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traps.c

/*
 * 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 - 2005 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.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/stringify.h>
#include <linux/kallsyms.h>
#include <linux/delay.h>

#include <asm/ptrace.h>
#include <asm/timex.h>
#include <asm/uaccess.h>
#include <asm/pgtable.h>
#include <asm/processor.h>

#ifdef CONFIG_KGDB
extern int gdb_enter;
extern int return_from_debug_flag;
#endif

/*
 * 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_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_UNALIGNED_USER
{ EXCCAUSE_UNALIGNED,         USER,    fast_unaligned },
#else
{ EXCCAUSE_UNALIGNED,         0,       do_unaligned_user },
#endif
{ EXCCAUSE_UNALIGNED,         KRNL,    fast_unaligned },
#endif
{ 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 },
/* XCCHAL_EXCCAUSE_FLOATING_POINT unhandled */
#if (XCHAL_CP_MASK & 1)
COPROCESSOR(0),
#endif
#if (XCHAL_CP_MASK & 2)
COPROCESSOR(1),
#endif
#if (XCHAL_CP_MASK & 4)
COPROCESSOR(2),
#endif
#if (XCHAL_CP_MASK & 8)
COPROCESSOR(3),
#endif
#if (XCHAL_CP_MASK & 16)
COPROCESSOR(4),
#endif
#if (XCHAL_CP_MASK & 32)
COPROCESSOR(5),
#endif
#if (XCHAL_CP_MASK & 64)
COPROCESSOR(6),
#endif
#if (XCHAL_CP_MASK & 128)
COPROCESSOR(7),
#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.
 */

unsigned long exc_table[EXC_TABLE_SIZE/4];

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);
}

/*
 * Level-1 interrupt.
 * We currently have no priority encoding.
 */

unsigned long ignored_level1_interrupts;
extern void do_IRQ(int, struct pt_regs *);

void do_interrupt (struct pt_regs *regs)
{
      unsigned long intread = get_sr (INTREAD);
      unsigned long intenable = get_sr (INTENABLE);
      int i, mask;

      /* Handle all interrupts (no priorities).
       * (Clear the interrupt before processing, in case it's
       *  edge-triggered or software-generated)
       */

      for (i=0, mask = 1; i < XCHAL_NUM_INTERRUPTS; i++, mask <<= 1) {
            if (mask & (intread & intenable)) {
                  set_sr (mask, INTCLEAR);
                  do_IRQ (i,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
#ifndef CONFIG_UNALIGNED_USER
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
#endif

void
do_debug(struct pt_regs *regs)
{
#ifdef CONFIG_KGDB
      /* If remote debugging is configured AND enabled, we give control to
       * kgdb.  Otherwise, we fall through, perhaps giving control to the
       * native debugger.
       */

      if (gdb_enter) {
            extern void gdb_handle_exception(struct pt_regs *);
            gdb_handle_exception(regs);
            return_from_debug_flag = 1;
            return;
      }
#endif

      __die_if_kernel("Breakpoint in kernel", regs, SIGKILL);

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

      force_sig(SIGTRAP, current);
}


/*
 * 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.
 */

#define set_handler(idx,handler) (exc_table[idx] = (unsigned long) (handler))

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. */

      i = (unsigned long)exc_table;
      __asm__ __volatile__("wsr  %0, "__stringify(EXCSAVE_1)"\n" : : "a" (i));
}

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

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

      wmask = regs->wmask & ~1;

      for (i = 0; i < 32; i++) {
            if (wmask & (1 << (i / 4)))
                  break;
            if ((i % 8) == 0)
                  printk ("\n" KERN_INFO "a%02d: ", i);
            printk("%08lx ", regs->areg[i]);
      }
      printk("\n");

      printk("pc: %08lx, ps: %08lx, depc: %08lx, excvaddr: %08lx\n",
             regs->pc, regs->ps, regs->depc, regs->excvaddr);
      printk("lbeg: %08lx, lend: %08lx lcount: %08lx, sar: %08lx\n",
             regs->lbeg, regs->lend, regs->lcount, regs->sar);
      if (user_mode(regs))
            printk("wb: %08lx, ws: %08lx, wmask: %08lx, syscall: %ld\n",
                   regs->windowbase, regs->windowstart, regs->wmask,
                   regs->syscall);
}

void show_trace(struct task_struct *task, unsigned long *sp)
{
      unsigned long a0, a1, pc;
      unsigned long sp_start, sp_end;

      a1 = (unsigned long)sp;

      if (a1 == 0)
            __asm__ __volatile__ ("mov %0, a1\n" : "=a"(a1));


      sp_start = a1 & ~(THREAD_SIZE-1);
      sp_end = sp_start + THREAD_SIZE;

      printk("Call Trace:");
#ifdef CONFIG_KALLSYMS
      printk("\n");
#endif
      spill_registers();

      while (a1 > sp_start && a1 < sp_end) {
            sp = (unsigned long*)a1;

            a0 = *(sp - 4);
            a1 = *(sp - 3);

            if (a1 <= (unsigned long) sp)
                  break;

            pc = MAKE_PC_FROM_RA(a0, a1);

            if (kernel_text_address(pc)) {
                  printk(" [<%08lx>] ", pc);
                  print_symbol("%s\n", pc);
            }
      }
      printk("\n");
}

/*
 * This routine abuses get_user()/put_user() to reference pointers
 * with at least a bit of error checking ...
 */

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 == 0)
            __asm__ __volatile__ ("mov %0, a1\n" : "=a"(sp));

      stack = sp;

      printk("\nStack: ");

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

void dump_stack(void)
{
      show_stack(current, NULL);
}

EXPORT_SYMBOL(dump_stack);


void show_code(unsigned int *pc)
{
      long i;

      printk("\nCode:");

      for(i = -3 ; i < 6 ; i++) {
            unsigned long insn;
            if (__get_user(insn, pc + i)) {
                  printk(" (Bad address in pc)\n");
                  break;
            }
            printk("%c%08lx%c",(i?' ':'<'),insn,(i?' ':'>'));
      }
}

DEFINE_SPINLOCK(die_lock);

void die(const char * str, struct pt_regs * regs, long err)
{
      static int die_counter;
      int nl = 0;

      console_verbose();
      spin_lock_irq(&die_lock);

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

      add_taint(TAINT_DIE);
      spin_unlock_irq(&die_lock);

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

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

      do_exit(err);
}



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