summaryrefslogtreecommitdiffstats
path: root/arch/avr32/kernel/ptrace.c
blob: 41a14e96a1dbafd81ac3eca17ef40509acff9d62 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
/*
 * Copyright (C) 2004-2006 Atmel Corporation
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#undef DEBUG
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/sched/task_stack.h>
#include <linux/mm.h>
#include <linux/ptrace.h>
#include <linux/errno.h>
#include <linux/user.h>
#include <linux/security.h>
#include <linux/unistd.h>
#include <linux/notifier.h>

#include <asm/traps.h>
#include <linux/uaccess.h>
#include <asm/ocd.h>
#include <asm/mmu_context.h>
#include <linux/kdebug.h>

static struct pt_regs *get_user_regs(struct task_struct *tsk)
{
	return (struct pt_regs *)((unsigned long)task_stack_page(tsk) +
				  THREAD_SIZE - sizeof(struct pt_regs));
}

void user_enable_single_step(struct task_struct *tsk)
{
	pr_debug("user_enable_single_step: pid=%u, PC=0x%08lx, SR=0x%08lx\n",
		 tsk->pid, task_pt_regs(tsk)->pc, task_pt_regs(tsk)->sr);

	/*
	 * We can't schedule in Debug mode, so when TIF_BREAKPOINT is
	 * set, the system call or exception handler will do a
	 * breakpoint to enter monitor mode before returning to
	 * userspace.
	 *
	 * The monitor code will then notice that TIF_SINGLE_STEP is
	 * set and return to userspace with single stepping enabled.
	 * The CPU will then enter monitor mode again after exactly
	 * one instruction has been executed, and the monitor code
	 * will then send a SIGTRAP to the process.
	 */
	set_tsk_thread_flag(tsk, TIF_BREAKPOINT);
	set_tsk_thread_flag(tsk, TIF_SINGLE_STEP);
}

void user_disable_single_step(struct task_struct *child)
{
	/* XXX(hch): a no-op here seems wrong.. */
}

/*
 * Called by kernel/ptrace.c when detaching
 *
 * Make sure any single step bits, etc. are not set
 */
void ptrace_disable(struct task_struct *child)
{
	clear_tsk_thread_flag(child, TIF_SINGLE_STEP);
	clear_tsk_thread_flag(child, TIF_BREAKPOINT);
	ocd_disable(child);
}

/*
 * Read the word at offset "offset" into the task's "struct user". We
 * actually access the pt_regs struct stored on the kernel stack.
 */
static int ptrace_read_user(struct task_struct *tsk, unsigned long offset,
			    unsigned long __user *data)
{
	unsigned long *regs;
	unsigned long value;

	if (offset & 3 || offset >= sizeof(struct user)) {
		printk("ptrace_read_user: invalid offset 0x%08lx\n", offset);
		return -EIO;
	}

	regs = (unsigned long *)get_user_regs(tsk);

	value = 0;
	if (offset < sizeof(struct pt_regs))
		value = regs[offset / sizeof(regs[0])];

	pr_debug("ptrace_read_user(%s[%u], %#lx, %p) -> %#lx\n",
		 tsk->comm, tsk->pid, offset, data, value);

	return put_user(value, data);
}

/*
 * Write the word "value" to offset "offset" into the task's "struct
 * user". We actually access the pt_regs struct stored on the kernel
 * stack.
 */
static int ptrace_write_user(struct task_struct *tsk, unsigned long offset,
			     unsigned long value)
{
	unsigned long *regs;

	pr_debug("ptrace_write_user(%s[%u], %#lx, %#lx)\n",
			tsk->comm, tsk->pid, offset, value);

	if (offset & 3 || offset >= sizeof(struct user)) {
		pr_debug("  invalid offset 0x%08lx\n", offset);
		return -EIO;
	}

	if (offset >= sizeof(struct pt_regs))
		return 0;

	regs = (unsigned long *)get_user_regs(tsk);
	regs[offset / sizeof(regs[0])] = value;

	return 0;
}

static int ptrace_getregs(struct task_struct *tsk, void __user *uregs)
{
	struct pt_regs *regs = get_user_regs(tsk);

	return copy_to_user(uregs, regs, sizeof(*regs)) ? -EFAULT : 0;
}

static int ptrace_setregs(struct task_struct *tsk, const void __user *uregs)
{
	struct pt_regs newregs;
	int ret;

	ret = -EFAULT;
	if (copy_from_user(&newregs, uregs, sizeof(newregs)) == 0) {
		struct pt_regs *regs = get_user_regs(tsk);

		ret = -EINVAL;
		if (valid_user_regs(&newregs)) {
			*regs = newregs;
			ret = 0;
		}
	}

	return ret;
}

long arch_ptrace(struct task_struct *child, long request,
		 unsigned long addr, unsigned long data)
{
	int ret;
	void __user *datap = (void __user *) data;

	switch (request) {
	/* Read the word at location addr in the child process */
	case PTRACE_PEEKTEXT:
	case PTRACE_PEEKDATA:
		ret = generic_ptrace_peekdata(child, addr, data);
		break;

	case PTRACE_PEEKUSR:
		ret = ptrace_read_user(child, addr, datap);
		break;

	/* Write the word in data at location addr */
	case PTRACE_POKETEXT:
	case PTRACE_POKEDATA:
		ret = generic_ptrace_pokedata(child, addr, data);
		break;

	case PTRACE_POKEUSR:
		ret = ptrace_write_user(child, addr, data);
		break;

	case PTRACE_GETREGS:
		ret = ptrace_getregs(child, datap);
		break;

	case PTRACE_SETREGS:
		ret = ptrace_setregs(child, datap);
		break;

	default:
		ret = ptrace_request(child, request, addr, data);
		break;
	}

	return ret;
}

asmlinkage void syscall_trace(void)
{
	if (!test_thread_flag(TIF_SYSCALL_TRACE))
		return;
	if (!(current->ptrace & PT_PTRACED))
		return;

	/* The 0x80 provides a way for the tracing parent to
	 * distinguish between a syscall stop and SIGTRAP delivery */
	ptrace_notify(SIGTRAP | ((current->ptrace & PT_TRACESYSGOOD)
				 ? 0x80 : 0));

	/*
	 * this isn't the same as continuing with a signal, but it
	 * will do for normal use.  strace only continues with a
	 * signal if the stopping signal is not SIGTRAP.  -brl
	 */
	if (current->exit_code) {
		pr_debug("syscall_trace: sending signal %d to PID %u\n",
			 current->exit_code, current->pid);
		send_sig(current->exit_code, current, 1);
		current->exit_code = 0;
	}
}

/*
 * debug_trampoline() is an assembly stub which will store all user
 * registers on the stack and execute a breakpoint instruction.
 *
 * If we single-step into an exception handler which runs with
 * interrupts disabled the whole time so it doesn't have to check for
 * pending work, its return address will be modified so that it ends
 * up returning to debug_trampoline.
 *
 * If the exception handler decides to store the user context and
 * enable interrupts after all, it will restore the original return
 * address and status register value. Before it returns, it will
 * notice that TIF_BREAKPOINT is set and execute a breakpoint
 * instruction.
 */
extern void debug_trampoline(void);

asmlinkage struct pt_regs *do_debug(struct pt_regs *regs)
{
	struct thread_info	*ti;
	unsigned long		trampoline_addr;
	u32			status;
	u32			ctrl;
	int			code;

	status = ocd_read(DS);
	ti = current_thread_info();
	code = TRAP_BRKPT;

	pr_debug("do_debug: status=0x%08x PC=0x%08lx SR=0x%08lx tif=0x%08lx\n",
			status, regs->pc, regs->sr, ti->flags);

	if (!user_mode(regs)) {
		unsigned long	die_val = DIE_BREAKPOINT;

		if (status & (1 << OCD_DS_SSS_BIT))
			die_val = DIE_SSTEP;

		if (notify_die(die_val, "ptrace", regs, 0, 0, SIGTRAP)
				== NOTIFY_STOP)
			return regs;

		if ((status & (1 << OCD_DS_SWB_BIT))
				&& test_and_clear_ti_thread_flag(
					ti, TIF_BREAKPOINT)) {
			/*
			 * Explicit breakpoint from trampoline or
			 * exception/syscall/interrupt handler.
			 *
			 * The real saved regs are on the stack right
			 * after the ones we saved on entry.
			 */
			regs++;
			pr_debug("  -> TIF_BREAKPOINT done, adjusted regs:"
					"PC=0x%08lx SR=0x%08lx\n",
					regs->pc, regs->sr);
			BUG_ON(!user_mode(regs));

			if (test_thread_flag(TIF_SINGLE_STEP)) {
				pr_debug("Going to do single step...\n");
				return regs;
			}

			/*
			 * No TIF_SINGLE_STEP means we're done
			 * stepping over a syscall. Do the trap now.
			 */
			code = TRAP_TRACE;
		} else if ((status & (1 << OCD_DS_SSS_BIT))
				&& test_ti_thread_flag(ti, TIF_SINGLE_STEP)) {

			pr_debug("Stepped into something, "
					"setting TIF_BREAKPOINT...\n");
			set_ti_thread_flag(ti, TIF_BREAKPOINT);

			/*
			 * We stepped into an exception, interrupt or
			 * syscall handler. Some exception handlers
			 * don't check for pending work, so we need to
			 * set up a trampoline just in case.
			 *
			 * The exception entry code will undo the
			 * trampoline stuff if it does a full context
			 * save (which also means that it'll check for
			 * pending work later.)
			 */
			if ((regs->sr & MODE_MASK) == MODE_EXCEPTION) {
				trampoline_addr
					= (unsigned long)&debug_trampoline;

				pr_debug("Setting up trampoline...\n");
				ti->rar_saved = sysreg_read(RAR_EX);
				ti->rsr_saved = sysreg_read(RSR_EX);
				sysreg_write(RAR_EX, trampoline_addr);
				sysreg_write(RSR_EX, (MODE_EXCEPTION
							| SR_EM | SR_GM));
				BUG_ON(ti->rsr_saved & MODE_MASK);
			}

			/*
			 * If we stepped into a system call, we
			 * shouldn't do a single step after we return
			 * since the return address is right after the
			 * "scall" instruction we were told to step
			 * over.
			 */
			if ((regs->sr & MODE_MASK) == MODE_SUPERVISOR) {
				pr_debug("Supervisor; no single step\n");
				clear_ti_thread_flag(ti, TIF_SINGLE_STEP);
			}

			ctrl = ocd_read(DC);
			ctrl &= ~(1 << OCD_DC_SS_BIT);
			ocd_write(DC, ctrl);

			return regs;
		} else {
			printk(KERN_ERR "Unexpected OCD_DS value: 0x%08x\n",
					status);
			printk(KERN_ERR "Thread flags: 0x%08lx\n", ti->flags);
			die("Unhandled debug trap in kernel mode",
					regs, SIGTRAP);
		}
	} else if (status & (1 << OCD_DS_SSS_BIT)) {
		/* Single step in user mode */
		code = TRAP_TRACE;

		ctrl = ocd_read(DC);
		ctrl &= ~(1 << OCD_DC_SS_BIT);
		ocd_write(DC, ctrl);
	}

	pr_debug("Sending SIGTRAP: code=%d PC=0x%08lx SR=0x%08lx\n",
			code, regs->pc, regs->sr);

	clear_thread_flag(TIF_SINGLE_STEP);
	_exception(SIGTRAP, regs, code, instruction_pointer(regs));

	return regs;
}
OpenPOWER on IntegriCloud