aboutsummaryrefslogtreecommitdiff
path: root/arch/ppc64/kernel/kprobes.c
blob: 8c0920a6d03e277d36c8f3d2767db8f363eb6e4e (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
/*
 *  Kernel Probes (KProbes)
 *  arch/ppc64/kernel/kprobes.c
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 * Copyright (C) IBM Corporation, 2002, 2004
 *
 * 2002-Oct	Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
 *		Probes initial implementation ( includes contributions from
 *		Rusty Russell).
 * 2004-July	Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
 *		interface to access function arguments.
 * 2004-Nov	Ananth N Mavinakayanahalli <ananth@in.ibm.com> kprobes port
 *		for PPC64
 */

#include <linux/config.h>
#include <linux/kprobes.h>
#include <linux/ptrace.h>
#include <linux/spinlock.h>
#include <linux/preempt.h>
#include <asm/cacheflush.h>
#include <asm/kdebug.h>
#include <asm/sstep.h>

/* kprobe_status settings */
#define KPROBE_HIT_ACTIVE	0x00000001
#define KPROBE_HIT_SS		0x00000002

static struct kprobe *current_kprobe;
static unsigned long kprobe_status, kprobe_saved_msr;
static struct pt_regs jprobe_saved_regs;

int arch_prepare_kprobe(struct kprobe *p)
{
	int ret = 0;
	kprobe_opcode_t insn = *p->addr;

	if ((unsigned long)p->addr & 0x03) {
		printk("Attempt to register kprobe at an unaligned address\n");
		ret = -EINVAL;
	} else if (IS_MTMSRD(insn) || IS_RFID(insn)) {
		printk("Cannot register a kprobe on rfid or mtmsrd\n");
		ret = -EINVAL;
	}
	return ret;
}

void arch_copy_kprobe(struct kprobe *p)
{
	memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
	p->opcode = *p->addr;
}

void arch_arm_kprobe(struct kprobe *p)
{
	*p->addr = BREAKPOINT_INSTRUCTION;
	flush_icache_range((unsigned long) p->addr,
			   (unsigned long) p->addr + sizeof(kprobe_opcode_t));
}

void arch_disarm_kprobe(struct kprobe *p)
{
	*p->addr = p->opcode;
	flush_icache_range((unsigned long) p->addr,
			   (unsigned long) p->addr + sizeof(kprobe_opcode_t));
}

void arch_remove_kprobe(struct kprobe *p)
{
}

static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
{
	regs->msr |= MSR_SE;
	/*single step inline if it a breakpoint instruction*/
	if (p->opcode == BREAKPOINT_INSTRUCTION)
		regs->nip = (unsigned long)p->addr;
	else
		regs->nip = (unsigned long)&p->ainsn.insn;
}

static inline int kprobe_handler(struct pt_regs *regs)
{
	struct kprobe *p;
	int ret = 0;
	unsigned int *addr = (unsigned int *)regs->nip;

	/* Check we're not actually recursing */
	if (kprobe_running()) {
		/* We *are* holding lock here, so this is safe.
		   Disarm the probe we just hit, and ignore it. */
		p = get_kprobe(addr);
		if (p) {
			if (kprobe_status == KPROBE_HIT_SS) {
				regs->msr &= ~MSR_SE;
				regs->msr |= kprobe_saved_msr;
				unlock_kprobes();
				goto no_kprobe;
			}
			arch_disarm_kprobe(p);
			regs->nip = (unsigned long)p->addr;
			ret = 1;
		} else {
			p = current_kprobe;
			if (p->break_handler && p->break_handler(p, regs)) {
				goto ss_probe;
			}
		}
		/* If it's not ours, can't be delete race, (we hold lock). */
		goto no_kprobe;
	}

	lock_kprobes();
	p = get_kprobe(addr);
	if (!p) {
		unlock_kprobes();
		if (*addr != BREAKPOINT_INSTRUCTION) {
			/*
			 * PowerPC has multiple variants of the "trap"
			 * instruction. If the current instruction is a
			 * trap variant, it could belong to someone else
			 */
			kprobe_opcode_t cur_insn = *addr;
			if (IS_TW(cur_insn) || IS_TD(cur_insn) ||
					IS_TWI(cur_insn) || IS_TDI(cur_insn))
		       		goto no_kprobe;
			/*
			 * The breakpoint instruction was removed right
			 * after we hit it.  Another cpu has removed
			 * either a probepoint or a debugger breakpoint
			 * at this address.  In either case, no further
			 * handling of this interrupt is appropriate.
			 */
			ret = 1;
		}
		/* Not one of ours: let kernel handle it */
		goto no_kprobe;
	}

	kprobe_status = KPROBE_HIT_ACTIVE;
	current_kprobe = p;
	kprobe_saved_msr = regs->msr;
	if (p->pre_handler && p->pre_handler(p, regs))
		/* handler has already set things up, so skip ss setup */
		return 1;

ss_probe:
	prepare_singlestep(p, regs);
	kprobe_status = KPROBE_HIT_SS;
	/*
	 * This preempt_disable() matches the preempt_enable_no_resched()
	 * in post_kprobe_handler().
	 */
	preempt_disable();
	return 1;

no_kprobe:
	return ret;
}

/*
 * Called after single-stepping.  p->addr is the address of the
 * instruction whose first byte has been replaced by the "breakpoint"
 * instruction.  To avoid the SMP problems that can occur when we
 * temporarily put back the original opcode to single-step, we
 * single-stepped a copy of the instruction.  The address of this
 * copy is p->ainsn.insn.
 */
static void resume_execution(struct kprobe *p, struct pt_regs *regs)
{
	int ret;

	regs->nip = (unsigned long)p->addr;
	ret = emulate_step(regs, p->ainsn.insn[0]);
	if (ret == 0)
		regs->nip = (unsigned long)p->addr + 4;
}

static inline int post_kprobe_handler(struct pt_regs *regs)
{
	if (!kprobe_running())
		return 0;

	if (current_kprobe->post_handler)
		current_kprobe->post_handler(current_kprobe, regs, 0);

	resume_execution(current_kprobe, regs);
	regs->msr |= kprobe_saved_msr;

	unlock_kprobes();
	preempt_enable_no_resched();

	/*
	 * if somebody else is singlestepping across a probe point, msr
	 * will have SE set, in which case, continue the remaining processing
	 * of do_debug, as if this is not a probe hit.
	 */
	if (regs->msr & MSR_SE)
		return 0;

	return 1;
}

/* Interrupts disabled, kprobe_lock held. */
static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
{
	if (current_kprobe->fault_handler
	    && current_kprobe->fault_handler(current_kprobe, regs, trapnr))
		return 1;

	if (kprobe_status & KPROBE_HIT_SS) {
		resume_execution(current_kprobe, regs);
		regs->msr &= ~MSR_SE;
		regs->msr |= kprobe_saved_msr;

		unlock_kprobes();
		preempt_enable_no_resched();
	}
	return 0;
}

/*
 * Wrapper routine to for handling exceptions.
 */
int kprobe_exceptions_notify(struct notifier_block *self, unsigned long val,
			     void *data)
{
	struct die_args *args = (struct die_args *)data;
	int ret = NOTIFY_DONE;

	/*
	 * Interrupts are not disabled here.  We need to disable
	 * preemption, because kprobe_running() uses smp_processor_id().
	 */
	preempt_disable();
	switch (val) {
	case DIE_BPT:
		if (kprobe_handler(args->regs))
			ret = NOTIFY_STOP;
		break;
	case DIE_SSTEP:
		if (post_kprobe_handler(args->regs))
			ret = NOTIFY_STOP;
		break;
	case DIE_GPF:
	case DIE_PAGE_FAULT:
		if (kprobe_running() &&
		    kprobe_fault_handler(args->regs, args->trapnr))
			ret = NOTIFY_STOP;
		break;
	default:
		break;
	}
	preempt_enable();
	return ret;
}

int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
{
	struct jprobe *jp = container_of(p, struct jprobe, kp);

	memcpy(&jprobe_saved_regs, regs, sizeof(struct pt_regs));

	/* setup return addr to the jprobe handler routine */
	regs->nip = (unsigned long)(((func_descr_t *)jp->entry)->entry);
	regs->gpr[2] = (unsigned long)(((func_descr_t *)jp->entry)->toc);

	return 1;
}

void jprobe_return(void)
{
	asm volatile("trap" ::: "memory");
}

void jprobe_return_end(void)
{
};

int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
{
	/*
	 * FIXME - we should ideally be validating that we got here 'cos
	 * of the "trap" in jprobe_return() above, before restoring the
	 * saved regs...
	 */
	memcpy(regs, &jprobe_saved_regs, sizeof(struct pt_regs));
	return 1;
}