/*
 * 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 <asm/system.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(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.
 */
SYSCALL_DEFINE2(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) {
                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 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)
                        pr_err("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 CHIP_HAS_TILE_DMA() || CHIP_HAS_SN_PROC()
        /*
         * 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
        }
#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))
                        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!",
                      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;
        }
        pr_alert("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__

/* 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\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_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);
        }

        /*
         * 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
}