl(MSR_IA32_MCG_STATUS, 0);

out:

	sync_core();



	if (recover_paddr == ~0ull)

		goto done;



	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.

	 */

	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");

		force_sig(SIGBUS, current);

	}

	local_irq_disable();

	ist_end_non_atomic();

done:

	ist_exit(regs, prev_state);

}

EXPORT_SYMBOL_GPL(do_machine_check);
@@ -1237,42 +1214,6 @@ int memory_failure(unsigned long pfn, int vector, int flags) 
}

#endif



/*

 * Called in process context that interrupted by MCE and marked with

 * TIF_MCE_NOTIFY, just before returning to erroneous userland.

 * This code is allowed to sleep.

 * Attempt possible recovery such as calling the high level VM handler to

 * process any corrupted pages, and kill/signal current process if required.

 * Action required errors are handled here.

 */

void mce_notify_process(void)

{

	unsigned long pfn;

	struct mce_info *mi = mce_find_info();

	int flags = MF_ACTION_REQUIRED;



	if (!mi)

		mce_panic("Lost physical address for unconsumed uncorrectable error", NULL, NULL);

	pfn = mi->paddr >> PAGE_SHIFT;



	clear_thread_flag(TIF_MCE_NOTIFY);



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

		 mi->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.

	 */

	if (!mi->restartable)

		flags |= MF_MUST_KILL;

	if (memory_failure(pfn, MCE_VECTOR, flags) < 0) {

		pr_err("Memory error not recovered");

		force_sig(SIGBUS, current);

	}

	mce_clear_info(mi);

}



/*

 * Action optional processing happens here (picking up

 * from the list of faulting pages that do_machine_check()

arch/x86/kernel/signal.c

+0 −6
Original line number Diff line number Diff line
@@ -740,12 +740,6 @@ do_notify_resume(struct pt_regs *regs, void *unused, __u32 thread_info_flags) 
{

	user_exit();



#ifdef CONFIG_X86_MCE

	/* notify userspace of pending MCEs */

	if (thread_info_flags & _TIF_MCE_NOTIFY)

		mce_notify_process();

#endif /* CONFIG_X86_64 && CONFIG_X86_MCE */



	if (thread_info_flags & _TIF_UPROBE)

		uprobe_notify_resume(regs);