File: /usr/src/linux/arch/alpha/kernel/ptrace.c
1 /* ptrace.c */
2 /* By Ross Biro 1/23/92 */
3 /* edited by Linus Torvalds */
4 /* mangled further by Bob Manson (manson@santafe.edu) */
5 /* more mutilation by David Mosberger (davidm@azstarnet.com) */
6
7 #include <linux/kernel.h>
8 #include <linux/sched.h>
9 #include <linux/mm.h>
10 #include <linux/smp.h>
11 #include <linux/smp_lock.h>
12 #include <linux/errno.h>
13 #include <linux/ptrace.h>
14 #include <linux/user.h>
15 #include <linux/slab.h>
16
17 #include <asm/uaccess.h>
18 #include <asm/pgtable.h>
19 #include <asm/system.h>
20 #include <asm/fpu.h>
21
22 #include "proto.h"
23
24 #define DEBUG DBG_MEM
25 #undef DEBUG
26
27 #ifdef DEBUG
28 enum {
29 DBG_MEM = (1<<0),
30 DBG_BPT = (1<<1),
31 DBG_MEM_ALL = (1<<2)
32 };
33 #define DBG(fac,args) {if ((fac) & DEBUG) printk args;}
34 #else
35 #define DBG(fac,args)
36 #endif
37
38 #define BREAKINST 0x00000080 /* call_pal bpt */
39
40 /*
41 * does not yet catch signals sent when the child dies.
42 * in exit.c or in signal.c.
43 */
44
45 /*
46 * Processes always block with the following stack-layout:
47 *
48 * +================================+ <---- task + 2*PAGE_SIZE
49 * | PALcode saved frame (ps, pc, | ^
50 * | gp, a0, a1, a2) | |
51 * +================================+ | struct pt_regs
52 * | | |
53 * | frame generated by SAVE_ALL | |
54 * | | v
55 * +================================+
56 * | | ^
57 * | frame saved by do_switch_stack | | struct switch_stack
58 * | | v
59 * +================================+
60 */
61
62 /*
63 * The following table maps a register index into the stack offset at
64 * which the register is saved. Register indices are 0-31 for integer
65 * regs, 32-63 for fp regs, and 64 for the pc. Notice that sp and
66 * zero have no stack-slot and need to be treated specially (see
67 * get_reg/put_reg below).
68 */
69 enum {
70 REG_R0 = 0, REG_F0 = 32, REG_FPCR = 63, REG_PC = 64
71 };
72
73 static int regoff[] = {
74 PT_REG( r0), PT_REG( r1), PT_REG( r2), PT_REG( r3),
75 PT_REG( r4), PT_REG( r5), PT_REG( r6), PT_REG( r7),
76 PT_REG( r8), SW_REG( r9), SW_REG( r10), SW_REG( r11),
77 SW_REG( r12), SW_REG( r13), SW_REG( r14), SW_REG( r15),
78 PT_REG( r16), PT_REG( r17), PT_REG( r18), PT_REG( r19),
79 PT_REG( r20), PT_REG( r21), PT_REG( r22), PT_REG( r23),
80 PT_REG( r24), PT_REG( r25), PT_REG( r26), PT_REG( r27),
81 PT_REG( r28), PT_REG( gp), -1, -1,
82 SW_REG(fp[ 0]), SW_REG(fp[ 1]), SW_REG(fp[ 2]), SW_REG(fp[ 3]),
83 SW_REG(fp[ 4]), SW_REG(fp[ 5]), SW_REG(fp[ 6]), SW_REG(fp[ 7]),
84 SW_REG(fp[ 8]), SW_REG(fp[ 9]), SW_REG(fp[10]), SW_REG(fp[11]),
85 SW_REG(fp[12]), SW_REG(fp[13]), SW_REG(fp[14]), SW_REG(fp[15]),
86 SW_REG(fp[16]), SW_REG(fp[17]), SW_REG(fp[18]), SW_REG(fp[19]),
87 SW_REG(fp[20]), SW_REG(fp[21]), SW_REG(fp[22]), SW_REG(fp[23]),
88 SW_REG(fp[24]), SW_REG(fp[25]), SW_REG(fp[26]), SW_REG(fp[27]),
89 SW_REG(fp[28]), SW_REG(fp[29]), SW_REG(fp[30]), SW_REG(fp[31]),
90 PT_REG( pc)
91 };
92
93 static long zero;
94
95 /*
96 * Get address of register REGNO in task TASK.
97 */
98 static long *
99 get_reg_addr(struct task_struct * task, unsigned long regno)
100 {
101 long *addr;
102
103 if (regno == 30) {
104 addr = &task->thread.usp;
105 } else if (regno == 31 || regno > 64) {
106 zero = 0;
107 addr = &zero;
108 } else {
109 addr = (long *)((long)task + regoff[regno]);
110 }
111 return addr;
112 }
113
114 /*
115 * Get contents of register REGNO in task TASK.
116 */
117 static long
118 get_reg(struct task_struct * task, unsigned long regno)
119 {
120 /* Special hack for fpcr -- combine hardware and software bits. */
121 if (regno == 63) {
122 unsigned long fpcr = *get_reg_addr(task, regno);
123 unsigned long swcr = task->thread.flags & IEEE_SW_MASK;
124 swcr = swcr_update_status(swcr, fpcr);
125 return fpcr | swcr;
126 }
127 return *get_reg_addr(task, regno);
128 }
129
130 /*
131 * Write contents of register REGNO in task TASK.
132 */
133 static int
134 put_reg(struct task_struct *task, unsigned long regno, long data)
135 {
136 if (regno == 63) {
137 task->thread.flags = ((task->thread.flags & ~IEEE_SW_MASK)
138 | (data & IEEE_SW_MASK));
139 data = (data & FPCR_DYN_MASK) | ieee_swcr_to_fpcr(data);
140 }
141 *get_reg_addr(task, regno) = data;
142 return 0;
143 }
144
145 static inline int
146 read_int(struct task_struct *task, unsigned long addr, int * data)
147 {
148 int copied = access_process_vm(task, addr, data, sizeof(int), 0);
149 return (copied == sizeof(int)) ? 0 : -EIO;
150 }
151
152 static inline int
153 write_int(struct task_struct *task, unsigned long addr, int data)
154 {
155 int copied = access_process_vm(task, addr, &data, sizeof(int), 1);
156 return (copied == sizeof(int)) ? 0 : -EIO;
157 }
158
159 /*
160 * Set breakpoint.
161 */
162 int
163 ptrace_set_bpt(struct task_struct * child)
164 {
165 int displ, i, res, reg_b, nsaved = 0;
166 u32 insn, op_code;
167 unsigned long pc;
168
169 pc = get_reg(child, REG_PC);
170 res = read_int(child, pc, &insn);
171 if (res < 0)
172 return res;
173
174 op_code = insn >> 26;
175 if (op_code >= 0x30) {
176 /*
177 * It's a branch: instead of trying to figure out
178 * whether the branch will be taken or not, we'll put
179 * a breakpoint at either location. This is simpler,
180 * more reliable, and probably not a whole lot slower
181 * than the alternative approach of emulating the
182 * branch (emulation can be tricky for fp branches).
183 */
184 displ = ((s32)(insn << 11)) >> 9;
185 child->thread.bpt_addr[nsaved++] = pc + 4;
186 if (displ) /* guard against unoptimized code */
187 child->thread.bpt_addr[nsaved++] = pc + 4 + displ;
188 DBG(DBG_BPT, ("execing branch\n"));
189 } else if (op_code == 0x1a) {
190 reg_b = (insn >> 16) & 0x1f;
191 child->thread.bpt_addr[nsaved++] = get_reg(child, reg_b);
192 DBG(DBG_BPT, ("execing jump\n"));
193 } else {
194 child->thread.bpt_addr[nsaved++] = pc + 4;
195 DBG(DBG_BPT, ("execing normal insn\n"));
196 }
197
198 /* install breakpoints: */
199 for (i = 0; i < nsaved; ++i) {
200 res = read_int(child, child->thread.bpt_addr[i], &insn);
201 if (res < 0)
202 return res;
203 child->thread.bpt_insn[i] = insn;
204 DBG(DBG_BPT, (" -> next_pc=%lx\n", child->thread.bpt_addr[i]));
205 res = write_int(child, child->thread.bpt_addr[i], BREAKINST);
206 if (res < 0)
207 return res;
208 }
209 child->thread.bpt_nsaved = nsaved;
210 return 0;
211 }
212
213 /*
214 * Ensure no single-step breakpoint is pending. Returns non-zero
215 * value if child was being single-stepped.
216 */
217 int
218 ptrace_cancel_bpt(struct task_struct * child)
219 {
220 int i, nsaved = child->thread.bpt_nsaved;
221
222 child->thread.bpt_nsaved = 0;
223
224 if (nsaved > 2) {
225 printk("ptrace_cancel_bpt: bogus nsaved: %d!\n", nsaved);
226 nsaved = 2;
227 }
228
229 for (i = 0; i < nsaved; ++i) {
230 write_int(child, child->thread.bpt_addr[i],
231 child->thread.bpt_insn[i]);
232 }
233 return (nsaved != 0);
234 }
235
236 /*
237 * Called by kernel/ptrace.c when detaching..
238 *
239 * Make sure the single step bit is not set.
240 */
241 void ptrace_disable(struct task_struct *child)
242 {
243 ptrace_cancel_bpt(child);
244 }
245
246 asmlinkage long
247 sys_ptrace(long request, long pid, long addr, long data,
248 int a4, int a5, struct pt_regs regs)
249 {
250 struct task_struct *child;
251 long ret;
252
253 lock_kernel();
254 DBG(DBG_MEM, ("request=%ld pid=%ld addr=0x%lx data=0x%lx\n",
255 request, pid, addr, data));
256 ret = -EPERM;
257 if (request == PTRACE_TRACEME) {
258 /* are we already being traced? */
259 if (current->ptrace & PT_PTRACED)
260 goto out_notsk;
261 /* set the ptrace bit in the process ptrace flags. */
262 current->ptrace |= PT_PTRACED;
263 ret = 0;
264 goto out_notsk;
265 }
266 if (pid == 1) /* you may not mess with init */
267 goto out_notsk;
268 ret = -ESRCH;
269 read_lock(&tasklist_lock);
270 child = find_task_by_pid(pid);
271 if (child)
272 get_task_struct(child);
273 read_unlock(&tasklist_lock);
274 if (!child)
275 goto out_notsk;
276 if (request == PTRACE_ATTACH) {
277 ret = ptrace_attach(child);
278 goto out;
279 }
280 ret = -ESRCH;
281 if (!(child->ptrace & PT_PTRACED)) {
282 DBG(DBG_MEM, ("child not traced\n"));
283 goto out;
284 }
285 if (child->state != TASK_STOPPED) {
286 DBG(DBG_MEM, ("child process not stopped\n"));
287 if (request != PTRACE_KILL)
288 goto out;
289 }
290 if (child->p_pptr != current) {
291 DBG(DBG_MEM, ("child not parent of this process\n"));
292 goto out;
293 }
294
295 switch (request) {
296 /* When I and D space are separate, these will need to be fixed. */
297 case PTRACE_PEEKTEXT: /* read word at location addr. */
298 case PTRACE_PEEKDATA: {
299 unsigned long tmp;
300 int copied = access_process_vm(child, addr, &tmp, sizeof(tmp), 0);
301 ret = -EIO;
302 if (copied != sizeof(tmp))
303 goto out;
304
305 regs.r0 = 0; /* special return: no errors */
306 ret = tmp;
307 goto out;
308 }
309
310 /* Read register number ADDR. */
311 case PTRACE_PEEKUSR:
312 regs.r0 = 0; /* special return: no errors */
313 ret = get_reg(child, addr);
314 DBG(DBG_MEM, ("peek $%ld->%#lx\n", addr, ret));
315 goto out;
316
317 /* When I and D space are separate, this will have to be fixed. */
318 case PTRACE_POKETEXT: /* write the word at location addr. */
319 case PTRACE_POKEDATA: {
320 unsigned long tmp = data;
321 int copied = access_process_vm(child, addr, &tmp, sizeof(tmp), 1);
322 ret = (copied == sizeof(tmp)) ? 0 : -EIO;
323 goto out;
324 }
325
326 case PTRACE_POKEUSR: /* write the specified register */
327 DBG(DBG_MEM, ("poke $%ld<-%#lx\n", addr, data));
328 ret = put_reg(child, addr, data);
329 goto out;
330
331 case PTRACE_SYSCALL: /* continue and stop at next
332 (return from) syscall */
333 case PTRACE_CONT: /* restart after signal. */
334 ret = -EIO;
335 if ((unsigned long) data > _NSIG)
336 goto out;
337 if (request == PTRACE_SYSCALL)
338 child->ptrace |= PT_TRACESYS;
339 else
340 child->ptrace &= ~PT_TRACESYS;
341 child->exit_code = data;
342 wake_up_process(child);
343 /* make sure single-step breakpoint is gone. */
344 ptrace_cancel_bpt(child);
345 ret = data;
346 goto out;
347
348 /*
349 * Make the child exit. Best I can do is send it a sigkill.
350 * perhaps it should be put in the status that it wants to
351 * exit.
352 */
353 case PTRACE_KILL:
354 if (child->state != TASK_ZOMBIE) {
355 wake_up_process(child);
356 child->exit_code = SIGKILL;
357 }
358 /* make sure single-step breakpoint is gone. */
359 ptrace_cancel_bpt(child);
360 ret = 0;
361 goto out;
362
363 case PTRACE_SINGLESTEP: /* execute single instruction. */
364 ret = -EIO;
365 if ((unsigned long) data > _NSIG)
366 goto out;
367 child->thread.bpt_nsaved = -1; /* mark single-stepping */
368 child->ptrace &= ~PT_TRACESYS;
369 wake_up_process(child);
370 child->exit_code = data;
371 /* give it a chance to run. */
372 ret = 0;
373 goto out;
374
375 case PTRACE_DETACH: /* detach a process that was attached. */
376 ret = ptrace_detach(child, data);
377 goto out;
378
379 default:
380 ret = -EIO;
381 goto out;
382 }
383 out:
384 free_task_struct(child);
385 out_notsk:
386 unlock_kernel();
387 return ret;
388 }
389
390 asmlinkage void
391 syscall_trace(void)
392 {
393 if ((current->ptrace & (PT_PTRACED|PT_TRACESYS))
394 != (PT_PTRACED|PT_TRACESYS))
395 return;
396 current->exit_code = SIGTRAP;
397 current->state = TASK_STOPPED;
398 notify_parent(current, SIGCHLD);
399 schedule();
400 /*
401 * This isn't the same as continuing with a signal, but it will do
402 * for normal use. strace only continues with a signal if the
403 * stopping signal is not SIGTRAP. -brl
404 */
405 if (current->exit_code) {
406 send_sig(current->exit_code, current, 1);
407 current->exit_code = 0;
408 }
409 }
410