/*
 * fault.c:  Page fault handlers for the Sparc.
 *
 * Copyright (C) 1995 David S. Miller (davem@caip.rutgers.edu)
 * Copyright (C) 1996 Eddie C. Dost (ecd@skynet.be)
 * Copyright (C) 1997 Jakub Jelinek (jj@sunsite.mff.cuni.cz)
 */

#include <asm/head.h>

#include <linux/string.h>
#include <linux/types.h>
#include <linux/sched.h>
#include <linux/ptrace.h>
#include <linux/mman.h>
#include <linux/threads.h>
#include <linux/kernel.h>
#include <linux/signal.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/kdebug.h>

#include <asm/system.h>
#include <asm/page.h>
#include <asm/pgtable.h>
#include <asm/memreg.h>
#include <asm/openprom.h>
#include <asm/oplib.h>
#include <asm/smp.h>
#include <asm/traps.h>
#include <asm/uaccess.h>

extern int prom_node_root;

/* At boot time we determine these two values necessary for setting
 * up the segment maps and page table entries (pte's).
 */

int num_segmaps, num_contexts;
int invalid_segment;

/* various Virtual Address Cache parameters we find at boot time... */

int vac_size, vac_linesize, vac_do_hw_vac_flushes;
int vac_entries_per_context, vac_entries_per_segment;
int vac_entries_per_page;

/* Return how much physical memory we have.  */
unsigned long probe_memory(void)
{
        unsigned long total = 0;
        int i;

        for (i = 0; sp_banks[i].num_bytes; i++)
                total += sp_banks[i].num_bytes;

        return total;
}

extern void sun4c_complete_all_stores(void);

/* Whee, a level 15 NMI interrupt memory error.  Let's have fun... */
asmlinkage void sparc_lvl15_nmi(struct pt_regs *regs, unsigned long serr,
                                unsigned long svaddr, unsigned long aerr,
                                unsigned long avaddr)
{
        sun4c_complete_all_stores();
        printk("FAULT: NMI received\n");
        printk("SREGS: Synchronous Error %08lx\n", serr);
        printk("       Synchronous Vaddr %08lx\n", svaddr);
        printk("      Asynchronous Error %08lx\n", aerr);
        printk("      Asynchronous Vaddr %08lx\n", avaddr);
        if (sun4c_memerr_reg)
                printk("     Memory Parity Error %08lx\n", *sun4c_memerr_reg);
        printk("REGISTER DUMP:\n");
        show_regs(regs);
        prom_halt();
}

static void unhandled_fault(unsigned long, struct task_struct *,
                struct pt_regs *) __attribute__ ((noreturn));

static void unhandled_fault(unsigned long address, struct task_struct *tsk,
                     struct pt_regs *regs)
{
        if((unsigned long) address < PAGE_SIZE) {
                printk(KERN_ALERT
                    "Unable to handle kernel NULL pointer dereference\n");
        } else {
                printk(KERN_ALERT "Unable to handle kernel paging request "
                       "at virtual address %08lx\n", address);
        }
        printk(KERN_ALERT "tsk->{mm,active_mm}->context = %08lx\n",
                (tsk->mm ? tsk->mm->context : tsk->active_mm->context));
        printk(KERN_ALERT "tsk->{mm,active_mm}->pgd = %08lx\n",
                (tsk->mm ? (unsigned long) tsk->mm->pgd :
                        (unsigned long) tsk->active_mm->pgd));
        die_if_kernel("Oops", regs);
}

asmlinkage int lookup_fault(unsigned long pc, unsigned long ret_pc, 
                            unsigned long address)
{
        struct pt_regs regs;
        unsigned long g2;
        unsigned int insn;
        int i;
        
        i = search_extables_range(ret_pc, &g2);
        switch (i) {
        case 3:
                /* load & store will be handled by fixup */
                return 3;

        case 1:
                /* store will be handled by fixup, load will bump out */
                /* for _to_ macros */
                insn = *((unsigned int *) pc);
                if ((insn >> 21) & 1)
                        return 1;
                break;

        case 2:
                /* load will be handled by fixup, store will bump out */
                /* for _from_ macros */
                insn = *((unsigned int *) pc);
                if (!((insn >> 21) & 1) || ((insn>>19)&0x3f) == 15)
                        return 2; 
                break; 

        default:
                break;
        };

        memset(&regs, 0, sizeof (regs));
        regs.pc = pc;
        regs.npc = pc + 4;
        __asm__ __volatile__(
                "rd %%psr, %0\n\t"
                "nop\n\t"
                "nop\n\t"
                "nop\n" : "=r" (regs.psr));
        unhandled_fault(address, current, &regs);

        /* Not reached */
        return 0;
}

extern unsigned long safe_compute_effective_address(struct pt_regs *,
                                                    unsigned int);

static unsigned long compute_si_addr(struct pt_regs *regs, int text_fault)
{
        unsigned int insn;

        if (text_fault)
                return regs->pc;

        if (regs->psr & PSR_PS) {
                insn = *(unsigned int *) regs->pc;
        } else {
                __get_user(insn, (unsigned int *) regs->pc);
        }

        return safe_compute_effective_address(regs, insn);
}

asmlinkage void do_sparc_fault(struct pt_regs *regs, int text_fault, int write,
                               unsigned long address)
{
        struct vm_area_struct *vma;
        struct task_struct *tsk = current;
        struct mm_struct *mm = tsk->mm;
        unsigned int fixup;
        unsigned long g2;
        siginfo_t info;
        int from_user = !(regs->psr & PSR_PS);
        int fault;

        if(text_fault)
                address = regs->pc;

        /*
         * 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.
         */
        if (!ARCH_SUN4C && address >= TASK_SIZE)
                goto vmalloc_fault;

        info.si_code = SEGV_MAPERR;

        /*
         * If we're in an interrupt or have no user
         * context, we must not take the fault..
         */
        if (in_atomic() || !mm)
                goto no_context;

        down_read(&mm->mmap_sem);

        /*
         * The kernel referencing a bad kernel pointer can lock up
         * a sun4c machine completely, so we must attempt recovery.
         */
        if(!from_user && address >= PAGE_OFFSET)
                goto bad_area;

        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(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:
        info.si_code = SEGV_ACCERR;
        if(write) {
                if(!(vma->vm_flags & VM_WRITE))
                        goto bad_area;
        } else {
                /* Allow reads even for write-only mappings */
                if(!(vma->vm_flags & (VM_READ | VM_EXEC)))
                        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, write ? FAULT_FLAG_WRITE : 0);
        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)
                current->maj_flt++;
        else
                current->min_flt++;
        up_read(&mm->mmap_sem);
        return;

        /*
         * 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(from_user) {
#if 0
                printk("Fault whee %s [%d]: segfaults at %08lx pc=%08lx\n",
                       tsk->comm, tsk->pid, address, regs->pc);
#endif
                info.si_signo = SIGSEGV;
                info.si_errno = 0;
                /* info.si_code set above to make clear whether
                   this was a SEGV_MAPERR or SEGV_ACCERR fault.  */
                info.si_addr = (void __user *)compute_si_addr(regs, text_fault);
                info.si_trapno = 0;
                force_sig_info (SIGSEGV, &info, tsk);
                return;
        }

        /* Is this in ex_table? */
no_context:
        g2 = regs->u_regs[UREG_G2];
        if (!from_user) {
                fixup = search_extables_range(regs->pc, &g2);
                if (fixup > 10) { /* Values below are reserved for other things */
                        extern const unsigned __memset_start[];
                        extern const unsigned __memset_end[];
                        extern const unsigned __csum_partial_copy_start[];
                        extern const unsigned __csum_partial_copy_end[];

#ifdef DEBUG_EXCEPTIONS
                        printk("Exception: PC<%08lx> faddr<%08lx>\n", regs->pc, address);
                        printk("EX_TABLE: insn<%08lx> fixup<%08x> g2<%08lx>\n",
                                regs->pc, fixup, g2);
#endif
                        if ((regs->pc >= (unsigned long)__memset_start &&
                             regs->pc < (unsigned long)__memset_end) ||
                            (regs->pc >= (unsigned long)__csum_partial_copy_start &&
                             regs->pc < (unsigned long)__csum_partial_copy_end)) {
                                regs->u_regs[UREG_I4] = address;
                                regs->u_regs[UREG_I5] = regs->pc;
                        }
                        regs->u_regs[UREG_G2] = g2;
                        regs->pc = fixup;
                        regs->npc = regs->pc + 4;
                        return;
                }
        }
        
        unhandled_fault (address, tsk, regs);
        do_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 (from_user) {
                pagefault_out_of_memory();
                return;
        }
        goto no_context;

do_sigbus:
        up_read(&mm->mmap_sem);
        info.si_signo = SIGBUS;
        info.si_errno = 0;
        info.si_code = BUS_ADRERR;
        info.si_addr = (void __user *) compute_si_addr(regs, text_fault);
        info.si_trapno = 0;
        force_sig_info (SIGBUS, &info, tsk);
        if (!from_user)
                goto no_context;

vmalloc_fault:
        {
                /*
                 * Synchronize this task's top level page-table
                 * with the 'reference' page table.
                 */
                int offset = pgd_index(address);
                pgd_t *pgd, *pgd_k;
                pmd_t *pmd, *pmd_k;

                pgd = tsk->active_mm->pgd + offset;
                pgd_k = init_mm.pgd + offset;

                if (!pgd_present(*pgd)) {
                        if (!pgd_present(*pgd_k))
                                goto bad_area_nosemaphore;
                        pgd_val(*pgd) = pgd_val(*pgd_k);
                        return;
                }

                pmd = pmd_offset(pgd, address);
                pmd_k = pmd_offset(pgd_k, address);

                if (pmd_present(*pmd) || !pmd_present(*pmd_k))
                        goto bad_area_nosemaphore;
                *pmd = *pmd_k;
                return;
        }
}

asmlinkage void do_sun4c_fault(struct pt_regs *regs, int text_fault, int write,
                               unsigned long address)
{
        extern void sun4c_update_mmu_cache(struct vm_area_struct *,
                                           unsigned long,pte_t);
        extern pte_t *sun4c_pte_offset_kernel(pmd_t *,unsigned long);
        struct task_struct *tsk = current;
        struct mm_struct *mm = tsk->mm;
        pgd_t *pgdp;
        pte_t *ptep;

        if (text_fault) {
                address = regs->pc;
        } else if (!write &&
                   !(regs->psr & PSR_PS)) {
                unsigned int insn, __user *ip;

                ip = (unsigned int __user *)regs->pc;
                if (!get_user(insn, ip)) {
                        if ((insn & 0xc1680000) == 0xc0680000)
                                write = 1;
                }
        }

        if (!mm) {
                /* We are oopsing. */
                do_sparc_fault(regs, text_fault, write, address);
                BUG();  /* P3 Oops already, you bitch */
        }

        pgdp = pgd_offset(mm, address);
        ptep = sun4c_pte_offset_kernel((pmd_t *) pgdp, address);

        if (pgd_val(*pgdp)) {
            if (write) {
                if ((pte_val(*ptep) & (_SUN4C_PAGE_WRITE|_SUN4C_PAGE_PRESENT))
                                   == (_SUN4C_PAGE_WRITE|_SUN4C_PAGE_PRESENT)) {
                        unsigned long flags;

                        *ptep = __pte(pte_val(*ptep) | _SUN4C_PAGE_ACCESSED |
                                      _SUN4C_PAGE_MODIFIED |
                                      _SUN4C_PAGE_VALID |
                                      _SUN4C_PAGE_DIRTY);

                        local_irq_save(flags);
                        if (sun4c_get_segmap(address) != invalid_segment) {
                                sun4c_put_pte(address, pte_val(*ptep));
                                local_irq_restore(flags);
                                return;
                        }
                        local_irq_restore(flags);
                }
            } else {
                if ((pte_val(*ptep) & (_SUN4C_PAGE_READ|_SUN4C_PAGE_PRESENT))
                                   == (_SUN4C_PAGE_READ|_SUN4C_PAGE_PRESENT)) {
                        unsigned long flags;

                        *ptep = __pte(pte_val(*ptep) | _SUN4C_PAGE_ACCESSED |
                                      _SUN4C_PAGE_VALID);

                        local_irq_save(flags);
                        if (sun4c_get_segmap(address) != invalid_segment) {
                                sun4c_put_pte(address, pte_val(*ptep));
                                local_irq_restore(flags);
                                return;
                        }
                        local_irq_restore(flags);
                }
            }
        }

        /* This conditional is 'interesting'. */
        if (pgd_val(*pgdp) && !(write && !(pte_val(*ptep) & _SUN4C_PAGE_WRITE))
            && (pte_val(*ptep) & _SUN4C_PAGE_VALID))
                /* Note: It is safe to not grab the MMAP semaphore here because
                 *       we know that update_mmu_cache() will not sleep for
                 *       any reason (at least not in the current implementation)
                 *       and therefore there is no danger of another thread getting
                 *       on the CPU and doing a shrink_mmap() on this vma.
                 */
                sun4c_update_mmu_cache (find_vma(current->mm, address), address,
                                        *ptep);
        else
                do_sparc_fault(regs, text_fault, write, address);
}

/* This always deals with user addresses. */
static void force_user_fault(unsigned long address, int write)
{
        struct vm_area_struct *vma;
        struct task_struct *tsk = current;
        struct mm_struct *mm = tsk->mm;
        siginfo_t info;

        info.si_code = SEGV_MAPERR;

#if 0
        printk("wf<pid=%d,wr=%d,addr=%08lx>\n",
               tsk->pid, write, address);
#endif
        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(expand_stack(vma, address))
                goto bad_area;
good_area:
        info.si_code = SEGV_ACCERR;
        if(write) {
                if(!(vma->vm_flags & VM_WRITE))
                        goto bad_area;
        } else {
                if(!(vma->vm_flags & (VM_READ | VM_EXEC)))
                        goto bad_area;
        }
        switch (handle_mm_fault(mm, vma, address, write ? FAULT_FLAG_WRITE : 0)) {
        case VM_FAULT_SIGBUS:
        case VM_FAULT_OOM:
                goto do_sigbus;
        }
        up_read(&mm->mmap_sem);
        return;
bad_area:
        up_read(&mm->mmap_sem);
#if 0
        printk("Window whee %s [%d]: segfaults at %08lx\n",
               tsk->comm, tsk->pid, address);
#endif
        info.si_signo = SIGSEGV;
        info.si_errno = 0;
        /* info.si_code set above to make clear whether
           this was a SEGV_MAPERR or SEGV_ACCERR fault.  */
        info.si_addr = (void __user *) address;
        info.si_trapno = 0;
        force_sig_info (SIGSEGV, &info, tsk);
        return;

do_sigbus:
        up_read(&mm->mmap_sem);
        info.si_signo = SIGBUS;
        info.si_errno = 0;
        info.si_code = BUS_ADRERR;
        info.si_addr = (void __user *) address;
        info.si_trapno = 0;
        force_sig_info (SIGBUS, &info, tsk);
}

void window_overflow_fault(void)
{
        unsigned long sp;

        sp = current_thread_info()->rwbuf_stkptrs[0];
        if(((sp + 0x38) & PAGE_MASK) != (sp & PAGE_MASK))
                force_user_fault(sp + 0x38, 1);
        force_user_fault(sp, 1);
}

void window_underflow_fault(unsigned long sp)
{
        if(((sp + 0x38) & PAGE_MASK) != (sp & PAGE_MASK))
                force_user_fault(sp + 0x38, 0);
        force_user_fault(sp, 0);
}

void window_ret_fault(struct pt_regs *regs)
{
        unsigned long sp;

        sp = regs->u_regs[UREG_FP];
        if(((sp + 0x38) & PAGE_MASK) != (sp & PAGE_MASK))
                force_user_fault(sp + 0x38, 0);
        force_user_fault(sp, 0);
}