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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/export.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#include <asm/user.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 = this_cpu_ptr(&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 = this_cpu_ptr(&cpu_dr7);
128 *dr7 |= encode_dr7(i, info->len, info->type);
129
130 set_debugreg(*dr7, 7);
131 if (info->mask)
132 set_dr_addr_mask(info->mask, i);
133
134 return 0;
135}
136
137/*
138 * Uninstall the breakpoint contained in the given counter.
139 *
140 * First we search the debug address register it uses and then we disable
141 * it.
142 *
143 * Atomic: we hold the counter->ctx->lock and we only handle variables
144 * and registers local to this cpu.
145 */
146void arch_uninstall_hw_breakpoint(struct perf_event *bp)
147{
148 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
149 unsigned long *dr7;
150 int i;
151
152 for (i = 0; i < HBP_NUM; i++) {
153 struct perf_event **slot = this_cpu_ptr(&bp_per_reg[i]);
154
155 if (*slot == bp) {
156 *slot = NULL;
157 break;
158 }
159 }
160
161 if (WARN_ONCE(i == HBP_NUM, "Can't find any breakpoint slot"))
162 return;
163
164 dr7 = this_cpu_ptr(&cpu_dr7);
165 *dr7 &= ~__encode_dr7(i, info->len, info->type);
166
167 set_debugreg(*dr7, 7);
168 if (info->mask)
169 set_dr_addr_mask(0, i);
170}
171
172/*
173 * Check for virtual address in kernel space.
174 */
175int arch_check_bp_in_kernelspace(struct perf_event *bp)
176{
177 unsigned int len;
178 unsigned long va;
179 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
180
181 va = info->address;
182 len = bp->attr.bp_len;
183
184 /*
185 * We don't need to worry about va + len - 1 overflowing:
186 * we already require that va is aligned to a multiple of len.
187 */
188 return (va >= TASK_SIZE_MAX) || ((va + len - 1) >= TASK_SIZE_MAX);
189}
190
191int arch_bp_generic_fields(int x86_len, int x86_type,
192 int *gen_len, int *gen_type)
193{
194 /* Type */
195 switch (x86_type) {
196 case X86_BREAKPOINT_EXECUTE:
197 if (x86_len != X86_BREAKPOINT_LEN_X)
198 return -EINVAL;
199
200 *gen_type = HW_BREAKPOINT_X;
201 *gen_len = sizeof(long);
202 return 0;
203 case X86_BREAKPOINT_WRITE:
204 *gen_type = HW_BREAKPOINT_W;
205 break;
206 case X86_BREAKPOINT_RW:
207 *gen_type = HW_BREAKPOINT_W | HW_BREAKPOINT_R;
208 break;
209 default:
210 return -EINVAL;
211 }
212
213 /* Len */
214 switch (x86_len) {
215 case X86_BREAKPOINT_LEN_1:
216 *gen_len = HW_BREAKPOINT_LEN_1;
217 break;
218 case X86_BREAKPOINT_LEN_2:
219 *gen_len = HW_BREAKPOINT_LEN_2;
220 break;
221 case X86_BREAKPOINT_LEN_4:
222 *gen_len = HW_BREAKPOINT_LEN_4;
223 break;
224#ifdef CONFIG_X86_64
225 case X86_BREAKPOINT_LEN_8:
226 *gen_len = HW_BREAKPOINT_LEN_8;
227 break;
228#endif
229 default:
230 return -EINVAL;
231 }
232
233 return 0;
234}
235
236
237static int arch_build_bp_info(struct perf_event *bp)
238{
239 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
240
241 info->address = bp->attr.bp_addr;
242
243 /* Type */
244 switch (bp->attr.bp_type) {
245 case HW_BREAKPOINT_W:
246 info->type = X86_BREAKPOINT_WRITE;
247 break;
248 case HW_BREAKPOINT_W | HW_BREAKPOINT_R:
249 info->type = X86_BREAKPOINT_RW;
250 break;
251 case HW_BREAKPOINT_X:
252 /*
253 * We don't allow kernel breakpoints in places that are not
254 * acceptable for kprobes. On non-kprobes kernels, we don't
255 * allow kernel breakpoints at all.
256 */
257 if (bp->attr.bp_addr >= TASK_SIZE_MAX) {
258#ifdef CONFIG_KPROBES
259 if (within_kprobe_blacklist(bp->attr.bp_addr))
260 return -EINVAL;
261#else
262 return -EINVAL;
263#endif
264 }
265
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 info->mask = 0;
282
283 switch (bp->attr.bp_len) {
284 case HW_BREAKPOINT_LEN_1:
285 info->len = X86_BREAKPOINT_LEN_1;
286 break;
287 case HW_BREAKPOINT_LEN_2:
288 info->len = X86_BREAKPOINT_LEN_2;
289 break;
290 case HW_BREAKPOINT_LEN_4:
291 info->len = X86_BREAKPOINT_LEN_4;
292 break;
293#ifdef CONFIG_X86_64
294 case HW_BREAKPOINT_LEN_8:
295 info->len = X86_BREAKPOINT_LEN_8;
296 break;
297#endif
298 default:
299 /* AMD range breakpoint */
300 if (!is_power_of_2(bp->attr.bp_len))
301 return -EINVAL;
302 if (bp->attr.bp_addr & (bp->attr.bp_len - 1))
303 return -EINVAL;
304
305 if (!boot_cpu_has(X86_FEATURE_BPEXT))
306 return -EOPNOTSUPP;
307
308 /*
309 * It's impossible to use a range breakpoint to fake out
310 * user vs kernel detection because bp_len - 1 can't
311 * have the high bit set. If we ever allow range instruction
312 * breakpoints, then we'll have to check for kprobe-blacklisted
313 * addresses anywhere in the range.
314 */
315 info->mask = bp->attr.bp_len - 1;
316 info->len = X86_BREAKPOINT_LEN_1;
317 }
318
319 return 0;
320}
321
322/*
323 * Validate the arch-specific HW Breakpoint register settings
324 */
325int arch_validate_hwbkpt_settings(struct perf_event *bp)
326{
327 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
328 unsigned int align;
329 int ret;
330
331
332 ret = arch_build_bp_info(bp);
333 if (ret)
334 return ret;
335
336 switch (info->len) {
337 case X86_BREAKPOINT_LEN_1:
338 align = 0;
339 if (info->mask)
340 align = info->mask;
341 break;
342 case X86_BREAKPOINT_LEN_2:
343 align = 1;
344 break;
345 case X86_BREAKPOINT_LEN_4:
346 align = 3;
347 break;
348#ifdef CONFIG_X86_64
349 case X86_BREAKPOINT_LEN_8:
350 align = 7;
351 break;
352#endif
353 default:
354 WARN_ON_ONCE(1);
355 }
356
357 /*
358 * Check that the low-order bits of the address are appropriate
359 * for the alignment implied by len.
360 */
361 if (info->address & align)
362 return -EINVAL;
363
364 return 0;
365}
366
367/*
368 * Dump the debug register contents to the user.
369 * We can't dump our per cpu values because it
370 * may contain cpu wide breakpoint, something that
371 * doesn't belong to the current task.
372 *
373 * TODO: include non-ptrace user breakpoints (perf)
374 */
375void aout_dump_debugregs(struct user *dump)
376{
377 int i;
378 int dr7 = 0;
379 struct perf_event *bp;
380 struct arch_hw_breakpoint *info;
381 struct thread_struct *thread = ¤t->thread;
382
383 for (i = 0; i < HBP_NUM; i++) {
384 bp = thread->ptrace_bps[i];
385
386 if (bp && !bp->attr.disabled) {
387 dump->u_debugreg[i] = bp->attr.bp_addr;
388 info = counter_arch_bp(bp);
389 dr7 |= encode_dr7(i, info->len, info->type);
390 } else {
391 dump->u_debugreg[i] = 0;
392 }
393 }
394
395 dump->u_debugreg[4] = 0;
396 dump->u_debugreg[5] = 0;
397 dump->u_debugreg[6] = current->thread.debugreg6;
398
399 dump->u_debugreg[7] = dr7;
400}
401EXPORT_SYMBOL_GPL(aout_dump_debugregs);
402
403/*
404 * Release the user breakpoints used by ptrace
405 */
406void flush_ptrace_hw_breakpoint(struct task_struct *tsk)
407{
408 int i;
409 struct thread_struct *t = &tsk->thread;
410
411 for (i = 0; i < HBP_NUM; i++) {
412 unregister_hw_breakpoint(t->ptrace_bps[i]);
413 t->ptrace_bps[i] = NULL;
414 }
415
416 t->debugreg6 = 0;
417 t->ptrace_dr7 = 0;
418}
419
420void hw_breakpoint_restore(void)
421{
422 set_debugreg(__this_cpu_read(cpu_debugreg[0]), 0);
423 set_debugreg(__this_cpu_read(cpu_debugreg[1]), 1);
424 set_debugreg(__this_cpu_read(cpu_debugreg[2]), 2);
425 set_debugreg(__this_cpu_read(cpu_debugreg[3]), 3);
426 set_debugreg(current->thread.debugreg6, 6);
427 set_debugreg(__this_cpu_read(cpu_dr7), 7);
428}
429EXPORT_SYMBOL_GPL(hw_breakpoint_restore);
430
431/*
432 * Handle debug exception notifications.
433 *
434 * Return value is either NOTIFY_STOP or NOTIFY_DONE as explained below.
435 *
436 * NOTIFY_DONE returned if one of the following conditions is true.
437 * i) When the causative address is from user-space and the exception
438 * is a valid one, i.e. not triggered as a result of lazy debug register
439 * switching
440 * ii) When there are more bits than trap<n> set in DR6 register (such
441 * as BD, BS or BT) indicating that more than one debug condition is
442 * met and requires some more action in do_debug().
443 *
444 * NOTIFY_STOP returned for all other cases
445 *
446 */
447static int hw_breakpoint_handler(struct die_args *args)
448{
449 int i, cpu, rc = NOTIFY_STOP;
450 struct perf_event *bp;
451 unsigned long dr7, dr6;
452 unsigned long *dr6_p;
453
454 /* The DR6 value is pointed by args->err */
455 dr6_p = (unsigned long *)ERR_PTR(args->err);
456 dr6 = *dr6_p;
457
458 /* If it's a single step, TRAP bits are random */
459 if (dr6 & DR_STEP)
460 return NOTIFY_DONE;
461
462 /* Do an early return if no trap bits are set in DR6 */
463 if ((dr6 & DR_TRAP_BITS) == 0)
464 return NOTIFY_DONE;
465
466 get_debugreg(dr7, 7);
467 /* Disable breakpoints during exception handling */
468 set_debugreg(0UL, 7);
469 /*
470 * Assert that local interrupts are disabled
471 * Reset the DRn bits in the virtualized register value.
472 * The ptrace trigger routine will add in whatever is needed.
473 */
474 current->thread.debugreg6 &= ~DR_TRAP_BITS;
475 cpu = get_cpu();
476
477 /* Handle all the breakpoints that were triggered */
478 for (i = 0; i < HBP_NUM; ++i) {
479 if (likely(!(dr6 & (DR_TRAP0 << i))))
480 continue;
481
482 /*
483 * The counter may be concurrently released but that can only
484 * occur from a call_rcu() path. We can then safely fetch
485 * the breakpoint, use its callback, touch its counter
486 * while we are in an rcu_read_lock() path.
487 */
488 rcu_read_lock();
489
490 bp = per_cpu(bp_per_reg[i], cpu);
491 /*
492 * Reset the 'i'th TRAP bit in dr6 to denote completion of
493 * exception handling
494 */
495 (*dr6_p) &= ~(DR_TRAP0 << i);
496 /*
497 * bp can be NULL due to lazy debug register switching
498 * or due to concurrent perf counter removing.
499 */
500 if (!bp) {
501 rcu_read_unlock();
502 break;
503 }
504
505 perf_bp_event(bp, args->regs);
506
507 /*
508 * Set up resume flag to avoid breakpoint recursion when
509 * returning back to origin.
510 */
511 if (bp->hw.info.type == X86_BREAKPOINT_EXECUTE)
512 args->regs->flags |= X86_EFLAGS_RF;
513
514 rcu_read_unlock();
515 }
516 /*
517 * Further processing in do_debug() is needed for a) user-space
518 * breakpoints (to generate signals) and b) when the system has
519 * taken exception due to multiple causes
520 */
521 if ((current->thread.debugreg6 & DR_TRAP_BITS) ||
522 (dr6 & (~DR_TRAP_BITS)))
523 rc = NOTIFY_DONE;
524
525 set_debugreg(dr7, 7);
526 put_cpu();
527
528 return rc;
529}
530
531/*
532 * Handle debug exception notifications.
533 */
534int hw_breakpoint_exceptions_notify(
535 struct notifier_block *unused, unsigned long val, void *data)
536{
537 if (val != DIE_DEBUG)
538 return NOTIFY_DONE;
539
540 return hw_breakpoint_handler(data);
541}
542
543void hw_breakpoint_pmu_read(struct perf_event *bp)
544{
545 /* TODO */
546}
1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 *
4 * Copyright (C) 2007 Alan Stern
5 * Copyright (C) 2009 IBM Corporation
6 * Copyright (C) 2009 Frederic Weisbecker <fweisbec@gmail.com>
7 *
8 * Authors: Alan Stern <stern@rowland.harvard.edu>
9 * K.Prasad <prasad@linux.vnet.ibm.com>
10 * Frederic Weisbecker <fweisbec@gmail.com>
11 */
12
13/*
14 * HW_breakpoint: a unified kernel/user-space hardware breakpoint facility,
15 * using the CPU's debug registers.
16 */
17
18#include <linux/perf_event.h>
19#include <linux/hw_breakpoint.h>
20#include <linux/irqflags.h>
21#include <linux/notifier.h>
22#include <linux/kallsyms.h>
23#include <linux/kprobes.h>
24#include <linux/percpu.h>
25#include <linux/kdebug.h>
26#include <linux/kernel.h>
27#include <linux/export.h>
28#include <linux/sched.h>
29#include <linux/smp.h>
30
31#include <asm/hw_breakpoint.h>
32#include <asm/processor.h>
33#include <asm/debugreg.h>
34#include <asm/user.h>
35#include <asm/desc.h>
36#include <asm/tlbflush.h>
37
38/* Per cpu debug control register value */
39DEFINE_PER_CPU(unsigned long, cpu_dr7);
40EXPORT_PER_CPU_SYMBOL(cpu_dr7);
41
42/* Per cpu debug address registers values */
43static DEFINE_PER_CPU(unsigned long, cpu_debugreg[HBP_NUM]);
44
45/*
46 * Stores the breakpoints currently in use on each breakpoint address
47 * register for each cpus
48 */
49static DEFINE_PER_CPU(struct perf_event *, bp_per_reg[HBP_NUM]);
50
51
52static inline unsigned long
53__encode_dr7(int drnum, unsigned int len, unsigned int type)
54{
55 unsigned long bp_info;
56
57 bp_info = (len | type) & 0xf;
58 bp_info <<= (DR_CONTROL_SHIFT + drnum * DR_CONTROL_SIZE);
59 bp_info |= (DR_GLOBAL_ENABLE << (drnum * DR_ENABLE_SIZE));
60
61 return bp_info;
62}
63
64/*
65 * Encode the length, type, Exact, and Enable bits for a particular breakpoint
66 * as stored in debug register 7.
67 */
68unsigned long encode_dr7(int drnum, unsigned int len, unsigned int type)
69{
70 return __encode_dr7(drnum, len, type) | DR_GLOBAL_SLOWDOWN;
71}
72
73/*
74 * Decode the length and type bits for a particular breakpoint as
75 * stored in debug register 7. Return the "enabled" status.
76 */
77int decode_dr7(unsigned long dr7, int bpnum, unsigned *len, unsigned *type)
78{
79 int bp_info = dr7 >> (DR_CONTROL_SHIFT + bpnum * DR_CONTROL_SIZE);
80
81 *len = (bp_info & 0xc) | 0x40;
82 *type = (bp_info & 0x3) | 0x80;
83
84 return (dr7 >> (bpnum * DR_ENABLE_SIZE)) & 0x3;
85}
86
87/*
88 * Install a perf counter breakpoint.
89 *
90 * We seek a free debug address register and use it for this
91 * breakpoint. Eventually we enable it in the debug control register.
92 *
93 * Atomic: we hold the counter->ctx->lock and we only handle variables
94 * and registers local to this cpu.
95 */
96int arch_install_hw_breakpoint(struct perf_event *bp)
97{
98 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
99 unsigned long *dr7;
100 int i;
101
102 lockdep_assert_irqs_disabled();
103
104 for (i = 0; i < HBP_NUM; i++) {
105 struct perf_event **slot = this_cpu_ptr(&bp_per_reg[i]);
106
107 if (!*slot) {
108 *slot = bp;
109 break;
110 }
111 }
112
113 if (WARN_ONCE(i == HBP_NUM, "Can't find any breakpoint slot"))
114 return -EBUSY;
115
116 set_debugreg(info->address, i);
117 __this_cpu_write(cpu_debugreg[i], info->address);
118
119 dr7 = this_cpu_ptr(&cpu_dr7);
120 *dr7 |= encode_dr7(i, info->len, info->type);
121
122 /*
123 * Ensure we first write cpu_dr7 before we set the DR7 register.
124 * This ensures an NMI never see cpu_dr7 0 when DR7 is not.
125 */
126 barrier();
127
128 set_debugreg(*dr7, 7);
129 if (info->mask)
130 set_dr_addr_mask(info->mask, i);
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 lockdep_assert_irqs_disabled();
151
152 for (i = 0; i < HBP_NUM; i++) {
153 struct perf_event **slot = this_cpu_ptr(&bp_per_reg[i]);
154
155 if (*slot == bp) {
156 *slot = NULL;
157 break;
158 }
159 }
160
161 if (WARN_ONCE(i == HBP_NUM, "Can't find any breakpoint slot"))
162 return;
163
164 dr7 = this_cpu_read(cpu_dr7);
165 dr7 &= ~__encode_dr7(i, info->len, info->type);
166
167 set_debugreg(dr7, 7);
168 if (info->mask)
169 set_dr_addr_mask(0, i);
170
171 /*
172 * Ensure the write to cpu_dr7 is after we've set the DR7 register.
173 * This ensures an NMI never see cpu_dr7 0 when DR7 is not.
174 */
175 barrier();
176
177 this_cpu_write(cpu_dr7, dr7);
178}
179
180static int arch_bp_generic_len(int x86_len)
181{
182 switch (x86_len) {
183 case X86_BREAKPOINT_LEN_1:
184 return HW_BREAKPOINT_LEN_1;
185 case X86_BREAKPOINT_LEN_2:
186 return HW_BREAKPOINT_LEN_2;
187 case X86_BREAKPOINT_LEN_4:
188 return HW_BREAKPOINT_LEN_4;
189#ifdef CONFIG_X86_64
190 case X86_BREAKPOINT_LEN_8:
191 return HW_BREAKPOINT_LEN_8;
192#endif
193 default:
194 return -EINVAL;
195 }
196}
197
198int arch_bp_generic_fields(int x86_len, int x86_type,
199 int *gen_len, int *gen_type)
200{
201 int len;
202
203 /* Type */
204 switch (x86_type) {
205 case X86_BREAKPOINT_EXECUTE:
206 if (x86_len != X86_BREAKPOINT_LEN_X)
207 return -EINVAL;
208
209 *gen_type = HW_BREAKPOINT_X;
210 *gen_len = sizeof(long);
211 return 0;
212 case X86_BREAKPOINT_WRITE:
213 *gen_type = HW_BREAKPOINT_W;
214 break;
215 case X86_BREAKPOINT_RW:
216 *gen_type = HW_BREAKPOINT_W | HW_BREAKPOINT_R;
217 break;
218 default:
219 return -EINVAL;
220 }
221
222 /* Len */
223 len = arch_bp_generic_len(x86_len);
224 if (len < 0)
225 return -EINVAL;
226 *gen_len = len;
227
228 return 0;
229}
230
231/*
232 * Check for virtual address in kernel space.
233 */
234int arch_check_bp_in_kernelspace(struct arch_hw_breakpoint *hw)
235{
236 unsigned long va;
237 int len;
238
239 va = hw->address;
240 len = arch_bp_generic_len(hw->len);
241 WARN_ON_ONCE(len < 0);
242
243 /*
244 * We don't need to worry about va + len - 1 overflowing:
245 * we already require that va is aligned to a multiple of len.
246 */
247 return (va >= TASK_SIZE_MAX) || ((va + len - 1) >= TASK_SIZE_MAX);
248}
249
250/*
251 * Checks whether the range [addr, end], overlaps the area [base, base + size).
252 */
253static inline bool within_area(unsigned long addr, unsigned long end,
254 unsigned long base, unsigned long size)
255{
256 return end >= base && addr < (base + size);
257}
258
259/*
260 * Checks whether the range from addr to end, inclusive, overlaps the fixed
261 * mapped CPU entry area range or other ranges used for CPU entry.
262 */
263static inline bool within_cpu_entry(unsigned long addr, unsigned long end)
264{
265 int cpu;
266
267 /* CPU entry erea is always used for CPU entry */
268 if (within_area(addr, end, CPU_ENTRY_AREA_BASE,
269 CPU_ENTRY_AREA_TOTAL_SIZE))
270 return true;
271
272 for_each_possible_cpu(cpu) {
273 /* The original rw GDT is being used after load_direct_gdt() */
274 if (within_area(addr, end, (unsigned long)get_cpu_gdt_rw(cpu),
275 GDT_SIZE))
276 return true;
277
278 /*
279 * cpu_tss_rw is not directly referenced by hardware, but
280 * cpu_tss_rw is also used in CPU entry code,
281 */
282 if (within_area(addr, end,
283 (unsigned long)&per_cpu(cpu_tss_rw, cpu),
284 sizeof(struct tss_struct)))
285 return true;
286
287 /*
288 * cpu_tlbstate.user_pcid_flush_mask is used for CPU entry.
289 * If a data breakpoint on it, it will cause an unwanted #DB.
290 * Protect the full cpu_tlbstate structure to be sure.
291 */
292 if (within_area(addr, end,
293 (unsigned long)&per_cpu(cpu_tlbstate, cpu),
294 sizeof(struct tlb_state)))
295 return true;
296 }
297
298 return false;
299}
300
301static int arch_build_bp_info(struct perf_event *bp,
302 const struct perf_event_attr *attr,
303 struct arch_hw_breakpoint *hw)
304{
305 unsigned long bp_end;
306
307 bp_end = attr->bp_addr + attr->bp_len - 1;
308 if (bp_end < attr->bp_addr)
309 return -EINVAL;
310
311 /*
312 * Prevent any breakpoint of any type that overlaps the CPU
313 * entry area and data. This protects the IST stacks and also
314 * reduces the chance that we ever find out what happens if
315 * there's a data breakpoint on the GDT, IDT, or TSS.
316 */
317 if (within_cpu_entry(attr->bp_addr, bp_end))
318 return -EINVAL;
319
320 hw->address = attr->bp_addr;
321 hw->mask = 0;
322
323 /* Type */
324 switch (attr->bp_type) {
325 case HW_BREAKPOINT_W:
326 hw->type = X86_BREAKPOINT_WRITE;
327 break;
328 case HW_BREAKPOINT_W | HW_BREAKPOINT_R:
329 hw->type = X86_BREAKPOINT_RW;
330 break;
331 case HW_BREAKPOINT_X:
332 /*
333 * We don't allow kernel breakpoints in places that are not
334 * acceptable for kprobes. On non-kprobes kernels, we don't
335 * allow kernel breakpoints at all.
336 */
337 if (attr->bp_addr >= TASK_SIZE_MAX) {
338 if (within_kprobe_blacklist(attr->bp_addr))
339 return -EINVAL;
340 }
341
342 hw->type = X86_BREAKPOINT_EXECUTE;
343 /*
344 * x86 inst breakpoints need to have a specific undefined len.
345 * But we still need to check userspace is not trying to setup
346 * an unsupported length, to get a range breakpoint for example.
347 */
348 if (attr->bp_len == sizeof(long)) {
349 hw->len = X86_BREAKPOINT_LEN_X;
350 return 0;
351 }
352 fallthrough;
353 default:
354 return -EINVAL;
355 }
356
357 /* Len */
358 switch (attr->bp_len) {
359 case HW_BREAKPOINT_LEN_1:
360 hw->len = X86_BREAKPOINT_LEN_1;
361 break;
362 case HW_BREAKPOINT_LEN_2:
363 hw->len = X86_BREAKPOINT_LEN_2;
364 break;
365 case HW_BREAKPOINT_LEN_4:
366 hw->len = X86_BREAKPOINT_LEN_4;
367 break;
368#ifdef CONFIG_X86_64
369 case HW_BREAKPOINT_LEN_8:
370 hw->len = X86_BREAKPOINT_LEN_8;
371 break;
372#endif
373 default:
374 /* AMD range breakpoint */
375 if (!is_power_of_2(attr->bp_len))
376 return -EINVAL;
377 if (attr->bp_addr & (attr->bp_len - 1))
378 return -EINVAL;
379
380 if (!boot_cpu_has(X86_FEATURE_BPEXT))
381 return -EOPNOTSUPP;
382
383 /*
384 * It's impossible to use a range breakpoint to fake out
385 * user vs kernel detection because bp_len - 1 can't
386 * have the high bit set. If we ever allow range instruction
387 * breakpoints, then we'll have to check for kprobe-blacklisted
388 * addresses anywhere in the range.
389 */
390 hw->mask = attr->bp_len - 1;
391 hw->len = X86_BREAKPOINT_LEN_1;
392 }
393
394 return 0;
395}
396
397/*
398 * Validate the arch-specific HW Breakpoint register settings
399 */
400int hw_breakpoint_arch_parse(struct perf_event *bp,
401 const struct perf_event_attr *attr,
402 struct arch_hw_breakpoint *hw)
403{
404 unsigned int align;
405 int ret;
406
407
408 ret = arch_build_bp_info(bp, attr, hw);
409 if (ret)
410 return ret;
411
412 switch (hw->len) {
413 case X86_BREAKPOINT_LEN_1:
414 align = 0;
415 if (hw->mask)
416 align = hw->mask;
417 break;
418 case X86_BREAKPOINT_LEN_2:
419 align = 1;
420 break;
421 case X86_BREAKPOINT_LEN_4:
422 align = 3;
423 break;
424#ifdef CONFIG_X86_64
425 case X86_BREAKPOINT_LEN_8:
426 align = 7;
427 break;
428#endif
429 default:
430 WARN_ON_ONCE(1);
431 return -EINVAL;
432 }
433
434 /*
435 * Check that the low-order bits of the address are appropriate
436 * for the alignment implied by len.
437 */
438 if (hw->address & align)
439 return -EINVAL;
440
441 return 0;
442}
443
444/*
445 * Dump the debug register contents to the user.
446 * We can't dump our per cpu values because it
447 * may contain cpu wide breakpoint, something that
448 * doesn't belong to the current task.
449 *
450 * TODO: include non-ptrace user breakpoints (perf)
451 */
452void aout_dump_debugregs(struct user *dump)
453{
454 int i;
455 int dr7 = 0;
456 struct perf_event *bp;
457 struct arch_hw_breakpoint *info;
458 struct thread_struct *thread = ¤t->thread;
459
460 for (i = 0; i < HBP_NUM; i++) {
461 bp = thread->ptrace_bps[i];
462
463 if (bp && !bp->attr.disabled) {
464 dump->u_debugreg[i] = bp->attr.bp_addr;
465 info = counter_arch_bp(bp);
466 dr7 |= encode_dr7(i, info->len, info->type);
467 } else {
468 dump->u_debugreg[i] = 0;
469 }
470 }
471
472 dump->u_debugreg[4] = 0;
473 dump->u_debugreg[5] = 0;
474 dump->u_debugreg[6] = current->thread.debugreg6;
475
476 dump->u_debugreg[7] = dr7;
477}
478EXPORT_SYMBOL_GPL(aout_dump_debugregs);
479
480/*
481 * Release the user breakpoints used by ptrace
482 */
483void flush_ptrace_hw_breakpoint(struct task_struct *tsk)
484{
485 int i;
486 struct thread_struct *t = &tsk->thread;
487
488 for (i = 0; i < HBP_NUM; i++) {
489 unregister_hw_breakpoint(t->ptrace_bps[i]);
490 t->ptrace_bps[i] = NULL;
491 }
492
493 t->debugreg6 = 0;
494 t->ptrace_dr7 = 0;
495}
496
497void hw_breakpoint_restore(void)
498{
499 set_debugreg(__this_cpu_read(cpu_debugreg[0]), 0);
500 set_debugreg(__this_cpu_read(cpu_debugreg[1]), 1);
501 set_debugreg(__this_cpu_read(cpu_debugreg[2]), 2);
502 set_debugreg(__this_cpu_read(cpu_debugreg[3]), 3);
503 set_debugreg(current->thread.debugreg6, 6);
504 set_debugreg(__this_cpu_read(cpu_dr7), 7);
505}
506EXPORT_SYMBOL_GPL(hw_breakpoint_restore);
507
508/*
509 * Handle debug exception notifications.
510 *
511 * Return value is either NOTIFY_STOP or NOTIFY_DONE as explained below.
512 *
513 * NOTIFY_DONE returned if one of the following conditions is true.
514 * i) When the causative address is from user-space and the exception
515 * is a valid one, i.e. not triggered as a result of lazy debug register
516 * switching
517 * ii) When there are more bits than trap<n> set in DR6 register (such
518 * as BD, BS or BT) indicating that more than one debug condition is
519 * met and requires some more action in do_debug().
520 *
521 * NOTIFY_STOP returned for all other cases
522 *
523 */
524static int hw_breakpoint_handler(struct die_args *args)
525{
526 int i, cpu, rc = NOTIFY_STOP;
527 struct perf_event *bp;
528 unsigned long dr6;
529 unsigned long *dr6_p;
530
531 /* The DR6 value is pointed by args->err */
532 dr6_p = (unsigned long *)ERR_PTR(args->err);
533 dr6 = *dr6_p;
534
535 /* If it's a single step, TRAP bits are random */
536 if (dr6 & DR_STEP)
537 return NOTIFY_DONE;
538
539 /* Do an early return if no trap bits are set in DR6 */
540 if ((dr6 & DR_TRAP_BITS) == 0)
541 return NOTIFY_DONE;
542
543 /*
544 * Assert that local interrupts are disabled
545 * Reset the DRn bits in the virtualized register value.
546 * The ptrace trigger routine will add in whatever is needed.
547 */
548 current->thread.debugreg6 &= ~DR_TRAP_BITS;
549 cpu = get_cpu();
550
551 /* Handle all the breakpoints that were triggered */
552 for (i = 0; i < HBP_NUM; ++i) {
553 if (likely(!(dr6 & (DR_TRAP0 << i))))
554 continue;
555
556 /*
557 * The counter may be concurrently released but that can only
558 * occur from a call_rcu() path. We can then safely fetch
559 * the breakpoint, use its callback, touch its counter
560 * while we are in an rcu_read_lock() path.
561 */
562 rcu_read_lock();
563
564 bp = per_cpu(bp_per_reg[i], cpu);
565 /*
566 * Reset the 'i'th TRAP bit in dr6 to denote completion of
567 * exception handling
568 */
569 (*dr6_p) &= ~(DR_TRAP0 << i);
570 /*
571 * bp can be NULL due to lazy debug register switching
572 * or due to concurrent perf counter removing.
573 */
574 if (!bp) {
575 rcu_read_unlock();
576 break;
577 }
578
579 perf_bp_event(bp, args->regs);
580
581 /*
582 * Set up resume flag to avoid breakpoint recursion when
583 * returning back to origin.
584 */
585 if (bp->hw.info.type == X86_BREAKPOINT_EXECUTE)
586 args->regs->flags |= X86_EFLAGS_RF;
587
588 rcu_read_unlock();
589 }
590 /*
591 * Further processing in do_debug() is needed for a) user-space
592 * breakpoints (to generate signals) and b) when the system has
593 * taken exception due to multiple causes
594 */
595 if ((current->thread.debugreg6 & DR_TRAP_BITS) ||
596 (dr6 & (~DR_TRAP_BITS)))
597 rc = NOTIFY_DONE;
598
599 put_cpu();
600
601 return rc;
602}
603
604/*
605 * Handle debug exception notifications.
606 */
607int hw_breakpoint_exceptions_notify(
608 struct notifier_block *unused, unsigned long val, void *data)
609{
610 if (val != DIE_DEBUG)
611 return NOTIFY_DONE;
612
613 return hw_breakpoint_handler(data);
614}
615
616void hw_breakpoint_pmu_read(struct perf_event *bp)
617{
618 /* TODO */
619}