Initial import

1 files changed, 921 insertions, 0 deletions

diff --git a/arch/tile/mm/fault.c b/arch/tile/mm/fault.c
new file mode 100644
index 000000000..e83cc999d
--- /dev/null
+++ b/arch/tile/mm/fault.c
@@ -0,0 +1,921 @@
+/*
+ * Copyright 2010 Tilera Corporation. All Rights Reserved.
+ *
+ *   This program is free software; you can redistribute it and/or
+ *   modify it under the terms of the GNU General Public License
+ *   as published by the Free Software Foundation, version 2.
+ *
+ *   This program is distributed in the hope that it will be useful, but
+ *   WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
+ *   NON INFRINGEMENT.  See the GNU General Public License for
+ *   more details.
+ *
+ * From i386 code copyright (C) 1995  Linus Torvalds
+ */
+
+#include <linux/signal.h>
+#include <linux/sched.h>
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/string.h>
+#include <linux/types.h>
+#include <linux/ptrace.h>
+#include <linux/mman.h>
+#include <linux/mm.h>
+#include <linux/smp.h>
+#include <linux/interrupt.h>
+#include <linux/init.h>
+#include <linux/tty.h>
+#include <linux/vt_kern.h>		/* For unblank_screen() */
+#include <linux/highmem.h>
+#include <linux/module.h>
+#include <linux/kprobes.h>
+#include <linux/hugetlb.h>
+#include <linux/syscalls.h>
+#include <linux/uaccess.h>
+#include <linux/kdebug.h>
+#include <linux/context_tracking.h>
+
+#include <asm/pgalloc.h>
+#include <asm/sections.h>
+#include <asm/traps.h>
+#include <asm/syscalls.h>
+
+#include <arch/interrupts.h>
+
+static noinline void force_sig_info_fault(const char *type, int si_signo,
+					  int si_code, unsigned long address,
+					  int fault_num,
+					  struct task_struct *tsk,
+					  struct pt_regs *regs)
+{
+	siginfo_t info;
+
+	if (unlikely(tsk->pid < 2)) {
+		panic("Signal %d (code %d) at %#lx sent to %s!",
+		      si_signo, si_code & 0xffff, address,
+		      is_idle_task(tsk) ? "the idle task" : "init");
+	}
+
+	info.si_signo = si_signo;
+	info.si_errno = 0;
+	info.si_code = si_code;
+	info.si_addr = (void __user *)address;
+	info.si_trapno = fault_num;
+	trace_unhandled_signal(type, regs, address, si_signo);
+	force_sig_info(si_signo, &info, tsk);
+}
+
+#ifndef __tilegx__
+/*
+ * Synthesize the fault a PL0 process would get by doing a word-load of
+ * an unaligned address or a high kernel address.
+ */
+SYSCALL_DEFINE1(cmpxchg_badaddr, unsigned long, address)
+{
+	struct pt_regs *regs = current_pt_regs();
+
+	if (address >= PAGE_OFFSET)
+		force_sig_info_fault("atomic segfault", SIGSEGV, SEGV_MAPERR,
+				     address, INT_DTLB_MISS, current, regs);
+	else
+		force_sig_info_fault("atomic alignment fault", SIGBUS,
+				     BUS_ADRALN, address,
+				     INT_UNALIGN_DATA, current, regs);
+
+	/*
+	 * Adjust pc to point at the actual instruction, which is unusual
+	 * for syscalls normally, but is appropriate when we are claiming
+	 * that a syscall swint1 caused a page fault or bus error.
+	 */
+	regs->pc -= 8;
+
+	/*
+	 * Mark this as a caller-save interrupt, like a normal page fault,
+	 * so that when we go through the signal handler path we will
+	 * properly restore r0, r1, and r2 for the signal handler arguments.
+	 */
+	regs->flags |= PT_FLAGS_CALLER_SAVES;
+
+	return 0;
+}
+#endif
+
+static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
+{
+	unsigned index = pgd_index(address);
+	pgd_t *pgd_k;
+	pud_t *pud, *pud_k;
+	pmd_t *pmd, *pmd_k;
+
+	pgd += index;
+	pgd_k = init_mm.pgd + index;
+
+	if (!pgd_present(*pgd_k))
+		return NULL;
+
+	pud = pud_offset(pgd, address);
+	pud_k = pud_offset(pgd_k, address);
+	if (!pud_present(*pud_k))
+		return NULL;
+
+	pmd = pmd_offset(pud, address);
+	pmd_k = pmd_offset(pud_k, address);
+	if (!pmd_present(*pmd_k))
+		return NULL;
+	if (!pmd_present(*pmd))
+		set_pmd(pmd, *pmd_k);
+	else
+		BUG_ON(pmd_ptfn(*pmd) != pmd_ptfn(*pmd_k));
+	return pmd_k;
+}
+
+/*
+ * Handle a fault on the vmalloc area.
+ */
+static inline int vmalloc_fault(pgd_t *pgd, unsigned long address)
+{
+	pmd_t *pmd_k;
+	pte_t *pte_k;
+
+	/* Make sure we are in vmalloc area */
+	if (!(address >= VMALLOC_START && address < VMALLOC_END))
+		return -1;
+
+	/*
+	 * Synchronize this task's top level page-table
+	 * with the 'reference' page table.
+	 */
+	pmd_k = vmalloc_sync_one(pgd, address);
+	if (!pmd_k)
+		return -1;
+	pte_k = pte_offset_kernel(pmd_k, address);
+	if (!pte_present(*pte_k))
+		return -1;
+	return 0;
+}
+
+/* Wait until this PTE has completed migration. */
+static void wait_for_migration(pte_t *pte)
+{
+	if (pte_migrating(*pte)) {
+		/*
+		 * Wait until the migrater fixes up this pte.
+		 * We scale the loop count by the clock rate so we'll wait for
+		 * a few seconds here.
+		 */
+		int retries = 0;
+		int bound = get_clock_rate();
+		while (pte_migrating(*pte)) {
+			barrier();
+			if (++retries > bound)
+				panic("Hit migrating PTE (%#llx) and page PFN %#lx still migrating",
+				      pte->val, pte_pfn(*pte));
+		}
+	}
+}
+
+/*
+ * It's not generally safe to use "current" to get the page table pointer,
+ * since we might be running an oprofile interrupt in the middle of a
+ * task switch.
+ */
+static pgd_t *get_current_pgd(void)
+{
+	HV_Context ctx = hv_inquire_context();
+	unsigned long pgd_pfn = ctx.page_table >> PAGE_SHIFT;
+	struct page *pgd_page = pfn_to_page(pgd_pfn);
+	BUG_ON(PageHighMem(pgd_page));
+	return (pgd_t *) __va(ctx.page_table);
+}
+
+/*
+ * We can receive a page fault from a migrating PTE at any time.
+ * Handle it by just waiting until the fault resolves.
+ *
+ * It's also possible to get a migrating kernel PTE that resolves
+ * itself during the downcall from hypervisor to Linux.  We just check
+ * here to see if the PTE seems valid, and if so we retry it.
+ *
+ * NOTE! We MUST NOT take any locks for this case.  We may be in an
+ * interrupt or a critical region, and must do as little as possible.
+ * Similarly, we can't use atomic ops here, since we may be handling a
+ * fault caused by an atomic op access.
+ *
+ * If we find a migrating PTE while we're in an NMI context, and we're
+ * at a PC that has a registered exception handler, we don't wait,
+ * since this thread may (e.g.) have been interrupted while migrating
+ * its own stack, which would then cause us to self-deadlock.
+ */
+static int handle_migrating_pte(pgd_t *pgd, int fault_num,
+				unsigned long address, unsigned long pc,
+				int is_kernel_mode, int write)
+{
+	pud_t *pud;
+	pmd_t *pmd;
+	pte_t *pte;
+	pte_t pteval;
+
+	if (pgd_addr_invalid(address))
+		return 0;
+
+	pgd += pgd_index(address);
+	pud = pud_offset(pgd, address);
+	if (!pud || !pud_present(*pud))
+		return 0;
+	pmd = pmd_offset(pud, address);
+	if (!pmd || !pmd_present(*pmd))
+		return 0;
+	pte = pmd_huge_page(*pmd) ? ((pte_t *)pmd) :
+		pte_offset_kernel(pmd, address);
+	pteval = *pte;
+	if (pte_migrating(pteval)) {
+		if (in_nmi() && search_exception_tables(pc))
+			return 0;
+		wait_for_migration(pte);
+		return 1;
+	}
+
+	if (!is_kernel_mode || !pte_present(pteval))
+		return 0;
+	if (fault_num == INT_ITLB_MISS) {
+		if (pte_exec(pteval))
+			return 1;
+	} else if (write) {
+		if (pte_write(pteval))
+			return 1;
+	} else {
+		if (pte_read(pteval))
+			return 1;
+	}
+
+	return 0;
+}
+
+/*
+ * This routine is responsible for faulting in user pages.
+ * It passes the work off to one of the appropriate routines.
+ * It returns true if the fault was successfully handled.
+ */
+static int handle_page_fault(struct pt_regs *regs,
+			     int fault_num,
+			     int is_page_fault,
+			     unsigned long address,
+			     int write)
+{
+	struct task_struct *tsk;
+	struct mm_struct *mm;
+	struct vm_area_struct *vma;
+	unsigned long stack_offset;
+	int fault;
+	int si_code;
+	int is_kernel_mode;
+	pgd_t *pgd;
+	unsigned int flags;
+
+	/* on TILE, protection faults are always writes */
+	if (!is_page_fault)
+		write = 1;
+
+	flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
+
+	is_kernel_mode = !user_mode(regs);
+
+	tsk = validate_current();
+
+	/*
+	 * Check to see if we might be overwriting the stack, and bail
+	 * out if so.  The page fault code is a relatively likely
+	 * place to get trapped in an infinite regress, and once we
+	 * overwrite the whole stack, it becomes very hard to recover.
+	 */
+	stack_offset = stack_pointer & (THREAD_SIZE-1);
+	if (stack_offset < THREAD_SIZE / 8) {
+		pr_alert("Potential stack overrun: sp %#lx\n", stack_pointer);
+		show_regs(regs);
+		pr_alert("Killing current process %d/%s\n",
+			 tsk->pid, tsk->comm);
+		do_group_exit(SIGKILL);
+	}
+
+	/*
+	 * Early on, we need to check for migrating PTE entries;
+	 * see homecache.c.  If we find a migrating PTE, we wait until
+	 * the backing page claims to be done migrating, then we proceed.
+	 * For kernel PTEs, we rewrite the PTE and return and retry.
+	 * Otherwise, we treat the fault like a normal "no PTE" fault,
+	 * rather than trying to patch up the existing PTE.
+	 */
+	pgd = get_current_pgd();
+	if (handle_migrating_pte(pgd, fault_num, address, regs->pc,
+				 is_kernel_mode, write))
+		return 1;
+
+	si_code = SEGV_MAPERR;
+
+	/*
+	 * We fault-in kernel-space virtual memory on-demand. The
+	 * 'reference' page table is init_mm.pgd.
+	 *
+	 * NOTE! We MUST NOT take any locks for this case. We may
+	 * be in an interrupt or a critical region, and should
+	 * only copy the information from the master page table,
+	 * nothing more.
+	 *
+	 * This verifies that the fault happens in kernel space
+	 * and that the fault was not a protection fault.
+	 */
+	if (unlikely(address >= TASK_SIZE &&
+		     !is_arch_mappable_range(address, 0))) {
+		if (is_kernel_mode && is_page_fault &&
+		    vmalloc_fault(pgd, address) >= 0)
+			return 1;
+		/*
+		 * Don't take the mm semaphore here. If we fixup a prefetch
+		 * fault we could otherwise deadlock.
+		 */
+		mm = NULL;  /* happy compiler */
+		vma = NULL;
+		goto bad_area_nosemaphore;
+	}
+
+	/*
+	 * If we're trying to touch user-space addresses, we must
+	 * be either at PL0, or else with interrupts enabled in the
+	 * kernel, so either way we can re-enable interrupts here
+	 * unless we are doing atomic access to user space with
+	 * interrupts disabled.
+	 */
+	if (!(regs->flags & PT_FLAGS_DISABLE_IRQ))
+		local_irq_enable();
+
+	mm = tsk->mm;
+
+	/*
+	 * If we're in an interrupt, have no user context or are running in an
+	 * atomic region then we must not take the fault.
+	 */
+	if (in_atomic() || !mm) {
+		vma = NULL;  /* happy compiler */
+		goto bad_area_nosemaphore;
+	}
+
+	if (!is_kernel_mode)
+		flags |= FAULT_FLAG_USER;
+
+	/*
+	 * When running in the kernel we expect faults to occur only to
+	 * addresses in user space.  All other faults represent errors in the
+	 * kernel and should generate an OOPS.  Unfortunately, in the case of an
+	 * erroneous fault occurring in a code path which already holds mmap_sem
+	 * we will deadlock attempting to validate the fault against the
+	 * address space.  Luckily the kernel only validly references user
+	 * space from well defined areas of code, which are listed in the
+	 * exceptions table.
+	 *
+	 * As the vast majority of faults will be valid we will only perform
+	 * the source reference check when there is a possibility of a deadlock.
+	 * Attempt to lock the address space, if we cannot we then validate the
+	 * source.  If this is invalid we can skip the address space check,
+	 * thus avoiding the deadlock.
+	 */
+	if (!down_read_trylock(&mm->mmap_sem)) {
+		if (is_kernel_mode &&
+		    !search_exception_tables(regs->pc)) {
+			vma = NULL;  /* happy compiler */
+			goto bad_area_nosemaphore;
+		}
+
+retry:
+		down_read(&mm->mmap_sem);
+	}
+
+	vma = find_vma(mm, address);
+	if (!vma)
+		goto bad_area;
+	if (vma->vm_start <= address)
+		goto good_area;
+	if (!(vma->vm_flags & VM_GROWSDOWN))
+		goto bad_area;
+	if (regs->sp < PAGE_OFFSET) {
+		/*
+		 * accessing the stack below sp is always a bug.
+		 */
+		if (address < regs->sp)
+			goto bad_area;
+	}
+	if (expand_stack(vma, address))
+		goto bad_area;
+
+/*
+ * Ok, we have a good vm_area for this memory access, so
+ * we can handle it..
+ */
+good_area:
+	si_code = SEGV_ACCERR;
+	if (fault_num == INT_ITLB_MISS) {
+		if (!(vma->vm_flags & VM_EXEC))
+			goto bad_area;
+	} else if (write) {
+#ifdef TEST_VERIFY_AREA
+		if (!is_page_fault && regs->cs == KERNEL_CS)
+			pr_err("WP fault at " REGFMT "\n", regs->eip);
+#endif
+		if (!(vma->vm_flags & VM_WRITE))
+			goto bad_area;
+		flags |= FAULT_FLAG_WRITE;
+	} else {
+		if (!is_page_fault || !(vma->vm_flags & VM_READ))
+			goto bad_area;
+	}
+
+	/*
+	 * If for any reason at all we couldn't handle the fault,
+	 * make sure we exit gracefully rather than endlessly redo
+	 * the fault.
+	 */
+	fault = handle_mm_fault(mm, vma, address, flags);
+
+	if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
+		return 0;
+
+	if (unlikely(fault & VM_FAULT_ERROR)) {
+		if (fault & VM_FAULT_OOM)
+			goto out_of_memory;
+		else if (fault & VM_FAULT_SIGSEGV)
+			goto bad_area;
+		else if (fault & VM_FAULT_SIGBUS)
+			goto do_sigbus;
+		BUG();
+	}
+	if (flags & FAULT_FLAG_ALLOW_RETRY) {
+		if (fault & VM_FAULT_MAJOR)
+			tsk->maj_flt++;
+		else
+			tsk->min_flt++;
+		if (fault & VM_FAULT_RETRY) {
+			flags &= ~FAULT_FLAG_ALLOW_RETRY;
+			flags |= FAULT_FLAG_TRIED;
+
+			 /*
+			  * No need to up_read(&mm->mmap_sem) as we would
+			  * have already released it in __lock_page_or_retry
+			  * in mm/filemap.c.
+			  */
+			goto retry;
+		}
+	}
+
+#if CHIP_HAS_TILE_DMA()
+	/* If this was a DMA TLB fault, restart the DMA engine. */
+	switch (fault_num) {
+	case INT_DMATLB_MISS:
+	case INT_DMATLB_MISS_DWNCL:
+	case INT_DMATLB_ACCESS:
+	case INT_DMATLB_ACCESS_DWNCL:
+		__insn_mtspr(SPR_DMA_CTR, SPR_DMA_CTR__REQUEST_MASK);
+		break;
+	}
+#endif
+
+	up_read(&mm->mmap_sem);
+	return 1;
+
+/*
+ * Something tried to access memory that isn't in our memory map..
+ * Fix it, but check if it's kernel or user first..
+ */
+bad_area:
+	up_read(&mm->mmap_sem);
+
+bad_area_nosemaphore:
+	/* User mode accesses just cause a SIGSEGV */
+	if (!is_kernel_mode) {
+		/*
+		 * It's possible to have interrupts off here.
+		 */
+		local_irq_enable();
+
+		force_sig_info_fault("segfault", SIGSEGV, si_code, address,
+				     fault_num, tsk, regs);
+		return 0;
+	}
+
+no_context:
+	/* Are we prepared to handle this kernel fault?  */
+	if (fixup_exception(regs))
+		return 0;
+
+/*
+ * Oops. The kernel tried to access some bad page. We'll have to
+ * terminate things with extreme prejudice.
+ */
+
+	bust_spinlocks(1);
+
+	/* FIXME: no lookup_address() yet */
+#ifdef SUPPORT_LOOKUP_ADDRESS
+	if (fault_num == INT_ITLB_MISS) {
+		pte_t *pte = lookup_address(address);
+
+		if (pte && pte_present(*pte) && !pte_exec_kernel(*pte))
+			pr_crit("kernel tried to execute non-executable page - exploit attempt? (uid: %d)\n",
+				current->uid);
+	}
+#endif
+	if (address < PAGE_SIZE)
+		pr_alert("Unable to handle kernel NULL pointer dereference\n");
+	else
+		pr_alert("Unable to handle kernel paging request\n");
+	pr_alert(" at virtual address " REGFMT ", pc " REGFMT "\n",
+		 address, regs->pc);
+
+	show_regs(regs);
+
+	if (unlikely(tsk->pid < 2)) {
+		panic("Kernel page fault running %s!",
+		      is_idle_task(tsk) ? "the idle task" : "init");
+	}
+
+	/*
+	 * More FIXME: we should probably copy the i386 here and
+	 * implement a generic die() routine.  Not today.
+	 */
+#ifdef SUPPORT_DIE
+	die("Oops", regs);
+#endif
+	bust_spinlocks(1);
+
+	do_group_exit(SIGKILL);
+
+/*
+ * We ran out of memory, or some other thing happened to us that made
+ * us unable to handle the page fault gracefully.
+ */
+out_of_memory:
+	up_read(&mm->mmap_sem);
+	if (is_kernel_mode)
+		goto no_context;
+	pagefault_out_of_memory();
+	return 0;
+
+do_sigbus:
+	up_read(&mm->mmap_sem);
+
+	/* Kernel mode? Handle exceptions or die */
+	if (is_kernel_mode)
+		goto no_context;
+
+	force_sig_info_fault("bus error", SIGBUS, BUS_ADRERR, address,
+			     fault_num, tsk, regs);
+	return 0;
+}
+
+#ifndef __tilegx__
+
+/* We must release ICS before panicking or we won't get anywhere. */
+#define ics_panic(fmt, ...)					\
+do {								\
+	__insn_mtspr(SPR_INTERRUPT_CRITICAL_SECTION, 0);	\
+	panic(fmt, ##__VA_ARGS__);				\
+} while (0)
+
+/*
+ * When we take an ITLB or DTLB fault or access violation in the
+ * supervisor while the critical section bit is set, the hypervisor is
+ * reluctant to write new values into the EX_CONTEXT_K_x registers,
+ * since that might indicate we have not yet squirreled the SPR
+ * contents away and can thus safely take a recursive interrupt.
+ * Accordingly, the hypervisor passes us the PC via SYSTEM_SAVE_K_2.
+ *
+ * Note that this routine is called before homecache_tlb_defer_enter(),
+ * which means that we can properly unlock any atomics that might
+ * be used there (good), but also means we must be very sensitive
+ * to not touch any data structures that might be located in memory
+ * that could migrate, as we could be entering the kernel on a dataplane
+ * cpu that has been deferring kernel TLB updates.  This means, for
+ * example, that we can't migrate init_mm or its pgd.
+ */
+struct intvec_state do_page_fault_ics(struct pt_regs *regs, int fault_num,
+				      unsigned long address,
+				      unsigned long info)
+{
+	unsigned long pc = info & ~1;
+	int write = info & 1;
+	pgd_t *pgd = get_current_pgd();
+
+	/* Retval is 1 at first since we will handle the fault fully. */
+	struct intvec_state state = {
+		do_page_fault, fault_num, address, write, 1
+	};
+
+	/* Validate that we are plausibly in the right routine. */
+	if ((pc & 0x7) != 0 || pc < PAGE_OFFSET ||
+	    (fault_num != INT_DTLB_MISS &&
+	     fault_num != INT_DTLB_ACCESS)) {
+		unsigned long old_pc = regs->pc;
+		regs->pc = pc;
+		ics_panic("Bad ICS page fault args: old PC %#lx, fault %d/%d at %#lx",
+			  old_pc, fault_num, write, address);
+	}
+
+	/* We might be faulting on a vmalloc page, so check that first. */
+	if (fault_num != INT_DTLB_ACCESS && vmalloc_fault(pgd, address) >= 0)
+		return state;
+
+	/*
+	 * If we faulted with ICS set in sys_cmpxchg, we are providing
+	 * a user syscall service that should generate a signal on
+	 * fault.  We didn't set up a kernel stack on initial entry to
+	 * sys_cmpxchg, but instead had one set up by the fault, which
+	 * (because sys_cmpxchg never releases ICS) came to us via the
+	 * SYSTEM_SAVE_K_2 mechanism, and thus EX_CONTEXT_K_[01] are
+	 * still referencing the original user code.  We release the
+	 * atomic lock and rewrite pt_regs so that it appears that we
+	 * came from user-space directly, and after we finish the
+	 * fault we'll go back to user space and re-issue the swint.
+	 * This way the backtrace information is correct if we need to
+	 * emit a stack dump at any point while handling this.
+	 *
+	 * Must match register use in sys_cmpxchg().
+	 */
+	if (pc >= (unsigned long) sys_cmpxchg &&
+	    pc < (unsigned long) __sys_cmpxchg_end) {
+#ifdef CONFIG_SMP
+		/* Don't unlock before we could have locked. */
+		if (pc >= (unsigned long)__sys_cmpxchg_grab_lock) {
+			int *lock_ptr = (int *)(regs->regs[ATOMIC_LOCK_REG]);
+			__atomic_fault_unlock(lock_ptr);
+		}
+#endif
+		regs->sp = regs->regs[27];
+	}
+
+	/*
+	 * We can also fault in the atomic assembly, in which
+	 * case we use the exception table to do the first-level fixup.
+	 * We may re-fixup again in the real fault handler if it
+	 * turns out the faulting address is just bad, and not,
+	 * for example, migrating.
+	 */
+	else if (pc >= (unsigned long) __start_atomic_asm_code &&
+		   pc < (unsigned long) __end_atomic_asm_code) {
+		const struct exception_table_entry *fixup;
+#ifdef CONFIG_SMP
+		/* Unlock the atomic lock. */
+		int *lock_ptr = (int *)(regs->regs[ATOMIC_LOCK_REG]);
+		__atomic_fault_unlock(lock_ptr);
+#endif
+		fixup = search_exception_tables(pc);
+		if (!fixup)
+			ics_panic("ICS atomic fault not in table: PC %#lx, fault %d",
+				  pc, fault_num);
+		regs->pc = fixup->fixup;
+		regs->ex1 = PL_ICS_EX1(KERNEL_PL, 0);
+	}
+
+	/*
+	 * Now that we have released the atomic lock (if necessary),
+	 * it's safe to spin if the PTE that caused the fault was migrating.
+	 */
+	if (fault_num == INT_DTLB_ACCESS)
+		write = 1;
+	if (handle_migrating_pte(pgd, fault_num, address, pc, 1, write))
+		return state;
+
+	/* Return zero so that we continue on with normal fault handling. */
+	state.retval = 0;
+	return state;
+}
+
+#endif /* !__tilegx__ */
+
+/*
+ * This routine handles page faults.  It determines the address, and the
+ * problem, and then passes it handle_page_fault() for normal DTLB and
+ * ITLB issues, and for DMA or SN processor faults when we are in user
+ * space.  For the latter, if we're in kernel mode, we just save the
+ * interrupt away appropriately and return immediately.  We can't do
+ * page faults for user code while in kernel mode.
+ */
+void do_page_fault(struct pt_regs *regs, int fault_num,
+		   unsigned long address, unsigned long write)
+{
+	int is_page_fault;
+	enum ctx_state prev_state = exception_enter();
+
+#ifdef CONFIG_KPROBES
+	/*
+	 * This is to notify the fault handler of the kprobes.  The
+	 * exception code is redundant as it is also carried in REGS,
+	 * but we pass it anyhow.
+	 */
+	if (notify_die(DIE_PAGE_FAULT, "page fault", regs, -1,
+		       regs->faultnum, SIGSEGV) == NOTIFY_STOP)
+		goto done;
+#endif
+
+#ifdef __tilegx__
+	/*
+	 * We don't need early do_page_fault_ics() support, since unlike
+	 * Pro we don't need to worry about unlocking the atomic locks.
+	 * There is only one current case in GX where we touch any memory
+	 * under ICS other than our own kernel stack, and we handle that
+	 * here.  (If we crash due to trying to touch our own stack,
+	 * we're in too much trouble for C code to help out anyway.)
+	 */
+	if (write & ~1) {
+		unsigned long pc = write & ~1;
+		if (pc >= (unsigned long) __start_unalign_asm_code &&
+		    pc < (unsigned long) __end_unalign_asm_code) {
+			struct thread_info *ti = current_thread_info();
+			/*
+			 * Our EX_CONTEXT is still what it was from the
+			 * initial unalign exception, but now we've faulted
+			 * on the JIT page.  We would like to complete the
+			 * page fault however is appropriate, and then retry
+			 * the instruction that caused the unalign exception.
+			 * Our state has been "corrupted" by setting the low
+			 * bit in "sp", and stashing r0..r3 in the
+			 * thread_info area, so we revert all of that, then
+			 * continue as if this were a normal page fault.
+			 */
+			regs->sp &= ~1UL;
+			regs->regs[0] = ti->unalign_jit_tmp[0];
+			regs->regs[1] = ti->unalign_jit_tmp[1];
+			regs->regs[2] = ti->unalign_jit_tmp[2];
+			regs->regs[3] = ti->unalign_jit_tmp[3];
+			write &= 1;
+		} else {
+			pr_alert("%s/%d: ICS set at page fault at %#lx: %#lx\n",
+				 current->comm, current->pid, pc, address);
+			show_regs(regs);
+			do_group_exit(SIGKILL);
+		}
+	}
+#else
+	/* This case should have been handled by do_page_fault_ics(). */
+	BUG_ON(write & ~1);
+#endif
+
+#if CHIP_HAS_TILE_DMA()
+	/*
+	 * If it's a DMA fault, suspend the transfer while we're
+	 * handling the miss; we'll restart after it's handled.  If we
+	 * don't suspend, it's possible that this process could swap
+	 * out and back in, and restart the engine since the DMA is
+	 * still 'running'.
+	 */
+	if (fault_num == INT_DMATLB_MISS ||
+	    fault_num == INT_DMATLB_ACCESS ||
+	    fault_num == INT_DMATLB_MISS_DWNCL ||
+	    fault_num == INT_DMATLB_ACCESS_DWNCL) {
+		__insn_mtspr(SPR_DMA_CTR, SPR_DMA_CTR__SUSPEND_MASK);
+		while (__insn_mfspr(SPR_DMA_USER_STATUS) &
+		       SPR_DMA_STATUS__BUSY_MASK)
+			;
+	}
+#endif
+
+	/* Validate fault num and decide if this is a first-time page fault. */
+	switch (fault_num) {
+	case INT_ITLB_MISS:
+	case INT_DTLB_MISS:
+#if CHIP_HAS_TILE_DMA()
+	case INT_DMATLB_MISS:
+	case INT_DMATLB_MISS_DWNCL:
+#endif
+		is_page_fault = 1;
+		break;
+
+	case INT_DTLB_ACCESS:
+#if CHIP_HAS_TILE_DMA()
+	case INT_DMATLB_ACCESS:
+	case INT_DMATLB_ACCESS_DWNCL:
+#endif
+		is_page_fault = 0;
+		break;
+
+	default:
+		panic("Bad fault number %d in do_page_fault", fault_num);
+	}
+
+#if CHIP_HAS_TILE_DMA()
+	if (!user_mode(regs)) {
+		struct async_tlb *async;
+		switch (fault_num) {
+#if CHIP_HAS_TILE_DMA()
+		case INT_DMATLB_MISS:
+		case INT_DMATLB_ACCESS:
+		case INT_DMATLB_MISS_DWNCL:
+		case INT_DMATLB_ACCESS_DWNCL:
+			async = &current->thread.dma_async_tlb;
+			break;
+#endif
+		default:
+			async = NULL;
+		}
+		if (async) {
+
+			/*
+			 * No vmalloc check required, so we can allow
+			 * interrupts immediately at this point.
+			 */
+			local_irq_enable();
+
+			set_thread_flag(TIF_ASYNC_TLB);
+			if (async->fault_num != 0) {
+				panic("Second async fault %d; old fault was %d (%#lx/%ld)",
+				      fault_num, async->fault_num,
+				      address, write);
+			}
+			BUG_ON(fault_num == 0);
+			async->fault_num = fault_num;
+			async->is_fault = is_page_fault;
+			async->is_write = write;
+			async->address = address;
+			goto done;
+		}
+	}
+#endif
+
+	handle_page_fault(regs, fault_num, is_page_fault, address, write);
+
+done:
+	exception_exit(prev_state);
+}
+
+
+#if CHIP_HAS_TILE_DMA()
+/*
+ * This routine effectively re-issues asynchronous page faults
+ * when we are returning to user space.
+ */
+void do_async_page_fault(struct pt_regs *regs)
+{
+	struct async_tlb *async = &current->thread.dma_async_tlb;
+
+	/*
+	 * Clear thread flag early.  If we re-interrupt while processing
+	 * code here, we will reset it and recall this routine before
+	 * returning to user space.
+	 */
+	clear_thread_flag(TIF_ASYNC_TLB);
+
+	if (async->fault_num) {
+		/*
+		 * Clear async->fault_num before calling the page-fault
+		 * handler so that if we re-interrupt before returning
+		 * from the function we have somewhere to put the
+		 * information from the new interrupt.
+		 */
+		int fault_num = async->fault_num;
+		async->fault_num = 0;
+		handle_page_fault(regs, fault_num, async->is_fault,
+				  async->address, async->is_write);
+	}
+}
+#endif /* CHIP_HAS_TILE_DMA() */
+
+
+void vmalloc_sync_all(void)
+{
+#ifdef __tilegx__
+	/* Currently all L1 kernel pmd's are static and shared. */
+	BUILD_BUG_ON(pgd_index(VMALLOC_END - PAGE_SIZE) !=
+		     pgd_index(VMALLOC_START));
+#else
+	/*
+	 * Note that races in the updates of insync and start aren't
+	 * problematic: insync can only get set bits added, and updates to
+	 * start are only improving performance (without affecting correctness
+	 * if undone).
+	 */
+	static DECLARE_BITMAP(insync, PTRS_PER_PGD);
+	static unsigned long start = PAGE_OFFSET;
+	unsigned long address;
+
+	BUILD_BUG_ON(PAGE_OFFSET & ~PGDIR_MASK);
+	for (address = start; address >= PAGE_OFFSET; address += PGDIR_SIZE) {
+		if (!test_bit(pgd_index(address), insync)) {
+			unsigned long flags;
+			struct list_head *pos;
+
+			spin_lock_irqsave(&pgd_lock, flags);
+			list_for_each(pos, &pgd_list)
+				if (!vmalloc_sync_one(list_to_pgd(pos),
+								address)) {
+					/* Must be at first entry in list. */
+					BUG_ON(pos != pgd_list.next);
+					break;
+				}
+			spin_unlock_irqrestore(&pgd_lock, flags);
+			if (pos != pgd_list.next)
+				set_bit(pgd_index(address), insync);
+		}
+		if (address == start && test_bit(pgd_index(address), insync))
+			start = address + PGDIR_SIZE;
+	}
+#endif
+}