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*/
1 /* ptrace.c */
2 /* By Ross Biro 1/23/92 */
3 /* edited by Linus Torvalds */
4
5 #include <linux/head.h>
6 #include <linux/kernel.h>
7 #include <linux/sched.h>
8 #include <linux/mm.h>
9 #include <linux/errno.h>
10 #include <linux/ptrace.h>
11
12 #include <asm/segment.h>
13 #include <asm/system.h>
14
15 /*
16 * does not yet catch signals sent when the child dies.
17 * in exit.c or in signal.c.
18 */
19
20 /* determines which flags the user has access to. */
21 /* 1 = access 0 = no access */
22 #define FLAG_MASK 0x00044dd5
23
24 /* set's the trap flag. */
25 #define TRAP_FLAG 0x100
26
27 /*
28 * this is the number to subtract from the top of the stack. To find
29 * the local frame.
30 */
31 #define MAGICNUMBER 68
32
33 /* change a pid into a task struct. */
34 static inline struct task_struct * get_task(int pid)
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*/
35 {
36 int i;
37
38 for (i = 1; i < NR_TASKS; i++) {
39 if (task[i] != NULL && (task[i]->pid == pid))
40 return task[i];
41 }
42 return NULL;
43 }
44
45 /*
46 * this routine will get a word off of the processes priviledged stack.
47 * the offset is how far from the base addr as stored in the TSS.
48 * this routine assumes that all the priviledged stacks are in our
49 * data space.
50 */
51 static inline int get_stack_long(struct task_struct *task, int offset)
/* ![[previous]](../icons/left.png)
*/
52 {
53 unsigned char *stack;
54
55 stack = (unsigned char *)task->tss.esp0;
56 stack += offset;
57 return (*((int *)stack));
58 }
59
60 /*
61 * this routine will put a word on the processes priviledged stack.
62 * the offset is how far from the base addr as stored in the TSS.
63 * this routine assumes that all the priviledged stacks are in our
64 * data space.
65 */
66 static inline int put_stack_long(struct task_struct *task, int offset,
/* */
67 unsigned long data)
68 {
69 unsigned char * stack;
70
71 stack = (unsigned char *) task->tss.esp0;
72 stack += offset;
73 *(unsigned long *) stack = data;
74 return 0;
75 }
76
77 /*
78 * This routine gets a long from any process space by following the page
79 * tables. NOTE! You should check that the long isn't on a page boundary,
80 * and that it is in the task area before calling this: this routine does
81 * no checking.
82 *
83 * NOTE2! This uses "tsk->tss.cr3" even though we know it's currently always
84 * zero. This routine shouldn't have to change when we make a better mm.
85 */
86 static unsigned long get_long(struct task_struct * tsk,
/* */
87 unsigned long addr)
88 {
89 unsigned long page;
90
91 repeat:
92 page = *PAGE_DIR_OFFSET(tsk->tss.cr3,addr);
93 if (page & PAGE_PRESENT) {
94 page &= PAGE_MASK;
95 page += PAGE_PTR(addr);
96 page = *((unsigned long *) page);
97 }
98 if (!(page & PAGE_PRESENT)) {
99 do_no_page(0,addr,tsk,0);
100 goto repeat;
101 }
102 page &= PAGE_MASK;
103 page += addr & ~PAGE_MASK;
104 return *(unsigned long *) page;
105 }
106
107 /*
108 * This routine puts a long into any process space by following the page
109 * tables. NOTE! You should check that the long isn't on a page boundary,
110 * and that it is in the task area before calling this: this routine does
111 * no checking.
112 */
113 static void put_long(struct task_struct * tsk, unsigned long addr,
/* */
114 unsigned long data)
115 {
116 unsigned long page, pte;
117
118 repeat:
119 page = *PAGE_DIR_OFFSET(tsk->tss.cr3,addr);
120 if (page & PAGE_PRESENT) {
121 page &= PAGE_MASK;
122 page += PAGE_PTR(addr);
123 pte = page;
124 page = *((unsigned long *) page);
125 }
126 if (!(page & PAGE_PRESENT)) {
127 do_no_page(PAGE_RW,addr,tsk,0);
128 goto repeat;
129 }
130 if (!(page & PAGE_RW)) {
131 do_wp_page(PAGE_RW | PAGE_PRESENT,addr,tsk,0);
132 goto repeat;
133 }
134 /* we're bypassing pagetables, so we have to set the dirty bit ourselves */
135 *(unsigned long *) pte |= (PAGE_DIRTY|PAGE_COW);
136 page &= PAGE_MASK;
137 page += addr & ~PAGE_MASK;
138 *(unsigned long *) page = data;
139 }
140
141 /*
142 * This routine checks the page boundaries, and that the offset is
143 * within the task area. It then calls get_long() to read a long.
144 */
145 static int read_long(struct task_struct * tsk, unsigned long addr,
/* */
146 unsigned long * result)
147 {
148 unsigned long low,high;
149
150 if (addr > TASK_SIZE-sizeof(long))
151 return -EIO;
152 if ((addr & ~PAGE_MASK) > PAGE_SIZE-sizeof(long)) {
153 low = get_long(tsk,addr & ~(sizeof(long)-1));
154 high = get_long(tsk,(addr+sizeof(long)) & ~(sizeof(long)-1));
155 switch (addr & (sizeof(long)-1)) {
156 case 1:
157 low >>= 8;
158 low |= high << 24;
159 break;
160 case 2:
161 low >>= 16;
162 low |= high << 16;
163 break;
164 case 3:
165 low >>= 24;
166 low |= high << 8;
167 break;
168 }
169 *result = low;
170 } else
171 *result = get_long(tsk,addr);
172 return 0;
173 }
174
175 /*
176 * This routine checks the page boundaries, and that the offset is
177 * within the task area. It then calls put_long() to write a long.
178 */
179 static int write_long(struct task_struct * tsk, unsigned long addr,
/* */
180 unsigned long data)
181 {
182 unsigned long low,high;
183
184 if (addr > TASK_SIZE-sizeof(long))
185 return -EIO;
186 if ((addr & ~PAGE_MASK) > PAGE_SIZE-sizeof(long)) {
187 low = get_long(tsk,addr & ~(sizeof(long)-1));
188 high = get_long(tsk,(addr+sizeof(long)) & ~(sizeof(long)-1));
189 switch (addr & (sizeof(long)-1)) {
190 case 0: /* shouldn't happen, but safety first */
191 low = data;
192 break;
193 case 1:
194 low &= 0x000000ff;
195 low |= data << 8;
196 high &= ~0xff;
197 high |= data >> 24;
198 break;
199 case 2:
200 low &= 0x0000ffff;
201 low |= data << 16;
202 high &= ~0xffff;
203 high |= data >> 16;
204 break;
205 case 3:
206 low &= 0x00ffffff;
207 low |= data << 24;
208 high &= ~0xffffff;
209 high |= data >> 8;
210 break;
211 }
212 put_long(tsk,addr & ~(sizeof(long)-1),low);
213 put_long(tsk,(addr+sizeof(long)) & ~(sizeof(long)-1),high);
214 } else
215 put_long(tsk,addr,data);
216 return 0;
217 }
218
219 asmlinkage int sys_ptrace(long request, long pid, long addr, long data)
/* */
220 {
221 struct task_struct *child;
222
223 if (request == PTRACE_TRACEME) {
224 /* are we already being traced? */
225 if (current->flags & PF_PTRACED)
226 return -EPERM;
227 /* set the ptrace bit in the proccess flags. */
228 current->flags |= PF_PTRACED;
229 return 0;
230 }
231 if (pid == 1) /* you may not mess with init */
232 return -EPERM;
233 if (!(child = get_task(pid)))
234 return -ESRCH;
235 if (request == PTRACE_ATTACH) {
236 if (child == current)
237 return -EPERM;
238 if ((!child->dumpable || (current->uid != child->euid) ||
239 (current->gid != child->egid)) && !suser())
240 return -EPERM;
241 /* the same process cannot be attached many times */
242 if (child->flags & PF_PTRACED)
243 return -EPERM;
244 child->flags |= PF_PTRACED;
245 if (child->p_pptr != current) {
246 REMOVE_LINKS(child);
247 child->p_pptr = current;
248 SET_LINKS(child);
249 }
250 send_sig(SIGSTOP, child, 1);
251 return 0;
252 }
253 if (!(child->flags & PF_PTRACED))
254 return -ESRCH;
255 if (child->state != TASK_STOPPED && request != PTRACE_DETACH)
256 return -ESRCH;
257 if (child->p_pptr != current)
258 return -ESRCH;
259
260 switch (request) {
261 /* when I and D space are seperate, these will need to be fixed. */
262 case PTRACE_PEEKTEXT: /* read word at location addr. */
263 case PTRACE_PEEKDATA: {
264 unsigned long tmp;
265 int res;
266
267 res = read_long(child, addr, &tmp);
268 if (res < 0)
269 return res;
270 res = verify_area(VERIFY_WRITE, (void *) data, sizeof(long));
271 if (!res)
272 put_fs_long(tmp,(unsigned long *) data);
273 return res;
274 }
275
276 /* read the word at location addr in the USER area. */
277 case PTRACE_PEEKUSR: {
278 unsigned long tmp;
279 int res;
280
281 addr = addr >> 2; /* temporary hack. */
282 if (addr < 0 || addr >= 17)
283 return -EIO;
284 res = verify_area(VERIFY_WRITE, (void *) data, sizeof(long));
285 if (res)
286 return res;
287 tmp = get_stack_long(child, sizeof(long)*addr - MAGICNUMBER);
288 if (addr == DS || addr == ES ||
289 addr == FS || addr == GS ||
290 addr == CS || addr == SS)
291 tmp &= 0xffff;
292 put_fs_long(tmp,(unsigned long *) data);
293 return 0;
294 }
295
296 /* when I and D space are seperate, this will have to be fixed. */
297 case PTRACE_POKETEXT: /* write the word at location addr. */
298 case PTRACE_POKEDATA:
299 return write_long(child,addr,data);
300
301 case PTRACE_POKEUSR: /* write the word at location addr in the USER area */
302 addr = addr >> 2; /* temproary hack. */
303 if (addr < 0 || addr >= 17)
304 return -EIO;
305 if (addr == ORIG_EAX)
306 return -EIO;
307 if (addr == DS || addr == ES ||
308 addr == FS || addr == GS ||
309 addr == CS || addr == SS) {
310 data &= 0xffff;
311 if (data && (data & 3) != 3)
312 return -EIO;
313 }
314 if (addr == EFL) { /* flags. */
315 data &= FLAG_MASK;
316 data |= get_stack_long(child, EFL*sizeof(long)-MAGICNUMBER) & ~FLAG_MASK;
317 }
318 if (put_stack_long(child, sizeof(long)*addr-MAGICNUMBER, data))
319 return -EIO;
320 return 0;
321
322 case PTRACE_SYSCALL: /* continue and stop at next (return from) syscall */
323 case PTRACE_CONT: { /* restart after signal. */
324 long tmp;
325
326 if ((unsigned long) data > NSIG)
327 return -EIO;
328 if (request == PTRACE_SYSCALL)
329 child->flags |= PF_TRACESYS;
330 else
331 child->flags &= ~PF_TRACESYS;
332 child->exit_code = data;
333 child->state = TASK_RUNNING;
334 /* make sure the single step bit is not set. */
335 tmp = get_stack_long(child, sizeof(long)*EFL-MAGICNUMBER) & ~TRAP_FLAG;
336 put_stack_long(child, sizeof(long)*EFL-MAGICNUMBER,tmp);
337 return 0;
338 }
339
340 /*
341 * make the child exit. Best I can do is send it a sigkill.
342 * perhaps it should be put in the status that it want's to
343 * exit.
344 */
345 case PTRACE_KILL: {
346 long tmp;
347
348 child->state = TASK_RUNNING;
349 child->exit_code = SIGKILL;
350 /* make sure the single step bit is not set. */
351 tmp = get_stack_long(child, sizeof(long)*EFL-MAGICNUMBER) & ~TRAP_FLAG;
352 put_stack_long(child, sizeof(long)*EFL-MAGICNUMBER,tmp);
353 return 0;
354 }
355
356 case PTRACE_SINGLESTEP: { /* set the trap flag. */
357 long tmp;
358
359 if ((unsigned long) data > NSIG)
360 return -EIO;
361 child->flags &= ~PF_TRACESYS;
362 tmp = get_stack_long(child, sizeof(long)*EFL-MAGICNUMBER) | TRAP_FLAG;
363 put_stack_long(child, sizeof(long)*EFL-MAGICNUMBER,tmp);
364 child->state = TASK_RUNNING;
365 child->exit_code = data;
366 /* give it a chance to run. */
367 return 0;
368 }
369
370 case PTRACE_DETACH: { /* detach a process that was attached. */
371 long tmp;
372
373 if ((unsigned long) data > NSIG)
374 return -EIO;
375 child->flags &= ~(PF_PTRACED|PF_TRACESYS);
376 child->state = TASK_RUNNING;
377 child->exit_code = data;
378 REMOVE_LINKS(child);
379 child->p_pptr = child->p_opptr;
380 SET_LINKS(child);
381 /* make sure the single step bit is not set. */
382 tmp = get_stack_long(child, sizeof(long)*EFL-MAGICNUMBER) & ~TRAP_FLAG;
383 put_stack_long(child, sizeof(long)*EFL-MAGICNUMBER,tmp);
384 return 0;
385 }
386
387 default:
388 return -EIO;
389 }
390 }
391
392 asmlinkage void syscall_trace(void)
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*/
393 {
394 if ((current->flags & (PF_PTRACED|PF_TRACESYS))
395 != (PF_PTRACED|PF_TRACESYS))
396 return;
397 current->exit_code = SIGTRAP;
398 current->state = TASK_STOPPED;
399 notify_parent(current);
400 schedule();
401 /*
402 * this isn't the same as continuing with a signal, but it will do
403 * for normal use. strace only continues with a signal if the
404 * stopping signal is not SIGTRAP. -brl
405 */
406 if (current->exit_code)
407 current->signal |= (1 << (current->exit_code - 1));
408 current->exit_code = 0;
409 }
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*/