1 /*
2 * arch/sh/kernel/hw_breakpoint.c
3 *
4 * Unified kernel/user-space hardware breakpoint facility for the on-chip UBC.
5 *
6 * Copyright (C) 2009 - 2010 Paul Mundt
7 *
8 * This file is subject to the terms and conditions of the GNU General Public
9 * License. See the file "COPYING" in the main directory of this archive
10 * for more details.
11 */
12 #include <linux/init.h>
13 #include <linux/perf_event.h>
14 #include <linux/hw_breakpoint.h>
15 #include <linux/percpu.h>
16 #include <linux/kallsyms.h>
17 #include <linux/notifier.h>
18 #include <linux/kprobes.h>
19 #include <linux/kdebug.h>
20 #include <linux/io.h>
21 #include <linux/clk.h>
22 #include <asm/hw_breakpoint.h>
23 #include <asm/mmu_context.h>
24 #include <asm/ptrace.h>
25 #include <asm/traps.h>
26
27 /*
28 * Stores the breakpoints currently in use on each breakpoint address
29 * register for each cpus
30 */
31 static DEFINE_PER_CPU(struct perf_event *, bp_per_reg[HBP_NUM]);
32
33 /*
34 * A dummy placeholder for early accesses until the CPUs get a chance to
35 * register their UBCs later in the boot process.
36 */
37 static struct sh_ubc ubc_dummy = { .num_events = 0 };
38
39 static struct sh_ubc *sh_ubc __read_mostly = &ubc_dummy;
40
41 /*
42 * Install a perf counter breakpoint.
43 *
44 * We seek a free UBC channel and use it for this breakpoint.
45 *
46 * Atomic: we hold the counter->ctx->lock and we only handle variables
47 * and registers local to this cpu.
48 */
arch_install_hw_breakpoint(struct perf_event * bp)49 int arch_install_hw_breakpoint(struct perf_event *bp)
50 {
51 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
52 int i;
53
54 for (i = 0; i < sh_ubc->num_events; i++) {
55 struct perf_event **slot = this_cpu_ptr(&bp_per_reg[i]);
56
57 if (!*slot) {
58 *slot = bp;
59 break;
60 }
61 }
62
63 if (WARN_ONCE(i == sh_ubc->num_events, "Can't find any breakpoint slot"))
64 return -EBUSY;
65
66 clk_enable(sh_ubc->clk);
67 sh_ubc->enable(info, i);
68
69 return 0;
70 }
71
72 /*
73 * Uninstall the breakpoint contained in the given counter.
74 *
75 * First we search the debug address register it uses and then we disable
76 * it.
77 *
78 * Atomic: we hold the counter->ctx->lock and we only handle variables
79 * and registers local to this cpu.
80 */
arch_uninstall_hw_breakpoint(struct perf_event * bp)81 void arch_uninstall_hw_breakpoint(struct perf_event *bp)
82 {
83 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
84 int i;
85
86 for (i = 0; i < sh_ubc->num_events; i++) {
87 struct perf_event **slot = this_cpu_ptr(&bp_per_reg[i]);
88
89 if (*slot == bp) {
90 *slot = NULL;
91 break;
92 }
93 }
94
95 if (WARN_ONCE(i == sh_ubc->num_events, "Can't find any breakpoint slot"))
96 return;
97
98 sh_ubc->disable(info, i);
99 clk_disable(sh_ubc->clk);
100 }
101
get_hbp_len(u16 hbp_len)102 static int get_hbp_len(u16 hbp_len)
103 {
104 unsigned int len_in_bytes = 0;
105
106 switch (hbp_len) {
107 case SH_BREAKPOINT_LEN_1:
108 len_in_bytes = 1;
109 break;
110 case SH_BREAKPOINT_LEN_2:
111 len_in_bytes = 2;
112 break;
113 case SH_BREAKPOINT_LEN_4:
114 len_in_bytes = 4;
115 break;
116 case SH_BREAKPOINT_LEN_8:
117 len_in_bytes = 8;
118 break;
119 }
120 return len_in_bytes;
121 }
122
123 /*
124 * Check for virtual address in kernel space.
125 */
arch_check_bp_in_kernelspace(struct perf_event * bp)126 int arch_check_bp_in_kernelspace(struct perf_event *bp)
127 {
128 unsigned int len;
129 unsigned long va;
130 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
131
132 va = info->address;
133 len = get_hbp_len(info->len);
134
135 return (va >= TASK_SIZE) && ((va + len - 1) >= TASK_SIZE);
136 }
137
arch_bp_generic_fields(int sh_len,int sh_type,int * gen_len,int * gen_type)138 int arch_bp_generic_fields(int sh_len, int sh_type,
139 int *gen_len, int *gen_type)
140 {
141 /* Len */
142 switch (sh_len) {
143 case SH_BREAKPOINT_LEN_1:
144 *gen_len = HW_BREAKPOINT_LEN_1;
145 break;
146 case SH_BREAKPOINT_LEN_2:
147 *gen_len = HW_BREAKPOINT_LEN_2;
148 break;
149 case SH_BREAKPOINT_LEN_4:
150 *gen_len = HW_BREAKPOINT_LEN_4;
151 break;
152 case SH_BREAKPOINT_LEN_8:
153 *gen_len = HW_BREAKPOINT_LEN_8;
154 break;
155 default:
156 return -EINVAL;
157 }
158
159 /* Type */
160 switch (sh_type) {
161 case SH_BREAKPOINT_READ:
162 *gen_type = HW_BREAKPOINT_R;
163 case SH_BREAKPOINT_WRITE:
164 *gen_type = HW_BREAKPOINT_W;
165 break;
166 case SH_BREAKPOINT_RW:
167 *gen_type = HW_BREAKPOINT_W | HW_BREAKPOINT_R;
168 break;
169 default:
170 return -EINVAL;
171 }
172
173 return 0;
174 }
175
arch_build_bp_info(struct perf_event * bp)176 static int arch_build_bp_info(struct perf_event *bp)
177 {
178 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
179
180 info->address = bp->attr.bp_addr;
181
182 /* Len */
183 switch (bp->attr.bp_len) {
184 case HW_BREAKPOINT_LEN_1:
185 info->len = SH_BREAKPOINT_LEN_1;
186 break;
187 case HW_BREAKPOINT_LEN_2:
188 info->len = SH_BREAKPOINT_LEN_2;
189 break;
190 case HW_BREAKPOINT_LEN_4:
191 info->len = SH_BREAKPOINT_LEN_4;
192 break;
193 case HW_BREAKPOINT_LEN_8:
194 info->len = SH_BREAKPOINT_LEN_8;
195 break;
196 default:
197 return -EINVAL;
198 }
199
200 /* Type */
201 switch (bp->attr.bp_type) {
202 case HW_BREAKPOINT_R:
203 info->type = SH_BREAKPOINT_READ;
204 break;
205 case HW_BREAKPOINT_W:
206 info->type = SH_BREAKPOINT_WRITE;
207 break;
208 case HW_BREAKPOINT_W | HW_BREAKPOINT_R:
209 info->type = SH_BREAKPOINT_RW;
210 break;
211 default:
212 return -EINVAL;
213 }
214
215 return 0;
216 }
217
218 /*
219 * Validate the arch-specific HW Breakpoint register settings
220 */
arch_validate_hwbkpt_settings(struct perf_event * bp)221 int arch_validate_hwbkpt_settings(struct perf_event *bp)
222 {
223 struct arch_hw_breakpoint *info = counter_arch_bp(bp);
224 unsigned int align;
225 int ret;
226
227 ret = arch_build_bp_info(bp);
228 if (ret)
229 return ret;
230
231 ret = -EINVAL;
232
233 switch (info->len) {
234 case SH_BREAKPOINT_LEN_1:
235 align = 0;
236 break;
237 case SH_BREAKPOINT_LEN_2:
238 align = 1;
239 break;
240 case SH_BREAKPOINT_LEN_4:
241 align = 3;
242 break;
243 case SH_BREAKPOINT_LEN_8:
244 align = 7;
245 break;
246 default:
247 return ret;
248 }
249
250 /*
251 * For kernel-addresses, either the address or symbol name can be
252 * specified.
253 */
254 if (info->name)
255 info->address = (unsigned long)kallsyms_lookup_name(info->name);
256
257 /*
258 * Check that the low-order bits of the address are appropriate
259 * for the alignment implied by len.
260 */
261 if (info->address & align)
262 return -EINVAL;
263
264 return 0;
265 }
266
267 /*
268 * Release the user breakpoints used by ptrace
269 */
flush_ptrace_hw_breakpoint(struct task_struct * tsk)270 void flush_ptrace_hw_breakpoint(struct task_struct *tsk)
271 {
272 int i;
273 struct thread_struct *t = &tsk->thread;
274
275 for (i = 0; i < sh_ubc->num_events; i++) {
276 unregister_hw_breakpoint(t->ptrace_bps[i]);
277 t->ptrace_bps[i] = NULL;
278 }
279 }
280
hw_breakpoint_handler(struct die_args * args)281 static int __kprobes hw_breakpoint_handler(struct die_args *args)
282 {
283 int cpu, i, rc = NOTIFY_STOP;
284 struct perf_event *bp;
285 unsigned int cmf, resume_mask;
286
287 /*
288 * Do an early return if none of the channels triggered.
289 */
290 cmf = sh_ubc->triggered_mask();
291 if (unlikely(!cmf))
292 return NOTIFY_DONE;
293
294 /*
295 * By default, resume all of the active channels.
296 */
297 resume_mask = sh_ubc->active_mask();
298
299 /*
300 * Disable breakpoints during exception handling.
301 */
302 sh_ubc->disable_all();
303
304 cpu = get_cpu();
305 for (i = 0; i < sh_ubc->num_events; i++) {
306 unsigned long event_mask = (1 << i);
307
308 if (likely(!(cmf & event_mask)))
309 continue;
310
311 /*
312 * The counter may be concurrently released but that can only
313 * occur from a call_rcu() path. We can then safely fetch
314 * the breakpoint, use its callback, touch its counter
315 * while we are in an rcu_read_lock() path.
316 */
317 rcu_read_lock();
318
319 bp = per_cpu(bp_per_reg[i], cpu);
320 if (bp)
321 rc = NOTIFY_DONE;
322
323 /*
324 * Reset the condition match flag to denote completion of
325 * exception handling.
326 */
327 sh_ubc->clear_triggered_mask(event_mask);
328
329 /*
330 * bp can be NULL due to concurrent perf counter
331 * removing.
332 */
333 if (!bp) {
334 rcu_read_unlock();
335 break;
336 }
337
338 /*
339 * Don't restore the channel if the breakpoint is from
340 * ptrace, as it always operates in one-shot mode.
341 */
342 if (bp->overflow_handler == ptrace_triggered)
343 resume_mask &= ~(1 << i);
344
345 perf_bp_event(bp, args->regs);
346
347 /* Deliver the signal to userspace */
348 if (!arch_check_bp_in_kernelspace(bp)) {
349 siginfo_t info;
350
351 info.si_signo = args->signr;
352 info.si_errno = notifier_to_errno(rc);
353 info.si_code = TRAP_HWBKPT;
354
355 force_sig_info(args->signr, &info, current);
356 }
357
358 rcu_read_unlock();
359 }
360
361 if (cmf == 0)
362 rc = NOTIFY_DONE;
363
364 sh_ubc->enable_all(resume_mask);
365
366 put_cpu();
367
368 return rc;
369 }
370
BUILD_TRAP_HANDLER(breakpoint)371 BUILD_TRAP_HANDLER(breakpoint)
372 {
373 unsigned long ex = lookup_exception_vector();
374 TRAP_HANDLER_DECL;
375
376 notify_die(DIE_BREAKPOINT, "breakpoint", regs, 0, ex, SIGTRAP);
377 }
378
379 /*
380 * Handle debug exception notifications.
381 */
hw_breakpoint_exceptions_notify(struct notifier_block * unused,unsigned long val,void * data)382 int __kprobes hw_breakpoint_exceptions_notify(struct notifier_block *unused,
383 unsigned long val, void *data)
384 {
385 struct die_args *args = data;
386
387 if (val != DIE_BREAKPOINT)
388 return NOTIFY_DONE;
389
390 /*
391 * If the breakpoint hasn't been triggered by the UBC, it's
392 * probably from a debugger, so don't do anything more here.
393 *
394 * This also permits the UBC interface clock to remain off for
395 * non-UBC breakpoints, as we don't need to check the triggered
396 * or active channel masks.
397 */
398 if (args->trapnr != sh_ubc->trap_nr)
399 return NOTIFY_DONE;
400
401 return hw_breakpoint_handler(data);
402 }
403
hw_breakpoint_pmu_read(struct perf_event * bp)404 void hw_breakpoint_pmu_read(struct perf_event *bp)
405 {
406 /* TODO */
407 }
408
register_sh_ubc(struct sh_ubc * ubc)409 int register_sh_ubc(struct sh_ubc *ubc)
410 {
411 /* Bail if it's already assigned */
412 if (sh_ubc != &ubc_dummy)
413 return -EBUSY;
414 sh_ubc = ubc;
415
416 pr_info("HW Breakpoints: %s UBC support registered\n", ubc->name);
417
418 WARN_ON(ubc->num_events > HBP_NUM);
419
420 return 0;
421 }
422