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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// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * ARMv8 single-step debug support and mdscr context switching.
4 *
5 * Copyright (C) 2012 ARM Limited
6 *
7 * Author: Will Deacon <will.deacon@arm.com>
8 */
9
10#include <linux/cpu.h>
11#include <linux/debugfs.h>
12#include <linux/hardirq.h>
13#include <linux/init.h>
14#include <linux/ptrace.h>
15#include <linux/kprobes.h>
16#include <linux/stat.h>
17#include <linux/uaccess.h>
18#include <linux/sched/task_stack.h>
19
20#include <asm/cpufeature.h>
21#include <asm/cputype.h>
22#include <asm/daifflags.h>
23#include <asm/debug-monitors.h>
24#include <asm/system_misc.h>
25#include <asm/traps.h>
26
27/* Determine debug architecture. */
28u8 debug_monitors_arch(void)
29{
30 return cpuid_feature_extract_unsigned_field(read_sanitised_ftr_reg(SYS_ID_AA64DFR0_EL1),
31 ID_AA64DFR0_DEBUGVER_SHIFT);
32}
33
34/*
35 * MDSCR access routines.
36 */
37static void mdscr_write(u32 mdscr)
38{
39 unsigned long flags;
40 flags = local_daif_save();
41 write_sysreg(mdscr, mdscr_el1);
42 local_daif_restore(flags);
43}
44NOKPROBE_SYMBOL(mdscr_write);
45
46static u32 mdscr_read(void)
47{
48 return read_sysreg(mdscr_el1);
49}
50NOKPROBE_SYMBOL(mdscr_read);
51
52/*
53 * Allow root to disable self-hosted debug from userspace.
54 * This is useful if you want to connect an external JTAG debugger.
55 */
56static bool debug_enabled = true;
57
58static int create_debug_debugfs_entry(void)
59{
60 debugfs_create_bool("debug_enabled", 0644, NULL, &debug_enabled);
61 return 0;
62}
63fs_initcall(create_debug_debugfs_entry);
64
65static int __init early_debug_disable(char *buf)
66{
67 debug_enabled = false;
68 return 0;
69}
70
71early_param("nodebugmon", early_debug_disable);
72
73/*
74 * Keep track of debug users on each core.
75 * The ref counts are per-cpu so we use a local_t type.
76 */
77static DEFINE_PER_CPU(int, mde_ref_count);
78static DEFINE_PER_CPU(int, kde_ref_count);
79
80void enable_debug_monitors(enum dbg_active_el el)
81{
82 u32 mdscr, enable = 0;
83
84 WARN_ON(preemptible());
85
86 if (this_cpu_inc_return(mde_ref_count) == 1)
87 enable = DBG_MDSCR_MDE;
88
89 if (el == DBG_ACTIVE_EL1 &&
90 this_cpu_inc_return(kde_ref_count) == 1)
91 enable |= DBG_MDSCR_KDE;
92
93 if (enable && debug_enabled) {
94 mdscr = mdscr_read();
95 mdscr |= enable;
96 mdscr_write(mdscr);
97 }
98}
99NOKPROBE_SYMBOL(enable_debug_monitors);
100
101void disable_debug_monitors(enum dbg_active_el el)
102{
103 u32 mdscr, disable = 0;
104
105 WARN_ON(preemptible());
106
107 if (this_cpu_dec_return(mde_ref_count) == 0)
108 disable = ~DBG_MDSCR_MDE;
109
110 if (el == DBG_ACTIVE_EL1 &&
111 this_cpu_dec_return(kde_ref_count) == 0)
112 disable &= ~DBG_MDSCR_KDE;
113
114 if (disable) {
115 mdscr = mdscr_read();
116 mdscr &= disable;
117 mdscr_write(mdscr);
118 }
119}
120NOKPROBE_SYMBOL(disable_debug_monitors);
121
122/*
123 * OS lock clearing.
124 */
125static int clear_os_lock(unsigned int cpu)
126{
127 write_sysreg(0, osdlr_el1);
128 write_sysreg(0, oslar_el1);
129 isb();
130 return 0;
131}
132
133static int __init debug_monitors_init(void)
134{
135 return cpuhp_setup_state(CPUHP_AP_ARM64_DEBUG_MONITORS_STARTING,
136 "arm64/debug_monitors:starting",
137 clear_os_lock, NULL);
138}
139postcore_initcall(debug_monitors_init);
140
141/*
142 * Single step API and exception handling.
143 */
144static void set_user_regs_spsr_ss(struct user_pt_regs *regs)
145{
146 regs->pstate |= DBG_SPSR_SS;
147}
148NOKPROBE_SYMBOL(set_user_regs_spsr_ss);
149
150static void clear_user_regs_spsr_ss(struct user_pt_regs *regs)
151{
152 regs->pstate &= ~DBG_SPSR_SS;
153}
154NOKPROBE_SYMBOL(clear_user_regs_spsr_ss);
155
156#define set_regs_spsr_ss(r) set_user_regs_spsr_ss(&(r)->user_regs)
157#define clear_regs_spsr_ss(r) clear_user_regs_spsr_ss(&(r)->user_regs)
158
159static DEFINE_SPINLOCK(debug_hook_lock);
160static LIST_HEAD(user_step_hook);
161static LIST_HEAD(kernel_step_hook);
162
163static void register_debug_hook(struct list_head *node, struct list_head *list)
164{
165 spin_lock(&debug_hook_lock);
166 list_add_rcu(node, list);
167 spin_unlock(&debug_hook_lock);
168
169}
170
171static void unregister_debug_hook(struct list_head *node)
172{
173 spin_lock(&debug_hook_lock);
174 list_del_rcu(node);
175 spin_unlock(&debug_hook_lock);
176 synchronize_rcu();
177}
178
179void register_user_step_hook(struct step_hook *hook)
180{
181 register_debug_hook(&hook->node, &user_step_hook);
182}
183
184void unregister_user_step_hook(struct step_hook *hook)
185{
186 unregister_debug_hook(&hook->node);
187}
188
189void register_kernel_step_hook(struct step_hook *hook)
190{
191 register_debug_hook(&hook->node, &kernel_step_hook);
192}
193
194void unregister_kernel_step_hook(struct step_hook *hook)
195{
196 unregister_debug_hook(&hook->node);
197}
198
199/*
200 * Call registered single step handlers
201 * There is no Syndrome info to check for determining the handler.
202 * So we call all the registered handlers, until the right handler is
203 * found which returns zero.
204 */
205static int call_step_hook(struct pt_regs *regs, unsigned int esr)
206{
207 struct step_hook *hook;
208 struct list_head *list;
209 int retval = DBG_HOOK_ERROR;
210
211 list = user_mode(regs) ? &user_step_hook : &kernel_step_hook;
212
213 /*
214 * Since single-step exception disables interrupt, this function is
215 * entirely not preemptible, and we can use rcu list safely here.
216 */
217 list_for_each_entry_rcu(hook, list, node) {
218 retval = hook->fn(regs, esr);
219 if (retval == DBG_HOOK_HANDLED)
220 break;
221 }
222
223 return retval;
224}
225NOKPROBE_SYMBOL(call_step_hook);
226
227static void send_user_sigtrap(int si_code)
228{
229 struct pt_regs *regs = current_pt_regs();
230
231 if (WARN_ON(!user_mode(regs)))
232 return;
233
234 if (interrupts_enabled(regs))
235 local_irq_enable();
236
237 arm64_force_sig_fault(SIGTRAP, si_code, instruction_pointer(regs),
238 "User debug trap");
239}
240
241static int single_step_handler(unsigned long unused, unsigned int esr,
242 struct pt_regs *regs)
243{
244 bool handler_found = false;
245
246 /*
247 * If we are stepping a pending breakpoint, call the hw_breakpoint
248 * handler first.
249 */
250 if (!reinstall_suspended_bps(regs))
251 return 0;
252
253 if (!handler_found && call_step_hook(regs, esr) == DBG_HOOK_HANDLED)
254 handler_found = true;
255
256 if (!handler_found && user_mode(regs)) {
257 send_user_sigtrap(TRAP_TRACE);
258
259 /*
260 * ptrace will disable single step unless explicitly
261 * asked to re-enable it. For other clients, it makes
262 * sense to leave it enabled (i.e. rewind the controls
263 * to the active-not-pending state).
264 */
265 user_rewind_single_step(current);
266 } else if (!handler_found) {
267 pr_warn("Unexpected kernel single-step exception at EL1\n");
268 /*
269 * Re-enable stepping since we know that we will be
270 * returning to regs.
271 */
272 set_regs_spsr_ss(regs);
273 }
274
275 return 0;
276}
277NOKPROBE_SYMBOL(single_step_handler);
278
279static LIST_HEAD(user_break_hook);
280static LIST_HEAD(kernel_break_hook);
281
282void register_user_break_hook(struct break_hook *hook)
283{
284 register_debug_hook(&hook->node, &user_break_hook);
285}
286
287void unregister_user_break_hook(struct break_hook *hook)
288{
289 unregister_debug_hook(&hook->node);
290}
291
292void register_kernel_break_hook(struct break_hook *hook)
293{
294 register_debug_hook(&hook->node, &kernel_break_hook);
295}
296
297void unregister_kernel_break_hook(struct break_hook *hook)
298{
299 unregister_debug_hook(&hook->node);
300}
301
302static int call_break_hook(struct pt_regs *regs, unsigned int esr)
303{
304 struct break_hook *hook;
305 struct list_head *list;
306 int (*fn)(struct pt_regs *regs, unsigned int esr) = NULL;
307
308 list = user_mode(regs) ? &user_break_hook : &kernel_break_hook;
309
310 /*
311 * Since brk exception disables interrupt, this function is
312 * entirely not preemptible, and we can use rcu list safely here.
313 */
314 list_for_each_entry_rcu(hook, list, node) {
315 unsigned int comment = esr & ESR_ELx_BRK64_ISS_COMMENT_MASK;
316
317 if ((comment & ~hook->mask) == hook->imm)
318 fn = hook->fn;
319 }
320
321 return fn ? fn(regs, esr) : DBG_HOOK_ERROR;
322}
323NOKPROBE_SYMBOL(call_break_hook);
324
325static int brk_handler(unsigned long unused, unsigned int esr,
326 struct pt_regs *regs)
327{
328 if (call_break_hook(regs, esr) == DBG_HOOK_HANDLED)
329 return 0;
330
331 if (user_mode(regs)) {
332 send_user_sigtrap(TRAP_BRKPT);
333 } else {
334 pr_warn("Unexpected kernel BRK exception at EL1\n");
335 return -EFAULT;
336 }
337
338 return 0;
339}
340NOKPROBE_SYMBOL(brk_handler);
341
342int aarch32_break_handler(struct pt_regs *regs)
343{
344 u32 arm_instr;
345 u16 thumb_instr;
346 bool bp = false;
347 void __user *pc = (void __user *)instruction_pointer(regs);
348
349 if (!compat_user_mode(regs))
350 return -EFAULT;
351
352 if (compat_thumb_mode(regs)) {
353 /* get 16-bit Thumb instruction */
354 __le16 instr;
355 get_user(instr, (__le16 __user *)pc);
356 thumb_instr = le16_to_cpu(instr);
357 if (thumb_instr == AARCH32_BREAK_THUMB2_LO) {
358 /* get second half of 32-bit Thumb-2 instruction */
359 get_user(instr, (__le16 __user *)(pc + 2));
360 thumb_instr = le16_to_cpu(instr);
361 bp = thumb_instr == AARCH32_BREAK_THUMB2_HI;
362 } else {
363 bp = thumb_instr == AARCH32_BREAK_THUMB;
364 }
365 } else {
366 /* 32-bit ARM instruction */
367 __le32 instr;
368 get_user(instr, (__le32 __user *)pc);
369 arm_instr = le32_to_cpu(instr);
370 bp = (arm_instr & ~0xf0000000) == AARCH32_BREAK_ARM;
371 }
372
373 if (!bp)
374 return -EFAULT;
375
376 send_user_sigtrap(TRAP_BRKPT);
377 return 0;
378}
379NOKPROBE_SYMBOL(aarch32_break_handler);
380
381void __init debug_traps_init(void)
382{
383 hook_debug_fault_code(DBG_ESR_EVT_HWSS, single_step_handler, SIGTRAP,
384 TRAP_TRACE, "single-step handler");
385 hook_debug_fault_code(DBG_ESR_EVT_BRK, brk_handler, SIGTRAP,
386 TRAP_BRKPT, "BRK handler");
387}
388
389/* Re-enable single step for syscall restarting. */
390void user_rewind_single_step(struct task_struct *task)
391{
392 /*
393 * If single step is active for this thread, then set SPSR.SS
394 * to 1 to avoid returning to the active-pending state.
395 */
396 if (test_tsk_thread_flag(task, TIF_SINGLESTEP))
397 set_regs_spsr_ss(task_pt_regs(task));
398}
399NOKPROBE_SYMBOL(user_rewind_single_step);
400
401void user_fastforward_single_step(struct task_struct *task)
402{
403 if (test_tsk_thread_flag(task, TIF_SINGLESTEP))
404 clear_regs_spsr_ss(task_pt_regs(task));
405}
406
407void user_regs_reset_single_step(struct user_pt_regs *regs,
408 struct task_struct *task)
409{
410 if (test_tsk_thread_flag(task, TIF_SINGLESTEP))
411 set_user_regs_spsr_ss(regs);
412 else
413 clear_user_regs_spsr_ss(regs);
414}
415
416/* Kernel API */
417void kernel_enable_single_step(struct pt_regs *regs)
418{
419 WARN_ON(!irqs_disabled());
420 set_regs_spsr_ss(regs);
421 mdscr_write(mdscr_read() | DBG_MDSCR_SS);
422 enable_debug_monitors(DBG_ACTIVE_EL1);
423}
424NOKPROBE_SYMBOL(kernel_enable_single_step);
425
426void kernel_disable_single_step(void)
427{
428 WARN_ON(!irqs_disabled());
429 mdscr_write(mdscr_read() & ~DBG_MDSCR_SS);
430 disable_debug_monitors(DBG_ACTIVE_EL1);
431}
432NOKPROBE_SYMBOL(kernel_disable_single_step);
433
434int kernel_active_single_step(void)
435{
436 WARN_ON(!irqs_disabled());
437 return mdscr_read() & DBG_MDSCR_SS;
438}
439NOKPROBE_SYMBOL(kernel_active_single_step);
440
441/* ptrace API */
442void user_enable_single_step(struct task_struct *task)
443{
444 struct thread_info *ti = task_thread_info(task);
445
446 if (!test_and_set_ti_thread_flag(ti, TIF_SINGLESTEP))
447 set_regs_spsr_ss(task_pt_regs(task));
448}
449NOKPROBE_SYMBOL(user_enable_single_step);
450
451void user_disable_single_step(struct task_struct *task)
452{
453 clear_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP);
454}
455NOKPROBE_SYMBOL(user_disable_single_step);