arch/v850/kernel/ptrace.c

   1 /*
   2  * arch/v850/kernel/ptrace.c -- `ptrace' system call
   3  *
   4  *  Copyright (C) 2002,03,04  NEC Electronics Corporation
   5  *  Copyright (C) 2002,03,04  Miles Bader <miles@gnu.org>
   6  *
   7  * Derived from arch/mips/kernel/ptrace.c:
   8  *
   9  *  Copyright (C) 1992 Ross Biro
  10  *  Copyright (C) Linus Torvalds
  11  *  Copyright (C) 1994, 95, 96, 97, 98, 2000 Ralf Baechle
  12  *  Copyright (C) 1996 David S. Miller
  13  *  Kevin D. Kissell, kevink@mips.com and Carsten Langgaard, carstenl@mips.com
  14  *  Copyright (C) 1999 MIPS Technologies, Inc.
  15  *
  16  * This file is subject to the terms and conditions of the GNU General
  17  * Public License.  See the file COPYING in the main directory of this
  18  * archive for more details.
  19  */
  20
  21 #include <linux/kernel.h>
  22 #include <linux/mm.h>
  23 #include <linux/sched.h>
  24 #include <linux/smp_lock.h>
  25 #include <linux/ptrace.h>
  26 #include <linux/signal.h>
  27
  28 #include <asm/errno.h>
  29 #include <asm/ptrace.h>
  30 #include <asm/processor.h>
  31 #include <asm/uaccess.h>
  32
  33 /* Returns the address where the register at REG_OFFS in P is stashed away.  */
  34 static v850_reg_t *reg_save_addr (unsigned reg_offs, struct task_struct *t)
  35 {
  36         struct pt_regs *regs;
  37
  38         /* Three basic cases:
  39
  40            (1) A register normally saved before calling the scheduler, is
  41                available in the kernel entry pt_regs structure at the top
  42                of the kernel stack.  The kernel trap/irq exit path takes
  43                care to save/restore almost all registers for ptrace'd
  44                processes.
  45
  46            (2) A call-clobbered register, where the process P entered the
  47                kernel via [syscall] trap, is not stored anywhere; that's
  48                OK, because such registers are not expected to be preserved
  49                when the trap returns anyway (so we don't actually bother to
  50                test for this case).
  51
  52            (3) A few registers not used at all by the kernel, and so
  53                normally never saved except by context-switches, are in the
  54                context switch state.  */
  55
  56         if (reg_offs == PT_CTPC || reg_offs == PT_CTPSW || reg_offs == PT_CTBP)
  57                 /* Register saved during context switch.  */
  58                 regs = thread_saved_regs (t);
  59         else
  60                 /* Register saved during kernel entry (or not available).  */
  61                 regs = task_regs (t);
  62
  63         return (v850_reg_t *)((char *)regs + reg_offs);
  64 }
  65
  66 /* Set the bits SET and clear the bits CLEAR in the v850e DIR
  67    (`debug information register').  Returns the new value of DIR.  */
  68 static inline v850_reg_t set_dir (v850_reg_t set, v850_reg_t clear)
  69 {
  70         register v850_reg_t rval asm ("r10");
  71         register v850_reg_t arg0 asm ("r6") = set;
  72         register v850_reg_t arg1 asm ("r7") = clear;
  73
  74         /* The dbtrap handler has exactly this functionality when called
  75            from kernel mode.  0xf840 is a `dbtrap' insn.  */
  76         asm (".short 0xf840" : "=r" (rval) : "r" (arg0), "r" (arg1));
  77
  78         return rval;
  79 }
  80
  81 /* Makes sure hardware single-stepping is (globally) enabled.
  82    Returns true if successful.  */
  83 static inline int enable_single_stepping (void)
  84 {
  85         static int enabled = 0; /* Remember whether we already did it.  */
  86         if (! enabled) {
  87                 /* Turn on the SE (`single-step enable') bit, 0x100, in the
  88                    DIR (`debug information register').  This may fail if a
  89                    processor doesn't support it or something.  We also try
  90                    to clear bit 0x40 (`INI'), which is necessary to use the
  91                    debug stuff on the v850e2; on the v850e, clearing 0x40
  92                    shouldn't cause any problem.  */
  93                 v850_reg_t dir = set_dir (0x100, 0x40);
  94                 /* Make sure it really got set.  */
  95                 if (dir & 0x100)
  96                         enabled = 1;
  97         }
  98         return enabled;
  99 }
 100
 101 /* Try to set CHILD's single-step flag to VAL.  Returns true if successful.  */
 102 static int set_single_step (struct task_struct *t, int val)
 103 {
 104         v850_reg_t *psw_addr = reg_save_addr(PT_PSW, t);
 105         if (val) {
 106                 /* Make sure single-stepping is enabled.  */
 107                 if (! enable_single_stepping ())
 108                         return 0;
 109                 /* Set T's single-step flag.  */
 110                 *psw_addr |= 0x800;
 111         } else
 112                 *psw_addr &= ~0x800;
 113         return 1;
 114 }
 115
 116 int sys_ptrace(long request, long pid, long addr, long data)
 117 {
 118         struct task_struct *child;
 119         int rval;
 120
 121         lock_kernel();
 122
 123         if (request == PTRACE_TRACEME) {
 124                 /* are we already being traced? */
 125                 if (current->ptrace & PT_PTRACED) {
 126                         rval = -EPERM;
 127                         goto out;
 128                 }
 129                 /* set the ptrace bit in the process flags. */
 130                 current->ptrace |= PT_PTRACED;
 131                 rval = 0;
 132                 goto out;
 133         }
 134         rval = -ESRCH;
 135         read_lock(&tasklist_lock);
 136         child = find_task_by_pid(pid);
 137         if (child)
 138                 get_task_struct(child);
 139         read_unlock(&tasklist_lock);
 140         if (!child)
 141                 goto out;
 142
 143         rval = -EPERM;
 144         if (pid == 1)           /* you may not mess with init */
 145                 goto out_tsk;
 146
 147         if (request == PTRACE_ATTACH) {
 148                 rval = ptrace_attach(child);
 149                 goto out_tsk;
 150         }
 151         rval = ptrace_check_attach(child, request == PTRACE_KILL);
 152         if (rval < 0)
 153                 goto out_tsk;
 154
 155         switch (request) {
 156                 unsigned long val, copied;
 157
 158         case PTRACE_PEEKTEXT: /* read word at location addr. */
 159         case PTRACE_PEEKDATA:
 160                 copied = access_process_vm(child, addr, &val, sizeof(val), 0);
 161                 rval = -EIO;
 162                 if (copied != sizeof(val))
 163                         break;
 164                 rval = put_user(val, (unsigned long *)data);
 165                 goto out;
 166
 167         case PTRACE_POKETEXT: /* write the word at location addr. */
 168         case PTRACE_POKEDATA:
 169                 rval = 0;
 170                 if (access_process_vm(child, addr, &data, sizeof(data), 1)
 171                     == sizeof(data))
 172                         break;
 173                 rval = -EIO;
 174                 goto out;
 175
 176         /* Read/write the word at location ADDR in the registers.  */
 177         case PTRACE_PEEKUSR:
 178         case PTRACE_POKEUSR:
 179                 rval = 0;
 180                 if (addr >= PT_SIZE && request == PTRACE_PEEKUSR) {
 181                         /* Special requests that don't actually correspond
 182                            to offsets in struct pt_regs.  */
 183                         if (addr == PT_TEXT_ADDR)
 184                                 val = child->mm->start_code;
 185                         else if (addr == PT_DATA_ADDR)
 186                                 val = child->mm->start_data;
 187                         else if (addr == PT_TEXT_LEN)
 188                                 val = child->mm->end_code
 189                                         - child->mm->start_code;
 190                         else
 191                                 rval = -EIO;
 192                 } else if (addr >= 0 && addr < PT_SIZE && (addr & 0x3) == 0) {
 193                         v850_reg_t *reg_addr = reg_save_addr(addr, child);
 194                         if (request == PTRACE_PEEKUSR)
 195                                 val = *reg_addr;
 196                         else
 197                                 *reg_addr = data;
 198                 } else
 199                         rval = -EIO;
 200
 201                 if (rval == 0 && request == PTRACE_PEEKUSR)
 202                         rval = put_user (val, (unsigned long *)data);
 203                 goto out;
 204
 205         /* Continue and stop at next (return from) syscall */
 206         case PTRACE_SYSCALL:
 207         /* Restart after a signal.  */
 208         case PTRACE_CONT:
 209         /* Execute a single instruction. */
 210         case PTRACE_SINGLESTEP:
 211                 rval = -EIO;
 212                 if (!valid_signal(data))
 213                         break;
 214
 215                 /* Turn CHILD's single-step flag on or off.  */
 216                 if (! set_single_step (child, request == PTRACE_SINGLESTEP))
 217                         break;
 218
 219                 if (request == PTRACE_SYSCALL)
 220                         set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 221                 else
 222                         clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 223
 224                 child->exit_code = data;
 225                 wake_up_process(child);
 226                 rval = 0;
 227                 break;
 228
 229         /*
 230          * make the child exit.  Best I can do is send it a sigkill.
 231          * perhaps it should be put in the status that it wants to
 232          * exit.
 233          */
 234         case PTRACE_KILL:
 235                 rval = 0;
 236                 if (child->exit_state == EXIT_ZOMBIE)   /* already dead */
 237                         break;
 238                 child->exit_code = SIGKILL;
 239                 wake_up_process(child);
 240                 break;
 241
 242         case PTRACE_DETACH: /* detach a process that was attached. */
 243                 set_single_step (child, 0);  /* Clear single-step flag */
 244                 rval = ptrace_detach(child, data);
 245                 break;
 246
 247         default:
 248                 rval = -EIO;
 249                 goto out;
 250         }
 251
 252 out_tsk:
 253         put_task_struct(child);
 254 out:
 255         unlock_kernel();
 256         return rval;
 257 }
 258
 259 asmlinkage void syscall_trace(void)
 260 {
 261         if (!test_thread_flag(TIF_SYSCALL_TRACE))
 262                 return;
 263         if (!(current->ptrace & PT_PTRACED))
 264                 return;
 265         /* The 0x80 provides a way for the tracing parent to distinguish
 266            between a syscall stop and SIGTRAP delivery */
 267         ptrace_notify(SIGTRAP | ((current->ptrace & PT_TRACESYSGOOD)
 268                                  ? 0x80 : 0));
 269         /*
 270          * this isn't the same as continuing with a signal, but it will do
 271          * for normal use.  strace only continues with a signal if the
 272          * stopping signal is not SIGTRAP.  -brl
 273          */
 274         if (current->exit_code) {
 275                 send_sig(current->exit_code, current, 1);
 276                 current->exit_code = 0;
 277         }
 278 }
 279
 280 void ptrace_disable (struct task_struct *child)
 281 {
 282         /* nothing to do */
 283 }