/*
 * arch/xtensa/kernel/traps.c
 *
 * Exception handling.
 *
 * Derived from code with the following copyrights:
 * Copyright (C) 1994 - 1999 by Ralf Baechle
 * Modified for R3000 by Paul M. Antoine, 1995, 1996
 * Complete output from die() by Ulf Carlsson, 1998
 * Copyright (C) 1999 Silicon Graphics, Inc.
 *
 * Essentially rewritten for the Xtensa architecture port.
 *
 * Copyright (C) 2001 - 2013 Tensilica Inc.
 *
 * Joe Taylor   <joe@tensilica.com, joetylr@yahoo.com>
 * Chris Zankel <chris@zankel.net>
 * Marc Gauthier<marc@tensilica.com, marc@alumni.uwaterloo.ca>
 * Kevin Chea
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 */

#include <linux/kernel.h>
#include <linux/sched/signal.h>
#include <linux/sched/debug.h>
#include <linux/sched/task_stack.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/stringify.h>
#include <linux/kallsyms.h>
#include <linux/delay.h>
#include <linux/hardirq.h>

#include <asm/stacktrace.h>
#include <asm/ptrace.h>
#include <asm/timex.h>
#include <linux/uaccess.h>
#include <asm/pgtable.h>
#include <asm/processor.h>
#include <asm/traps.h>
#include <asm/hw_breakpoint.h>

/*
 * Machine specific interrupt handlers
 */

extern void kernel_exception(void);
extern void user_exception(void);

extern void fast_syscall_kernel(void);
extern void fast_syscall_user(void);
extern void fast_alloca(void);
extern void fast_unaligned(void);
extern void fast_second_level_miss(void);
extern void fast_store_prohibited(void);
extern void fast_coprocessor(void);

extern void do_illegal_instruction (struct pt_regs*);
extern void do_interrupt (struct pt_regs*);
extern void do_nmi(struct pt_regs *);
extern void do_unaligned_user (struct pt_regs*);
extern void do_multihit (struct pt_regs*, unsigned long);
extern void do_page_fault (struct pt_regs*, unsigned long);
extern void do_debug (struct pt_regs*);
extern void system_call (struct pt_regs*);

/*
 * The vector table must be preceded by a save area (which
 * implies it must be in RAM, unless one places RAM immediately
 * before a ROM and puts the vector at the start of the ROM (!))
 */

#define KRNL            0x01
#define USER            0x02

#define COPROCESSOR(x)                                                  \
{ EXCCAUSE_COPROCESSOR ## x ## _DISABLED, USER, fast_coprocessor }

typedef struct {
        int cause;
        int fast;
        void* handler;
} dispatch_init_table_t;

static dispatch_init_table_t __initdata dispatch_init_table[] = {

{ EXCCAUSE_ILLEGAL_INSTRUCTION, 0,         do_illegal_instruction},
{ EXCCAUSE_SYSTEM_CALL,         KRNL,      fast_syscall_kernel },
{ EXCCAUSE_SYSTEM_CALL,         USER,      fast_syscall_user },
{ EXCCAUSE_SYSTEM_CALL,         0,         system_call },
/* EXCCAUSE_INSTRUCTION_FETCH unhandled */
/* EXCCAUSE_LOAD_STORE_ERROR unhandled*/
{ EXCCAUSE_LEVEL1_INTERRUPT,    0,         do_interrupt },
{ EXCCAUSE_ALLOCA,              USER|KRNL, fast_alloca },
/* EXCCAUSE_INTEGER_DIVIDE_BY_ZERO unhandled */
/* EXCCAUSE_PRIVILEGED unhandled */
#if XCHAL_UNALIGNED_LOAD_EXCEPTION || XCHAL_UNALIGNED_STORE_EXCEPTION
#ifdef CONFIG_XTENSA_UNALIGNED_USER
{ EXCCAUSE_UNALIGNED,           USER,      fast_unaligned },
#endif
{ EXCCAUSE_UNALIGNED,           0,         do_unaligned_user },
{ EXCCAUSE_UNALIGNED,           KRNL,      fast_unaligned },
#endif
#ifdef CONFIG_MMU
{ EXCCAUSE_ITLB_MISS,           0,         do_page_fault },
{ EXCCAUSE_ITLB_MISS,           USER|KRNL, fast_second_level_miss},
{ EXCCAUSE_ITLB_MULTIHIT,               0,         do_multihit },
{ EXCCAUSE_ITLB_PRIVILEGE,      0,         do_page_fault },
/* EXCCAUSE_SIZE_RESTRICTION unhandled */
{ EXCCAUSE_FETCH_CACHE_ATTRIBUTE,       0,         do_page_fault },
{ EXCCAUSE_DTLB_MISS,           USER|KRNL, fast_second_level_miss},
{ EXCCAUSE_DTLB_MISS,           0,         do_page_fault },
{ EXCCAUSE_DTLB_MULTIHIT,               0,         do_multihit },
{ EXCCAUSE_DTLB_PRIVILEGE,      0,         do_page_fault },
/* EXCCAUSE_DTLB_SIZE_RESTRICTION unhandled */
{ EXCCAUSE_STORE_CACHE_ATTRIBUTE,       USER|KRNL, fast_store_prohibited },
{ EXCCAUSE_STORE_CACHE_ATTRIBUTE,       0,         do_page_fault },
{ EXCCAUSE_LOAD_CACHE_ATTRIBUTE,        0,         do_page_fault },
#endif /* CONFIG_MMU */
/* XCCHAL_EXCCAUSE_FLOATING_POINT unhandled */
#if XTENSA_HAVE_COPROCESSOR(0)
COPROCESSOR(0),
#endif
#if XTENSA_HAVE_COPROCESSOR(1)
COPROCESSOR(1),
#endif
#if XTENSA_HAVE_COPROCESSOR(2)
COPROCESSOR(2),
#endif
#if XTENSA_HAVE_COPROCESSOR(3)
COPROCESSOR(3),
#endif
#if XTENSA_HAVE_COPROCESSOR(4)
COPROCESSOR(4),
#endif
#if XTENSA_HAVE_COPROCESSOR(5)
COPROCESSOR(5),
#endif
#if XTENSA_HAVE_COPROCESSOR(6)
COPROCESSOR(6),
#endif
#if XTENSA_HAVE_COPROCESSOR(7)
COPROCESSOR(7),
#endif
#if XTENSA_FAKE_NMI
{ EXCCAUSE_MAPPED_NMI,                  0,              do_nmi },
#endif
{ EXCCAUSE_MAPPED_DEBUG,                0,              do_debug },
{ -1, -1, 0 }

};

/* The exception table <exc_table> serves two functions:
 * 1. it contains three dispatch tables (fast_user, fast_kernel, default-c)
 * 2. it is a temporary memory buffer for the exception handlers.
 */

DEFINE_PER_CPU(unsigned long, exc_table[EXC_TABLE_SIZE/4]);

DEFINE_PER_CPU(struct debug_table, debug_table);

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

static inline void
__die_if_kernel(const char *str, struct pt_regs *regs, long err)
{
        if (!user_mode(regs))
                die(str, regs, err);
}

/*
 * Unhandled Exceptions. Kill user task or panic if in kernel space.
 */

void do_unhandled(struct pt_regs *regs, unsigned long exccause)
{
        __die_if_kernel("Caught unhandled exception - should not happen",
                        regs, SIGKILL);

        /* If in user mode, send SIGILL signal to current process */
        printk("Caught unhandled exception in '%s' "
               "(pid = %d, pc = %#010lx) - should not happen\n"
               "\tEXCCAUSE is %ld\n",
               current->comm, task_pid_nr(current), regs->pc, exccause);
        force_sig(SIGILL, current);
}

/*
 * Multi-hit exception. This if fatal!
 */

void do_multihit(struct pt_regs *regs, unsigned long exccause)
{
        die("Caught multihit exception", regs, SIGKILL);
}

/*
 * IRQ handler.
 */

extern void do_IRQ(int, struct pt_regs *);

#if XTENSA_FAKE_NMI

#define IS_POW2(v) (((v) & ((v) - 1)) == 0)

#if !(PROFILING_INTLEVEL == XCHAL_EXCM_LEVEL && \
      IS_POW2(XTENSA_INTLEVEL_MASK(PROFILING_INTLEVEL)))
#warning "Fake NMI is requested for PMM, but there are other IRQs at or above its level."
#warning "Fake NMI will be used, but there will be a bugcheck if one of those IRQs fire."

static inline void check_valid_nmi(void)
{
        unsigned intread = get_sr(interrupt);
        unsigned intenable = get_sr(intenable);

        BUG_ON(intread & intenable &
               ~(XTENSA_INTLEVEL_ANDBELOW_MASK(PROFILING_INTLEVEL) ^
                 XTENSA_INTLEVEL_MASK(PROFILING_INTLEVEL) ^
                 BIT(XCHAL_PROFILING_INTERRUPT)));
}

#else

static inline void check_valid_nmi(void)
{
}

#endif

irqreturn_t xtensa_pmu_irq_handler(int irq, void *dev_id);

DEFINE_PER_CPU(unsigned long, nmi_count);

void do_nmi(struct pt_regs *regs)
{
        struct pt_regs *old_regs;

        if ((regs->ps & PS_INTLEVEL_MASK) < LOCKLEVEL)
                trace_hardirqs_off();

        old_regs = set_irq_regs(regs);
        nmi_enter();
        ++*this_cpu_ptr(&nmi_count);
        check_valid_nmi();
        xtensa_pmu_irq_handler(0, NULL);
        nmi_exit();
        set_irq_regs(old_regs);
}
#endif

void do_interrupt(struct pt_regs *regs)
{
        static const unsigned int_level_mask[] = {
                0,
                XCHAL_INTLEVEL1_MASK,
                XCHAL_INTLEVEL2_MASK,
                XCHAL_INTLEVEL3_MASK,
                XCHAL_INTLEVEL4_MASK,
                XCHAL_INTLEVEL5_MASK,
                XCHAL_INTLEVEL6_MASK,
                XCHAL_INTLEVEL7_MASK,
        };
        struct pt_regs *old_regs;

        trace_hardirqs_off();

        old_regs = set_irq_regs(regs);
        irq_enter();

        for (;;) {
                unsigned intread = get_sr(interrupt);
                unsigned intenable = get_sr(intenable);
                unsigned int_at_level = intread & intenable;
                unsigned level;

                for (level = LOCKLEVEL; level > 0; --level) {
                        if (int_at_level & int_level_mask[level]) {
                                int_at_level &= int_level_mask[level];
                                break;
                        }
                }

                if (level == 0)
                        break;

                do_IRQ(__ffs(int_at_level), regs);
        }

        irq_exit();
        set_irq_regs(old_regs);
}

/*
 * Illegal instruction. Fatal if in kernel space.
 */

void
do_illegal_instruction(struct pt_regs *regs)
{
        __die_if_kernel("Illegal instruction in kernel", regs, SIGKILL);

        /* If in user mode, send SIGILL signal to current process. */

        printk("Illegal Instruction in '%s' (pid = %d, pc = %#010lx)\n",
            current->comm, task_pid_nr(current), regs->pc);
        force_sig(SIGILL, current);
}


/*
 * Handle unaligned memory accesses from user space. Kill task.
 *
 * If CONFIG_UNALIGNED_USER is not set, we don't allow unaligned memory
 * accesses causes from user space.
 */

#if XCHAL_UNALIGNED_LOAD_EXCEPTION || XCHAL_UNALIGNED_STORE_EXCEPTION
void
do_unaligned_user (struct pt_regs *regs)
{
        siginfo_t info;

        __die_if_kernel("Unhandled unaligned exception in kernel",
                        regs, SIGKILL);

        current->thread.bad_vaddr = regs->excvaddr;
        current->thread.error_code = -3;
        printk("Unaligned memory access to %08lx in '%s' "
               "(pid = %d, pc = %#010lx)\n",
               regs->excvaddr, current->comm, task_pid_nr(current), regs->pc);
        info.si_signo = SIGBUS;
        info.si_errno = 0;
        info.si_code = BUS_ADRALN;
        info.si_addr = (void *) regs->excvaddr;
        force_sig_info(SIGSEGV, &info, current);

}
#endif

/* Handle debug events.
 * When CONFIG_HAVE_HW_BREAKPOINT is on this handler is called with
 * preemption disabled to avoid rescheduling and keep mapping of hardware
 * breakpoint structures to debug registers intact, so that
 * DEBUGCAUSE.DBNUM could be used in case of data breakpoint hit.
 */
void
do_debug(struct pt_regs *regs)
{
#ifdef CONFIG_HAVE_HW_BREAKPOINT
        int ret = check_hw_breakpoint(regs);

        preempt_enable();
        if (ret == 0)
                return;
#endif
        __die_if_kernel("Breakpoint in kernel", regs, SIGKILL);

        /* If in user mode, send SIGTRAP signal to current process */

        force_sig(SIGTRAP, current);
}


static void set_handler(int idx, void *handler)
{
        unsigned int cpu;

        for_each_possible_cpu(cpu)
                per_cpu(exc_table, cpu)[idx] = (unsigned long)handler;
}

/* Set exception C handler - for temporary use when probing exceptions */

void * __init trap_set_handler(int cause, void *handler)
{
        void *previous = (void *)per_cpu(exc_table, 0)[
                EXC_TABLE_DEFAULT / 4 + cause];
        set_handler(EXC_TABLE_DEFAULT / 4 + cause, handler);
        return previous;
}


static void trap_init_excsave(void)
{
        unsigned long excsave1 = (unsigned long)this_cpu_ptr(exc_table);
        __asm__ __volatile__("wsr  %0, excsave1\n" : : "a" (excsave1));
}

static void trap_init_debug(void)
{
        unsigned long debugsave = (unsigned long)this_cpu_ptr(&debug_table);

        this_cpu_ptr(&debug_table)->debug_exception = debug_exception;
        __asm__ __volatile__("wsr %0, excsave" __stringify(XCHAL_DEBUGLEVEL)
                             :: "a"(debugsave));
}

/*
 * Initialize dispatch tables.
 *
 * The exception vectors are stored compressed the __init section in the
 * dispatch_init_table. This function initializes the following three tables
 * from that compressed table:
 * - fast user          first dispatch table for user exceptions
 * - fast kernel        first dispatch table for kernel exceptions
 * - default C-handler  C-handler called by the default fast handler.
 *
 * See vectors.S for more details.
 */

void __init trap_init(void)
{
        int i;

        /* Setup default vectors. */

        for(i = 0; i < 64; i++) {
                set_handler(EXC_TABLE_FAST_USER/4   + i, user_exception);
                set_handler(EXC_TABLE_FAST_KERNEL/4 + i, kernel_exception);
                set_handler(EXC_TABLE_DEFAULT/4 + i, do_unhandled);
        }

        /* Setup specific handlers. */

        for(i = 0; dispatch_init_table[i].cause >= 0; i++) {

                int fast = dispatch_init_table[i].fast;
                int cause = dispatch_init_table[i].cause;
                void *handler = dispatch_init_table[i].handler;

                if (fast == 0)
                        set_handler (EXC_TABLE_DEFAULT/4 + cause, handler);
                if (fast && fast & USER)
                        set_handler (EXC_TABLE_FAST_USER/4 + cause, handler);
                if (fast && fast & KRNL)
                        set_handler (EXC_TABLE_FAST_KERNEL/4 + cause, handler);
        }

        /* Initialize EXCSAVE_1 to hold the address of the exception table. */
        trap_init_excsave();
        trap_init_debug();
}

#ifdef CONFIG_SMP
void secondary_trap_init(void)
{
        trap_init_excsave();
        trap_init_debug();
}
#endif

/*
 * This function dumps the current valid window frame and other base registers.
 */

void show_regs(struct pt_regs * regs)
{
        int i, wmask;

        show_regs_print_info(KERN_DEFAULT);

        wmask = regs->wmask & ~1;

        for (i = 0; i < 16; i++) {
                if ((i % 8) == 0)
                        pr_info("a%02d:", i);
                pr_cont(" %08lx", regs->areg[i]);
        }
        pr_cont("\n");
        pr_info("pc: %08lx, ps: %08lx, depc: %08lx, excvaddr: %08lx\n",
                regs->pc, regs->ps, regs->depc, regs->excvaddr);
        pr_info("lbeg: %08lx, lend: %08lx lcount: %08lx, sar: %08lx\n",
                regs->lbeg, regs->lend, regs->lcount, regs->sar);
        if (user_mode(regs))
                pr_cont("wb: %08lx, ws: %08lx, wmask: %08lx, syscall: %ld\n",
                        regs->windowbase, regs->windowstart, regs->wmask,
                        regs->syscall);
}

static int show_trace_cb(struct stackframe *frame, void *data)
{
        if (kernel_text_address(frame->pc))
                pr_cont(" [<%08lx>] %pB\n", frame->pc, (void *)frame->pc);
        return 0;
}

void show_trace(struct task_struct *task, unsigned long *sp)
{
        if (!sp)
                sp = stack_pointer(task);

        pr_info("Call Trace:\n");
        walk_stackframe(sp, show_trace_cb, NULL);
#ifndef CONFIG_KALLSYMS
        pr_cont("\n");
#endif
}

static int kstack_depth_to_print = 24;

void show_stack(struct task_struct *task, unsigned long *sp)
{
        int i = 0;
        unsigned long *stack;

        if (!sp)
                sp = stack_pointer(task);
        stack = sp;

        pr_info("Stack:\n");

        for (i = 0; i < kstack_depth_to_print; i++) {
                if (kstack_end(sp))
                        break;
                pr_cont(" %08lx", *sp++);
                if (i % 8 == 7)
                        pr_cont("\n");
        }
        show_trace(task, stack);
}

DEFINE_SPINLOCK(die_lock);

void die(const char * str, struct pt_regs * regs, long err)
{
        static int die_counter;

        console_verbose();
        spin_lock_irq(&die_lock);

        pr_info("%s: sig: %ld [#%d]%s\n", str, err, ++die_counter,
                IS_ENABLED(CONFIG_PREEMPT) ? " PREEMPT" : "");
        show_regs(regs);
        if (!user_mode(regs))
                show_stack(NULL, (unsigned long*)regs->areg[1]);

        add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE);
        spin_unlock_irq(&die_lock);

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

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

        do_exit(err);
}