arch/tile: core support for Tilera 32-bit chips.

This change is the core kernel support for TILEPro and TILE64 chips.
No driver support (except the console driver) is included yet.

This includes the relevant Linux headers in asm/; the low-level
low-level "Tile architecture" headers in arch/, which are
shared with the hypervisor, etc., and are build-system agnostic;
and the relevant hypervisor headers in hv/.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Reviewed-by: Paul Mundt <lethal@linux-sh.org>

1 files changed, 905 insertions, 0 deletions

diff --git a/arch/tile/mm/fault.c b/arch/tile/mm/fault.c
new file mode 100644
index 000000000000..9b6b92f07def
--- /dev/null
+++ b/arch/tile/mm/fault.c
@@ -0,0 +1,905 @@
+/*
+ * 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/smp_lock.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 <asm/system.h>
+#include <asm/pgalloc.h>
+#include <asm/sections.h>
+
+#include <arch/interrupts.h>
+
+/*
+ * Unlock any spinlocks which will prevent us from getting the
+ * message out
+ */
+void bust_spinlocks(int yes)
+{
+        int loglevel_save = console_loglevel;
+
+        if (yes) {
+                oops_in_progress = 1;
+                return;
+        }
+        oops_in_progress = 0;
+        /*
+         * OK, the message is on the console.  Now we call printk()
+         * without oops_in_progress set so that printk will give klogd
+         * a poke.  Hold onto your hats...
+         */
+        console_loglevel = 15;  /* NMI oopser may have shut the console up */
+        printk(" ");
+        console_loglevel = loglevel_save;
+}
+
+static noinline void force_sig_info_fault(int si_signo, int si_code,
+        unsigned long address, int fault_num, struct task_struct *tsk)
+{
+        siginfo_t info;
+
+        if (unlikely(tsk->pid < 2)) {
+                panic("Signal %d (code %d) at %#lx sent to %s!",
+                      si_signo, si_code & 0xffff, address,
+                      tsk->pid ? "init" : "the idle task");
+        }
+
+        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;
+        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.  Called indirectly
+ * from sys_cmpxchg() in kernel/intvec.S.
+ */
+int _sys_cmpxchg_badaddr(unsigned long address, struct pt_regs *regs)
+{
+        if (address >= PAGE_OFFSET)
+                force_sig_info_fault(SIGSEGV, SEGV_MAPERR, address,
+                                     INT_DTLB_MISS, current);
+        else
+                force_sig_info_fault(SIGBUS, BUS_ADRALN, address,
+                                     INT_UNALIGN_DATA, current);
+
+        /*
+         * 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);
+                arch_flush_lazy_mmu_mode();
+        } else
+                BUG_ON(pmd_ptfn(*pmd) != pmd_ptfn(*pmd_k));
+        return pmd_k;
+}
+
+/*
+ * Handle a fault on the vmalloc or module mapping 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;
+        if (pmd_huge(*pmd_k))
+                return 0;   /* support TILE huge_vmap() API */
+        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));   /* oops, HIGHPTE? */
+        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.
+ */
+static int handle_migrating_pte(pgd_t *pgd, int fault_num,
+                                unsigned long address,
+                                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)) {
+                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;
+
+        /* on TILE, protection faults are always writes */
+        if (!is_page_fault)
+                write = 1;
+
+        is_kernel_mode = (EX1_PL(regs->ex1) != USER_PL);
+
+        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) {
+                printk(KERN_ALERT "Potential stack overrun: sp %#lx\n",
+                       stack_pointer);
+                show_regs(regs);
+                printk(KERN_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 procede.
+         * 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,
+                                 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.
+         */
+        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;
+        }
+
+        /*
+         * 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;
+                }
+                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)
+                        printk("WP fault at "REGFMT"\n", regs->eip);
+#endif
+                if (!(vma->vm_flags & VM_WRITE))
+                        goto bad_area;
+        } else {
+                if (!is_page_fault || !(vma->vm_flags & VM_READ))
+                        goto bad_area;
+        }
+
+ survive:
+        /*
+         * 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, write);
+        if (unlikely(fault & VM_FAULT_ERROR)) {
+                if (fault & VM_FAULT_OOM)
+                        goto out_of_memory;
+                else if (fault & VM_FAULT_SIGBUS)
+                        goto do_sigbus;
+                BUG();
+        }
+        if (fault & VM_FAULT_MAJOR)
+                tsk->maj_flt++;
+        else
+                tsk->min_flt++;
+
+        /*
+         * If this was an asynchronous fault,
+         * restart the appropriate engine.
+         */
+        switch (fault_num) {
+#if CHIP_HAS_TILE_DMA()
+        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
+#if CHIP_HAS_SN_PROC()
+        case INT_SNITLB_MISS:
+        case INT_SNITLB_MISS_DWNCL:
+                __insn_mtspr(SPR_SNCTL,
+                             __insn_mfspr(SPR_SNCTL) &
+                             ~SPR_SNCTL__FRZPROC_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(SIGSEGV, si_code, address,
+                                     fault_num, tsk);
+                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))
+                        printk(KERN_CRIT "kernel tried to execute"
+                               " non-executable page - exploit attempt?"
+                               " (uid: %d)\n", current->uid);
+        }
+#endif
+        if (address < PAGE_SIZE)
+                printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference\n");
+        else
+                printk(KERN_ALERT "Unable to handle kernel paging request\n");
+        printk(" at virtual address "REGFMT", pc "REGFMT"\n",
+               address, regs->pc);
+
+        show_regs(regs);
+
+        if (unlikely(tsk->pid < 2)) {
+                panic("Kernel page fault running %s!",
+                      tsk->pid ? "init" : "the idle task");
+        }
+
+        /*
+         * 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_global_init(tsk)) {
+                yield();
+                down_read(&mm->mmap_sem);
+                goto survive;
+        }
+        printk("VM: killing process %s\n", tsk->comm);
+        if (!is_kernel_mode)
+                do_group_exit(SIGKILL);
+        goto no_context;
+
+do_sigbus:
+        up_read(&mm->mmap_sem);
+
+        /* Kernel mode? Handle exceptions or die */
+        if (is_kernel_mode)
+                goto no_context;
+
+        force_sig_info_fault(SIGBUS, BUS_ADRERR, address, fault_num, tsk);
+        return 0;
+}
+
+#ifndef __tilegx__
+
+extern char sys_cmpxchg[], __sys_cmpxchg_end[];
+extern char __sys_cmpxchg_grab_lock[];
+extern char __start_atomic_asm_code[], __end_atomic_asm_code[];
+
+/*
+ * We return this structure in registers to avoid having to write
+ * additional save/restore code in the intvec.S caller.
+ */
+struct intvec_state {
+        void *handler;
+        unsigned long vecnum;
+        unsigned long fault_num;
+        unsigned long info;
+        unsigned long retval;
+};
+
+/* 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)
+
+void do_page_fault(struct pt_regs *regs, int fault_num,
+                   unsigned long address, unsigned long write);
+
+/*
+ * 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_1_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_1_2.
+ */
+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\n",
+                          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_1_2 mechanism, and thus EX_CONTEXT_1_[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);
+        }
+
+        /*
+         * NOTE: the one other type of access that might bring us here
+         * are the memory ops in __tns_atomic_acquire/__tns_atomic_release,
+         * but we don't have to check specially for them since we can
+         * always safely return to the address of the fault and retry,
+         * since no separate atomic locks are involved.
+         */
+
+        /*
+         * 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, 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;
+
+        /* This case should have been handled by do_page_fault_ics(). */
+        BUG_ON(write & ~1);
+
+#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
+#if CHIP_HAS_SN_PROC()
+        case INT_SNITLB_MISS:
+        case INT_SNITLB_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 (EX1_PL(regs->ex1) != USER_PL) {
+                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
+#if CHIP_HAS_SN_PROC()
+                case INT_SNITLB_MISS:
+                case INT_SNITLB_MISS_DWNCL:
+                        async = &current->thread.sn_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;
+                        return;
+                }
+        }
+
+        handle_page_fault(regs, fault_num, is_page_fault, address, write);
+}
+
+
+#if CHIP_HAS_TILE_DMA() || CHIP_HAS_SN_PROC()
+/*
+ * Check an async_tlb structure to see if a deferred fault is waiting,
+ * and if so pass it to the page-fault code.
+ */
+static void handle_async_page_fault(struct pt_regs *regs,
+                                    struct async_tlb *async)
+{
+        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() || CHIP_HAS_SN_PROC() */
+
+
+/*
+ * This routine effectively re-issues asynchronous page faults
+ * when we are returning to user space.
+ */
+void do_async_page_fault(struct pt_regs *regs)
+{
+        /*
+         * 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 CHIP_HAS_TILE_DMA()
+        handle_async_page_fault(regs, &current->thread.dma_async_tlb);
+#endif
+#if CHIP_HAS_SN_PROC()
+        handle_async_page_fault(regs, &current->thread.sn_async_tlb);
+#endif
+}
+
+void vmalloc_sync_all(void)
+{
+#ifdef __tilegx__
+        /* Currently all L1 kernel pmd's are static and shared. */
+        BUG_ON(pgd_index(VMALLOC_END) != 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
+}