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 if (child->signal->flags & SIGNAL_GROUP_EXIT) { 60 sigaddset(&child->pending.signal, SIGKILL); 61 signal_wake_up(child, 1); 62 } 63 spin_unlock(&child->sighand->siglock); 64 } 65 66 /* 67 * unptrace a task: move it back to its original parent and 68 * remove it from the ptrace list. 69 * 70 * Must be called with the tasklist lock write-held. 71 */ 72 void __ptrace_unlink(task_t *child) 73 { 74 if (!child->ptrace) 75 BUG(); 76 child->ptrace = 0; 77 if (!list_empty(&child->ptrace_list)) { 78 list_del_init(&child->ptrace_list); 79 REMOVE_LINKS(child); 80 child->parent = child->real_parent; 81 SET_LINKS(child); 82 } 83 84 ptrace_untrace(child); 85 } 86 87 /* 88 * Check that we have indeed attached to the thing.. 89 */ 90 int ptrace_check_attach(struct task_struct *child, int kill) 91 { 92 int ret = -ESRCH; 93 94 /* 95 * We take the read lock around doing both checks to close a 96 * possible race where someone else was tracing our child and 97 * detached between these two checks. After this locked check, 98 * we are sure that this is our traced child and that can only 99 * be changed by us so it's not changing right after this. 100 */ 101 read_lock(&tasklist_lock); 102 if ((child->ptrace & PT_PTRACED) && child->parent == current && 103 (!(child->ptrace & PT_ATTACHED) || child->real_parent != current) 104 && child->signal != NULL) { 105 ret = 0; 106 spin_lock_irq(&child->sighand->siglock); 107 if (child->state == TASK_STOPPED) { 108 child->state = TASK_TRACED; 109 } else if (child->state != TASK_TRACED && !kill) { 110 ret = -ESRCH; 111 } 112 spin_unlock_irq(&child->sighand->siglock); 113 } 114 read_unlock(&tasklist_lock); 115 116 if (!ret && !kill) { 117 wait_task_inactive(child); 118 } 119 120 /* All systems go.. */ 121 return ret; 122 } 123 124 static int may_attach(struct task_struct *task) 125 { 126 if (!task->mm) 127 return -EPERM; 128 if (((current->uid != task->euid) || 129 (current->uid != task->suid) || 130 (current->uid != task->uid) || 131 (current->gid != task->egid) || 132 (current->gid != task->sgid) || 133 (current->gid != task->gid)) && !capable(CAP_SYS_PTRACE)) 134 return -EPERM; 135 smp_rmb(); 136 if (!task->mm->dumpable && !capable(CAP_SYS_PTRACE)) 137 return -EPERM; 138 139 return security_ptrace(current, task); 140 } 141 142 int ptrace_may_attach(struct task_struct *task) 143 { 144 int err; 145 task_lock(task); 146 err = may_attach(task); 147 task_unlock(task); 148 return !err; 149 } 150 151 int ptrace_attach(struct task_struct *task) 152 { 153 int retval; 154 task_lock(task); 155 retval = -EPERM; 156 if (task->pid <= 1) 157 goto bad; 158 if (task == current) 159 goto bad; 160 /* the same process cannot be attached many times */ 161 if (task->ptrace & PT_PTRACED) 162 goto bad; 163 retval = may_attach(task); 164 if (retval) 165 goto bad; 166 167 /* Go */ 168 task->ptrace |= PT_PTRACED | ((task->real_parent != current) 169 ? PT_ATTACHED : 0); 170 if (capable(CAP_SYS_PTRACE)) 171 task->ptrace |= PT_PTRACE_CAP; 172 task_unlock(task); 173 174 write_lock_irq(&tasklist_lock); 175 __ptrace_link(task, current); 176 write_unlock_irq(&tasklist_lock); 177 178 force_sig_specific(SIGSTOP, task); 179 return 0; 180 181 bad: 182 task_unlock(task); 183 return retval; 184 } 185 186 int ptrace_detach(struct task_struct *child, unsigned int data) 187 { 188 if (!valid_signal(data)) 189 return -EIO; 190 191 /* Architecture-specific hardware disable .. */ 192 ptrace_disable(child); 193 194 /* .. re-parent .. */ 195 child->exit_code = data; 196 197 write_lock_irq(&tasklist_lock); 198 __ptrace_unlink(child); 199 /* .. and wake it up. */ 200 if (child->exit_state != EXIT_ZOMBIE) 201 wake_up_process(child); 202 write_unlock_irq(&tasklist_lock); 203 204 return 0; 205 } 206 207 /* 208 * Access another process' address space. 209 * Source/target buffer must be kernel space, 210 * Do not walk the page table directly, use get_user_pages 211 */ 212 213 int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write) 214 { 215 struct mm_struct *mm; 216 struct vm_area_struct *vma; 217 struct page *page; 218 void *old_buf = buf; 219 220 mm = get_task_mm(tsk); 221 if (!mm) 222 return 0; 223 224 down_read(&mm->mmap_sem); 225 /* ignore errors, just check how much was sucessfully transfered */ 226 while (len) { 227 int bytes, ret, offset; 228 void *maddr; 229 230 ret = get_user_pages(tsk, mm, addr, 1, 231 write, 1, &page, &vma); 232 if (ret <= 0) 233 break; 234 235 bytes = len; 236 offset = addr & (PAGE_SIZE-1); 237 if (bytes > PAGE_SIZE-offset) 238 bytes = PAGE_SIZE-offset; 239 240 maddr = kmap(page); 241 if (write) { 242 copy_to_user_page(vma, page, addr, 243 maddr + offset, buf, bytes); 244 set_page_dirty_lock(page); 245 } else { 246 copy_from_user_page(vma, page, addr, 247 buf, maddr + offset, bytes); 248 } 249 kunmap(page); 250 page_cache_release(page); 251 len -= bytes; 252 buf += bytes; 253 addr += bytes; 254 } 255 up_read(&mm->mmap_sem); 256 mmput(mm); 257 258 return buf - old_buf; 259 } 260 261 int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len) 262 { 263 int copied = 0; 264 265 while (len > 0) { 266 char buf[128]; 267 int this_len, retval; 268 269 this_len = (len > sizeof(buf)) ? sizeof(buf) : len; 270 retval = access_process_vm(tsk, src, buf, this_len, 0); 271 if (!retval) { 272 if (copied) 273 break; 274 return -EIO; 275 } 276 if (copy_to_user(dst, buf, retval)) 277 return -EFAULT; 278 copied += retval; 279 src += retval; 280 dst += retval; 281 len -= retval; 282 } 283 return copied; 284 } 285 286 int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len) 287 { 288 int copied = 0; 289 290 while (len > 0) { 291 char buf[128]; 292 int this_len, retval; 293 294 this_len = (len > sizeof(buf)) ? sizeof(buf) : len; 295 if (copy_from_user(buf, src, this_len)) 296 return -EFAULT; 297 retval = access_process_vm(tsk, dst, buf, this_len, 1); 298 if (!retval) { 299 if (copied) 300 break; 301 return -EIO; 302 } 303 copied += retval; 304 src += retval; 305 dst += retval; 306 len -= retval; 307 } 308 return copied; 309 } 310 311 static int ptrace_setoptions(struct task_struct *child, long data) 312 { 313 child->ptrace &= ~PT_TRACE_MASK; 314 315 if (data & PTRACE_O_TRACESYSGOOD) 316 child->ptrace |= PT_TRACESYSGOOD; 317 318 if (data & PTRACE_O_TRACEFORK) 319 child->ptrace |= PT_TRACE_FORK; 320 321 if (data & PTRACE_O_TRACEVFORK) 322 child->ptrace |= PT_TRACE_VFORK; 323 324 if (data & PTRACE_O_TRACECLONE) 325 child->ptrace |= PT_TRACE_CLONE; 326 327 if (data & PTRACE_O_TRACEEXEC) 328 child->ptrace |= PT_TRACE_EXEC; 329 330 if (data & PTRACE_O_TRACEVFORKDONE) 331 child->ptrace |= PT_TRACE_VFORK_DONE; 332 333 if (data & PTRACE_O_TRACEEXIT) 334 child->ptrace |= PT_TRACE_EXIT; 335 336 return (data & ~PTRACE_O_MASK) ? -EINVAL : 0; 337 } 338 339 static int ptrace_getsiginfo(struct task_struct *child, siginfo_t __user * data) 340 { 341 siginfo_t lastinfo; 342 int error = -ESRCH; 343 344 read_lock(&tasklist_lock); 345 if (likely(child->sighand != NULL)) { 346 error = -EINVAL; 347 spin_lock_irq(&child->sighand->siglock); 348 if (likely(child->last_siginfo != NULL)) { 349 lastinfo = *child->last_siginfo; 350 error = 0; 351 } 352 spin_unlock_irq(&child->sighand->siglock); 353 } 354 read_unlock(&tasklist_lock); 355 if (!error) 356 return copy_siginfo_to_user(data, &lastinfo); 357 return error; 358 } 359 360 static int ptrace_setsiginfo(struct task_struct *child, siginfo_t __user * data) 361 { 362 siginfo_t newinfo; 363 int error = -ESRCH; 364 365 if (copy_from_user(&newinfo, data, sizeof (siginfo_t))) 366 return -EFAULT; 367 368 read_lock(&tasklist_lock); 369 if (likely(child->sighand != NULL)) { 370 error = -EINVAL; 371 spin_lock_irq(&child->sighand->siglock); 372 if (likely(child->last_siginfo != NULL)) { 373 *child->last_siginfo = newinfo; 374 error = 0; 375 } 376 spin_unlock_irq(&child->sighand->siglock); 377 } 378 read_unlock(&tasklist_lock); 379 return error; 380 } 381 382 int ptrace_request(struct task_struct *child, long request, 383 long addr, long data) 384 { 385 int ret = -EIO; 386 387 switch (request) { 388 #ifdef PTRACE_OLDSETOPTIONS 389 case PTRACE_OLDSETOPTIONS: 390 #endif 391 case PTRACE_SETOPTIONS: 392 ret = ptrace_setoptions(child, data); 393 break; 394 case PTRACE_GETEVENTMSG: 395 ret = put_user(child->ptrace_message, (unsigned long __user *) data); 396 break; 397 case PTRACE_GETSIGINFO: 398 ret = ptrace_getsiginfo(child, (siginfo_t __user *) data); 399 break; 400 case PTRACE_SETSIGINFO: 401 ret = ptrace_setsiginfo(child, (siginfo_t __user *) data); 402 break; 403 default: 404 break; 405 } 406 407 return ret; 408 } 409