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