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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> | |
30 | #include <asm/local.h> | |
31 | #include <asm/cputype.h> | |
32 | #include <asm/system_misc.h> | |
33 | ||
34 | /* Low-level stepping controls. */ | |
35 | #define DBG_MDSCR_SS (1 << 0) | |
36 | #define DBG_SPSR_SS (1 << 21) | |
37 | ||
38 | /* MDSCR_EL1 enabling bits */ | |
39 | #define DBG_MDSCR_KDE (1 << 13) | |
40 | #define DBG_MDSCR_MDE (1 << 15) | |
41 | #define DBG_MDSCR_MASK ~(DBG_MDSCR_KDE | DBG_MDSCR_MDE) | |
42 | ||
43 | /* Determine debug architecture. */ | |
44 | u8 debug_monitors_arch(void) | |
45 | { | |
46 | return read_cpuid(ID_AA64DFR0_EL1) & 0xf; | |
47 | } | |
48 | ||
49 | /* | |
50 | * MDSCR access routines. | |
51 | */ | |
52 | static void mdscr_write(u32 mdscr) | |
53 | { | |
54 | unsigned long flags; | |
55 | local_dbg_save(flags); | |
56 | asm volatile("msr mdscr_el1, %0" :: "r" (mdscr)); | |
57 | local_dbg_restore(flags); | |
58 | } | |
59 | ||
60 | static u32 mdscr_read(void) | |
61 | { | |
62 | u32 mdscr; | |
63 | asm volatile("mrs %0, mdscr_el1" : "=r" (mdscr)); | |
64 | return mdscr; | |
65 | } | |
66 | ||
67 | /* | |
68 | * Allow root to disable self-hosted debug from userspace. | |
69 | * This is useful if you want to connect an external JTAG debugger. | |
70 | */ | |
71 | static u32 debug_enabled = 1; | |
72 | ||
73 | static int create_debug_debugfs_entry(void) | |
74 | { | |
75 | debugfs_create_bool("debug_enabled", 0644, NULL, &debug_enabled); | |
76 | return 0; | |
77 | } | |
78 | fs_initcall(create_debug_debugfs_entry); | |
79 | ||
80 | static int __init early_debug_disable(char *buf) | |
81 | { | |
82 | debug_enabled = 0; | |
83 | return 0; | |
84 | } | |
85 | ||
86 | early_param("nodebugmon", early_debug_disable); | |
87 | ||
88 | /* | |
89 | * Keep track of debug users on each core. | |
90 | * The ref counts are per-cpu so we use a local_t type. | |
91 | */ | |
92 | static DEFINE_PER_CPU(local_t, mde_ref_count); | |
93 | static DEFINE_PER_CPU(local_t, kde_ref_count); | |
94 | ||
95 | void enable_debug_monitors(enum debug_el el) | |
96 | { | |
97 | u32 mdscr, enable = 0; | |
98 | ||
99 | WARN_ON(preemptible()); | |
100 | ||
101 | if (local_inc_return(&__get_cpu_var(mde_ref_count)) == 1) | |
102 | enable = DBG_MDSCR_MDE; | |
103 | ||
104 | if (el == DBG_ACTIVE_EL1 && | |
105 | local_inc_return(&__get_cpu_var(kde_ref_count)) == 1) | |
106 | enable |= DBG_MDSCR_KDE; | |
107 | ||
108 | if (enable && debug_enabled) { | |
109 | mdscr = mdscr_read(); | |
110 | mdscr |= enable; | |
111 | mdscr_write(mdscr); | |
112 | } | |
113 | } | |
114 | ||
115 | void disable_debug_monitors(enum debug_el el) | |
116 | { | |
117 | u32 mdscr, disable = 0; | |
118 | ||
119 | WARN_ON(preemptible()); | |
120 | ||
121 | if (local_dec_and_test(&__get_cpu_var(mde_ref_count))) | |
122 | disable = ~DBG_MDSCR_MDE; | |
123 | ||
124 | if (el == DBG_ACTIVE_EL1 && | |
125 | local_dec_and_test(&__get_cpu_var(kde_ref_count))) | |
126 | disable &= ~DBG_MDSCR_KDE; | |
127 | ||
128 | if (disable) { | |
129 | mdscr = mdscr_read(); | |
130 | mdscr &= disable; | |
131 | mdscr_write(mdscr); | |
132 | } | |
133 | } | |
134 | ||
135 | /* | |
136 | * OS lock clearing. | |
137 | */ | |
138 | static void clear_os_lock(void *unused) | |
139 | { | |
478fcb2c WD |
140 | asm volatile("msr oslar_el1, %0" : : "r" (0)); |
141 | isb(); | |
142 | } | |
143 | ||
b8c6453a | 144 | static int os_lock_notify(struct notifier_block *self, |
478fcb2c WD |
145 | unsigned long action, void *data) |
146 | { | |
147 | int cpu = (unsigned long)data; | |
148 | if (action == CPU_ONLINE) | |
149 | smp_call_function_single(cpu, clear_os_lock, NULL, 1); | |
150 | return NOTIFY_OK; | |
151 | } | |
152 | ||
b8c6453a | 153 | static struct notifier_block os_lock_nb = { |
478fcb2c WD |
154 | .notifier_call = os_lock_notify, |
155 | }; | |
156 | ||
b8c6453a | 157 | static int debug_monitors_init(void) |
478fcb2c WD |
158 | { |
159 | /* Clear the OS lock. */ | |
160 | smp_call_function(clear_os_lock, NULL, 1); | |
161 | clear_os_lock(NULL); | |
162 | ||
163 | /* Register hotplug handler. */ | |
164 | register_cpu_notifier(&os_lock_nb); | |
165 | return 0; | |
166 | } | |
167 | postcore_initcall(debug_monitors_init); | |
168 | ||
169 | /* | |
170 | * Single step API and exception handling. | |
171 | */ | |
172 | static void set_regs_spsr_ss(struct pt_regs *regs) | |
173 | { | |
174 | unsigned long spsr; | |
175 | ||
176 | spsr = regs->pstate; | |
177 | spsr &= ~DBG_SPSR_SS; | |
178 | spsr |= DBG_SPSR_SS; | |
179 | regs->pstate = spsr; | |
180 | } | |
181 | ||
182 | static void clear_regs_spsr_ss(struct pt_regs *regs) | |
183 | { | |
184 | unsigned long spsr; | |
185 | ||
186 | spsr = regs->pstate; | |
187 | spsr &= ~DBG_SPSR_SS; | |
188 | regs->pstate = spsr; | |
189 | } | |
190 | ||
191 | static int single_step_handler(unsigned long addr, unsigned int esr, | |
192 | struct pt_regs *regs) | |
193 | { | |
194 | siginfo_t info; | |
195 | ||
196 | /* | |
197 | * If we are stepping a pending breakpoint, call the hw_breakpoint | |
198 | * handler first. | |
199 | */ | |
200 | if (!reinstall_suspended_bps(regs)) | |
201 | return 0; | |
202 | ||
203 | if (user_mode(regs)) { | |
204 | info.si_signo = SIGTRAP; | |
205 | info.si_errno = 0; | |
206 | info.si_code = TRAP_HWBKPT; | |
207 | info.si_addr = (void __user *)instruction_pointer(regs); | |
208 | force_sig_info(SIGTRAP, &info, current); | |
209 | ||
210 | /* | |
211 | * ptrace will disable single step unless explicitly | |
212 | * asked to re-enable it. For other clients, it makes | |
213 | * sense to leave it enabled (i.e. rewind the controls | |
214 | * to the active-not-pending state). | |
215 | */ | |
216 | user_rewind_single_step(current); | |
217 | } else { | |
218 | /* TODO: route to KGDB */ | |
219 | pr_warning("Unexpected kernel single-step exception at EL1\n"); | |
220 | /* | |
221 | * Re-enable stepping since we know that we will be | |
222 | * returning to regs. | |
223 | */ | |
224 | set_regs_spsr_ss(regs); | |
225 | } | |
226 | ||
227 | return 0; | |
228 | } | |
229 | ||
1442b6ed WD |
230 | static int brk_handler(unsigned long addr, unsigned int esr, |
231 | struct pt_regs *regs) | |
232 | { | |
233 | siginfo_t info; | |
234 | ||
235 | if (!user_mode(regs)) | |
236 | return -EFAULT; | |
237 | ||
238 | info = (siginfo_t) { | |
239 | .si_signo = SIGTRAP, | |
240 | .si_errno = 0, | |
241 | .si_code = TRAP_BRKPT, | |
242 | .si_addr = (void __user *)instruction_pointer(regs), | |
243 | }; | |
244 | ||
245 | force_sig_info(SIGTRAP, &info, current); | |
246 | return 0; | |
247 | } | |
248 | ||
249 | int aarch32_break_handler(struct pt_regs *regs) | |
250 | { | |
251 | siginfo_t info; | |
252 | unsigned int instr; | |
253 | bool bp = false; | |
254 | void __user *pc = (void __user *)instruction_pointer(regs); | |
255 | ||
256 | if (!compat_user_mode(regs)) | |
257 | return -EFAULT; | |
258 | ||
259 | if (compat_thumb_mode(regs)) { | |
260 | /* get 16-bit Thumb instruction */ | |
261 | get_user(instr, (u16 __user *)pc); | |
262 | if (instr == AARCH32_BREAK_THUMB2_LO) { | |
263 | /* get second half of 32-bit Thumb-2 instruction */ | |
264 | get_user(instr, (u16 __user *)(pc + 2)); | |
265 | bp = instr == AARCH32_BREAK_THUMB2_HI; | |
266 | } else { | |
267 | bp = instr == AARCH32_BREAK_THUMB; | |
268 | } | |
269 | } else { | |
270 | /* 32-bit ARM instruction */ | |
271 | get_user(instr, (u32 __user *)pc); | |
272 | bp = (instr & ~0xf0000000) == AARCH32_BREAK_ARM; | |
273 | } | |
274 | ||
275 | if (!bp) | |
276 | return -EFAULT; | |
277 | ||
278 | info = (siginfo_t) { | |
279 | .si_signo = SIGTRAP, | |
280 | .si_errno = 0, | |
281 | .si_code = TRAP_BRKPT, | |
282 | .si_addr = pc, | |
283 | }; | |
284 | ||
285 | force_sig_info(SIGTRAP, &info, current); | |
286 | return 0; | |
287 | } | |
288 | ||
289 | static int __init debug_traps_init(void) | |
478fcb2c WD |
290 | { |
291 | hook_debug_fault_code(DBG_ESR_EVT_HWSS, single_step_handler, SIGTRAP, | |
292 | TRAP_HWBKPT, "single-step handler"); | |
1442b6ed WD |
293 | hook_debug_fault_code(DBG_ESR_EVT_BRK, brk_handler, SIGTRAP, |
294 | TRAP_BRKPT, "ptrace BRK handler"); | |
478fcb2c WD |
295 | return 0; |
296 | } | |
1442b6ed | 297 | arch_initcall(debug_traps_init); |
478fcb2c WD |
298 | |
299 | /* Re-enable single step for syscall restarting. */ | |
300 | void user_rewind_single_step(struct task_struct *task) | |
301 | { | |
302 | /* | |
303 | * If single step is active for this thread, then set SPSR.SS | |
304 | * to 1 to avoid returning to the active-pending state. | |
305 | */ | |
306 | if (test_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP)) | |
307 | set_regs_spsr_ss(task_pt_regs(task)); | |
308 | } | |
309 | ||
310 | void user_fastforward_single_step(struct task_struct *task) | |
311 | { | |
312 | if (test_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP)) | |
313 | clear_regs_spsr_ss(task_pt_regs(task)); | |
314 | } | |
315 | ||
316 | /* Kernel API */ | |
317 | void kernel_enable_single_step(struct pt_regs *regs) | |
318 | { | |
319 | WARN_ON(!irqs_disabled()); | |
320 | set_regs_spsr_ss(regs); | |
321 | mdscr_write(mdscr_read() | DBG_MDSCR_SS); | |
322 | enable_debug_monitors(DBG_ACTIVE_EL1); | |
323 | } | |
324 | ||
325 | void kernel_disable_single_step(void) | |
326 | { | |
327 | WARN_ON(!irqs_disabled()); | |
328 | mdscr_write(mdscr_read() & ~DBG_MDSCR_SS); | |
329 | disable_debug_monitors(DBG_ACTIVE_EL1); | |
330 | } | |
331 | ||
332 | int kernel_active_single_step(void) | |
333 | { | |
334 | WARN_ON(!irqs_disabled()); | |
335 | return mdscr_read() & DBG_MDSCR_SS; | |
336 | } | |
337 | ||
338 | /* ptrace API */ | |
339 | void user_enable_single_step(struct task_struct *task) | |
340 | { | |
341 | set_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP); | |
342 | set_regs_spsr_ss(task_pt_regs(task)); | |
343 | } | |
344 | ||
345 | void user_disable_single_step(struct task_struct *task) | |
346 | { | |
347 | clear_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP); | |
348 | } |