traps.c

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/*
 * Kernel traps/events for Hexagon processor
 *
 * Copyright (c) 2010-2011, The Linux Foundation. All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 and
 * only version 2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 */

#include <linux/init.h>
#include <linux/sched.h>
#include <linux/module.h>
#include <linux/kallsyms.h>
#include <linux/kdebug.h>
#include <linux/syscalls.h>
#include <linux/signal.h>
#include <linux/tracehook.h>
#include <asm/traps.h>
#include <asm/vm_fault.h>
#include <asm/syscall.h>
#include <asm/registers.h>
#include <asm/unistd.h>
#include <asm/sections.h>
#ifdef CONFIG_KGDB
# include <linux/kgdb.h>
#endif

#define TRAP_SYSCALL    1
#define TRAP_DEBUG  0xdb

void __init trap_init(void)
{
}

#ifdef CONFIG_GENERIC_BUG
/* Maybe should resemble arch/sh/kernel/traps.c ?? */
int is_valid_bugaddr(unsigned long addr)
{
    return 1;
}
#endif /* CONFIG_GENERIC_BUG */

static const char *ex_name(int ex)
{
    switch (ex) {
    case HVM_GE_C_XPROT:
    case HVM_GE_C_XUSER:
        return "Execute protection fault";
    case HVM_GE_C_RPROT:
    case HVM_GE_C_RUSER:
        return "Read protection fault";
    case HVM_GE_C_WPROT:
    case HVM_GE_C_WUSER:
        return "Write protection fault";
    case HVM_GE_C_XMAL:
        return "Misaligned instruction";
    case HVM_GE_C_RMAL:
        return "Misaligned data load";
    case HVM_GE_C_WMAL:
        return "Misaligned data store";
    case HVM_GE_C_INVI:
    case HVM_GE_C_PRIVI:
        return "Illegal instruction";
    case HVM_GE_C_BUS:
        return "Precise bus error";
    case HVM_GE_C_CACHE:
        return "Cache error";

    case 0xdb:
        return "Debugger trap";

    default:
        return "Unrecognized exception";
    }
}

static void do_show_stack(struct task_struct *task, unsigned long *fp,
              unsigned long ip)
{
    int kstack_depth_to_print = 24;
    unsigned long offset, size;
    const char *name = NULL;
    unsigned long *newfp;
    unsigned long low, high;
    char tmpstr[128];
    char *modname;
    int i;

    if (task == NULL)
        task = current;

    printk(KERN_INFO "CPU#%d, %s/%d, Call Trace:\n",
           raw_smp_processor_id(), task->comm,
           task_pid_nr(task));

    if (fp == NULL) {
        if (task == current) {
            asm("%0 = r30" : "=r" (fp));
        } else {
            fp = (unsigned long *)
                 ((struct hexagon_switch_stack *)
                 task->thread.switch_sp)->fp;
        }
    }

    if ((((unsigned long) fp) & 0x3) || ((unsigned long) fp < 0x1000)) {
        printk(KERN_INFO "-- Corrupt frame pointer %p\n", fp);
        return;
    }

    /* Saved link reg is one word above FP */
    if (!ip)
        ip = *(fp+1);

    /* Expect kernel stack to be in-bounds */
    low = (unsigned long)task_stack_page(task);
    high = low + THREAD_SIZE - 8;
    low += sizeof(struct thread_info);

    for (i = 0; i < kstack_depth_to_print; i++) {

        name = kallsyms_lookup(ip, &size, &offset, &modname, tmpstr);

        printk(KERN_INFO "[%p] 0x%lx: %s + 0x%lx", fp, ip, name,
            offset);
        if (((unsigned long) fp < low) || (high < (unsigned long) fp))
            printk(KERN_CONT " (FP out of bounds!)");
        if (modname)
            printk(KERN_CONT " [%s] ", modname);
        printk(KERN_CONT "\n");

        newfp = (unsigned long *) *fp;

        if (((unsigned long) newfp) & 0x3) {
            printk(KERN_INFO "-- Corrupt frame pointer %p\n",
                newfp);
            break;
        }

        /* Attempt to continue past exception. */
        if (0 == newfp) {
            struct pt_regs *regs = (struct pt_regs *) (((void *)fp)
                        + 8);

            if (regs->syscall_nr != -1) {
                printk(KERN_INFO "-- trap0 -- syscall_nr: %ld",
                    regs->syscall_nr);
                printk(KERN_CONT "  psp: %lx  elr: %lx\n",
                     pt_psp(regs), pt_elr(regs));
                break;
            } else {
                /* really want to see more ... */
                kstack_depth_to_print += 6;
                printk(KERN_INFO "-- %s (0x%lx)  badva: %lx\n",
                    ex_name(pt_cause(regs)), pt_cause(regs),
                    pt_badva(regs));
            }

            newfp = (unsigned long *) regs->r30;
            ip = pt_elr(regs);
        } else {
            ip = *(newfp + 1);
        }

        /* If link reg is null, we are done. */
        if (ip == 0x0)
            break;

        /* If newfp isn't larger, we're tracing garbage. */
        if (newfp > fp)
            fp = newfp;
        else
            break;
    }
}

void show_stack(struct task_struct *task, unsigned long *fp)
{
    /* Saved link reg is one word above FP */
    do_show_stack(task, fp, 0);
}

void dump_stack(void)
{
    unsigned long *fp;
    asm("%0 = r30" : "=r" (fp));
    show_stack(current, fp);
}
EXPORT_SYMBOL(dump_stack);

int die(const char *str, struct pt_regs *regs, long err)
{
    static struct {
        spinlock_t lock;
        int counter;
    } die = {
        .lock = __SPIN_LOCK_UNLOCKED(die.lock),
        .counter = 0
    };

    console_verbose();
    oops_enter();

    spin_lock_irq(&die.lock);
    bust_spinlocks(1);
    printk(KERN_EMERG "Oops: %s[#%d]:\n", str, ++die.counter);

    if (notify_die(DIE_OOPS, str, regs, err, pt_cause(regs), SIGSEGV) ==
        NOTIFY_STOP)
        return 1;

    print_modules();
    show_regs(regs);
    do_show_stack(current, &regs->r30, pt_elr(regs));

    bust_spinlocks(0);
    add_taint(TAINT_DIE);

    spin_unlock_irq(&die.lock);

    if (in_interrupt())
        panic("Fatal exception in interrupt");

    if (panic_on_oops)
        panic("Fatal exception");

    oops_exit();
    do_exit(err);
    return 0;
}

int die_if_kernel(char *str, struct pt_regs *regs, long err)
{
    if (!user_mode(regs))
        return die(str, regs, err);
    else
        return 0;
}

/*
 * It's not clear that misaligned fetches are ever recoverable.
 */
static void misaligned_instruction(struct pt_regs *regs)
{
    die_if_kernel("Misaligned Instruction", regs, 0);
    force_sig(SIGBUS, current);
}

/*
 * Misaligned loads and stores, on the other hand, can be
 * emulated, and probably should be, some day.  But for now
 * they will be considered fatal.
 */
static void misaligned_data_load(struct pt_regs *regs)
{
    die_if_kernel("Misaligned Data Load", regs, 0);
    force_sig(SIGBUS, current);
}

static void misaligned_data_store(struct pt_regs *regs)
{
    die_if_kernel("Misaligned Data Store", regs, 0);
    force_sig(SIGBUS, current);
}

static void illegal_instruction(struct pt_regs *regs)
{
    die_if_kernel("Illegal Instruction", regs, 0);
    force_sig(SIGILL, current);
}

/*
 * Precise bus errors may be recoverable with a a retry,
 * but for now, treat them as irrecoverable.
 */
static void precise_bus_error(struct pt_regs *regs)
{
    die_if_kernel("Precise Bus Error", regs, 0);
    force_sig(SIGBUS, current);
}

/*
 * If anything is to be done here other than panic,
 * it will probably be complex and migrate to another
 * source module.  For now, just die.
 */
static void cache_error(struct pt_regs *regs)
{
    die("Cache Error", regs, 0);
}

/*
 * General exception handler
 */
void do_genex(struct pt_regs *regs)
{
    /*
     * Decode Cause and Dispatch
     */
    switch (pt_cause(regs)) {
    case HVM_GE_C_XPROT:
    case HVM_GE_C_XUSER:
        execute_protection_fault(regs);
        break;
    case HVM_GE_C_RPROT:
    case HVM_GE_C_RUSER:
        read_protection_fault(regs);
        break;
    case HVM_GE_C_WPROT:
    case HVM_GE_C_WUSER:
        write_protection_fault(regs);
        break;
    case HVM_GE_C_XMAL:
        misaligned_instruction(regs);
        break;
    case HVM_GE_C_RMAL:
        misaligned_data_load(regs);
        break;
    case HVM_GE_C_WMAL:
        misaligned_data_store(regs);
        break;
    case HVM_GE_C_INVI:
    case HVM_GE_C_PRIVI:
        illegal_instruction(regs);
        break;
    case HVM_GE_C_BUS:
        precise_bus_error(regs);
        break;
    case HVM_GE_C_CACHE:
        cache_error(regs);
        break;
    default:
        /* Halt and catch fire */
        panic("Unrecognized exception 0x%lx\n", pt_cause(regs));
        break;
    }
}

/* Indirect system call dispatch */
long sys_syscall(void)
{
    printk(KERN_ERR "sys_syscall invoked!\n");
    return -ENOSYS;
}

void do_trap0(struct pt_regs *regs)
{
    unsigned long syscallret = 0;
    syscall_fn syscall;

    switch (pt_cause(regs)) {
    case TRAP_SYSCALL:
        /* System call is trap0 #1 */

        /* allow strace to catch syscall args  */
        if (unlikely(test_thread_flag(TIF_SYSCALL_TRACE) &&
            tracehook_report_syscall_entry(regs)))
            return;  /*  return -ENOSYS somewhere?  */

        /* Interrupts should be re-enabled for syscall processing */
        __vmsetie(VM_INT_ENABLE);

        /*
         * System call number is in r6, arguments in r0..r5.
         * Fortunately, no Linux syscall has more than 6 arguments,
         * and Hexagon ABI passes first 6 arguments in registers.
         * 64-bit arguments are passed in odd/even register pairs.
         * Fortunately, we have no system calls that take more
         * than three arguments with more than one 64-bit value.
         * Should that change, we'd need to redesign to copy
         * between user and kernel stacks.
         */
        regs->syscall_nr = regs->r06;

        /*
         * GPR R0 carries the first parameter, and is also used
         * to report the return value.  We need a backup of
         * the user's value in case we need to do a late restart
         * of the system call.
         */
        regs->restart_r0 = regs->r00;

        if ((unsigned long) regs->syscall_nr >= __NR_syscalls) {
            regs->r00 = -1;
        } else {
            syscall = (syscall_fn)
                  (sys_call_table[regs->syscall_nr]);
            syscallret = syscall(regs->r00, regs->r01,
                   regs->r02, regs->r03,
                   regs->r04, regs->r05);
        }

        /*
         * If it was a sigreturn system call, don't overwrite
         * r0 value in stack frame with return value.
         *
         * __NR_sigreturn doesn't seem to exist in new unistd.h
         */

        if (regs->syscall_nr != __NR_rt_sigreturn)
            regs->r00 = syscallret;

        /* allow strace to get the syscall return state  */
        if (unlikely(test_thread_flag(TIF_SYSCALL_TRACE)))
            tracehook_report_syscall_exit(regs, 0);

        break;
    case TRAP_DEBUG:
        /* Trap0 0xdb is debug breakpoint */
        if (user_mode(regs)) {
            struct siginfo info;

            info.si_signo = SIGTRAP;
            info.si_errno = 0;
            /*
             * Some architecures add some per-thread state
             * to distinguish between breakpoint traps and
             * trace traps.  We may want to do that, and
             * set the si_code value appropriately, or we
             * may want to use a different trap0 flavor.
             */
            info.si_code = TRAP_BRKPT;
            info.si_addr = (void __user *) pt_elr(regs);
            send_sig_info(SIGTRAP, &info, current);
        } else {
#ifdef CONFIG_KGDB
            kgdb_handle_exception(pt_cause(regs), SIGTRAP,
                          TRAP_BRKPT, regs);
#endif
        }
        break;
    }
    /* Ignore other trap0 codes for now, especially 0 (Angel calls) */
}

/*
 * Machine check exception handler
 */
void do_machcheck(struct pt_regs *regs)
{
    /* Halt and catch fire */
    __vmstop();
}