[PATCH] oom-kill: update comments to reflect current code

[pv_ops_mirror.git] / arch / m32r / mm / fault.c

/*
 *  linux/arch/m32r/mm/fault.c
 *
 *  Copyright (c) 2001, 2002  Hitoshi Yamamoto, and H. Kondo
 *  Copyright (c) 2004  Naoto Sugai, NIIBE Yutaka
 *
 *  Some code taken from i386 version.
 *    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 <asm/m32r.h>
#include <asm/system.h>
#include <asm/uaccess.h>
#include <asm/hardirq.h>
#include <asm/mmu_context.h>
#include <asm/tlbflush.h>

extern void die(const char *, struct pt_regs *, long);

#ifndef CONFIG_SMP
asmlinkage unsigned int tlb_entry_i_dat;
asmlinkage unsigned int tlb_entry_d_dat;
#define tlb_entry_i tlb_entry_i_dat
#define tlb_entry_d tlb_entry_d_dat
#else
unsigned int tlb_entry_i_dat[NR_CPUS];
unsigned int tlb_entry_d_dat[NR_CPUS];
#define tlb_entry_i tlb_entry_i_dat[smp_processor_id()]
#define tlb_entry_d tlb_entry_d_dat[smp_processor_id()]
#endif

extern void init_tlb(void);

/*
 * 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;
        }
#ifdef CONFIG_VT
        unblank_screen();
#endif
        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;
}

/*======================================================================*
 * do_page_fault()
 *======================================================================*
 * This routine handles page faults.  It determines the address,
 * and the problem, and then passes it off to one of the appropriate
 * routines.
 *
 * ARGUMENT:
 *  regs       : M32R SP reg.
 *  error_code : See below
 *  address    : M32R MMU MDEVA reg. (Operand ACE)
 *             : M32R BPC reg. (Instruction ACE)
 *
 * error_code :
 *  bit 0 == 0 means no page found, 1 means protection fault
 *  bit 1 == 0 means read, 1 means write
 *  bit 2 == 0 means kernel, 1 means user-mode
 *  bit 3 == 0 means data, 1 means instruction
 *======================================================================*/
#define ACE_PROTECTION          1
#define ACE_WRITE               2
#define ACE_USERMODE            4
#define ACE_INSTRUCTION         8

asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long error_code,
  unsigned long address)
{
        struct task_struct *tsk;
        struct mm_struct *mm;
        struct vm_area_struct * vma;
        unsigned long page, addr;
        int write;
        siginfo_t info;

        /*
         * If BPSW IE bit enable --> set PSW IE bit
         */
        if (regs->psw & M32R_PSW_BIE)
                local_irq_enable();

        tsk = current;

        info.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
         * (error_code & ACE_USERMODE) == 0, and that the fault was not a
         * protection error (error_code & ACE_PROTECTION) == 0.
         */
        if (address >= TASK_SIZE && !(error_code & ACE_USERMODE))
                goto vmalloc_fault;

        mm = tsk->mm;

        /*
         * If we're in an interrupt or have no user context or are running in an
         * atomic region then we must not take the fault..
         */
        if (in_atomic() || !mm)
                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.  Unfortunatly, 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 possibilty 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 ((error_code & ACE_USERMODE) == 0 &&
                    !search_exception_tables(regs->psw))
                        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 0
        if (error_code & ACE_USERMODE) {
                /*
                 * accessing the stack below "spu" is always a bug.
                 * The "+ 4" is there due to the push instruction
                 * doing pre-decrement on the stack and that
                 * doesn't show up until later..
                 */
                if (address + 4 < regs->spu)
                        goto bad_area;
        }
#endif
        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;
        write = 0;
        switch (error_code & (ACE_WRITE|ACE_PROTECTION)) {
                default:        /* 3: write, present */
                        /* fall through */
                case ACE_WRITE: /* write, not present */
                        if (!(vma->vm_flags & VM_WRITE))
                                goto bad_area;
                        write++;
                        break;
                case ACE_PROTECTION:    /* read, present */
                case 0:         /* read, not present */
                        if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
                                goto bad_area;
        }

        /*
         * For instruction access exception, check if the area is executable
         */
        if ((error_code & ACE_INSTRUCTION) && !(vma->vm_flags & VM_EXEC))
          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.
         */
        addr = (address & PAGE_MASK);
        set_thread_fault_code(error_code);
        switch (handle_mm_fault(mm, vma, addr, write)) {
                case VM_FAULT_MINOR:
                        tsk->min_flt++;
                        break;
                case VM_FAULT_MAJOR:
                        tsk->maj_flt++;
                        break;
                case VM_FAULT_SIGBUS:
                        goto do_sigbus;
                case VM_FAULT_OOM:
                        goto out_of_memory;
                default:
                        BUG();
        }
        set_thread_fault_code(0);
        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 (error_code & ACE_USERMODE) {
                tsk->thread.address = address;
                tsk->thread.error_code = error_code | (address >= TASK_SIZE);
                tsk->thread.trap_no = 14;
                info.si_signo = SIGSEGV;
                info.si_errno = 0;
                /* info.si_code has been set above */
                info.si_addr = (void __user *)address;
                force_sig_info(SIGSEGV, &info, tsk);
                return;
        }

no_context:
        /* Are we prepared to handle this kernel fault?  */
        if (fixup_exception(regs))
                return;

/*
 * Oops. The kernel tried to access some bad page. We'll have to
 * terminate things with extreme prejudice.
 */

        bust_spinlocks(1);

        if (address < PAGE_SIZE)
                printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference");
        else
                printk(KERN_ALERT "Unable to handle kernel paging request");
        printk(" at virtual address %08lx\n",address);
        printk(KERN_ALERT " printing bpc:\n");
        printk("%08lx\n", regs->bpc);
        page = *(unsigned long *)MPTB;
        page = ((unsigned long *) page)[address >> PGDIR_SHIFT];
        printk(KERN_ALERT "*pde = %08lx\n", page);
        if (page & _PAGE_PRESENT) {
                page &= PAGE_MASK;
                address &= 0x003ff000;
                page = ((unsigned long *) __va(page))[address >> PAGE_SHIFT];
                printk(KERN_ALERT "*pte = %08lx\n", page);
        }
        die("Oops", regs, error_code);
        bust_spinlocks(0);
        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 (tsk->pid == 1) {
                yield();
                down_read(&mm->mmap_sem);
                goto survive;
        }
        printk("VM: killing process %s\n", tsk->comm);
        if (error_code & ACE_USERMODE)
                do_exit(SIGKILL);
        goto no_context;

do_sigbus:
        up_read(&mm->mmap_sem);

        /* Kernel mode? Handle exception or die */
        if (!(error_code & ACE_USERMODE))
                goto no_context;

        tsk->thread.address = address;
        tsk->thread.error_code = error_code;
        tsk->thread.trap_no = 14;
        info.si_signo = SIGBUS;
        info.si_errno = 0;
        info.si_code = BUS_ADRERR;
        info.si_addr = (void __user *)address;
        force_sig_info(SIGBUS, &info, tsk);
        return;

vmalloc_fault:
        {
                /*
                 * Synchronize this task's top level page-table
                 * with the 'reference' page table.
                 *
                 * Do _not_ use "tsk" here. We might be inside
                 * an interrupt in the middle of a task switch..
                 */
                int offset = pgd_index(address);
                pgd_t *pgd, *pgd_k;
                pmd_t *pmd, *pmd_k;
                pte_t *pte_k;

                pgd = (pgd_t *)*(unsigned long *)MPTB;
                pgd = offset + (pgd_t *)pgd;
                pgd_k = init_mm.pgd + offset;

                if (!pgd_present(*pgd_k))
                        goto no_context;

                /*
                 * set_pgd(pgd, *pgd_k); here would be useless on PAE
                 * and redundant with the set_pmd() on non-PAE.
                 */

                pmd = pmd_offset(pgd, address);
                pmd_k = pmd_offset(pgd_k, address);
                if (!pmd_present(*pmd_k))
                        goto no_context;
                set_pmd(pmd, *pmd_k);

                pte_k = pte_offset_kernel(pmd_k, address);
                if (!pte_present(*pte_k))
                        goto no_context;

                addr = (address & PAGE_MASK) | (error_code & ACE_INSTRUCTION);
                update_mmu_cache(NULL, addr, *pte_k);
                return;
        }
}

/*======================================================================*
 * update_mmu_cache()
 *======================================================================*/
#define TLB_MASK        (NR_TLB_ENTRIES - 1)
#define ITLB_END        (unsigned long *)(ITLB_BASE + (NR_TLB_ENTRIES * 8))
#define DTLB_END        (unsigned long *)(DTLB_BASE + (NR_TLB_ENTRIES * 8))
void update_mmu_cache(struct vm_area_struct *vma, unsigned long vaddr,
        pte_t pte)
{
        unsigned long *entry1, *entry2;
        unsigned long pte_data, flags;
        unsigned int *entry_dat;
        int inst = get_thread_fault_code() & ACE_INSTRUCTION;
        int i;

        /* Ptrace may call this routine. */
        if (vma && current->active_mm != vma->vm_mm)
                return;

        local_irq_save(flags);

        vaddr = (vaddr & PAGE_MASK) | get_asid();

#ifdef CONFIG_CHIP_OPSP
        entry1 = (unsigned long *)ITLB_BASE;
        for(i = 0 ; i < NR_TLB_ENTRIES; i++) {
                if(*entry1++ == vaddr) {
                        pte_data = pte_val(pte);
                        set_tlb_data(entry1, pte_data);
                        break;
                }
                entry1++;
        }
        entry2 = (unsigned long *)DTLB_BASE;
        for(i = 0 ; i < NR_TLB_ENTRIES ; i++) {
                if(*entry2++ == vaddr) {
                        pte_data = pte_val(pte);
                        set_tlb_data(entry2, pte_data);
                        break;
                }
                entry2++;
        }
        local_irq_restore(flags);
        return;
#else
        pte_data = pte_val(pte);

        /*
         * Update TLB entries
         *  entry1: ITLB entry address
         *  entry2: DTLB entry address
         */
        __asm__ __volatile__ (
                "seth   %0, #high(%4)   \n\t"
                "st     %2, @(%5, %0)   \n\t"
                "ldi    %1, #1          \n\t"
                "st     %1, @(%6, %0)   \n\t"
                "add3   r4, %0, %7      \n\t"
                ".fillinsn              \n"
                "1:                     \n\t"
                "ld     %1, @(%6, %0)   \n\t"
                "bnez   %1, 1b          \n\t"
                "ld     %0, @r4+        \n\t"
                "ld     %1, @r4         \n\t"
                "st     %3, @+%0        \n\t"
                "st     %3, @+%1        \n\t"
                : "=&r" (entry1), "=&r" (entry2)
                : "r" (vaddr), "r" (pte_data), "i" (MMU_REG_BASE),
                "i" (MSVA_offset), "i" (MTOP_offset), "i" (MIDXI_offset)
                : "r4", "memory"
        );

        if ((!inst && entry2 >= DTLB_END) || (inst && entry1 >= ITLB_END))
                goto notfound;

found:
        local_irq_restore(flags);

        return;

        /* Valid entry not found */
notfound:
        /*
         * Update ITLB or DTLB entry
         *  entry1: TLB entry address
         *  entry2: TLB base address
         */
        if (!inst) {
                entry2 = (unsigned long *)DTLB_BASE;
                entry_dat = &tlb_entry_d;
        } else {
                entry2 = (unsigned long *)ITLB_BASE;
                entry_dat = &tlb_entry_i;
        }
        entry1 = entry2 + (((*entry_dat - 1) & TLB_MASK) << 1);

        for (i = 0 ; i < NR_TLB_ENTRIES ; i++) {
                if (!(entry1[1] & 2))   /* Valid bit check */
                        break;

                if (entry1 != entry2)
                        entry1 -= 2;
                else
                        entry1 += TLB_MASK << 1;
        }

        if (i >= NR_TLB_ENTRIES) {      /* Empty entry not found */
                entry1 = entry2 + (*entry_dat << 1);
                *entry_dat = (*entry_dat + 1) & TLB_MASK;
        }
        *entry1++ = vaddr;      /* Set TLB tag */
        set_tlb_data(entry1, pte_data);

        goto found;
#endif
}

/*======================================================================*
 * flush_tlb_page() : flushes one page
 *======================================================================*/
void local_flush_tlb_page(struct vm_area_struct *vma, unsigned long page)
{
        if (vma->vm_mm && mm_context(vma->vm_mm) != NO_CONTEXT) {
                unsigned long flags;

                local_irq_save(flags);
                page &= PAGE_MASK;
                page |= (mm_context(vma->vm_mm) & MMU_CONTEXT_ASID_MASK);
                __flush_tlb_page(page);
                local_irq_restore(flags);
        }
}

/*======================================================================*
 * flush_tlb_range() : flushes a range of pages
 *======================================================================*/
void local_flush_tlb_range(struct vm_area_struct *vma, unsigned long start,
        unsigned long end)
{
        struct mm_struct *mm;

        mm = vma->vm_mm;
        if (mm_context(mm) != NO_CONTEXT) {
                unsigned long flags;
                int size;

                local_irq_save(flags);
                size = (end - start + (PAGE_SIZE - 1)) >> PAGE_SHIFT;
                if (size > (NR_TLB_ENTRIES / 4)) { /* Too many TLB to flush */
                        mm_context(mm) = NO_CONTEXT;
                        if (mm == current->mm)
                                activate_context(mm);
                } else {
                        unsigned long asid;

                        asid = mm_context(mm) & MMU_CONTEXT_ASID_MASK;
                        start &= PAGE_MASK;
                        end += (PAGE_SIZE - 1);
                        end &= PAGE_MASK;

                        start |= asid;
                        end   |= asid;
                        while (start < end) {
                                __flush_tlb_page(start);
                                start += PAGE_SIZE;
                        }
                }
                local_irq_restore(flags);
        }
}

/*======================================================================*
 * flush_tlb_mm() : flushes the specified mm context TLB's
 *======================================================================*/
void local_flush_tlb_mm(struct mm_struct *mm)
{
        /* Invalidate all TLB of this process. */
        /* Instead of invalidating each TLB, we get new MMU context. */
        if (mm_context(mm) != NO_CONTEXT) {
                unsigned long flags;

                local_irq_save(flags);
                mm_context(mm) = NO_CONTEXT;
                if (mm == current->mm)
                        activate_context(mm);
                local_irq_restore(flags);
        }
}

/*======================================================================*
 * flush_tlb_all() : flushes all processes TLBs
 *======================================================================*/
void local_flush_tlb_all(void)
{
        unsigned long flags;

        local_irq_save(flags);
        __flush_tlb_all();
        local_irq_restore(flags);
}

/*======================================================================*
 * init_mmu()
 *======================================================================*/
void __init init_mmu(void)
{
        tlb_entry_i = 0;
        tlb_entry_d = 0;
        mmu_context_cache = MMU_CONTEXT_FIRST_VERSION;
        set_asid(mmu_context_cache & MMU_CONTEXT_ASID_MASK);
        *(volatile unsigned long *)MPTB = (unsigned long)swapper_pg_dir;
}