[S390] init task memory faults.

[linux-2.6/libata-dev.git] / arch / s390 / mm / fault.c

/*
 *  arch/s390/mm/fault.c
 *
 *  S390 version
 *    Copyright (C) 1999 IBM Deutschland Entwicklung GmbH, IBM Corporation
 *    Author(s): Hartmut Penner (hp@de.ibm.com)
 *               Ulrich Weigand (uweigand@de.ibm.com)
 *
 *  Derived from "arch/i386/mm/fault.c"
 *    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/init.h>
#include <linux/console.h>
#include <linux/module.h>
#include <linux/hardirq.h>
#include <linux/kprobes.h>

#include <asm/system.h>
#include <asm/uaccess.h>
#include <asm/pgtable.h>
#include <asm/kdebug.h>

#ifndef CONFIG_64BIT
#define __FAIL_ADDR_MASK 0x7ffff000
#define __FIXUP_MASK 0x7fffffff
#define __SUBCODE_MASK 0x0200
#define __PF_RES_FIELD 0ULL
#else /* CONFIG_64BIT */
#define __FAIL_ADDR_MASK -4096L
#define __FIXUP_MASK ~0L
#define __SUBCODE_MASK 0x0600
#define __PF_RES_FIELD 0x8000000000000000ULL
#endif /* CONFIG_64BIT */

#ifdef CONFIG_SYSCTL
extern int sysctl_userprocess_debug;
#endif

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

#ifdef CONFIG_KPROBES
ATOMIC_NOTIFIER_HEAD(notify_page_fault_chain);
int register_page_fault_notifier(struct notifier_block *nb)
{
        return atomic_notifier_chain_register(&notify_page_fault_chain, nb);
}

int unregister_page_fault_notifier(struct notifier_block *nb)
{
        return atomic_notifier_chain_unregister(&notify_page_fault_chain, nb);
}

static inline int notify_page_fault(enum die_val val, const char *str,
                        struct pt_regs *regs, long err, int trap, int sig)
{
        struct die_args args = {
                .regs = regs,
                .str = str,
                .err = err,
                .trapnr = trap,
                .signr = sig
        };
        return atomic_notifier_call_chain(&notify_page_fault_chain, val, &args);
}
#else
static inline int notify_page_fault(enum die_val val, const char *str,
                        struct pt_regs *regs, long err, int trap, int sig)
{
        return NOTIFY_DONE;
}
#endif

extern spinlock_t timerlist_lock;

/*
 * Unlock any spinlocks which will prevent us from getting the
 * message out (timerlist_lock is acquired through the
 * console unblank code)
 */
void bust_spinlocks(int yes)
{
        if (yes) {
                oops_in_progress = 1;
        } else {
                int loglevel_save = console_loglevel;
                console_unblank();
                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;
                printk(" ");
                console_loglevel = loglevel_save;
        }
}

/*
 * Check which address space is addressed by the access
 * register in S390_lowcore.exc_access_id.
 * Returns 1 for user space and 0 for kernel space.
 */
static int __check_access_register(struct pt_regs *regs, int error_code)
{
        int areg = S390_lowcore.exc_access_id;

        if (areg == 0)
                /* Access via access register 0 -> kernel address */
                return 0;
        save_access_regs(current->thread.acrs);
        if (regs && areg < NUM_ACRS && current->thread.acrs[areg] <= 1)
                /*
                 * access register contains 0 -> kernel address,
                 * access register contains 1 -> user space address
                 */
                return current->thread.acrs[areg];

        /* Something unhealthy was done with the access registers... */
        die("page fault via unknown access register", regs, error_code);
        do_exit(SIGKILL);
        return 0;
}

/*
 * Check which address space the address belongs to.
 * Returns 1 for user space and 0 for kernel space.
 */
static inline int check_user_space(struct pt_regs *regs, int error_code)
{
        /*
         * The lowest two bits of S390_lowcore.trans_exc_code indicate
         * which paging table was used:
         *   0: Primary Segment Table Descriptor
         *   1: STD determined via access register
         *   2: Secondary Segment Table Descriptor
         *   3: Home Segment Table Descriptor
         */
        int descriptor = S390_lowcore.trans_exc_code & 3;
        if (unlikely(descriptor == 1))
                return __check_access_register(regs, error_code);
        if (descriptor == 2)
                return current->thread.mm_segment.ar4;
        return descriptor != 0;
}

/*
 * Send SIGSEGV to task.  This is an external routine
 * to keep the stack usage of do_page_fault small.
 */
static void do_sigsegv(struct pt_regs *regs, unsigned long error_code,
                       int si_code, unsigned long address)
{
        struct siginfo si;

#if defined(CONFIG_SYSCTL) || defined(CONFIG_PROCESS_DEBUG)
#if defined(CONFIG_SYSCTL)
        if (sysctl_userprocess_debug)
#endif
        {
                printk("User process fault: interruption code 0x%lX\n",
                       error_code);
                printk("failing address: %lX\n", address);
                show_regs(regs);
        }
#endif
        si.si_signo = SIGSEGV;
        si.si_code = si_code;
        si.si_addr = (void __user *) address;
        force_sig_info(SIGSEGV, &si, current);
}

/*
 * This routine handles page faults.  It determines the address,
 * and the problem, and then passes it off to one of the appropriate
 * routines.
 *
 * error_code:
 *   04       Protection           ->  Write-Protection  (suprression)
 *   10       Segment translation  ->  Not present       (nullification)
 *   11       Page translation     ->  Not present       (nullification)
 *   3b       Region third trans.  ->  Not present       (nullification)
 */
static inline void __kprobes
do_exception(struct pt_regs *regs, unsigned long error_code, int is_protection)
{
        struct task_struct *tsk;
        struct mm_struct *mm;
        struct vm_area_struct * vma;
        unsigned long address;
        int user_address;
        const struct exception_table_entry *fixup;
        int si_code = SEGV_MAPERR;

        tsk = current;
        mm = tsk->mm;
        
        if (notify_page_fault(DIE_PAGE_FAULT, "page fault", regs, error_code, 14,
                                        SIGSEGV) == NOTIFY_STOP)
                return;

        /* 
         * Check for low-address protection.  This needs to be treated
         * as a special case because the translation exception code 
         * field is not guaranteed to contain valid data in this case.
         */
        if (is_protection && !(S390_lowcore.trans_exc_code & 4)) {

                /* Low-address protection hit in kernel mode means 
                   NULL pointer write access in kernel mode.  */
                if (!(regs->psw.mask & PSW_MASK_PSTATE)) {
                        address = 0;
                        user_address = 0;
                        goto no_context;
                }

                /* Low-address protection hit in user mode 'cannot happen'.  */
                die ("Low-address protection", regs, error_code);
                do_exit(SIGKILL);
        }

        /* 
         * get the failing address 
         * more specific the segment and page table portion of 
         * the address 
         */
        address = S390_lowcore.trans_exc_code & __FAIL_ADDR_MASK;
        user_address = check_user_space(regs, error_code);

        /*
         * Verify that the fault happened in user space, that
         * we are not in an interrupt and that there is a 
         * user context.
         */
        if (user_address == 0 || in_atomic() || !mm)
                goto no_context;

        /*
         * When we get here, the fault happened in the current
         * task's user address space, so we can switch on the
         * interrupts again and then search the VMAs
         */
        local_irq_enable();

        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;
/*
 * Ok, we have a good vm_area for this memory access, so
 * we can handle it..
 */
good_area:
        si_code = SEGV_ACCERR;
        if (!is_protection) {
                /* page not present, check vm flags */
                if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
                        goto bad_area;
        } else {
                if (!(vma->vm_flags & VM_WRITE))
                        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.
         */
        switch (handle_mm_fault(mm, vma, address, is_protection)) {
        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();
        }

        up_read(&mm->mmap_sem);
        /*
         * The instruction that caused the program check will
         * be repeated. Don't signal single step via SIGTRAP.
         */
        clear_tsk_thread_flag(current, TIF_SINGLE_STEP);
        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);

        /* User mode accesses just cause a SIGSEGV */
        if (regs->psw.mask & PSW_MASK_PSTATE) {
                tsk->thread.prot_addr = address;
                tsk->thread.trap_no = error_code;
                do_sigsegv(regs, error_code, si_code, address);
                return;
        }

no_context:
        /* Are we prepared to handle this kernel fault?  */
        fixup = search_exception_tables(regs->psw.addr & __FIXUP_MASK);
        if (fixup) {
                regs->psw.addr = fixup->fixup | PSW_ADDR_AMODE;
                return;
        }

/*
 * Oops. The kernel tried to access some bad page. We'll have to
 * terminate things with extreme prejudice.
 */
        if (user_address == 0)
                printk(KERN_ALERT "Unable to handle kernel pointer dereference"
                       " at virtual kernel address %p\n", (void *)address);
        else
                printk(KERN_ALERT "Unable to handle kernel paging request"
                       " at virtual user address %p\n", (void *)address);

        die("Oops", regs, error_code);
        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 (regs->psw.mask & PSW_MASK_PSTATE)
                do_exit(SIGKILL);
        goto no_context;

do_sigbus:
        up_read(&mm->mmap_sem);

        /*
         * Send a sigbus, regardless of whether we were in kernel
         * or user mode.
         */
        tsk->thread.prot_addr = address;
        tsk->thread.trap_no = error_code;
        force_sig(SIGBUS, tsk);

        /* Kernel mode? Handle exceptions or die */
        if (!(regs->psw.mask & PSW_MASK_PSTATE))
                goto no_context;
}

void do_protection_exception(struct pt_regs *regs, unsigned long error_code)
{
        regs->psw.addr -= (error_code >> 16);
        do_exception(regs, 4, 1);
}

void do_dat_exception(struct pt_regs *regs, unsigned long error_code)
{
        do_exception(regs, error_code & 0xff, 0);
}

#ifdef CONFIG_PFAULT 
/*
 * 'pfault' pseudo page faults routines.
 */
static int pfault_disable = 0;

static int __init nopfault(char *str)
{
        pfault_disable = 1;
        return 1;
}

__setup("nopfault", nopfault);

typedef struct {
        __u16 refdiagc;
        __u16 reffcode;
        __u16 refdwlen;
        __u16 refversn;
        __u64 refgaddr;
        __u64 refselmk;
        __u64 refcmpmk;
        __u64 reserved;
} __attribute__ ((packed)) pfault_refbk_t;

int pfault_init(void)
{
        pfault_refbk_t refbk =
                { 0x258, 0, 5, 2, __LC_CURRENT, 1ULL << 48, 1ULL << 48,
                  __PF_RES_FIELD };
        int rc;

        if (pfault_disable)
                return -1;
        __asm__ __volatile__(
                "    diag  %1,%0,0x258\n"
                "0:  j     2f\n"
                "1:  la    %0,8\n"
                "2:\n"
                ".section __ex_table,\"a\"\n"
                "   .align 4\n"
#ifndef CONFIG_64BIT
                "   .long  0b,1b\n"
#else /* CONFIG_64BIT */
                "   .quad  0b,1b\n"
#endif /* CONFIG_64BIT */
                ".previous"
                : "=d" (rc) : "a" (&refbk), "m" (refbk) : "cc" );
        __ctl_set_bit(0, 9);
        return rc;
}

void pfault_fini(void)
{
        pfault_refbk_t refbk =
        { 0x258, 1, 5, 2, 0ULL, 0ULL, 0ULL, 0ULL };

        if (pfault_disable)
                return;
        __ctl_clear_bit(0,9);
        __asm__ __volatile__(
                "    diag  %0,0,0x258\n"
                "0:\n"
                ".section __ex_table,\"a\"\n"
                "   .align 4\n"
#ifndef CONFIG_64BIT
                "   .long  0b,0b\n"
#else /* CONFIG_64BIT */
                "   .quad  0b,0b\n"
#endif /* CONFIG_64BIT */
                ".previous"
                : : "a" (&refbk), "m" (refbk) : "cc" );
}

asmlinkage void
pfault_interrupt(struct pt_regs *regs, __u16 error_code)
{
        struct task_struct *tsk;
        __u16 subcode;

        /*
         * Get the external interruption subcode & pfault
         * initial/completion signal bit. VM stores this 
         * in the 'cpu address' field associated with the
         * external interrupt. 
         */
        subcode = S390_lowcore.cpu_addr;
        if ((subcode & 0xff00) != __SUBCODE_MASK)
                return;

        /*
         * Get the token (= address of the task structure of the affected task).
         */
        tsk = *(struct task_struct **) __LC_PFAULT_INTPARM;

        if (subcode & 0x0080) {
                /* signal bit is set -> a page has been swapped in by VM */
                if (xchg(&tsk->thread.pfault_wait, -1) != 0) {
                        /* Initial interrupt was faster than the completion
                         * interrupt. pfault_wait is valid. Set pfault_wait
                         * back to zero and wake up the process. This can
                         * safely be done because the task is still sleeping
                         * and can't produce new pfaults. */
                        tsk->thread.pfault_wait = 0;
                        wake_up_process(tsk);
                        put_task_struct(tsk);
                }
        } else {
                /* signal bit not set -> a real page is missing. */
                get_task_struct(tsk);
                set_task_state(tsk, TASK_UNINTERRUPTIBLE);
                if (xchg(&tsk->thread.pfault_wait, 1) != 0) {
                        /* Completion interrupt was faster than the initial
                         * interrupt (swapped in a -1 for pfault_wait). Set
                         * pfault_wait back to zero and exit. This can be
                         * done safely because tsk is running in kernel 
                         * mode and can't produce new pfaults. */
                        tsk->thread.pfault_wait = 0;
                        set_task_state(tsk, TASK_RUNNING);
                        put_task_struct(tsk);
                } else
                        set_tsk_need_resched(tsk);
        }
}
#endif