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/*

 *  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/kdebug.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 <linux/uaccess.h>

#include <asm/system.h>

#include <asm/pgtable.h>

#include <asm/s390_ext.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

static inline int notify_page_fault(struct pt_regs *regs, long err)

{

        int ret = 0;

        /* kprobe_running() needs smp_processor_id() */

        if (!user_mode(regs)) {

                preempt_disable();

                if (kprobe_running() && kprobe_fault_handler(regs, 14))

                        ret = 1;

                preempt_enable();

        }

        return ret;

}

#else

static inline int notify_page_fault(struct pt_regs *regs, long err)

{

        return 0;

}

#endif

/*

 * Unlock any spinlocks which will prevent us from getting the

 * message out.

 */

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;

        }

}

/*

 * Returns the address space associated with the fault.

 * Returns 0 for kernel space, 1 for user space and

 * 2 for code execution in user space with noexec=on.

 */

static inline int check_space(struct task_struct *tsk)

{

        /*

         * The lowest two bits of S390_lowcore.trans_exc_code

         * indicate which paging table was used.

         */

        int desc = S390_lowcore.trans_exc_code & 3;

        if (desc == 3)  /* Home Segment Table Descriptor */

                return switch_amode == 0;

        if (desc == 2)  /* Secondary Segment Table Descriptor */

                return tsk->thread.mm_segment.ar4;

#ifdef CONFIG_S390_SWITCH_AMODE

        if (unlikely(desc == 1)) { /* STD determined via access register */

                /* %a0 always indicates primary space. */

                if (S390_lowcore.exc_access_id != 0) {

                        save_access_regs(tsk->thread.acrs);

                        /*

                         * An alet of 0 indicates primary space.

                         * An alet of 1 indicates secondary space.

                         * Any other alet values generate an

                         * alen-translation exception.

                         */

                        if (tsk->thread.acrs[S390_lowcore.exc_access_id])

                                return tsk->thread.mm_segment.ar4;

                }

        }

#endif

        /* Primary Segment Table Descriptor */

        return switch_amode << s390_noexec;

}

/*

 * 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);

}

static void do_no_context(struct pt_regs *regs, unsigned long error_code,

                          unsigned long address)

{

        const struct exception_table_entry *fixup;

        /* 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 (check_space(current) == 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);

}

static void do_low_address(struct pt_regs *regs, unsigned long error_code)

{

        /* Low-address protection hit in kernel mode means

           NULL pointer write access in kernel mode.  */

        if (regs->psw.mask & PSW_MASK_PSTATE) {

                /* Low-address protection hit in user mode 'cannot happen'. */

                die ("Low-address protection", regs, error_code);

                do_exit(SIGKILL);

        }

        do_no_context(regs, error_code, 0);

}

/*

 * We ran out of memory, or some other thing happened to us that made

 * us unable to handle the page fault gracefully.

 */

static int do_out_of_memory(struct pt_regs *regs, unsigned long error_code,

                            unsigned long address)

{

        struct task_struct *tsk = current;

        struct mm_struct *mm = tsk->mm;

        up_read(&mm->mmap_sem);

        if (is_global_init(tsk)) {

                yield();

                down_read(&mm->mmap_sem);

                return 1;

        }

        printk("VM: killing process %s\n", tsk->comm);

        if (regs->psw.mask & PSW_MASK_PSTATE)

                do_group_exit(SIGKILL);

        do_no_context(regs, error_code, address);

        return 0;

}

static void do_sigbus(struct pt_regs *regs, unsigned long error_code,

                      unsigned long address)

{

        struct task_struct *tsk = current;

        struct mm_struct *mm = tsk->mm;

        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))

                do_no_context(regs, error_code, address);

}

#ifdef CONFIG_S390_EXEC_PROTECT

extern long sys_sigreturn(struct pt_regs *regs);

extern long sys_rt_sigreturn(struct pt_regs *regs);

extern long sys32_sigreturn(struct pt_regs *regs);

extern long sys32_rt_sigreturn(struct pt_regs *regs);

static int signal_return(struct mm_struct *mm, struct pt_regs *regs,

                         unsigned long address, unsigned long error_code)

{

        u16 instruction;

        int rc;

#ifdef CONFIG_COMPAT

        int compat;

#endif

        pagefault_disable();

        rc = __get_user(instruction, (u16 __user *) regs->psw.addr);

        pagefault_enable();

        if (rc)

                return -EFAULT;

        up_read(&mm->mmap_sem);

        clear_tsk_thread_flag(current, TIF_SINGLE_STEP);

#ifdef CONFIG_COMPAT

        compat = test_tsk_thread_flag(current, TIF_31BIT);

        if (compat && instruction == 0x0a77)

                sys32_sigreturn(regs);

        else if (compat && instruction == 0x0aad)

                sys32_rt_sigreturn(regs);

        else

#endif

        if (instruction == 0x0a77)

                sys_sigreturn(regs);

        else if (instruction == 0x0aad)

                sys_rt_sigreturn(regs);

        else {

                current->thread.prot_addr = address;

                current->thread.trap_no = error_code;

                do_sigsegv(regs, error_code, SEGV_MAPERR, address);

        }

        return 0;

}

#endif /* CONFIG_S390_EXEC_PROTECT */

/*

 * 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

do_exception(struct pt_regs *regs, unsigned long error_code, int write)

{

        struct task_struct *tsk;

        struct mm_struct *mm;

        struct vm_area_struct *vma;

        unsigned long address;

        int space;

        int si_code;

        int fault;

        if (notify_page_fault(regs, error_code))

                return;

        tsk = current;

        mm = tsk->mm;

        /* get the failing address and the affected space */

        address = S390_lowcore.trans_exc_code & __FAIL_ADDR_MASK;

        space = check_space(tsk);

        /*

         * Verify that the fault happened in user space, that

         * we are not in an interrupt and that there is a

         * user context.

         */

        if (unlikely(space == 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);

        si_code = SEGV_MAPERR;

        vma = find_vma(mm, address);

        if (!vma)

                goto bad_area;

#ifdef CONFIG_S390_EXEC_PROTECT

        if (unlikely((space == 2) && !(vma->vm_flags & VM_EXEC)))

                if (!signal_return(mm, regs, address, error_code))

                        /*

                         * signal_return() has done an up_read(&mm->mmap_sem)

                         * if it returns 0.

                         */

                        return;

#endif

        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 (!write) {

                /* 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.

         */

        fault = handle_mm_fault(mm, vma, address, write);

        if (unlikely(fault & VM_FAULT_ERROR)) {

                if (fault & VM_FAULT_OOM) {

                        if (do_out_of_memory(regs, error_code, address))

                                goto survive;

                        return;

                } else if (fault & VM_FAULT_SIGBUS) {

                        do_sigbus(regs, error_code, address);

                        return;

                }

                BUG();

        }

        if (fault & VM_FAULT_MAJOR)

                tsk->maj_flt++;

        else

                tsk->min_flt++;

        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(tsk, 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:

        do_no_context(regs, error_code, address);

}

void __kprobes do_protection_exception(struct pt_regs *regs,

                                       unsigned long error_code)

{

        /* Protection exception is supressing, decrement psw address. */

        regs->psw.addr -= (error_code >> 16);

        /*

         * 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 (unlikely(!(S390_lowcore.trans_exc_code & 4))) {

                do_low_address(regs, error_code);

                return;

        }

        do_exception(regs, 4, 1);

}

void __kprobes 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 ext_int_info_t ext_int_pfault;

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, aligned(8))) 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 (!MACHINE_IS_VM || pfault_disable)

                return -1;

        asm volatile(

                "       diag    %1,%0,0x258\n"

                "0:     j       2f\n"

                "1:     la      %0,8\n"

                "2:\n"

                EX_TABLE(0b,1b)

                : "=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 (!MACHINE_IS_VM || pfault_disable)

                return;

        __ctl_clear_bit(0,9);

        asm volatile(

                "       diag    %0,0,0x258\n"

                "0:\n"

                EX_TABLE(0b,0b)

                : : "a" (&refbk), "m" (refbk) : "cc");

}

static void pfault_interrupt(__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);

        }

}

void __init pfault_irq_init(void)

{

        if (!MACHINE_IS_VM)

                return;

        /*

         * Try to get pfault pseudo page faults going.

         */

        if (register_early_external_interrupt(0x2603, pfault_interrupt,

                                              &ext_int_pfault) != 0)

                panic("Couldn't request external interrupt 0x2603");

        if (pfault_init() == 0)

                return;

        /* Tough luck, no pfault. */

        pfault_disable = 1;

        unregister_early_external_interrupt(0x2603, pfault_interrupt,

                                            &ext_int_pfault);

}

#endif