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 int ptrace_attach(struct task_struct *task)
 122 {
 123         int retval;
 124         task_lock(task);
 125         retval = -EPERM;
 126         if (task->pid <= 1)
 127                 goto bad;
 128         if (task == current)
 129                 goto bad;
 130         if (!task->mm)
 131                 goto bad;
 132         if(((current->uid != task->euid) ||
 133             (current->uid != task->suid) ||
 134             (current->uid != task->uid) ||
 135             (current->gid != task->egid) ||
 136             (current->gid != task->sgid) ||
 137             (current->gid != task->gid)) && !capable(CAP_SYS_PTRACE))
 138                 goto bad;
 139         smp_rmb();
 140         if (!task->mm->dumpable && !capable(CAP_SYS_PTRACE))
 141                 goto bad;
 142         /* the same process cannot be attached many times */
 143         if (task->ptrace & PT_PTRACED)
 144                 goto bad;
 145         retval = security_ptrace(current, task);
 146         if (retval)
 147                 goto bad;
 148
 149         /* Go */
 150         task->ptrace |= PT_PTRACED | ((task->real_parent != current)
 151                                       ? PT_ATTACHED : 0);
 152         if (capable(CAP_SYS_PTRACE))
 153                 task->ptrace |= PT_PTRACE_CAP;
 154         task_unlock(task);
 155
 156         write_lock_irq(&tasklist_lock);
 157         __ptrace_link(task, current);
 158         write_unlock_irq(&tasklist_lock);
 159
 160         force_sig_specific(SIGSTOP, task);
 161         return 0;
 162
 163 bad:
 164         task_unlock(task);
 165         return retval;
 166 }
 167
 168 int ptrace_detach(struct task_struct *child, unsigned int data)
 169 {
 170         if (!valid_signal(data))
 171                 return  -EIO;
 172
 173         /* Architecture-specific hardware disable .. */
 174         ptrace_disable(child);
 175
 176         /* .. re-parent .. */
 177         child->exit_code = data;
 178
 179         write_lock_irq(&tasklist_lock);
 180         __ptrace_unlink(child);
 181         /* .. and wake it up. */
 182         if (child->exit_state != EXIT_ZOMBIE)
 183                 wake_up_process(child);
 184         write_unlock_irq(&tasklist_lock);
 185
 186         return 0;
 187 }
 188
 189 /*
 190  * Access another process' address space.
 191  * Source/target buffer must be kernel space,
 192  * Do not walk the page table directly, use get_user_pages
 193  */
 194
 195 int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write)
 196 {
 197         struct mm_struct *mm;
 198         struct vm_area_struct *vma;
 199         struct page *page;
 200         void *old_buf = buf;
 201
 202         mm = get_task_mm(tsk);
 203         if (!mm)
 204                 return 0;
 205
 206         down_read(&mm->mmap_sem);
 207         /* ignore errors, just check how much was sucessfully transfered */
 208         while (len) {
 209                 int bytes, ret, offset;
 210                 void *maddr;
 211
 212                 ret = get_user_pages(tsk, mm, addr, 1,
 213                                 write, 1, &page, &vma);
 214                 if (ret <= 0)
 215                         break;
 216
 217                 bytes = len;
 218                 offset = addr & (PAGE_SIZE-1);
 219                 if (bytes > PAGE_SIZE-offset)
 220                         bytes = PAGE_SIZE-offset;
 221
 222                 maddr = kmap(page);
 223                 if (write) {
 224                         copy_to_user_page(vma, page, addr,
 225                                           maddr + offset, buf, bytes);
 226                         set_page_dirty_lock(page);
 227                 } else {
 228                         copy_from_user_page(vma, page, addr,
 229                                             buf, maddr + offset, bytes);
 230                 }
 231                 kunmap(page);
 232                 page_cache_release(page);
 233                 len -= bytes;
 234                 buf += bytes;
 235                 addr += bytes;
 236         }
 237         up_read(&mm->mmap_sem);
 238         mmput(mm);
 239
 240         return buf - old_buf;
 241 }
 242
 243 int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)
 244 {
 245         int copied = 0;
 246
 247         while (len > 0) {
 248                 char buf[128];
 249                 int this_len, retval;
 250
 251                 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
 252                 retval = access_process_vm(tsk, src, buf, this_len, 0);
 253                 if (!retval) {
 254                         if (copied)
 255                                 break;
 256                         return -EIO;
 257                 }
 258                 if (copy_to_user(dst, buf, retval))
 259                         return -EFAULT;
 260                 copied += retval;
 261                 src += retval;
 262                 dst += retval;
 263                 len -= retval;
 264         }
 265         return copied;
 266 }
 267
 268 int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len)
 269 {
 270         int copied = 0;
 271
 272         while (len > 0) {
 273                 char buf[128];
 274                 int this_len, retval;
 275
 276                 this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
 277                 if (copy_from_user(buf, src, this_len))
 278                         return -EFAULT;
 279                 retval = access_process_vm(tsk, dst, buf, this_len, 1);
 280                 if (!retval) {
 281                         if (copied)
 282                                 break;
 283                         return -EIO;
 284                 }
 285                 copied += retval;
 286                 src += retval;
 287                 dst += retval;
 288                 len -= retval;
 289         }
 290         return copied;
 291 }
 292
 293 static int ptrace_setoptions(struct task_struct *child, long data)
 294 {
 295         child->ptrace &= ~PT_TRACE_MASK;
 296
 297         if (data & PTRACE_O_TRACESYSGOOD)
 298                 child->ptrace |= PT_TRACESYSGOOD;
 299
 300         if (data & PTRACE_O_TRACEFORK)
 301                 child->ptrace |= PT_TRACE_FORK;
 302
 303         if (data & PTRACE_O_TRACEVFORK)
 304                 child->ptrace |= PT_TRACE_VFORK;
 305
 306         if (data & PTRACE_O_TRACECLONE)
 307                 child->ptrace |= PT_TRACE_CLONE;
 308
 309         if (data & PTRACE_O_TRACEEXEC)
 310                 child->ptrace |= PT_TRACE_EXEC;
 311
 312         if (data & PTRACE_O_TRACEVFORKDONE)
 313                 child->ptrace |= PT_TRACE_VFORK_DONE;
 314
 315         if (data & PTRACE_O_TRACEEXIT)
 316                 child->ptrace |= PT_TRACE_EXIT;
 317
 318         return (data & ~PTRACE_O_MASK) ? -EINVAL : 0;
 319 }
 320
 321 static int ptrace_getsiginfo(struct task_struct *child, siginfo_t __user * data)
 322 {
 323         siginfo_t lastinfo;
 324         int error = -ESRCH;
 325
 326         read_lock(&tasklist_lock);
 327         if (likely(child->sighand != NULL)) {
 328                 error = -EINVAL;
 329                 spin_lock_irq(&child->sighand->siglock);
 330                 if (likely(child->last_siginfo != NULL)) {
 331                         lastinfo = *child->last_siginfo;
 332                         error = 0;
 333                 }
 334                 spin_unlock_irq(&child->sighand->siglock);
 335         }
 336         read_unlock(&tasklist_lock);
 337         if (!error)
 338                 return copy_siginfo_to_user(data, &lastinfo);
 339         return error;
 340 }
 341
 342 static int ptrace_setsiginfo(struct task_struct *child, siginfo_t __user * data)
 343 {
 344         siginfo_t newinfo;
 345         int error = -ESRCH;
 346
 347         if (copy_from_user(&newinfo, data, sizeof (siginfo_t)))
 348                 return -EFAULT;
 349
 350         read_lock(&tasklist_lock);
 351         if (likely(child->sighand != NULL)) {
 352                 error = -EINVAL;
 353                 spin_lock_irq(&child->sighand->siglock);
 354                 if (likely(child->last_siginfo != NULL)) {
 355                         *child->last_siginfo = newinfo;
 356                         error = 0;
 357                 }
 358                 spin_unlock_irq(&child->sighand->siglock);
 359         }
 360         read_unlock(&tasklist_lock);
 361         return error;
 362 }
 363
 364 int ptrace_request(struct task_struct *child, long request,
 365                    long addr, long data)
 366 {
 367         int ret = -EIO;
 368
 369         switch (request) {
 370 #ifdef PTRACE_OLDSETOPTIONS
 371         case PTRACE_OLDSETOPTIONS:
 372 #endif
 373         case PTRACE_SETOPTIONS:
 374                 ret = ptrace_setoptions(child, data);
 375                 break;
 376         case PTRACE_GETEVENTMSG:
 377                 ret = put_user(child->ptrace_message, (unsigned long __user *) data);
 378                 break;
 379         case PTRACE_GETSIGINFO:
 380                 ret = ptrace_getsiginfo(child, (siginfo_t __user *) data);
 381                 break;
 382         case PTRACE_SETSIGINFO:
 383                 ret = ptrace_setsiginfo(child, (siginfo_t __user *) data);
 384                 break;
 385         default:
 386                 break;
 387         }
 388
 389         return ret;
 390 }