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478fcb2c WD |
1 | /* |
2 | * ARMv8 single-step debug support and mdscr context switching. | |
3 | * | |
4 | * Copyright (C) 2012 ARM Limited | |
5 | * | |
6 | * This program is free software; you can redistribute it and/or modify | |
7 | * it under the terms of the GNU General Public License version 2 as | |
8 | * published by the Free Software Foundation. | |
9 | * | |
10 | * This program is distributed in the hope that it will be useful, | |
11 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
13 | * GNU General Public License for more details. | |
14 | * | |
15 | * You should have received a copy of the GNU General Public License | |
16 | * along with this program. If not, see <http://www.gnu.org/licenses/>. | |
17 | * | |
18 | * Author: Will Deacon <will.deacon@arm.com> | |
19 | */ | |
20 | ||
21 | #include <linux/cpu.h> | |
22 | #include <linux/debugfs.h> | |
23 | #include <linux/hardirq.h> | |
24 | #include <linux/init.h> | |
25 | #include <linux/ptrace.h> | |
26 | #include <linux/stat.h> | |
1442b6ed | 27 | #include <linux/uaccess.h> |
478fcb2c WD |
28 | |
29 | #include <asm/debug-monitors.h> | |
478fcb2c WD |
30 | #include <asm/cputype.h> |
31 | #include <asm/system_misc.h> | |
32 | ||
33 | /* Low-level stepping controls. */ | |
34 | #define DBG_MDSCR_SS (1 << 0) | |
35 | #define DBG_SPSR_SS (1 << 21) | |
36 | ||
37 | /* MDSCR_EL1 enabling bits */ | |
38 | #define DBG_MDSCR_KDE (1 << 13) | |
39 | #define DBG_MDSCR_MDE (1 << 15) | |
40 | #define DBG_MDSCR_MASK ~(DBG_MDSCR_KDE | DBG_MDSCR_MDE) | |
41 | ||
42 | /* Determine debug architecture. */ | |
43 | u8 debug_monitors_arch(void) | |
44 | { | |
45 | return read_cpuid(ID_AA64DFR0_EL1) & 0xf; | |
46 | } | |
47 | ||
48 | /* | |
49 | * MDSCR access routines. | |
50 | */ | |
51 | static void mdscr_write(u32 mdscr) | |
52 | { | |
53 | unsigned long flags; | |
54 | local_dbg_save(flags); | |
55 | asm volatile("msr mdscr_el1, %0" :: "r" (mdscr)); | |
56 | local_dbg_restore(flags); | |
57 | } | |
58 | ||
59 | static u32 mdscr_read(void) | |
60 | { | |
61 | u32 mdscr; | |
62 | asm volatile("mrs %0, mdscr_el1" : "=r" (mdscr)); | |
63 | return mdscr; | |
64 | } | |
65 | ||
66 | /* | |
67 | * Allow root to disable self-hosted debug from userspace. | |
68 | * This is useful if you want to connect an external JTAG debugger. | |
69 | */ | |
70 | static u32 debug_enabled = 1; | |
71 | ||
72 | static int create_debug_debugfs_entry(void) | |
73 | { | |
74 | debugfs_create_bool("debug_enabled", 0644, NULL, &debug_enabled); | |
75 | return 0; | |
76 | } | |
77 | fs_initcall(create_debug_debugfs_entry); | |
78 | ||
79 | static int __init early_debug_disable(char *buf) | |
80 | { | |
81 | debug_enabled = 0; | |
82 | return 0; | |
83 | } | |
84 | ||
85 | early_param("nodebugmon", early_debug_disable); | |
86 | ||
87 | /* | |
88 | * Keep track of debug users on each core. | |
89 | * The ref counts are per-cpu so we use a local_t type. | |
90 | */ | |
1436c1aa CL |
91 | static DEFINE_PER_CPU(int, mde_ref_count); |
92 | static DEFINE_PER_CPU(int, kde_ref_count); | |
478fcb2c WD |
93 | |
94 | void enable_debug_monitors(enum debug_el el) | |
95 | { | |
96 | u32 mdscr, enable = 0; | |
97 | ||
98 | WARN_ON(preemptible()); | |
99 | ||
1436c1aa | 100 | if (this_cpu_inc_return(mde_ref_count) == 1) |
478fcb2c WD |
101 | enable = DBG_MDSCR_MDE; |
102 | ||
103 | if (el == DBG_ACTIVE_EL1 && | |
1436c1aa | 104 | this_cpu_inc_return(kde_ref_count) == 1) |
478fcb2c WD |
105 | enable |= DBG_MDSCR_KDE; |
106 | ||
107 | if (enable && debug_enabled) { | |
108 | mdscr = mdscr_read(); | |
109 | mdscr |= enable; | |
110 | mdscr_write(mdscr); | |
111 | } | |
112 | } | |
113 | ||
114 | void disable_debug_monitors(enum debug_el el) | |
115 | { | |
116 | u32 mdscr, disable = 0; | |
117 | ||
118 | WARN_ON(preemptible()); | |
119 | ||
1436c1aa | 120 | if (this_cpu_dec_return(mde_ref_count) == 0) |
478fcb2c WD |
121 | disable = ~DBG_MDSCR_MDE; |
122 | ||
123 | if (el == DBG_ACTIVE_EL1 && | |
1436c1aa | 124 | this_cpu_dec_return(kde_ref_count) == 0) |
478fcb2c WD |
125 | disable &= ~DBG_MDSCR_KDE; |
126 | ||
127 | if (disable) { | |
128 | mdscr = mdscr_read(); | |
129 | mdscr &= disable; | |
130 | mdscr_write(mdscr); | |
131 | } | |
132 | } | |
133 | ||
134 | /* | |
135 | * OS lock clearing. | |
136 | */ | |
137 | static void clear_os_lock(void *unused) | |
138 | { | |
478fcb2c WD |
139 | asm volatile("msr oslar_el1, %0" : : "r" (0)); |
140 | isb(); | |
141 | } | |
142 | ||
b8c6453a | 143 | static int os_lock_notify(struct notifier_block *self, |
478fcb2c WD |
144 | unsigned long action, void *data) |
145 | { | |
146 | int cpu = (unsigned long)data; | |
147 | if (action == CPU_ONLINE) | |
148 | smp_call_function_single(cpu, clear_os_lock, NULL, 1); | |
149 | return NOTIFY_OK; | |
150 | } | |
151 | ||
b8c6453a | 152 | static struct notifier_block os_lock_nb = { |
478fcb2c WD |
153 | .notifier_call = os_lock_notify, |
154 | }; | |
155 | ||
b8c6453a | 156 | static int debug_monitors_init(void) |
478fcb2c WD |
157 | { |
158 | /* Clear the OS lock. */ | |
159 | smp_call_function(clear_os_lock, NULL, 1); | |
160 | clear_os_lock(NULL); | |
161 | ||
162 | /* Register hotplug handler. */ | |
163 | register_cpu_notifier(&os_lock_nb); | |
164 | return 0; | |
165 | } | |
166 | postcore_initcall(debug_monitors_init); | |
167 | ||
168 | /* | |
169 | * Single step API and exception handling. | |
170 | */ | |
171 | static void set_regs_spsr_ss(struct pt_regs *regs) | |
172 | { | |
173 | unsigned long spsr; | |
174 | ||
175 | spsr = regs->pstate; | |
176 | spsr &= ~DBG_SPSR_SS; | |
177 | spsr |= DBG_SPSR_SS; | |
178 | regs->pstate = spsr; | |
179 | } | |
180 | ||
181 | static void clear_regs_spsr_ss(struct pt_regs *regs) | |
182 | { | |
183 | unsigned long spsr; | |
184 | ||
185 | spsr = regs->pstate; | |
186 | spsr &= ~DBG_SPSR_SS; | |
187 | regs->pstate = spsr; | |
188 | } | |
189 | ||
ee6214ce SP |
190 | /* EL1 Single Step Handler hooks */ |
191 | static LIST_HEAD(step_hook); | |
192 | DEFINE_RWLOCK(step_hook_lock); | |
193 | ||
194 | void register_step_hook(struct step_hook *hook) | |
195 | { | |
196 | write_lock(&step_hook_lock); | |
197 | list_add(&hook->node, &step_hook); | |
198 | write_unlock(&step_hook_lock); | |
199 | } | |
200 | ||
201 | void unregister_step_hook(struct step_hook *hook) | |
202 | { | |
203 | write_lock(&step_hook_lock); | |
204 | list_del(&hook->node); | |
205 | write_unlock(&step_hook_lock); | |
206 | } | |
207 | ||
208 | /* | |
209 | * Call registered single step handers | |
210 | * There is no Syndrome info to check for determining the handler. | |
211 | * So we call all the registered handlers, until the right handler is | |
212 | * found which returns zero. | |
213 | */ | |
214 | static int call_step_hook(struct pt_regs *regs, unsigned int esr) | |
215 | { | |
216 | struct step_hook *hook; | |
217 | int retval = DBG_HOOK_ERROR; | |
218 | ||
219 | read_lock(&step_hook_lock); | |
220 | ||
221 | list_for_each_entry(hook, &step_hook, node) { | |
222 | retval = hook->fn(regs, esr); | |
223 | if (retval == DBG_HOOK_HANDLED) | |
224 | break; | |
225 | } | |
226 | ||
227 | read_unlock(&step_hook_lock); | |
228 | ||
229 | return retval; | |
230 | } | |
231 | ||
478fcb2c WD |
232 | static int single_step_handler(unsigned long addr, unsigned int esr, |
233 | struct pt_regs *regs) | |
234 | { | |
235 | siginfo_t info; | |
236 | ||
237 | /* | |
238 | * If we are stepping a pending breakpoint, call the hw_breakpoint | |
239 | * handler first. | |
240 | */ | |
241 | if (!reinstall_suspended_bps(regs)) | |
242 | return 0; | |
243 | ||
244 | if (user_mode(regs)) { | |
245 | info.si_signo = SIGTRAP; | |
246 | info.si_errno = 0; | |
247 | info.si_code = TRAP_HWBKPT; | |
248 | info.si_addr = (void __user *)instruction_pointer(regs); | |
249 | force_sig_info(SIGTRAP, &info, current); | |
250 | ||
251 | /* | |
252 | * ptrace will disable single step unless explicitly | |
253 | * asked to re-enable it. For other clients, it makes | |
254 | * sense to leave it enabled (i.e. rewind the controls | |
255 | * to the active-not-pending state). | |
256 | */ | |
257 | user_rewind_single_step(current); | |
258 | } else { | |
ee6214ce SP |
259 | if (call_step_hook(regs, esr) == DBG_HOOK_HANDLED) |
260 | return 0; | |
261 | ||
478fcb2c WD |
262 | pr_warning("Unexpected kernel single-step exception at EL1\n"); |
263 | /* | |
264 | * Re-enable stepping since we know that we will be | |
265 | * returning to regs. | |
266 | */ | |
267 | set_regs_spsr_ss(regs); | |
268 | } | |
269 | ||
270 | return 0; | |
271 | } | |
272 | ||
ee6214ce SP |
273 | /* |
274 | * Breakpoint handler is re-entrant as another breakpoint can | |
275 | * hit within breakpoint handler, especically in kprobes. | |
276 | * Use reader/writer locks instead of plain spinlock. | |
277 | */ | |
278 | static LIST_HEAD(break_hook); | |
279 | DEFINE_RWLOCK(break_hook_lock); | |
280 | ||
281 | void register_break_hook(struct break_hook *hook) | |
282 | { | |
283 | write_lock(&break_hook_lock); | |
284 | list_add(&hook->node, &break_hook); | |
285 | write_unlock(&break_hook_lock); | |
286 | } | |
287 | ||
288 | void unregister_break_hook(struct break_hook *hook) | |
289 | { | |
290 | write_lock(&break_hook_lock); | |
291 | list_del(&hook->node); | |
292 | write_unlock(&break_hook_lock); | |
293 | } | |
294 | ||
295 | static int call_break_hook(struct pt_regs *regs, unsigned int esr) | |
296 | { | |
297 | struct break_hook *hook; | |
298 | int (*fn)(struct pt_regs *regs, unsigned int esr) = NULL; | |
299 | ||
300 | read_lock(&break_hook_lock); | |
301 | list_for_each_entry(hook, &break_hook, node) | |
302 | if ((esr & hook->esr_mask) == hook->esr_val) | |
303 | fn = hook->fn; | |
304 | read_unlock(&break_hook_lock); | |
305 | ||
306 | return fn ? fn(regs, esr) : DBG_HOOK_ERROR; | |
307 | } | |
308 | ||
1442b6ed WD |
309 | static int brk_handler(unsigned long addr, unsigned int esr, |
310 | struct pt_regs *regs) | |
311 | { | |
312 | siginfo_t info; | |
313 | ||
ee6214ce SP |
314 | if (call_break_hook(regs, esr) == DBG_HOOK_HANDLED) |
315 | return 0; | |
316 | ||
317 | pr_warn("unexpected brk exception at %lx, esr=0x%x\n", | |
318 | (long)instruction_pointer(regs), esr); | |
319 | ||
1442b6ed WD |
320 | if (!user_mode(regs)) |
321 | return -EFAULT; | |
322 | ||
323 | info = (siginfo_t) { | |
324 | .si_signo = SIGTRAP, | |
325 | .si_errno = 0, | |
326 | .si_code = TRAP_BRKPT, | |
327 | .si_addr = (void __user *)instruction_pointer(regs), | |
328 | }; | |
329 | ||
330 | force_sig_info(SIGTRAP, &info, current); | |
331 | return 0; | |
332 | } | |
333 | ||
334 | int aarch32_break_handler(struct pt_regs *regs) | |
335 | { | |
336 | siginfo_t info; | |
2dacab73 ML |
337 | u32 arm_instr; |
338 | u16 thumb_instr; | |
1442b6ed WD |
339 | bool bp = false; |
340 | void __user *pc = (void __user *)instruction_pointer(regs); | |
341 | ||
342 | if (!compat_user_mode(regs)) | |
343 | return -EFAULT; | |
344 | ||
345 | if (compat_thumb_mode(regs)) { | |
346 | /* get 16-bit Thumb instruction */ | |
2dacab73 ML |
347 | get_user(thumb_instr, (u16 __user *)pc); |
348 | thumb_instr = le16_to_cpu(thumb_instr); | |
349 | if (thumb_instr == AARCH32_BREAK_THUMB2_LO) { | |
1442b6ed | 350 | /* get second half of 32-bit Thumb-2 instruction */ |
2dacab73 ML |
351 | get_user(thumb_instr, (u16 __user *)(pc + 2)); |
352 | thumb_instr = le16_to_cpu(thumb_instr); | |
353 | bp = thumb_instr == AARCH32_BREAK_THUMB2_HI; | |
1442b6ed | 354 | } else { |
2dacab73 | 355 | bp = thumb_instr == AARCH32_BREAK_THUMB; |
1442b6ed WD |
356 | } |
357 | } else { | |
358 | /* 32-bit ARM instruction */ | |
2dacab73 ML |
359 | get_user(arm_instr, (u32 __user *)pc); |
360 | arm_instr = le32_to_cpu(arm_instr); | |
361 | bp = (arm_instr & ~0xf0000000) == AARCH32_BREAK_ARM; | |
1442b6ed WD |
362 | } |
363 | ||
364 | if (!bp) | |
365 | return -EFAULT; | |
366 | ||
367 | info = (siginfo_t) { | |
368 | .si_signo = SIGTRAP, | |
369 | .si_errno = 0, | |
370 | .si_code = TRAP_BRKPT, | |
371 | .si_addr = pc, | |
372 | }; | |
373 | ||
374 | force_sig_info(SIGTRAP, &info, current); | |
375 | return 0; | |
376 | } | |
377 | ||
378 | static int __init debug_traps_init(void) | |
478fcb2c WD |
379 | { |
380 | hook_debug_fault_code(DBG_ESR_EVT_HWSS, single_step_handler, SIGTRAP, | |
381 | TRAP_HWBKPT, "single-step handler"); | |
1442b6ed WD |
382 | hook_debug_fault_code(DBG_ESR_EVT_BRK, brk_handler, SIGTRAP, |
383 | TRAP_BRKPT, "ptrace BRK handler"); | |
478fcb2c WD |
384 | return 0; |
385 | } | |
1442b6ed | 386 | arch_initcall(debug_traps_init); |
478fcb2c WD |
387 | |
388 | /* Re-enable single step for syscall restarting. */ | |
389 | void user_rewind_single_step(struct task_struct *task) | |
390 | { | |
391 | /* | |
392 | * If single step is active for this thread, then set SPSR.SS | |
393 | * to 1 to avoid returning to the active-pending state. | |
394 | */ | |
395 | if (test_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP)) | |
396 | set_regs_spsr_ss(task_pt_regs(task)); | |
397 | } | |
398 | ||
399 | void user_fastforward_single_step(struct task_struct *task) | |
400 | { | |
401 | if (test_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP)) | |
402 | clear_regs_spsr_ss(task_pt_regs(task)); | |
403 | } | |
404 | ||
405 | /* Kernel API */ | |
406 | void kernel_enable_single_step(struct pt_regs *regs) | |
407 | { | |
408 | WARN_ON(!irqs_disabled()); | |
409 | set_regs_spsr_ss(regs); | |
410 | mdscr_write(mdscr_read() | DBG_MDSCR_SS); | |
411 | enable_debug_monitors(DBG_ACTIVE_EL1); | |
412 | } | |
413 | ||
414 | void kernel_disable_single_step(void) | |
415 | { | |
416 | WARN_ON(!irqs_disabled()); | |
417 | mdscr_write(mdscr_read() & ~DBG_MDSCR_SS); | |
418 | disable_debug_monitors(DBG_ACTIVE_EL1); | |
419 | } | |
420 | ||
421 | int kernel_active_single_step(void) | |
422 | { | |
423 | WARN_ON(!irqs_disabled()); | |
424 | return mdscr_read() & DBG_MDSCR_SS; | |
425 | } | |
426 | ||
427 | /* ptrace API */ | |
428 | void user_enable_single_step(struct task_struct *task) | |
429 | { | |
430 | set_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP); | |
431 | set_regs_spsr_ss(task_pt_regs(task)); | |
432 | } | |
433 | ||
434 | void user_disable_single_step(struct task_struct *task) | |
435 | { | |
436 | clear_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP); | |
437 | } |