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