path: root/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/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_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,