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   1 /*
   2  * Copyright (C) 2000-2003, Axis Communications AB.
   3  */
   4
   5 #include <linux/kernel.h>
   6 #include <linux/sched.h>
   7 #include <linux/mm.h>
   8 #include <linux/smp.h>
   9 #include <linux/smp_lock.h>
  10 #include <linux/errno.h>
  11 #include <linux/ptrace.h>
  12 #include <linux/user.h>
  13
  14 #include <asm/uaccess.h>
  15 #include <asm/page.h>
  16 #include <asm/pgtable.h>
  17 #include <asm/system.h>
  18 #include <asm/processor.h>
  19
  20 /*
  21  * Determines which bits in DCCR the user has access to.
  22  * 1 = access, 0 = no access.
  23  */
  24 #define DCCR_MASK 0x0000001f     /* XNZVC */
  25
  26 /*
  27  * Get contents of register REGNO in task TASK.
  28  */
  29 inline long get_reg(struct task_struct *task, unsigned int regno)
  30 {
  31         /* USP is a special case, it's not in the pt_regs struct but
  32          * in the tasks thread struct
  33          */
  34
  35         if (regno == PT_USP)
  36                 return task->thread.usp;
  37         else if (regno < PT_MAX)
  38                 return ((unsigned long *)user_regs(task->thread_info))[regno];
  39         else
  40                 return 0;
  41 }
  42
  43 /*
  44  * Write contents of register REGNO in task TASK.
  45  */
  46 inline int put_reg(struct task_struct *task, unsigned int regno,
  47                           unsigned long data)
  48 {
  49         if (regno == PT_USP)
  50                 task->thread.usp = data;
  51         else if (regno < PT_MAX)
  52                 ((unsigned long *)user_regs(task->thread_info))[regno] = data;
  53         else
  54                 return -1;
  55         return 0;
  56 }
  57
  58 /*
  59  * Called by kernel/ptrace.c when detaching.
  60  *
  61  * Make sure the single step bit is not set.
  62  */
  63 void
  64 ptrace_disable(struct task_struct *child)
  65 {
  66        /* Todo - pending singlesteps? */
  67 }
  68
  69 /*
  70  * Note that this implementation of ptrace behaves differently from vanilla
  71  * ptrace.  Contrary to what the man page says, in the PTRACE_PEEKTEXT,
  72  * PTRACE_PEEKDATA, and PTRACE_PEEKUSER requests the data variable is not
  73  * ignored.  Instead, the data variable is expected to point at a location
  74  * (in user space) where the result of the ptrace call is written (instead of
  75  * being returned).
  76  */
  77 asmlinkage int
  78 sys_ptrace(long request, long pid, long addr, long data)
  79 {
  80         struct task_struct *child;
  81         int ret;
  82         unsigned long __user *datap = (unsigned long __user *)data;
  83
  84         lock_kernel();
  85         ret = -EPERM;
  86
  87         if (request == PTRACE_TRACEME) {
  88                 if (current->ptrace & PT_PTRACED)
  89                         goto out;
  90
  91                 current->ptrace |= PT_PTRACED;
  92                 ret = 0;
  93                 goto out;
  94         }
  95
  96         ret = -ESRCH;
  97         read_lock(&tasklist_lock);
  98         child = find_task_by_pid(pid);
  99
 100         if (child)
 101                 get_task_struct(child);
 102
 103         read_unlock(&tasklist_lock);
 104
 105         if (!child)
 106                 goto out;
 107
 108         ret = -EPERM;
 109
 110         if (pid == 1)           /* Leave the init process alone! */
 111                 goto out_tsk;
 112
 113         if (request == PTRACE_ATTACH) {
 114                 ret = ptrace_attach(child);
 115                 goto out_tsk;
 116         }
 117
 118         ret = ptrace_check_attach(child, request == PTRACE_KILL);
 119         if (ret < 0)
 120                 goto out_tsk;
 121
 122         switch (request) {
 123                 /* Read word at location address. */
 124                 case PTRACE_PEEKTEXT:
 125                 case PTRACE_PEEKDATA: {
 126                         unsigned long tmp;
 127                         int copied;
 128
 129                         copied = access_process_vm(child, addr, &tmp, sizeof(tmp), 0);
 130                         ret = -EIO;
 131
 132                         if (copied != sizeof(tmp))
 133                                 break;
 134
 135                         ret = put_user(tmp,datap);
 136                         break;
 137                 }
 138
 139                 /* Read the word at location address in the USER area. */
 140                 case PTRACE_PEEKUSR: {
 141                         unsigned long tmp;
 142
 143                         ret = -EIO;
 144                         if ((addr & 3) || addr < 0 || addr > PT_MAX << 2)
 145                                 break;
 146
 147                         tmp = get_reg(child, addr >> 2);
 148                         ret = put_user(tmp, datap);
 149                         break;
 150                 }
 151
 152                 /* Write the word at location address. */
 153                 case PTRACE_POKETEXT:
 154                 case PTRACE_POKEDATA:
 155                         ret = 0;
 156
 157                         if (access_process_vm(child, addr, &data, sizeof(data), 1) == sizeof(data))
 158                                 break;
 159
 160                         ret = -EIO;
 161                         break;
 162
 163                 /* Write the word at location address in the USER area. */
 164                 case PTRACE_POKEUSR:
 165                         ret = -EIO;
 166                         if ((addr & 3) || addr < 0 || addr > PT_MAX << 2)
 167                                 break;
 168
 169                         addr >>= 2;
 170
 171                         if (addr == PT_DCCR) {
 172                                 /* don't allow the tracing process to change stuff like
 173                                  * interrupt enable, kernel/user bit, dma enables etc.
 174                                  */
 175                                 data &= DCCR_MASK;
 176                                 data |= get_reg(child, PT_DCCR) & ~DCCR_MASK;
 177                         }
 178                         if (put_reg(child, addr, data))
 179                                 break;
 180                         ret = 0;
 181                         break;
 182
 183                 case PTRACE_SYSCALL:
 184                 case PTRACE_CONT:
 185                         ret = -EIO;
 186
 187                         if ((unsigned long) data > _NSIG)
 188                                 break;
 189
 190                         if (request == PTRACE_SYSCALL) {
 191                                 set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 192                         }
 193                         else {
 194                                 clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 195                         }
 196
 197                         child->exit_code = data;
 198
 199                         /* TODO: make sure any pending breakpoint is killed */
 200                         wake_up_process(child);
 201                         ret = 0;
 202
 203                         break;
 204
 205                 /* Make the child exit by sending it a sigkill. */
 206                 case PTRACE_KILL:
 207                         ret = 0;
 208
 209                         if (child->state == TASK_ZOMBIE)
 210                                 break;
 211
 212                         child->exit_code = SIGKILL;
 213
 214                         /* TODO: make sure any pending breakpoint is killed */
 215                         wake_up_process(child);
 216                         break;
 217
 218                 /* Set the trap flag. */
 219                 case PTRACE_SINGLESTEP:
 220                         ret = -EIO;
 221
 222                         if ((unsigned long) data > _NSIG)
 223                                 break;
 224
 225                         clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 226
 227                         /* TODO: set some clever breakpoint mechanism... */
 228
 229                         child->exit_code = data;
 230                         wake_up_process(child);
 231                         ret = 0;
 232                         break;
 233
 234                 case PTRACE_DETACH:
 235                         ret = ptrace_detach(child, data);
 236                         break;
 237
 238                 /* Get all GP registers from the child. */
 239                 case PTRACE_GETREGS: {
 240                         int i;
 241                         unsigned long tmp;
 242
 243                         for (i = 0; i <= PT_MAX; i++) {
 244                                 tmp = get_reg(child, i);
 245
 246                                 if (put_user(tmp, datap)) {
 247                                         ret = -EFAULT;
 248                                         goto out_tsk;
 249                                 }
 250
 251                                 data += sizeof(long);
 252                         }
 253
 254                         ret = 0;
 255                         break;
 256                 }
 257
 258                 /* Set all GP registers in the child. */
 259                 case PTRACE_SETREGS: {
 260                         int i;
 261                         unsigned long tmp;
 262
 263                         for (i = 0; i <= PT_MAX; i++) {
 264                                 if (get_user(tmp, datap)) {
 265                                         ret = -EFAULT;
 266                                         goto out_tsk;
 267                                 }
 268
 269                                 if (i == PT_DCCR) {
 270                                         tmp &= DCCR_MASK;
 271                                         tmp |= get_reg(child, PT_DCCR) & ~DCCR_MASK;
 272                                 }
 273
 274                                 put_reg(child, i, tmp);
 275                                 data += sizeof(long);
 276                         }
 277
 278                         ret = 0;
 279                         break;
 280                 }
 281
 282                 default:
 283                         ret = ptrace_request(child, request, addr, data);
 284                         break;
 285         }
 286 out_tsk:
 287         put_task_struct(child);
 288 out:
 289         unlock_kernel();
 290         return ret;
 291 }
 292
 293 void do_syscall_trace(void)
 294 {
 295         if (!test_thread_flag(TIF_SYSCALL_TRACE))
 296                 return;
 297
 298         if (!(current->ptrace & PT_PTRACED))
 299                 return;
 300
 301         /* the 0x80 provides a way for the tracing parent to distinguish
 302            between a syscall stop and SIGTRAP delivery */
 303         ptrace_notify(SIGTRAP | ((current->ptrace & PT_TRACESYSGOOD)
 304                                  ? 0x80 : 0));
 305
 306         /*
 307          * This isn't the same as continuing with a signal, but it will do for
 308          * normal use.
 309          */
 310         if (current->exit_code) {
 311                 send_sig(current->exit_code, current, 1);
 312                 current->exit_code = 0;
 313         }
 314 }