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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/kprobes.h>
27#include <linux/stat.h>
28#include <linux/uaccess.h>
29#include <linux/sched/task_stack.h>
30
31#include <asm/cpufeature.h>
32#include <asm/cputype.h>
33#include <asm/daifflags.h>
34#include <asm/debug-monitors.h>
35#include <asm/system_misc.h>
36#include <asm/traps.h>
37
38
39u8 debug_monitors_arch(void)
40{
41 return cpuid_feature_extract_unsigned_field(read_sanitised_ftr_reg(SYS_ID_AA64DFR0_EL1),
42 ID_AA64DFR0_DEBUGVER_SHIFT);
43}
44
45
46
47
48static void mdscr_write(u32 mdscr)
49{
50 unsigned long flags;
51 flags = local_daif_save();
52 write_sysreg(mdscr, mdscr_el1);
53 local_daif_restore(flags);
54}
55NOKPROBE_SYMBOL(mdscr_write);
56
57static u32 mdscr_read(void)
58{
59 return read_sysreg(mdscr_el1);
60}
61NOKPROBE_SYMBOL(mdscr_read);
62
63
64
65
66
67static bool debug_enabled = true;
68
69static int create_debug_debugfs_entry(void)
70{
71 debugfs_create_bool("debug_enabled", 0644, NULL, &debug_enabled);
72 return 0;
73}
74fs_initcall(create_debug_debugfs_entry);
75
76static int __init early_debug_disable(char *buf)
77{
78 debug_enabled = false;
79 return 0;
80}
81
82early_param("nodebugmon", early_debug_disable);
83
84
85
86
87
88static DEFINE_PER_CPU(int, mde_ref_count);
89static DEFINE_PER_CPU(int, kde_ref_count);
90
91void enable_debug_monitors(enum dbg_active_el el)
92{
93 u32 mdscr, enable = 0;
94
95 WARN_ON(preemptible());
96
97 if (this_cpu_inc_return(mde_ref_count) == 1)
98 enable = DBG_MDSCR_MDE;
99
100 if (el == DBG_ACTIVE_EL1 &&
101 this_cpu_inc_return(kde_ref_count) == 1)
102 enable |= DBG_MDSCR_KDE;
103
104 if (enable && debug_enabled) {
105 mdscr = mdscr_read();
106 mdscr |= enable;
107 mdscr_write(mdscr);
108 }
109}
110NOKPROBE_SYMBOL(enable_debug_monitors);
111
112void disable_debug_monitors(enum dbg_active_el el)
113{
114 u32 mdscr, disable = 0;
115
116 WARN_ON(preemptible());
117
118 if (this_cpu_dec_return(mde_ref_count) == 0)
119 disable = ~DBG_MDSCR_MDE;
120
121 if (el == DBG_ACTIVE_EL1 &&
122 this_cpu_dec_return(kde_ref_count) == 0)
123 disable &= ~DBG_MDSCR_KDE;
124
125 if (disable) {
126 mdscr = mdscr_read();
127 mdscr &= disable;
128 mdscr_write(mdscr);
129 }
130}
131NOKPROBE_SYMBOL(disable_debug_monitors);
132
133
134
135
136static int clear_os_lock(unsigned int cpu)
137{
138 write_sysreg(0, oslar_el1);
139 isb();
140 return 0;
141}
142
143static int debug_monitors_init(void)
144{
145 return cpuhp_setup_state(CPUHP_AP_ARM64_DEBUG_MONITORS_STARTING,
146 "arm64/debug_monitors:starting",
147 clear_os_lock, NULL);
148}
149postcore_initcall(debug_monitors_init);
150
151
152
153
154static void set_regs_spsr_ss(struct pt_regs *regs)
155{
156 regs->pstate |= DBG_SPSR_SS;
157}
158NOKPROBE_SYMBOL(set_regs_spsr_ss);
159
160static void clear_regs_spsr_ss(struct pt_regs *regs)
161{
162 regs->pstate &= ~DBG_SPSR_SS;
163}
164NOKPROBE_SYMBOL(clear_regs_spsr_ss);
165
166
167static LIST_HEAD(step_hook);
168static DEFINE_SPINLOCK(step_hook_lock);
169
170void register_step_hook(struct step_hook *hook)
171{
172 spin_lock(&step_hook_lock);
173 list_add_rcu(&hook->node, &step_hook);
174 spin_unlock(&step_hook_lock);
175}
176
177void unregister_step_hook(struct step_hook *hook)
178{
179 spin_lock(&step_hook_lock);
180 list_del_rcu(&hook->node);
181 spin_unlock(&step_hook_lock);
182 synchronize_rcu();
183}
184
185
186
187
188
189
190
191static int call_step_hook(struct pt_regs *regs, unsigned int esr)
192{
193 struct step_hook *hook;
194 int retval = DBG_HOOK_ERROR;
195
196 rcu_read_lock();
197
198 list_for_each_entry_rcu(hook, &step_hook, node) {
199 retval = hook->fn(regs, esr);
200 if (retval == DBG_HOOK_HANDLED)
201 break;
202 }
203
204 rcu_read_unlock();
205
206 return retval;
207}
208NOKPROBE_SYMBOL(call_step_hook);
209
210static void send_user_sigtrap(int si_code)
211{
212 struct pt_regs *regs = current_pt_regs();
213 siginfo_t info;
214
215 clear_siginfo(&info);
216 info.si_signo = SIGTRAP;
217 info.si_errno = 0;
218 info.si_code = si_code;
219 info.si_addr = (void __user *)instruction_pointer(regs);
220
221 if (WARN_ON(!user_mode(regs)))
222 return;
223
224 if (interrupts_enabled(regs))
225 local_irq_enable();
226
227 arm64_force_sig_info(&info, "User debug trap", current);
228}
229
230static int single_step_handler(unsigned long addr, unsigned int esr,
231 struct pt_regs *regs)
232{
233 bool handler_found = false;
234
235
236
237
238
239 if (!reinstall_suspended_bps(regs))
240 return 0;
241
242#ifdef CONFIG_KPROBES
243 if (kprobe_single_step_handler(regs, esr) == DBG_HOOK_HANDLED)
244 handler_found = true;
245#endif
246 if (!handler_found && call_step_hook(regs, esr) == DBG_HOOK_HANDLED)
247 handler_found = true;
248
249 if (!handler_found && user_mode(regs)) {
250 send_user_sigtrap(TRAP_TRACE);
251
252
253
254
255
256
257
258 user_rewind_single_step(current);
259 } else if (!handler_found) {
260 pr_warn("Unexpected kernel single-step exception at EL1\n");
261
262
263
264
265 set_regs_spsr_ss(regs);
266 }
267
268 return 0;
269}
270NOKPROBE_SYMBOL(single_step_handler);
271
272
273
274
275
276
277static LIST_HEAD(break_hook);
278static DEFINE_SPINLOCK(break_hook_lock);
279
280void register_break_hook(struct break_hook *hook)
281{
282 spin_lock(&break_hook_lock);
283 list_add_rcu(&hook->node, &break_hook);
284 spin_unlock(&break_hook_lock);
285}
286
287void unregister_break_hook(struct break_hook *hook)
288{
289 spin_lock(&break_hook_lock);
290 list_del_rcu(&hook->node);
291 spin_unlock(&break_hook_lock);
292 synchronize_rcu();
293}
294
295static 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 rcu_read_lock();
301 list_for_each_entry_rcu(hook, &break_hook, node)
302 if ((esr & hook->esr_mask) == hook->esr_val)
303 fn = hook->fn;
304 rcu_read_unlock();
305
306 return fn ? fn(regs, esr) : DBG_HOOK_ERROR;
307}
308NOKPROBE_SYMBOL(call_break_hook);
309
310static int brk_handler(unsigned long addr, unsigned int esr,
311 struct pt_regs *regs)
312{
313 bool handler_found = false;
314
315#ifdef CONFIG_KPROBES
316 if ((esr & BRK64_ESR_MASK) == BRK64_ESR_KPROBES) {
317 if (kprobe_breakpoint_handler(regs, esr) == DBG_HOOK_HANDLED)
318 handler_found = true;
319 }
320#endif
321 if (!handler_found && call_break_hook(regs, esr) == DBG_HOOK_HANDLED)
322 handler_found = true;
323
324 if (!handler_found && user_mode(regs)) {
325 send_user_sigtrap(TRAP_BRKPT);
326 } else if (!handler_found) {
327 pr_warn("Unexpected kernel BRK exception at EL1\n");
328 return -EFAULT;
329 }
330
331 return 0;
332}
333NOKPROBE_SYMBOL(brk_handler);
334
335int aarch32_break_handler(struct pt_regs *regs)
336{
337 u32 arm_instr;
338 u16 thumb_instr;
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
347 __le16 instr;
348 get_user(instr, (__le16 __user *)pc);
349 thumb_instr = le16_to_cpu(instr);
350 if (thumb_instr == AARCH32_BREAK_THUMB2_LO) {
351
352 get_user(instr, (__le16 __user *)(pc + 2));
353 thumb_instr = le16_to_cpu(instr);
354 bp = thumb_instr == AARCH32_BREAK_THUMB2_HI;
355 } else {
356 bp = thumb_instr == AARCH32_BREAK_THUMB;
357 }
358 } else {
359
360 __le32 instr;
361 get_user(instr, (__le32 __user *)pc);
362 arm_instr = le32_to_cpu(instr);
363 bp = (arm_instr & ~0xf0000000) == AARCH32_BREAK_ARM;
364 }
365
366 if (!bp)
367 return -EFAULT;
368
369 send_user_sigtrap(TRAP_BRKPT);
370 return 0;
371}
372NOKPROBE_SYMBOL(aarch32_break_handler);
373
374static int __init debug_traps_init(void)
375{
376 hook_debug_fault_code(DBG_ESR_EVT_HWSS, single_step_handler, SIGTRAP,
377 TRAP_TRACE, "single-step handler");
378 hook_debug_fault_code(DBG_ESR_EVT_BRK, brk_handler, SIGTRAP,
379 TRAP_BRKPT, "ptrace BRK handler");
380 return 0;
381}
382arch_initcall(debug_traps_init);
383
384
385void user_rewind_single_step(struct task_struct *task)
386{
387
388
389
390
391 if (test_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP))
392 set_regs_spsr_ss(task_pt_regs(task));
393}
394NOKPROBE_SYMBOL(user_rewind_single_step);
395
396void user_fastforward_single_step(struct task_struct *task)
397{
398 if (test_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP))
399 clear_regs_spsr_ss(task_pt_regs(task));
400}
401
402
403void kernel_enable_single_step(struct pt_regs *regs)
404{
405 WARN_ON(!irqs_disabled());
406 set_regs_spsr_ss(regs);
407 mdscr_write(mdscr_read() | DBG_MDSCR_SS);
408 enable_debug_monitors(DBG_ACTIVE_EL1);
409}
410NOKPROBE_SYMBOL(kernel_enable_single_step);
411
412void kernel_disable_single_step(void)
413{
414 WARN_ON(!irqs_disabled());
415 mdscr_write(mdscr_read() & ~DBG_MDSCR_SS);
416 disable_debug_monitors(DBG_ACTIVE_EL1);
417}
418NOKPROBE_SYMBOL(kernel_disable_single_step);
419
420int kernel_active_single_step(void)
421{
422 WARN_ON(!irqs_disabled());
423 return mdscr_read() & DBG_MDSCR_SS;
424}
425NOKPROBE_SYMBOL(kernel_active_single_step);
426
427
428void user_enable_single_step(struct task_struct *task)
429{
430 struct thread_info *ti = task_thread_info(task);
431
432 if (!test_and_set_ti_thread_flag(ti, TIF_SINGLESTEP))
433 set_regs_spsr_ss(task_pt_regs(task));
434}
435NOKPROBE_SYMBOL(user_enable_single_step);
436
437void user_disable_single_step(struct task_struct *task)
438{
439 clear_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP);
440}
441NOKPROBE_SYMBOL(user_disable_single_step);
442