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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/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/* Determine debug architecture. */
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 * MDSCR access routines.
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 * Allow root to disable self-hosted debug from userspace.
65 * This is useful if you want to connect an external JTAG debugger.
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 * Keep track of debug users on each core.
86 * The ref counts are per-cpu so we use a local_t type.
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 * OS lock clearing.
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 * Single step API and exception handling.
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/* EL1 Single Step Handler hooks */
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 * Call registered single step handlers
187 * There is no Syndrome info to check for determining the handler.
188 * So we call all the registered handlers, until the right handler is
189 * found which returns zero.
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 * If we are stepping a pending breakpoint, call the hw_breakpoint
237 * handler first.
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 * ptrace will disable single step unless explicitly
254 * asked to re-enable it. For other clients, it makes
255 * sense to leave it enabled (i.e. rewind the controls
256 * to the active-not-pending state).
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 * Re-enable stepping since we know that we will be
263 * returning to regs.
264 */
265 set_regs_spsr_ss(regs);
266 }
267
268 return 0;
269}
270NOKPROBE_SYMBOL(single_step_handler);
271
272/*
273 * Breakpoint handler is re-entrant as another breakpoint can
274 * hit within breakpoint handler, especically in kprobes.
275 * Use reader/writer locks instead of plain spinlock.
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 /* get 16-bit Thumb instruction */
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 /* get second half of 32-bit Thumb-2 instruction */
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 /* 32-bit ARM instruction */
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/* Re-enable single step for syscall restarting. */
385void user_rewind_single_step(struct task_struct *task)
386{
387 /*
388 * If single step is active for this thread, then set SPSR.SS
389 * to 1 to avoid returning to the active-pending state.
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/* Kernel API */
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/* ptrace API */
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);
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>
27#include <linux/uaccess.h>
28
29#include <asm/cpufeature.h>
30#include <asm/cputype.h>
31#include <asm/debug-monitors.h>
32#include <asm/system_misc.h>
33
34/* Determine debug architecture. */
35u8 debug_monitors_arch(void)
36{
37 return cpuid_feature_extract_unsigned_field(read_system_reg(SYS_ID_AA64DFR0_EL1),
38 ID_AA64DFR0_DEBUGVER_SHIFT);
39}
40
41/*
42 * MDSCR access routines.
43 */
44static void mdscr_write(u32 mdscr)
45{
46 unsigned long flags;
47 local_dbg_save(flags);
48 asm volatile("msr mdscr_el1, %0" :: "r" (mdscr));
49 local_dbg_restore(flags);
50}
51
52static u32 mdscr_read(void)
53{
54 u32 mdscr;
55 asm volatile("mrs %0, mdscr_el1" : "=r" (mdscr));
56 return mdscr;
57}
58
59/*
60 * Allow root to disable self-hosted debug from userspace.
61 * This is useful if you want to connect an external JTAG debugger.
62 */
63static bool debug_enabled = true;
64
65static int create_debug_debugfs_entry(void)
66{
67 debugfs_create_bool("debug_enabled", 0644, NULL, &debug_enabled);
68 return 0;
69}
70fs_initcall(create_debug_debugfs_entry);
71
72static int __init early_debug_disable(char *buf)
73{
74 debug_enabled = false;
75 return 0;
76}
77
78early_param("nodebugmon", early_debug_disable);
79
80/*
81 * Keep track of debug users on each core.
82 * The ref counts are per-cpu so we use a local_t type.
83 */
84static DEFINE_PER_CPU(int, mde_ref_count);
85static DEFINE_PER_CPU(int, kde_ref_count);
86
87void enable_debug_monitors(enum dbg_active_el el)
88{
89 u32 mdscr, enable = 0;
90
91 WARN_ON(preemptible());
92
93 if (this_cpu_inc_return(mde_ref_count) == 1)
94 enable = DBG_MDSCR_MDE;
95
96 if (el == DBG_ACTIVE_EL1 &&
97 this_cpu_inc_return(kde_ref_count) == 1)
98 enable |= DBG_MDSCR_KDE;
99
100 if (enable && debug_enabled) {
101 mdscr = mdscr_read();
102 mdscr |= enable;
103 mdscr_write(mdscr);
104 }
105}
106
107void disable_debug_monitors(enum dbg_active_el el)
108{
109 u32 mdscr, disable = 0;
110
111 WARN_ON(preemptible());
112
113 if (this_cpu_dec_return(mde_ref_count) == 0)
114 disable = ~DBG_MDSCR_MDE;
115
116 if (el == DBG_ACTIVE_EL1 &&
117 this_cpu_dec_return(kde_ref_count) == 0)
118 disable &= ~DBG_MDSCR_KDE;
119
120 if (disable) {
121 mdscr = mdscr_read();
122 mdscr &= disable;
123 mdscr_write(mdscr);
124 }
125}
126
127/*
128 * OS lock clearing.
129 */
130static void clear_os_lock(void *unused)
131{
132 asm volatile("msr oslar_el1, %0" : : "r" (0));
133}
134
135static int os_lock_notify(struct notifier_block *self,
136 unsigned long action, void *data)
137{
138 int cpu = (unsigned long)data;
139 if ((action & ~CPU_TASKS_FROZEN) == CPU_ONLINE)
140 smp_call_function_single(cpu, clear_os_lock, NULL, 1);
141 return NOTIFY_OK;
142}
143
144static struct notifier_block os_lock_nb = {
145 .notifier_call = os_lock_notify,
146};
147
148static int debug_monitors_init(void)
149{
150 cpu_notifier_register_begin();
151
152 /* Clear the OS lock. */
153 on_each_cpu(clear_os_lock, NULL, 1);
154 isb();
155 local_dbg_enable();
156
157 /* Register hotplug handler. */
158 __register_cpu_notifier(&os_lock_nb);
159
160 cpu_notifier_register_done();
161 return 0;
162}
163postcore_initcall(debug_monitors_init);
164
165/*
166 * Single step API and exception handling.
167 */
168static void set_regs_spsr_ss(struct pt_regs *regs)
169{
170 unsigned long spsr;
171
172 spsr = regs->pstate;
173 spsr &= ~DBG_SPSR_SS;
174 spsr |= DBG_SPSR_SS;
175 regs->pstate = spsr;
176}
177
178static void clear_regs_spsr_ss(struct pt_regs *regs)
179{
180 unsigned long spsr;
181
182 spsr = regs->pstate;
183 spsr &= ~DBG_SPSR_SS;
184 regs->pstate = spsr;
185}
186
187/* EL1 Single Step Handler hooks */
188static LIST_HEAD(step_hook);
189static DEFINE_SPINLOCK(step_hook_lock);
190
191void register_step_hook(struct step_hook *hook)
192{
193 spin_lock(&step_hook_lock);
194 list_add_rcu(&hook->node, &step_hook);
195 spin_unlock(&step_hook_lock);
196}
197
198void unregister_step_hook(struct step_hook *hook)
199{
200 spin_lock(&step_hook_lock);
201 list_del_rcu(&hook->node);
202 spin_unlock(&step_hook_lock);
203 synchronize_rcu();
204}
205
206/*
207 * Call registered single step handlers
208 * There is no Syndrome info to check for determining the handler.
209 * So we call all the registered handlers, until the right handler is
210 * found which returns zero.
211 */
212static int call_step_hook(struct pt_regs *regs, unsigned int esr)
213{
214 struct step_hook *hook;
215 int retval = DBG_HOOK_ERROR;
216
217 rcu_read_lock();
218
219 list_for_each_entry_rcu(hook, &step_hook, node) {
220 retval = hook->fn(regs, esr);
221 if (retval == DBG_HOOK_HANDLED)
222 break;
223 }
224
225 rcu_read_unlock();
226
227 return retval;
228}
229
230static void send_user_sigtrap(int si_code)
231{
232 struct pt_regs *regs = current_pt_regs();
233 siginfo_t info = {
234 .si_signo = SIGTRAP,
235 .si_errno = 0,
236 .si_code = si_code,
237 .si_addr = (void __user *)instruction_pointer(regs),
238 };
239
240 if (WARN_ON(!user_mode(regs)))
241 return;
242
243 if (interrupts_enabled(regs))
244 local_irq_enable();
245
246 force_sig_info(SIGTRAP, &info, current);
247}
248
249static int single_step_handler(unsigned long addr, unsigned int esr,
250 struct pt_regs *regs)
251{
252 /*
253 * If we are stepping a pending breakpoint, call the hw_breakpoint
254 * handler first.
255 */
256 if (!reinstall_suspended_bps(regs))
257 return 0;
258
259 if (user_mode(regs)) {
260 send_user_sigtrap(TRAP_HWBKPT);
261
262 /*
263 * ptrace will disable single step unless explicitly
264 * asked to re-enable it. For other clients, it makes
265 * sense to leave it enabled (i.e. rewind the controls
266 * to the active-not-pending state).
267 */
268 user_rewind_single_step(current);
269 } else {
270 if (call_step_hook(regs, esr) == DBG_HOOK_HANDLED)
271 return 0;
272
273 pr_warning("Unexpected kernel single-step exception at EL1\n");
274 /*
275 * Re-enable stepping since we know that we will be
276 * returning to regs.
277 */
278 set_regs_spsr_ss(regs);
279 }
280
281 return 0;
282}
283
284/*
285 * Breakpoint handler is re-entrant as another breakpoint can
286 * hit within breakpoint handler, especically in kprobes.
287 * Use reader/writer locks instead of plain spinlock.
288 */
289static LIST_HEAD(break_hook);
290static DEFINE_SPINLOCK(break_hook_lock);
291
292void register_break_hook(struct break_hook *hook)
293{
294 spin_lock(&break_hook_lock);
295 list_add_rcu(&hook->node, &break_hook);
296 spin_unlock(&break_hook_lock);
297}
298
299void unregister_break_hook(struct break_hook *hook)
300{
301 spin_lock(&break_hook_lock);
302 list_del_rcu(&hook->node);
303 spin_unlock(&break_hook_lock);
304 synchronize_rcu();
305}
306
307static int call_break_hook(struct pt_regs *regs, unsigned int esr)
308{
309 struct break_hook *hook;
310 int (*fn)(struct pt_regs *regs, unsigned int esr) = NULL;
311
312 rcu_read_lock();
313 list_for_each_entry_rcu(hook, &break_hook, node)
314 if ((esr & hook->esr_mask) == hook->esr_val)
315 fn = hook->fn;
316 rcu_read_unlock();
317
318 return fn ? fn(regs, esr) : DBG_HOOK_ERROR;
319}
320
321static int brk_handler(unsigned long addr, unsigned int esr,
322 struct pt_regs *regs)
323{
324 if (user_mode(regs)) {
325 send_user_sigtrap(TRAP_BRKPT);
326 } else if (call_break_hook(regs, esr) != DBG_HOOK_HANDLED) {
327 pr_warning("Unexpected kernel BRK exception at EL1\n");
328 return -EFAULT;
329 }
330
331 return 0;
332}
333
334int aarch32_break_handler(struct pt_regs *regs)
335{
336 u32 arm_instr;
337 u16 thumb_instr;
338 bool bp = false;
339 void __user *pc = (void __user *)instruction_pointer(regs);
340
341 if (!compat_user_mode(regs))
342 return -EFAULT;
343
344 if (compat_thumb_mode(regs)) {
345 /* get 16-bit Thumb instruction */
346 get_user(thumb_instr, (u16 __user *)pc);
347 thumb_instr = le16_to_cpu(thumb_instr);
348 if (thumb_instr == AARCH32_BREAK_THUMB2_LO) {
349 /* get second half of 32-bit Thumb-2 instruction */
350 get_user(thumb_instr, (u16 __user *)(pc + 2));
351 thumb_instr = le16_to_cpu(thumb_instr);
352 bp = thumb_instr == AARCH32_BREAK_THUMB2_HI;
353 } else {
354 bp = thumb_instr == AARCH32_BREAK_THUMB;
355 }
356 } else {
357 /* 32-bit ARM instruction */
358 get_user(arm_instr, (u32 __user *)pc);
359 arm_instr = le32_to_cpu(arm_instr);
360 bp = (arm_instr & ~0xf0000000) == AARCH32_BREAK_ARM;
361 }
362
363 if (!bp)
364 return -EFAULT;
365
366 send_user_sigtrap(TRAP_BRKPT);
367 return 0;
368}
369
370static int __init debug_traps_init(void)
371{
372 hook_debug_fault_code(DBG_ESR_EVT_HWSS, single_step_handler, SIGTRAP,
373 TRAP_HWBKPT, "single-step handler");
374 hook_debug_fault_code(DBG_ESR_EVT_BRK, brk_handler, SIGTRAP,
375 TRAP_BRKPT, "ptrace BRK handler");
376 return 0;
377}
378arch_initcall(debug_traps_init);
379
380/* Re-enable single step for syscall restarting. */
381void user_rewind_single_step(struct task_struct *task)
382{
383 /*
384 * If single step is active for this thread, then set SPSR.SS
385 * to 1 to avoid returning to the active-pending state.
386 */
387 if (test_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP))
388 set_regs_spsr_ss(task_pt_regs(task));
389}
390
391void user_fastforward_single_step(struct task_struct *task)
392{
393 if (test_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP))
394 clear_regs_spsr_ss(task_pt_regs(task));
395}
396
397/* Kernel API */
398void kernel_enable_single_step(struct pt_regs *regs)
399{
400 WARN_ON(!irqs_disabled());
401 set_regs_spsr_ss(regs);
402 mdscr_write(mdscr_read() | DBG_MDSCR_SS);
403 enable_debug_monitors(DBG_ACTIVE_EL1);
404}
405
406void kernel_disable_single_step(void)
407{
408 WARN_ON(!irqs_disabled());
409 mdscr_write(mdscr_read() & ~DBG_MDSCR_SS);
410 disable_debug_monitors(DBG_ACTIVE_EL1);
411}
412
413int kernel_active_single_step(void)
414{
415 WARN_ON(!irqs_disabled());
416 return mdscr_read() & DBG_MDSCR_SS;
417}
418
419/* ptrace API */
420void user_enable_single_step(struct task_struct *task)
421{
422 set_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP);
423 set_regs_spsr_ss(task_pt_regs(task));
424}
425
426void user_disable_single_step(struct task_struct *task)
427{
428 clear_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP);
429}