kernel/ptrace.c

   1 /*
   2  * linux/kernel/ptrace.c
   3  *
   4  * (C) Copyright 1999 Linus Torvalds
   5  *
   6  * Common interfaces for "ptrace()" which we do not want
   7  * to continually duplicate across every architecture.
   8  */
   9
  10 #include <linux/module.h>
  11 #include <linux/sched.h>
  12 #include <linux/errno.h>
  13 #include <linux/mm.h>
  14 #include <linux/highmem.h>
  15 #include <linux/pagemap.h>
  16 #include <linux/smp_lock.h>
  17 #include <linux/ptrace.h>
  18 #include <linux/security.h>
  19 #include <linux/signal.h>
  20
  21 #include <asm/pgtable.h>
  22 #include <asm/uaccess.h>
  23
  24 /*
  25  * ptrace a task: make the debugger its new parent and
  26  * move it to the ptrace list.
  27  *
  28  * Must be called with the tasklist lock write-held.
  29  */
  30 void __ptrace_link(task_t *child, task_t *new_parent)
  31 {
  32         if (!list_empty(&child->ptrace_list))
  33                 BUG();
  34         if (child->parent == new_parent)
  35                 return;
  36         list_add(&child->ptrace_list, &child->parent->ptrace_children);
  37         REMOVE_LINKS(child);
  38         child->parent = new_parent;
  39         SET_LINKS(child);
  40 }
  41
  42 /*
  43  * Turn a tracing stop into a normal stop now, since with no tracer there
  44  * would be no way to wake it up with SIGCONT or SIGKILL.  If there was a
  45  * signal sent that would resume the child, but didn't because it was in
  46  * TASK_TRACED, resume it now.
  47  * Requires that irqs be disabled.
  48  */
  49 void ptrace_untrace(task_t *child)
  50 {
  51         spin_lock(&child->sighand->siglock);
  52         if (child->state == TASK_TRACED) {
  53                 if (child->signal->flags & SIGNAL_STOP_STOPPED) {
  54                         child->state = TASK_STOPPED;
  55                 } else {
  56                         signal_wake_up(child, 1);
  57                 }
  58         }
  59         spin_unlock(&child->sighand->siglock);
  60 }
  61
  62 /*
  63  * unptrace a task: move it back to its original parent and
  64  * remove it from the ptrace list.
  65  *
  66  * Must be called with the tasklist lock write-held.
  67  */
  68 void __ptrace_unlink(task_t *child)
  69 {
  70         if (!child->ptrace)
  71                 BUG();
  72         child->ptrace = 0;
  73         if (!list_empty(&child->ptrace_list)) {
  74                 list_del_init(&child->ptrace_list);
  75                 REMOVE_LINKS(child);
  76                 child->parent = child->real_parent;
  77                 SET_LINKS(child);
  78         }
  79
  80         if (child->state == TASK_TRACED)
  81                 ptrace_untrace(child);
  82 }
  83
  84 /*
  85  * Check that we have indeed attached to the thing..
  86  */
  87 int ptrace_check_attach(struct task_struct *child, int kill)
  88 {
  89         int ret = -ESRCH;
  90
  91         /*
  92          * We take the read lock around doing both checks to close a
  93          * possible race where someone else was tracing our child and
  94          * detached between these two checks.  After this locked check,
  95          * we are sure that this is our traced child and that can only
  96          * be changed by us so it's not changing right after this.
  97          */
  98         read_lock(&tasklist_lock);
  99         if ((child->ptrace & PT_PTRACED) && child->parent == current &&
 100             (!(child->ptrace & PT_ATTACHED) || child->real_parent != current)
 101             && child->signal != NULL) {
 102                 ret = 0;
 103                 spin_lock_irq(&child->sighand->siglock);
 104                 if (child->state == TASK_STOPPED) {
 105                         child->state = TASK_TRACED;
 106                 } else if (child->state != TASK_TRACED && !kill) {
 107                         ret = -ESRCH;
 108                 }
 109                 spin_unlock_irq(&child->sighand->siglock);
 110         }
 111         read_unlock(&tasklist_lock);
 112
 113         if (!ret && !kill) {
 114                 wait_task_inactive(child);
 115         }
 116
 117         /* All systems go.. */
 118         return ret;
 119 }
 120
 121 static int may_attach(struct task_struct *task)
 122 {
 123         if (!task->mm)
 124                 return -EPERM;
 125         if (((current->uid != task->euid) ||
 126              (current->uid != task->suid) ||
 127              (current->uid != task->uid) ||
 128              (current->gid != task->egid) ||
 129              (current->gid != task->sgid) ||
 130              (current->gid != task->gid)) && !capable(CAP_SYS_PTRACE))
 131                 return -EPERM;
 132         smp_rmb();
 133         if (!task->mm->dumpable && !capable(CAP_SYS_PTRACE))
 134                 return -EPERM;
 135
 136         return security_ptrace(current, task);
 137 }
 138
 139 int ptrace_may_attach(struct task_struct *task)
 140 {
 141         int err;
 142         task_lock(task);
 143         err = may_attach(task);
 144         task_unlock(task);
 145         return !err;
 146 }
 147
 148 int ptrace_attach(struct task_struct *task)
 149 {
 150         int retval;
 151         task_lock(task);
 152         retval = -EPERM;
 153         if (task->pid <= 1)
 154                 goto bad;
 155         if (task == current)
 156                 goto bad;
 157         /* the same process cannot be attached many times */
 158         if (task->ptrace & PT_PTRACED)
 159                 goto bad;
 160         retval = may_attach(task);
 161         if (retval)
 162                 goto bad;
 163
 164         /* Go */
 165         task->ptrace |= PT_PTRACED | ((task->real_parent != current)
 166                                       ? PT_ATTACHED : 0);
 167         if (capable(CAP_SYS_PTRACE))
 168                 task->ptrace |= PT_PTRACE_CAP;
 169         task_unlock(task);
 170
 171         write_lock_irq(&tasklist_lock);
 172         __ptrace_link(task, current);
 173         write_unlock_irq(&tasklist_lock);
 174
 175         force_sig_specific(SIGSTOP, task);
 176         return 0;
 177
 178 bad:
 179         task_unlock(task);
 180         return retval;
 181 }
 182
 183 int ptrace_detach(struct task_struct *child, unsigned int data)
 184 {
 185         if (!valid_signal(data))
 186                 return  -EIO;
 187
 188         /* Architecture-specific hardware disable .. */
 189         ptrace_disable(child);
 190
 191         /* .. re-parent .. */
 192         child->exit_code = data;
 193
 194         write_lock_irq(&tasklist_lock);
 195         __ptrace_unlink(child);
 196         /* .. and wake it up. */
 197         if (child->exit_state != EXIT_ZOMBIE)
 198                 wake_up_process(child);
 199         write_unlock_irq(&tasklist_lock);
 200
 201         return 0;
 202 }
 203
 204 /*
 205  * Access another process' address space.
 206  * Source/target buffer must be kernel space,
 207  * Do not walk the page table directly, use get_user_pages
 208  */
 209
 210 int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write)
 211 {
 212         struct mm_struct *mm;
 213         struct vm_area_struct *vma;
 214         struct page *page;
 215         void *old_buf = buf;
 216
 217         mm = get_task_mm(tsk);
 218         if (!mm)
 219                 return 0;
 220
 221         down_read(&mm->mmap_sem);
 222         /* ignore errors, just check how much was sucessfully transfered */
 223         while (len) {
 224                 int bytes, ret, offset;
 225                 void *maddr;
 226
 227                 ret = get_user_pages(tsk, mm, addr, 1,
 228                                 write, 1, &page, &vma);
 229                 if (ret <= 0)
 230                         break;
 231
 232                 bytes = len;
 233                 offset = addr & (PAGE_SIZE-1);
 234                 if (bytes > PAGE_SIZE-offset)
 235                         bytes = PAGE_SIZE-offset;
 236
 237                 maddr = kmap(page);
 238                 if (write) {
 239                         copy_to_user_page(vma, page, addr,
 240                                           maddr + offset, buf, bytes);
 241                         set_page_dirty_lock(page);
 242                 } else {
 243                         copy_from_user_page(vma, page, addr,
 244                                             buf, maddr + offset, bytes);
 245                 }
 246                 kunmap(page);
 247                 page_cache_release(page);
 248                 len -= bytes;
 249                 buf += bytes;
 250                 addr += bytes;
 251         }
 252         up_read(&mm->mmap_sem);
 253         mmput(mm);
 254
 255         return buf - old_buf;
 256 }
 257
 258 int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)
 259 {
 260         int copied = 0;
 261
 262         while (len > 0) {
 263                 char buf[128];
 264                 int this_len, retval;
 265
 266                 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
 267                 retval = access_process_vm(tsk, src, buf, this_len, 0);
 268                 if (!retval) {
 269                         if (copied)
 270                                 break;
 271                         return -EIO;
 272                 }
 273                 if (copy_to_user(dst, buf, retval))
 274                         return -EFAULT;
 275                 copied += retval;
 276                 src += retval;
 277                 dst += retval;
 278                 len -= retval;
 279         }
 280         return copied;
 281 }
 282
 283 int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len)
 284 {
 285         int copied = 0;
 286
 287         while (len > 0) {
 288                 char buf[128];
 289                 int this_len, retval;
 290
 291                 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
 292                 if (copy_from_user(buf, src, this_len))
 293                         return -EFAULT;
 294                 retval = access_process_vm(tsk, dst, buf, this_len, 1);
 295                 if (!retval) {
 296                         if (copied)
 297                                 break;
 298                         return -EIO;
 299                 }
 300                 copied += retval;
 301                 src += retval;
 302                 dst += retval;
 303                 len -= retval;
 304         }
 305         return copied;
 306 }
 307
 308 static int ptrace_setoptions(struct task_struct *child, long data)
 309 {
 310         child->ptrace &= ~PT_TRACE_MASK;
 311
 312         if (data & PTRACE_O_TRACESYSGOOD)
 313                 child->ptrace |= PT_TRACESYSGOOD;
 314
 315         if (data & PTRACE_O_TRACEFORK)
 316                 child->ptrace |= PT_TRACE_FORK;
 317
 318         if (data & PTRACE_O_TRACEVFORK)
 319                 child->ptrace |= PT_TRACE_VFORK;
 320
 321         if (data & PTRACE_O_TRACECLONE)
 322                 child->ptrace |= PT_TRACE_CLONE;
 323
 324         if (data & PTRACE_O_TRACEEXEC)
 325                 child->ptrace |= PT_TRACE_EXEC;
 326
 327         if (data & PTRACE_O_TRACEVFORKDONE)
 328                 child->ptrace |= PT_TRACE_VFORK_DONE;
 329
 330         if (data & PTRACE_O_TRACEEXIT)
 331                 child->ptrace |= PT_TRACE_EXIT;
 332
 333         return (data & ~PTRACE_O_MASK) ? -EINVAL : 0;
 334 }
 335
 336 static int ptrace_getsiginfo(struct task_struct *child, siginfo_t __user * data)
 337 {
 338         siginfo_t lastinfo;
 339         int error = -ESRCH;
 340
 341         read_lock(&tasklist_lock);
 342         if (likely(child->sighand != NULL)) {
 343                 error = -EINVAL;
 344                 spin_lock_irq(&child->sighand->siglock);
 345                 if (likely(child->last_siginfo != NULL)) {
 346                         lastinfo = *child->last_siginfo;
 347                         error = 0;
 348                 }
 349                 spin_unlock_irq(&child->sighand->siglock);
 350         }
 351         read_unlock(&tasklist_lock);
 352         if (!error)
 353                 return copy_siginfo_to_user(data, &lastinfo);
 354         return error;
 355 }
 356
 357 static int ptrace_setsiginfo(struct task_struct *child, siginfo_t __user * data)
 358 {
 359         siginfo_t newinfo;
 360         int error = -ESRCH;
 361
 362         if (copy_from_user(&newinfo, data, sizeof (siginfo_t)))
 363                 return -EFAULT;
 364
 365         read_lock(&tasklist_lock);
 366         if (likely(child->sighand != NULL)) {
 367                 error = -EINVAL;
 368                 spin_lock_irq(&child->sighand->siglock);
 369                 if (likely(child->last_siginfo != NULL)) {
 370                         *child->last_siginfo = newinfo;
 371                         error = 0;
 372                 }
 373                 spin_unlock_irq(&child->sighand->siglock);
 374         }
 375         read_unlock(&tasklist_lock);
 376         return error;
 377 }
 378
 379 int ptrace_request(struct task_struct *child, long request,
 380                    long addr, long data)
 381 {
 382         int ret = -EIO;
 383
 384         switch (request) {
 385 #ifdef PTRACE_OLDSETOPTIONS
 386         case PTRACE_OLDSETOPTIONS:
 387 #endif
 388         case PTRACE_SETOPTIONS:
 389                 ret = ptrace_setoptions(child, data);
 390                 break;
 391         case PTRACE_GETEVENTMSG:
 392                 ret = put_user(child->ptrace_message, (unsigned long __user *) data);
 393                 break;
 394         case PTRACE_GETSIGINFO:
 395                 ret = ptrace_getsiginfo(child, (siginfo_t __user *) data);
 396                 break;
 397         case PTRACE_SETSIGINFO:
 398                 ret = ptrace_setsiginfo(child, (siginfo_t __user *) data);
 399                 break;
 400         default:
 401                 break;
 402         }
 403
 404         return ret;
 405 }