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1/*
2 * This program is free software; you can redistribute it and/or modify
3 * it under the terms of the GNU General Public License as published by
4 * the Free Software Foundation; either version 2 of the License, or
5 * (at your option) any later version.
6 *
7 * This program is distributed in the hope that it will be useful,
8 * but WITHOUT ANY WARRANTY; without even the implied warranty of
9 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
10 * GNU General Public License for more details.
11 *
12 * You should have received a copy of the GNU General Public License
13 * along with this program; if not, write to the Free Software
14 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
15 *
16 * Copyright (C) 2007 Alan Stern
17 * Copyright (C) 2009 IBM Corporation
18 * Copyright (C) 2009 Frederic Weisbecker <fweisbec@gmail.com>
19 *
20 * Authors: Alan Stern <stern@rowland.harvard.edu>
21 * K.Prasad <prasad@linux.vnet.ibm.com>
22 * Frederic Weisbecker <fweisbec@gmail.com>
23 */
24
25/*
26 * HW_breakpoint: a unified kernel/user-space hardware breakpoint facility,
27 * using the CPU's debug registers.
28 */
29
30#include <linux/perf_event.h>
31#include <linux/hw_breakpoint.h>
32#include <linux/irqflags.h>
33#include <linux/notifier.h>
34#include <linux/kallsyms.h>
35#include <linux/kprobes.h>
36#include <linux/percpu.h>
37#include <linux/kdebug.h>
38#include <linux/kernel.h>
39#include <linux/module.h>
40#include <linux/sched.h>
41#include <linux/init.h>
42#include <linux/smp.h>
43
44#include <asm/hw_breakpoint.h>
45#include <asm/processor.h>
46#include <asm/debugreg.h>
47
48/* Per cpu debug control register value */
49DEFINE_PER_CPU(unsigned long, cpu_dr7);
50EXPORT_PER_CPU_SYMBOL(cpu_dr7);
51
52/* Per cpu debug address registers values */
53static DEFINE_PER_CPU(unsigned long, cpu_debugreg[HBP_NUM]);
54
55/*
56 * Stores the breakpoints currently in use on each breakpoint address
57 * register for each cpus
58 */
59static DEFINE_PER_CPU(struct perf_event *, bp_per_reg[HBP_NUM]);
60
61
62static inline unsigned long
63__encode_dr7(int drnum, unsigned int len, unsigned int type)
64{
65 unsigned long bp_info;
66
67 bp_info = (len | type) & 0xf;
68 bp_info <<= (DR_CONTROL_SHIFT + drnum * DR_CONTROL_SIZE);
69 bp_info |= (DR_GLOBAL_ENABLE << (drnum * DR_ENABLE_SIZE));
70
71 return bp_info;
72}
73
74/*
75 * Encode the length, type, Exact, and Enable bits for a particular breakpoint
76 * as stored in debug register 7.
77 */
78unsigned long encode_dr7(int drnum, unsigned int len, unsigned int type)
79{
80 return __encode_dr7(drnum, len, type) | DR_GLOBAL_SLOWDOWN;
81}
82
83/*
84 * Decode the length and type bits for a particular breakpoint as
85 * stored in debug register 7. Return the "enabled" status.
86 */
87int decode_dr7(unsigned long dr7, int bpnum, unsigned *len, unsigned *type)
88{
89 int bp_info = dr7 >> (DR_CONTROL_SHIFT + bpnum * DR_CONTROL_SIZE);
90
91 *len = (bp_info & 0xc) | 0x40;
92 *type = (bp_info & 0x3) | 0x80;
93
94 return (dr7 >> (bpnum * DR_ENABLE_SIZE)) & 0x3;
95}
96
97/*
98 * Install a perf counter breakpoint.
99 *
100 * We seek a free debug address register and use it for this
101 * breakpoint. Eventually we enable it in the debug control register.
102 *
103 * Atomic: we hold the counter->ctx->lock and we only handle variables
104 * and registers local to this cpu.
105 */
106int arch_install_hw_breakpoint(struct perf_event *bp)
107{
108 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
109 unsigned long *dr7;
110 int i;
111
112 for (i = 0; i < HBP_NUM; i++) {
113 struct perf_event **slot = &__get_cpu_var(bp_per_reg[i]);
114
115 if (!*slot) {
116 *slot = bp;
117 break;
118 }
119 }
120
121 if (WARN_ONCE(i == HBP_NUM, "Can't find any breakpoint slot"))
122 return -EBUSY;
123
124 set_debugreg(info->address, i);
125 __this_cpu_write(cpu_debugreg[i], info->address);
126
127 dr7 = &__get_cpu_var(cpu_dr7);
128 *dr7 |= encode_dr7(i, info->len, info->type);
129
130 set_debugreg(*dr7, 7);
131
132 return 0;
133}
134
135/*
136 * Uninstall the breakpoint contained in the given counter.
137 *
138 * First we search the debug address register it uses and then we disable
139 * it.
140 *
141 * Atomic: we hold the counter->ctx->lock and we only handle variables
142 * and registers local to this cpu.
143 */
144void arch_uninstall_hw_breakpoint(struct perf_event *bp)
145{
146 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
147 unsigned long *dr7;
148 int i;
149
150 for (i = 0; i < HBP_NUM; i++) {
151 struct perf_event **slot = &__get_cpu_var(bp_per_reg[i]);
152
153 if (*slot == bp) {
154 *slot = NULL;
155 break;
156 }
157 }
158
159 if (WARN_ONCE(i == HBP_NUM, "Can't find any breakpoint slot"))
160 return;
161
162 dr7 = &__get_cpu_var(cpu_dr7);
163 *dr7 &= ~__encode_dr7(i, info->len, info->type);
164
165 set_debugreg(*dr7, 7);
166}
167
168static int get_hbp_len(u8 hbp_len)
169{
170 unsigned int len_in_bytes = 0;
171
172 switch (hbp_len) {
173 case X86_BREAKPOINT_LEN_1:
174 len_in_bytes = 1;
175 break;
176 case X86_BREAKPOINT_LEN_2:
177 len_in_bytes = 2;
178 break;
179 case X86_BREAKPOINT_LEN_4:
180 len_in_bytes = 4;
181 break;
182#ifdef CONFIG_X86_64
183 case X86_BREAKPOINT_LEN_8:
184 len_in_bytes = 8;
185 break;
186#endif
187 }
188 return len_in_bytes;
189}
190
191/*
192 * Check for virtual address in kernel space.
193 */
194int arch_check_bp_in_kernelspace(struct perf_event *bp)
195{
196 unsigned int len;
197 unsigned long va;
198 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
199
200 va = info->address;
201 len = get_hbp_len(info->len);
202
203 return (va >= TASK_SIZE) && ((va + len - 1) >= TASK_SIZE);
204}
205
206int arch_bp_generic_fields(int x86_len, int x86_type,
207 int *gen_len, int *gen_type)
208{
209 /* Type */
210 switch (x86_type) {
211 case X86_BREAKPOINT_EXECUTE:
212 if (x86_len != X86_BREAKPOINT_LEN_X)
213 return -EINVAL;
214
215 *gen_type = HW_BREAKPOINT_X;
216 *gen_len = sizeof(long);
217 return 0;
218 case X86_BREAKPOINT_WRITE:
219 *gen_type = HW_BREAKPOINT_W;
220 break;
221 case X86_BREAKPOINT_RW:
222 *gen_type = HW_BREAKPOINT_W | HW_BREAKPOINT_R;
223 break;
224 default:
225 return -EINVAL;
226 }
227
228 /* Len */
229 switch (x86_len) {
230 case X86_BREAKPOINT_LEN_1:
231 *gen_len = HW_BREAKPOINT_LEN_1;
232 break;
233 case X86_BREAKPOINT_LEN_2:
234 *gen_len = HW_BREAKPOINT_LEN_2;
235 break;
236 case X86_BREAKPOINT_LEN_4:
237 *gen_len = HW_BREAKPOINT_LEN_4;
238 break;
239#ifdef CONFIG_X86_64
240 case X86_BREAKPOINT_LEN_8:
241 *gen_len = HW_BREAKPOINT_LEN_8;
242 break;
243#endif
244 default:
245 return -EINVAL;
246 }
247
248 return 0;
249}
250
251
252static int arch_build_bp_info(struct perf_event *bp)
253{
254 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
255
256 info->address = bp->attr.bp_addr;
257
258 /* Type */
259 switch (bp->attr.bp_type) {
260 case HW_BREAKPOINT_W:
261 info->type = X86_BREAKPOINT_WRITE;
262 break;
263 case HW_BREAKPOINT_W | HW_BREAKPOINT_R:
264 info->type = X86_BREAKPOINT_RW;
265 break;
266 case HW_BREAKPOINT_X:
267 info->type = X86_BREAKPOINT_EXECUTE;
268 /*
269 * x86 inst breakpoints need to have a specific undefined len.
270 * But we still need to check userspace is not trying to setup
271 * an unsupported length, to get a range breakpoint for example.
272 */
273 if (bp->attr.bp_len == sizeof(long)) {
274 info->len = X86_BREAKPOINT_LEN_X;
275 return 0;
276 }
277 default:
278 return -EINVAL;
279 }
280
281 /* Len */
282 switch (bp->attr.bp_len) {
283 case HW_BREAKPOINT_LEN_1:
284 info->len = X86_BREAKPOINT_LEN_1;
285 break;
286 case HW_BREAKPOINT_LEN_2:
287 info->len = X86_BREAKPOINT_LEN_2;
288 break;
289 case HW_BREAKPOINT_LEN_4:
290 info->len = X86_BREAKPOINT_LEN_4;
291 break;
292#ifdef CONFIG_X86_64
293 case HW_BREAKPOINT_LEN_8:
294 info->len = X86_BREAKPOINT_LEN_8;
295 break;
296#endif
297 default:
298 return -EINVAL;
299 }
300
301 return 0;
302}
303/*
304 * Validate the arch-specific HW Breakpoint register settings
305 */
306int arch_validate_hwbkpt_settings(struct perf_event *bp)
307{
308 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
309 unsigned int align;
310 int ret;
311
312
313 ret = arch_build_bp_info(bp);
314 if (ret)
315 return ret;
316
317 ret = -EINVAL;
318
319 switch (info->len) {
320 case X86_BREAKPOINT_LEN_1:
321 align = 0;
322 break;
323 case X86_BREAKPOINT_LEN_2:
324 align = 1;
325 break;
326 case X86_BREAKPOINT_LEN_4:
327 align = 3;
328 break;
329#ifdef CONFIG_X86_64
330 case X86_BREAKPOINT_LEN_8:
331 align = 7;
332 break;
333#endif
334 default:
335 return ret;
336 }
337
338 /*
339 * Check that the low-order bits of the address are appropriate
340 * for the alignment implied by len.
341 */
342 if (info->address & align)
343 return -EINVAL;
344
345 return 0;
346}
347
348/*
349 * Dump the debug register contents to the user.
350 * We can't dump our per cpu values because it
351 * may contain cpu wide breakpoint, something that
352 * doesn't belong to the current task.
353 *
354 * TODO: include non-ptrace user breakpoints (perf)
355 */
356void aout_dump_debugregs(struct user *dump)
357{
358 int i;
359 int dr7 = 0;
360 struct perf_event *bp;
361 struct arch_hw_breakpoint *info;
362 struct thread_struct *thread = ¤t->thread;
363
364 for (i = 0; i < HBP_NUM; i++) {
365 bp = thread->ptrace_bps[i];
366
367 if (bp && !bp->attr.disabled) {
368 dump->u_debugreg[i] = bp->attr.bp_addr;
369 info = counter_arch_bp(bp);
370 dr7 |= encode_dr7(i, info->len, info->type);
371 } else {
372 dump->u_debugreg[i] = 0;
373 }
374 }
375
376 dump->u_debugreg[4] = 0;
377 dump->u_debugreg[5] = 0;
378 dump->u_debugreg[6] = current->thread.debugreg6;
379
380 dump->u_debugreg[7] = dr7;
381}
382EXPORT_SYMBOL_GPL(aout_dump_debugregs);
383
384/*
385 * Release the user breakpoints used by ptrace
386 */
387void flush_ptrace_hw_breakpoint(struct task_struct *tsk)
388{
389 int i;
390 struct thread_struct *t = &tsk->thread;
391
392 for (i = 0; i < HBP_NUM; i++) {
393 unregister_hw_breakpoint(t->ptrace_bps[i]);
394 t->ptrace_bps[i] = NULL;
395 }
396}
397
398void hw_breakpoint_restore(void)
399{
400 set_debugreg(__this_cpu_read(cpu_debugreg[0]), 0);
401 set_debugreg(__this_cpu_read(cpu_debugreg[1]), 1);
402 set_debugreg(__this_cpu_read(cpu_debugreg[2]), 2);
403 set_debugreg(__this_cpu_read(cpu_debugreg[3]), 3);
404 set_debugreg(current->thread.debugreg6, 6);
405 set_debugreg(__this_cpu_read(cpu_dr7), 7);
406}
407EXPORT_SYMBOL_GPL(hw_breakpoint_restore);
408
409/*
410 * Handle debug exception notifications.
411 *
412 * Return value is either NOTIFY_STOP or NOTIFY_DONE as explained below.
413 *
414 * NOTIFY_DONE returned if one of the following conditions is true.
415 * i) When the causative address is from user-space and the exception
416 * is a valid one, i.e. not triggered as a result of lazy debug register
417 * switching
418 * ii) When there are more bits than trap<n> set in DR6 register (such
419 * as BD, BS or BT) indicating that more than one debug condition is
420 * met and requires some more action in do_debug().
421 *
422 * NOTIFY_STOP returned for all other cases
423 *
424 */
425static int __kprobes hw_breakpoint_handler(struct die_args *args)
426{
427 int i, cpu, rc = NOTIFY_STOP;
428 struct perf_event *bp;
429 unsigned long dr7, dr6;
430 unsigned long *dr6_p;
431
432 /* The DR6 value is pointed by args->err */
433 dr6_p = (unsigned long *)ERR_PTR(args->err);
434 dr6 = *dr6_p;
435
436 /* If it's a single step, TRAP bits are random */
437 if (dr6 & DR_STEP)
438 return NOTIFY_DONE;
439
440 /* Do an early return if no trap bits are set in DR6 */
441 if ((dr6 & DR_TRAP_BITS) == 0)
442 return NOTIFY_DONE;
443
444 get_debugreg(dr7, 7);
445 /* Disable breakpoints during exception handling */
446 set_debugreg(0UL, 7);
447 /*
448 * Assert that local interrupts are disabled
449 * Reset the DRn bits in the virtualized register value.
450 * The ptrace trigger routine will add in whatever is needed.
451 */
452 current->thread.debugreg6 &= ~DR_TRAP_BITS;
453 cpu = get_cpu();
454
455 /* Handle all the breakpoints that were triggered */
456 for (i = 0; i < HBP_NUM; ++i) {
457 if (likely(!(dr6 & (DR_TRAP0 << i))))
458 continue;
459
460 /*
461 * The counter may be concurrently released but that can only
462 * occur from a call_rcu() path. We can then safely fetch
463 * the breakpoint, use its callback, touch its counter
464 * while we are in an rcu_read_lock() path.
465 */
466 rcu_read_lock();
467
468 bp = per_cpu(bp_per_reg[i], cpu);
469 /*
470 * Reset the 'i'th TRAP bit in dr6 to denote completion of
471 * exception handling
472 */
473 (*dr6_p) &= ~(DR_TRAP0 << i);
474 /*
475 * bp can be NULL due to lazy debug register switching
476 * or due to concurrent perf counter removing.
477 */
478 if (!bp) {
479 rcu_read_unlock();
480 break;
481 }
482
483 perf_bp_event(bp, args->regs);
484
485 /*
486 * Set up resume flag to avoid breakpoint recursion when
487 * returning back to origin.
488 */
489 if (bp->hw.info.type == X86_BREAKPOINT_EXECUTE)
490 args->regs->flags |= X86_EFLAGS_RF;
491
492 rcu_read_unlock();
493 }
494 /*
495 * Further processing in do_debug() is needed for a) user-space
496 * breakpoints (to generate signals) and b) when the system has
497 * taken exception due to multiple causes
498 */
499 if ((current->thread.debugreg6 & DR_TRAP_BITS) ||
500 (dr6 & (~DR_TRAP_BITS)))
501 rc = NOTIFY_DONE;
502
503 set_debugreg(dr7, 7);
504 put_cpu();
505
506 return rc;
507}
508
509/*
510 * Handle debug exception notifications.
511 */
512int __kprobes hw_breakpoint_exceptions_notify(
513 struct notifier_block *unused, unsigned long val, void *data)
514{
515 if (val != DIE_DEBUG)
516 return NOTIFY_DONE;
517
518 return hw_breakpoint_handler(data);
519}
520
521void hw_breakpoint_pmu_read(struct perf_event *bp)
522{
523 /* TODO */
524}
1/*
2 * This program is free software; you can redistribute it and/or modify
3 * it under the terms of the GNU General Public License as published by
4 * the Free Software Foundation; either version 2 of the License, or
5 * (at your option) any later version.
6 *
7 * This program is distributed in the hope that it will be useful,
8 * but WITHOUT ANY WARRANTY; without even the implied warranty of
9 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
10 * GNU General Public License for more details.
11 *
12 * You should have received a copy of the GNU General Public License
13 * along with this program; if not, write to the Free Software
14 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
15 *
16 * Copyright (C) 2007 Alan Stern
17 * Copyright (C) 2009 IBM Corporation
18 * Copyright (C) 2009 Frederic Weisbecker <fweisbec@gmail.com>
19 *
20 * Authors: Alan Stern <stern@rowland.harvard.edu>
21 * K.Prasad <prasad@linux.vnet.ibm.com>
22 * Frederic Weisbecker <fweisbec@gmail.com>
23 */
24
25/*
26 * HW_breakpoint: a unified kernel/user-space hardware breakpoint facility,
27 * using the CPU's debug registers.
28 */
29
30#include <linux/perf_event.h>
31#include <linux/hw_breakpoint.h>
32#include <linux/irqflags.h>
33#include <linux/notifier.h>
34#include <linux/kallsyms.h>
35#include <linux/kprobes.h>
36#include <linux/percpu.h>
37#include <linux/kdebug.h>
38#include <linux/kernel.h>
39#include <linux/module.h>
40#include <linux/sched.h>
41#include <linux/smp.h>
42
43#include <asm/hw_breakpoint.h>
44#include <asm/processor.h>
45#include <asm/debugreg.h>
46
47/* Per cpu debug control register value */
48DEFINE_PER_CPU(unsigned long, cpu_dr7);
49EXPORT_PER_CPU_SYMBOL(cpu_dr7);
50
51/* Per cpu debug address registers values */
52static DEFINE_PER_CPU(unsigned long, cpu_debugreg[HBP_NUM]);
53
54/*
55 * Stores the breakpoints currently in use on each breakpoint address
56 * register for each cpus
57 */
58static DEFINE_PER_CPU(struct perf_event *, bp_per_reg[HBP_NUM]);
59
60
61static inline unsigned long
62__encode_dr7(int drnum, unsigned int len, unsigned int type)
63{
64 unsigned long bp_info;
65
66 bp_info = (len | type) & 0xf;
67 bp_info <<= (DR_CONTROL_SHIFT + drnum * DR_CONTROL_SIZE);
68 bp_info |= (DR_GLOBAL_ENABLE << (drnum * DR_ENABLE_SIZE));
69
70 return bp_info;
71}
72
73/*
74 * Encode the length, type, Exact, and Enable bits for a particular breakpoint
75 * as stored in debug register 7.
76 */
77unsigned long encode_dr7(int drnum, unsigned int len, unsigned int type)
78{
79 return __encode_dr7(drnum, len, type) | DR_GLOBAL_SLOWDOWN;
80}
81
82/*
83 * Decode the length and type bits for a particular breakpoint as
84 * stored in debug register 7. Return the "enabled" status.
85 */
86int decode_dr7(unsigned long dr7, int bpnum, unsigned *len, unsigned *type)
87{
88 int bp_info = dr7 >> (DR_CONTROL_SHIFT + bpnum * DR_CONTROL_SIZE);
89
90 *len = (bp_info & 0xc) | 0x40;
91 *type = (bp_info & 0x3) | 0x80;
92
93 return (dr7 >> (bpnum * DR_ENABLE_SIZE)) & 0x3;
94}
95
96/*
97 * Install a perf counter breakpoint.
98 *
99 * We seek a free debug address register and use it for this
100 * breakpoint. Eventually we enable it in the debug control register.
101 *
102 * Atomic: we hold the counter->ctx->lock and we only handle variables
103 * and registers local to this cpu.
104 */
105int arch_install_hw_breakpoint(struct perf_event *bp)
106{
107 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
108 unsigned long *dr7;
109 int i;
110
111 for (i = 0; i < HBP_NUM; i++) {
112 struct perf_event **slot = &__get_cpu_var(bp_per_reg[i]);
113
114 if (!*slot) {
115 *slot = bp;
116 break;
117 }
118 }
119
120 if (WARN_ONCE(i == HBP_NUM, "Can't find any breakpoint slot"))
121 return -EBUSY;
122
123 set_debugreg(info->address, i);
124 __this_cpu_write(cpu_debugreg[i], info->address);
125
126 dr7 = &__get_cpu_var(cpu_dr7);
127 *dr7 |= encode_dr7(i, info->len, info->type);
128
129 set_debugreg(*dr7, 7);
130
131 return 0;
132}
133
134/*
135 * Uninstall the breakpoint contained in the given counter.
136 *
137 * First we search the debug address register it uses and then we disable
138 * it.
139 *
140 * Atomic: we hold the counter->ctx->lock and we only handle variables
141 * and registers local to this cpu.
142 */
143void arch_uninstall_hw_breakpoint(struct perf_event *bp)
144{
145 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
146 unsigned long *dr7;
147 int i;
148
149 for (i = 0; i < HBP_NUM; i++) {
150 struct perf_event **slot = &__get_cpu_var(bp_per_reg[i]);
151
152 if (*slot == bp) {
153 *slot = NULL;
154 break;
155 }
156 }
157
158 if (WARN_ONCE(i == HBP_NUM, "Can't find any breakpoint slot"))
159 return;
160
161 dr7 = &__get_cpu_var(cpu_dr7);
162 *dr7 &= ~__encode_dr7(i, info->len, info->type);
163
164 set_debugreg(*dr7, 7);
165}
166
167static int get_hbp_len(u8 hbp_len)
168{
169 unsigned int len_in_bytes = 0;
170
171 switch (hbp_len) {
172 case X86_BREAKPOINT_LEN_1:
173 len_in_bytes = 1;
174 break;
175 case X86_BREAKPOINT_LEN_2:
176 len_in_bytes = 2;
177 break;
178 case X86_BREAKPOINT_LEN_4:
179 len_in_bytes = 4;
180 break;
181#ifdef CONFIG_X86_64
182 case X86_BREAKPOINT_LEN_8:
183 len_in_bytes = 8;
184 break;
185#endif
186 }
187 return len_in_bytes;
188}
189
190/*
191 * Check for virtual address in kernel space.
192 */
193int arch_check_bp_in_kernelspace(struct perf_event *bp)
194{
195 unsigned int len;
196 unsigned long va;
197 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
198
199 va = info->address;
200 len = get_hbp_len(info->len);
201
202 return (va >= TASK_SIZE) && ((va + len - 1) >= TASK_SIZE);
203}
204
205int arch_bp_generic_fields(int x86_len, int x86_type,
206 int *gen_len, int *gen_type)
207{
208 /* Type */
209 switch (x86_type) {
210 case X86_BREAKPOINT_EXECUTE:
211 if (x86_len != X86_BREAKPOINT_LEN_X)
212 return -EINVAL;
213
214 *gen_type = HW_BREAKPOINT_X;
215 *gen_len = sizeof(long);
216 return 0;
217 case X86_BREAKPOINT_WRITE:
218 *gen_type = HW_BREAKPOINT_W;
219 break;
220 case X86_BREAKPOINT_RW:
221 *gen_type = HW_BREAKPOINT_W | HW_BREAKPOINT_R;
222 break;
223 default:
224 return -EINVAL;
225 }
226
227 /* Len */
228 switch (x86_len) {
229 case X86_BREAKPOINT_LEN_1:
230 *gen_len = HW_BREAKPOINT_LEN_1;
231 break;
232 case X86_BREAKPOINT_LEN_2:
233 *gen_len = HW_BREAKPOINT_LEN_2;
234 break;
235 case X86_BREAKPOINT_LEN_4:
236 *gen_len = HW_BREAKPOINT_LEN_4;
237 break;
238#ifdef CONFIG_X86_64
239 case X86_BREAKPOINT_LEN_8:
240 *gen_len = HW_BREAKPOINT_LEN_8;
241 break;
242#endif
243 default:
244 return -EINVAL;
245 }
246
247 return 0;
248}
249
250
251static int arch_build_bp_info(struct perf_event *bp)
252{
253 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
254
255 info->address = bp->attr.bp_addr;
256
257 /* Type */
258 switch (bp->attr.bp_type) {
259 case HW_BREAKPOINT_W:
260 info->type = X86_BREAKPOINT_WRITE;
261 break;
262 case HW_BREAKPOINT_W | HW_BREAKPOINT_R:
263 info->type = X86_BREAKPOINT_RW;
264 break;
265 case HW_BREAKPOINT_X:
266 info->type = X86_BREAKPOINT_EXECUTE;
267 /*
268 * x86 inst breakpoints need to have a specific undefined len.
269 * But we still need to check userspace is not trying to setup
270 * an unsupported length, to get a range breakpoint for example.
271 */
272 if (bp->attr.bp_len == sizeof(long)) {
273 info->len = X86_BREAKPOINT_LEN_X;
274 return 0;
275 }
276 default:
277 return -EINVAL;
278 }
279
280 /* Len */
281 switch (bp->attr.bp_len) {
282 case HW_BREAKPOINT_LEN_1:
283 info->len = X86_BREAKPOINT_LEN_1;
284 break;
285 case HW_BREAKPOINT_LEN_2:
286 info->len = X86_BREAKPOINT_LEN_2;
287 break;
288 case HW_BREAKPOINT_LEN_4:
289 info->len = X86_BREAKPOINT_LEN_4;
290 break;
291#ifdef CONFIG_X86_64
292 case HW_BREAKPOINT_LEN_8:
293 info->len = X86_BREAKPOINT_LEN_8;
294 break;
295#endif
296 default:
297 return -EINVAL;
298 }
299
300 return 0;
301}
302/*
303 * Validate the arch-specific HW Breakpoint register settings
304 */
305int arch_validate_hwbkpt_settings(struct perf_event *bp)
306{
307 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
308 unsigned int align;
309 int ret;
310
311
312 ret = arch_build_bp_info(bp);
313 if (ret)
314 return ret;
315
316 ret = -EINVAL;
317
318 switch (info->len) {
319 case X86_BREAKPOINT_LEN_1:
320 align = 0;
321 break;
322 case X86_BREAKPOINT_LEN_2:
323 align = 1;
324 break;
325 case X86_BREAKPOINT_LEN_4:
326 align = 3;
327 break;
328#ifdef CONFIG_X86_64
329 case X86_BREAKPOINT_LEN_8:
330 align = 7;
331 break;
332#endif
333 default:
334 return ret;
335 }
336
337 /*
338 * Check that the low-order bits of the address are appropriate
339 * for the alignment implied by len.
340 */
341 if (info->address & align)
342 return -EINVAL;
343
344 return 0;
345}
346
347/*
348 * Dump the debug register contents to the user.
349 * We can't dump our per cpu values because it
350 * may contain cpu wide breakpoint, something that
351 * doesn't belong to the current task.
352 *
353 * TODO: include non-ptrace user breakpoints (perf)
354 */
355void aout_dump_debugregs(struct user *dump)
356{
357 int i;
358 int dr7 = 0;
359 struct perf_event *bp;
360 struct arch_hw_breakpoint *info;
361 struct thread_struct *thread = ¤t->thread;
362
363 for (i = 0; i < HBP_NUM; i++) {
364 bp = thread->ptrace_bps[i];
365
366 if (bp && !bp->attr.disabled) {
367 dump->u_debugreg[i] = bp->attr.bp_addr;
368 info = counter_arch_bp(bp);
369 dr7 |= encode_dr7(i, info->len, info->type);
370 } else {
371 dump->u_debugreg[i] = 0;
372 }
373 }
374
375 dump->u_debugreg[4] = 0;
376 dump->u_debugreg[5] = 0;
377 dump->u_debugreg[6] = current->thread.debugreg6;
378
379 dump->u_debugreg[7] = dr7;
380}
381EXPORT_SYMBOL_GPL(aout_dump_debugregs);
382
383/*
384 * Release the user breakpoints used by ptrace
385 */
386void flush_ptrace_hw_breakpoint(struct task_struct *tsk)
387{
388 int i;
389 struct thread_struct *t = &tsk->thread;
390
391 for (i = 0; i < HBP_NUM; i++) {
392 unregister_hw_breakpoint(t->ptrace_bps[i]);
393 t->ptrace_bps[i] = NULL;
394 }
395
396 t->debugreg6 = 0;
397 t->ptrace_dr7 = 0;
398}
399
400void hw_breakpoint_restore(void)
401{
402 set_debugreg(__this_cpu_read(cpu_debugreg[0]), 0);
403 set_debugreg(__this_cpu_read(cpu_debugreg[1]), 1);
404 set_debugreg(__this_cpu_read(cpu_debugreg[2]), 2);
405 set_debugreg(__this_cpu_read(cpu_debugreg[3]), 3);
406 set_debugreg(current->thread.debugreg6, 6);
407 set_debugreg(__this_cpu_read(cpu_dr7), 7);
408}
409EXPORT_SYMBOL_GPL(hw_breakpoint_restore);
410
411/*
412 * Handle debug exception notifications.
413 *
414 * Return value is either NOTIFY_STOP or NOTIFY_DONE as explained below.
415 *
416 * NOTIFY_DONE returned if one of the following conditions is true.
417 * i) When the causative address is from user-space and the exception
418 * is a valid one, i.e. not triggered as a result of lazy debug register
419 * switching
420 * ii) When there are more bits than trap<n> set in DR6 register (such
421 * as BD, BS or BT) indicating that more than one debug condition is
422 * met and requires some more action in do_debug().
423 *
424 * NOTIFY_STOP returned for all other cases
425 *
426 */
427static int __kprobes hw_breakpoint_handler(struct die_args *args)
428{
429 int i, cpu, rc = NOTIFY_STOP;
430 struct perf_event *bp;
431 unsigned long dr7, dr6;
432 unsigned long *dr6_p;
433
434 /* The DR6 value is pointed by args->err */
435 dr6_p = (unsigned long *)ERR_PTR(args->err);
436 dr6 = *dr6_p;
437
438 /* If it's a single step, TRAP bits are random */
439 if (dr6 & DR_STEP)
440 return NOTIFY_DONE;
441
442 /* Do an early return if no trap bits are set in DR6 */
443 if ((dr6 & DR_TRAP_BITS) == 0)
444 return NOTIFY_DONE;
445
446 get_debugreg(dr7, 7);
447 /* Disable breakpoints during exception handling */
448 set_debugreg(0UL, 7);
449 /*
450 * Assert that local interrupts are disabled
451 * Reset the DRn bits in the virtualized register value.
452 * The ptrace trigger routine will add in whatever is needed.
453 */
454 current->thread.debugreg6 &= ~DR_TRAP_BITS;
455 cpu = get_cpu();
456
457 /* Handle all the breakpoints that were triggered */
458 for (i = 0; i < HBP_NUM; ++i) {
459 if (likely(!(dr6 & (DR_TRAP0 << i))))
460 continue;
461
462 /*
463 * The counter may be concurrently released but that can only
464 * occur from a call_rcu() path. We can then safely fetch
465 * the breakpoint, use its callback, touch its counter
466 * while we are in an rcu_read_lock() path.
467 */
468 rcu_read_lock();
469
470 bp = per_cpu(bp_per_reg[i], cpu);
471 /*
472 * Reset the 'i'th TRAP bit in dr6 to denote completion of
473 * exception handling
474 */
475 (*dr6_p) &= ~(DR_TRAP0 << i);
476 /*
477 * bp can be NULL due to lazy debug register switching
478 * or due to concurrent perf counter removing.
479 */
480 if (!bp) {
481 rcu_read_unlock();
482 break;
483 }
484
485 perf_bp_event(bp, args->regs);
486
487 /*
488 * Set up resume flag to avoid breakpoint recursion when
489 * returning back to origin.
490 */
491 if (bp->hw.info.type == X86_BREAKPOINT_EXECUTE)
492 args->regs->flags |= X86_EFLAGS_RF;
493
494 rcu_read_unlock();
495 }
496 /*
497 * Further processing in do_debug() is needed for a) user-space
498 * breakpoints (to generate signals) and b) when the system has
499 * taken exception due to multiple causes
500 */
501 if ((current->thread.debugreg6 & DR_TRAP_BITS) ||
502 (dr6 & (~DR_TRAP_BITS)))
503 rc = NOTIFY_DONE;
504
505 set_debugreg(dr7, 7);
506 put_cpu();
507
508 return rc;
509}
510
511/*
512 * Handle debug exception notifications.
513 */
514int __kprobes hw_breakpoint_exceptions_notify(
515 struct notifier_block *unused, unsigned long val, void *data)
516{
517 if (val != DIE_DEBUG)
518 return NOTIFY_DONE;
519
520 return hw_breakpoint_handler(data);
521}
522
523void hw_breakpoint_pmu_read(struct perf_event *bp)
524{
525 /* TODO */
526}