/*
 * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
 * Licensed under the GPL
 */

#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/hardirq.h>
#include <asm/current.h>
#include <asm/pgtable.h>
#include <asm/tlbflush.h>
#include "arch.h"
#include "as-layout.h"
#include "kern_util.h"
#include "os.h"
#include "sysdep/sigcontext.h"

/*
 * Note this is constrained to return 0, -EFAULT, -EACCESS, -ENOMEM by
 * segv().
 */
int handle_page_fault(unsigned long address, unsigned long ip,
                      int is_write, int is_user, int *code_out)
{
        struct mm_struct *mm = current->mm;
        struct vm_area_struct *vma;
        pgd_t *pgd;
        pud_t *pud;
        pmd_t *pmd;
        pte_t *pte;
        int err = -EFAULT;

        *code_out = SEGV_MAPERR;

        /*
         * If the fault was during atomic operation, don't take the fault, just
         * fail.
         */
        if (in_atomic())
                goto out_nosemaphore;

        down_read(&mm->mmap_sem);
        vma = find_vma(mm, address);
        if (!vma)
                goto out;
        else if (vma->vm_start <= address)
                goto good_area;
        else if (!(vma->vm_flags & VM_GROWSDOWN))
                goto out;
        else if (is_user && !ARCH_IS_STACKGROW(address))
                goto out;
        else if (expand_stack(vma, address))
                goto out;

good_area:
        *code_out = SEGV_ACCERR;
        if (is_write && !(vma->vm_flags & VM_WRITE))
                goto out;

        /* Don't require VM_READ|VM_EXEC for write faults! */
        if (!is_write && !(vma->vm_flags & (VM_READ | VM_EXEC)))
                goto out;

        do {
                int fault;
survive:
                fault = handle_mm_fault(mm, vma, address, is_write);
                if (unlikely(fault & VM_FAULT_ERROR)) {
                        if (fault & VM_FAULT_OOM) {
                                err = -ENOMEM;
                                goto out_of_memory;
                        } else if (fault & VM_FAULT_SIGBUS) {
                                err = -EACCES;
                                goto out;
                        }
                        BUG();
                }
                if (fault & VM_FAULT_MAJOR)
                        current->maj_flt++;
                else
                        current->min_flt++;

                pgd = pgd_offset(mm, address);
                pud = pud_offset(pgd, address);
                pmd = pmd_offset(pud, address);
                pte = pte_offset_kernel(pmd, address);
        } while (!pte_present(*pte));
        err = 0;
        /*
         * The below warning was added in place of
         *      pte_mkyoung(); if (is_write) pte_mkdirty();
         * If it's triggered, we'd see normally a hang here (a clean pte is
         * marked read-only to emulate the dirty bit).
         * However, the generic code can mark a PTE writable but clean on a
         * concurrent read fault, triggering this harmlessly. So comment it out.
         */
#if 0
        WARN_ON(!pte_young(*pte) || (is_write && !pte_dirty(*pte)));
#endif
        flush_tlb_page(vma, address);
out:
        up_read(&mm->mmap_sem);
out_nosemaphore:
        return err;

/*
 * 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:
        if (is_global_init(current)) {
                up_read(&mm->mmap_sem);
                yield();
                down_read(&mm->mmap_sem);
                goto survive;
        }
        goto out;
}

static void bad_segv(struct faultinfo fi, unsigned long ip)
{
        struct siginfo si;

        si.si_signo = SIGSEGV;
        si.si_code = SEGV_ACCERR;
        si.si_addr = (void __user *) FAULT_ADDRESS(fi);
        current->thread.arch.faultinfo = fi;
        force_sig_info(SIGSEGV, &si, current);
}

static void segv_handler(int sig, struct uml_pt_regs *regs)
{
        struct faultinfo * fi = UPT_FAULTINFO(regs);

        if (UPT_IS_USER(regs) && !SEGV_IS_FIXABLE(fi)) {
                bad_segv(*fi, UPT_IP(regs));
                return;
        }
        segv(*fi, UPT_IP(regs), UPT_IS_USER(regs), regs);
}

/*
 * We give a *copy* of the faultinfo in the regs to segv.
 * This must be done, since nesting SEGVs could overwrite
 * the info in the regs. A pointer to the info then would
 * give us bad data!
 */
unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user,
                   struct uml_pt_regs *regs)
{
        struct siginfo si;
        jmp_buf *catcher;
        int err;
        int is_write = FAULT_WRITE(fi);
        unsigned long address = FAULT_ADDRESS(fi);

        if (!is_user && (address >= start_vm) && (address < end_vm)) {
                flush_tlb_kernel_vm();
                return 0;
        }
        else if (current->mm == NULL) {
                show_regs(container_of(regs, struct pt_regs, regs));
                panic("Segfault with no mm");
        }

        if (SEGV_IS_FIXABLE(&fi) || SEGV_MAYBE_FIXABLE(&fi))
                err = handle_page_fault(address, ip, is_write, is_user,
                                        &si.si_code);
        else {
                err = -EFAULT;
                /*
                 * A thread accessed NULL, we get a fault, but CR2 is invalid.
                 * This code is used in __do_copy_from_user() of TT mode.
                 * XXX tt mode is gone, so maybe this isn't needed any more
                 */
                address = 0;
        }

        catcher = current->thread.fault_catcher;
        if (!err)
                return 0;
        else if (catcher != NULL) {
                current->thread.fault_addr = (void *) address;
                UML_LONGJMP(catcher, 1);
        }
        else if (current->thread.fault_addr != NULL)
                panic("fault_addr set but no fault catcher");
        else if (!is_user && arch_fixup(ip, regs))
                return 0;

        if (!is_user) {
                show_regs(container_of(regs, struct pt_regs, regs));
                panic("Kernel mode fault at addr 0x%lx, ip 0x%lx",
                      address, ip);
        }

        if (err == -EACCES) {
                si.si_signo = SIGBUS;
                si.si_errno = 0;
                si.si_code = BUS_ADRERR;
                si.si_addr = (void __user *)address;
                current->thread.arch.faultinfo = fi;
                force_sig_info(SIGBUS, &si, current);
        } else if (err == -ENOMEM) {
                printk(KERN_INFO "VM: killing process %s\n", current->comm);
                do_exit(SIGKILL);
        } else {
                BUG_ON(err != -EFAULT);
                si.si_signo = SIGSEGV;
                si.si_addr = (void __user *) address;
                current->thread.arch.faultinfo = fi;
                force_sig_info(SIGSEGV, &si, current);
        }
        return 0;
}

void relay_signal(int sig, struct uml_pt_regs *regs)
{
        if (arch_handle_signal(sig, regs))
                return;

        if (!UPT_IS_USER(regs)) {
                if (sig == SIGBUS)
                        printk(KERN_ERR "Bus error - the host /dev/shm or /tmp "
                               "mount likely just ran out of space\n");
                panic("Kernel mode signal %d", sig);
        }

        current->thread.arch.faultinfo = *UPT_FAULTINFO(regs);
        force_sig(sig, current);
}

static void bus_handler(int sig, struct uml_pt_regs *regs)
{
        if (current->thread.fault_catcher != NULL)
                UML_LONGJMP(current->thread.fault_catcher, 1);
        else relay_signal(sig, regs);
}

static void winch(int sig, struct uml_pt_regs *regs)
{
        do_IRQ(WINCH_IRQ, regs);
}

const struct kern_handlers handlinfo_kern = {
        .relay_signal = relay_signal,
        .winch = winch,
        .bus_handler = bus_handler,
        .page_fault = segv_handler,
        .sigio_handler = sigio_handler,
        .timer_handler = timer_handler
};

void trap_init(void)
{
}