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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 */ | |
49 | DEFINE_PER_CPU(unsigned long, cpu_dr7); | |
50 | EXPORT_PER_CPU_SYMBOL(cpu_dr7); | |
51 | ||
52 | /* Per cpu debug address registers values */ | |
53 | static 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 | */ | |
59 | static DEFINE_PER_CPU(struct perf_event *, bp_per_reg[HBP_NUM]); | |
60 | ||
61 | ||
62 | static 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 | */ | |
78 | unsigned 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 | */ | |
87 | int 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 | */ | |
106 | int 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 | */ | |
144 | void 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 | ||
168 | static 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 | */ | |
194 | int 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 | ||
206 | int 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 | ||
252 | static 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 | */ | |
306 | int 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 | */ | |
356 | void 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 | } | |
382 | EXPORT_SYMBOL_GPL(aout_dump_debugregs); | |
383 | ||
384 | /* | |
385 | * Release the user breakpoints used by ptrace | |
386 | */ | |
387 | void 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 | t->debugreg6 = 0; | |
398 | t->ptrace_dr7 = 0; | |
399 | } | |
400 | ||
401 | void hw_breakpoint_restore(void) | |
402 | { | |
403 | set_debugreg(__this_cpu_read(cpu_debugreg[0]), 0); | |
404 | set_debugreg(__this_cpu_read(cpu_debugreg[1]), 1); | |
405 | set_debugreg(__this_cpu_read(cpu_debugreg[2]), 2); | |
406 | set_debugreg(__this_cpu_read(cpu_debugreg[3]), 3); | |
407 | set_debugreg(current->thread.debugreg6, 6); | |
408 | set_debugreg(__this_cpu_read(cpu_dr7), 7); | |
409 | } | |
410 | EXPORT_SYMBOL_GPL(hw_breakpoint_restore); | |
411 | ||
412 | /* | |
413 | * Handle debug exception notifications. | |
414 | * | |
415 | * Return value is either NOTIFY_STOP or NOTIFY_DONE as explained below. | |
416 | * | |
417 | * NOTIFY_DONE returned if one of the following conditions is true. | |
418 | * i) When the causative address is from user-space and the exception | |
419 | * is a valid one, i.e. not triggered as a result of lazy debug register | |
420 | * switching | |
421 | * ii) When there are more bits than trap<n> set in DR6 register (such | |
422 | * as BD, BS or BT) indicating that more than one debug condition is | |
423 | * met and requires some more action in do_debug(). | |
424 | * | |
425 | * NOTIFY_STOP returned for all other cases | |
426 | * | |
427 | */ | |
428 | static int __kprobes hw_breakpoint_handler(struct die_args *args) | |
429 | { | |
430 | int i, cpu, rc = NOTIFY_STOP; | |
431 | struct perf_event *bp; | |
432 | unsigned long dr7, dr6; | |
433 | unsigned long *dr6_p; | |
434 | ||
435 | /* The DR6 value is pointed by args->err */ | |
436 | dr6_p = (unsigned long *)ERR_PTR(args->err); | |
437 | dr6 = *dr6_p; | |
438 | ||
439 | /* If it's a single step, TRAP bits are random */ | |
440 | if (dr6 & DR_STEP) | |
441 | return NOTIFY_DONE; | |
442 | ||
443 | /* Do an early return if no trap bits are set in DR6 */ | |
444 | if ((dr6 & DR_TRAP_BITS) == 0) | |
445 | return NOTIFY_DONE; | |
446 | ||
447 | get_debugreg(dr7, 7); | |
448 | /* Disable breakpoints during exception handling */ | |
449 | set_debugreg(0UL, 7); | |
450 | /* | |
451 | * Assert that local interrupts are disabled | |
452 | * Reset the DRn bits in the virtualized register value. | |
453 | * The ptrace trigger routine will add in whatever is needed. | |
454 | */ | |
455 | current->thread.debugreg6 &= ~DR_TRAP_BITS; | |
456 | cpu = get_cpu(); | |
457 | ||
458 | /* Handle all the breakpoints that were triggered */ | |
459 | for (i = 0; i < HBP_NUM; ++i) { | |
460 | if (likely(!(dr6 & (DR_TRAP0 << i)))) | |
461 | continue; | |
462 | ||
463 | /* | |
464 | * The counter may be concurrently released but that can only | |
465 | * occur from a call_rcu() path. We can then safely fetch | |
466 | * the breakpoint, use its callback, touch its counter | |
467 | * while we are in an rcu_read_lock() path. | |
468 | */ | |
469 | rcu_read_lock(); | |
470 | ||
471 | bp = per_cpu(bp_per_reg[i], cpu); | |
472 | /* | |
473 | * Reset the 'i'th TRAP bit in dr6 to denote completion of | |
474 | * exception handling | |
475 | */ | |
476 | (*dr6_p) &= ~(DR_TRAP0 << i); | |
477 | /* | |
478 | * bp can be NULL due to lazy debug register switching | |
479 | * or due to concurrent perf counter removing. | |
480 | */ | |
481 | if (!bp) { | |
482 | rcu_read_unlock(); | |
483 | break; | |
484 | } | |
485 | ||
486 | perf_bp_event(bp, args->regs); | |
487 | ||
488 | /* | |
489 | * Set up resume flag to avoid breakpoint recursion when | |
490 | * returning back to origin. | |
491 | */ | |
492 | if (bp->hw.info.type == X86_BREAKPOINT_EXECUTE) | |
493 | args->regs->flags |= X86_EFLAGS_RF; | |
494 | ||
495 | rcu_read_unlock(); | |
496 | } | |
497 | /* | |
498 | * Further processing in do_debug() is needed for a) user-space | |
499 | * breakpoints (to generate signals) and b) when the system has | |
500 | * taken exception due to multiple causes | |
501 | */ | |
502 | if ((current->thread.debugreg6 & DR_TRAP_BITS) || | |
503 | (dr6 & (~DR_TRAP_BITS))) | |
504 | rc = NOTIFY_DONE; | |
505 | ||
506 | set_debugreg(dr7, 7); | |
507 | put_cpu(); | |
508 | ||
509 | return rc; | |
510 | } | |
511 | ||
512 | /* | |
513 | * Handle debug exception notifications. | |
514 | */ | |
515 | int __kprobes hw_breakpoint_exceptions_notify( | |
516 | struct notifier_block *unused, unsigned long val, void *data) | |
517 | { | |
518 | if (val != DIE_DEBUG) | |
519 | return NOTIFY_DONE; | |
520 | ||
521 | return hw_breakpoint_handler(data); | |
522 | } | |
523 | ||
524 | void hw_breakpoint_pmu_read(struct perf_event *bp) | |
525 | { | |
526 | /* TODO */ | |
527 | } |