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
28enum {
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 */
69enum {
70	REG_R0 = 0, REG_F0 = 32, REG_FPCR = 63, REG_PC = 64
71};
72
73static 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
93static long zero;
94
95/*
96 * Get address of register REGNO in task TASK.
97 */
98static long *
99get_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 */
117static long
118get_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 */
133static int
134put_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
145static inline int
146read_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
152static inline int
153write_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 */
162int
163ptrace_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 */
217int
218ptrace_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 */
241void ptrace_disable(struct task_struct *child)
242{
243	ptrace_cancel_bpt(child);
244}
245
246asmlinkage long
247sys_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
390asmlinkage void
391syscall_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