| 1 | // SPDX-License-Identifier: GPL-2.0-only |
| 2 | /* |
| 3 | * Kernel Debug Core |
| 4 | * |
| 5 | * Maintainer: Jason Wessel <jason.wessel@windriver.com> |
| 6 | * |
| 7 | * Copyright (C) 2000-2001 VERITAS Software Corporation. |
| 8 | * Copyright (C) 2002-2004 Timesys Corporation |
| 9 | * Copyright (C) 2003-2004 Amit S. Kale <amitkale@linsyssoft.com> |
| 10 | * Copyright (C) 2004 Pavel Machek <pavel@ucw.cz> |
| 11 | * Copyright (C) 2004-2006 Tom Rini <trini@kernel.crashing.org> |
| 12 | * Copyright (C) 2004-2006 LinSysSoft Technologies Pvt. Ltd. |
| 13 | * Copyright (C) 2005-2009 Wind River Systems, Inc. |
| 14 | * Copyright (C) 2007 MontaVista Software, Inc. |
| 15 | * Copyright (C) 2008 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> |
| 16 | * |
| 17 | * Contributors at various stages not listed above: |
| 18 | * Jason Wessel ( jason.wessel@windriver.com ) |
| 19 | * George Anzinger <george@mvista.com> |
| 20 | * Anurekh Saxena (anurekh.saxena@timesys.com) |
| 21 | * Lake Stevens Instrument Division (Glenn Engel) |
| 22 | * Jim Kingdon, Cygnus Support. |
| 23 | * |
| 24 | * Original KGDB stub: David Grothe <dave@gcom.com>, |
| 25 | * Tigran Aivazian <tigran@sco.com> |
| 26 | */ |
| 27 | |
| 28 | #define pr_fmt(fmt) "KGDB: " fmt |
| 29 | |
| 30 | #include <linux/pid_namespace.h> |
| 31 | #include <linux/clocksource.h> |
| 32 | #include <linux/serial_core.h> |
| 33 | #include <linux/interrupt.h> |
| 34 | #include <linux/spinlock.h> |
| 35 | #include <linux/console.h> |
| 36 | #include <linux/threads.h> |
| 37 | #include <linux/uaccess.h> |
| 38 | #include <linux/kernel.h> |
| 39 | #include <linux/module.h> |
| 40 | #include <linux/ptrace.h> |
| 41 | #include <linux/string.h> |
| 42 | #include <linux/delay.h> |
| 43 | #include <linux/sched.h> |
| 44 | #include <linux/sysrq.h> |
| 45 | #include <linux/reboot.h> |
| 46 | #include <linux/init.h> |
| 47 | #include <linux/kgdb.h> |
| 48 | #include <linux/kdb.h> |
| 49 | #include <linux/nmi.h> |
| 50 | #include <linux/pid.h> |
| 51 | #include <linux/smp.h> |
| 52 | #include <linux/mm.h> |
| 53 | #include <linux/rcupdate.h> |
| 54 | #include <linux/irq.h> |
| 55 | #include <linux/security.h> |
| 56 | |
| 57 | #include <asm/cacheflush.h> |
| 58 | #include <asm/byteorder.h> |
| 59 | #include <linux/atomic.h> |
| 60 | |
| 61 | #include "debug_core.h" |
| 62 | |
| 63 | static int kgdb_break_asap; |
| 64 | |
| 65 | struct debuggerinfo_struct kgdb_info[NR_CPUS]; |
| 66 | |
| 67 | /* kgdb_connected - Is a host GDB connected to us? */ |
| 68 | int kgdb_connected; |
| 69 | EXPORT_SYMBOL_GPL(kgdb_connected); |
| 70 | |
| 71 | /* All the KGDB handlers are installed */ |
| 72 | int kgdb_io_module_registered; |
| 73 | |
| 74 | /* Guard for recursive entry */ |
| 75 | static int exception_level; |
| 76 | |
| 77 | struct kgdb_io *dbg_io_ops; |
| 78 | static DEFINE_SPINLOCK(kgdb_registration_lock); |
| 79 | |
| 80 | /* Action for the reboot notifier, a global allow kdb to change it */ |
| 81 | static int kgdbreboot; |
| 82 | /* kgdb console driver is loaded */ |
| 83 | static int kgdb_con_registered; |
| 84 | /* determine if kgdb console output should be used */ |
| 85 | static int kgdb_use_con; |
| 86 | /* Flag for alternate operations for early debugging */ |
| 87 | bool dbg_is_early = true; |
| 88 | /* Next cpu to become the master debug core */ |
| 89 | int dbg_switch_cpu; |
| 90 | |
| 91 | /* Use kdb or gdbserver mode */ |
| 92 | int dbg_kdb_mode = 1; |
| 93 | |
| 94 | module_param(kgdb_use_con, int, 0644); |
| 95 | module_param(kgdbreboot, int, 0644); |
| 96 | |
| 97 | /* |
| 98 | * Holds information about breakpoints in a kernel. These breakpoints are |
| 99 | * added and removed by gdb. |
| 100 | */ |
| 101 | static struct kgdb_bkpt kgdb_break[KGDB_MAX_BREAKPOINTS] = { |
| 102 | [0 ... KGDB_MAX_BREAKPOINTS-1] = { .state = BP_UNDEFINED } |
| 103 | }; |
| 104 | |
| 105 | /* |
| 106 | * The CPU# of the active CPU, or -1 if none: |
| 107 | */ |
| 108 | atomic_t kgdb_active = ATOMIC_INIT(-1); |
| 109 | EXPORT_SYMBOL_GPL(kgdb_active); |
| 110 | static DEFINE_RAW_SPINLOCK(dbg_master_lock); |
| 111 | static DEFINE_RAW_SPINLOCK(dbg_slave_lock); |
| 112 | |
| 113 | /* |
| 114 | * We use NR_CPUs not PERCPU, in case kgdb is used to debug early |
| 115 | * bootup code (which might not have percpu set up yet): |
| 116 | */ |
| 117 | static atomic_t masters_in_kgdb; |
| 118 | static atomic_t slaves_in_kgdb; |
| 119 | atomic_t kgdb_setting_breakpoint; |
| 120 | |
| 121 | struct task_struct *kgdb_usethread; |
| 122 | struct task_struct *kgdb_contthread; |
| 123 | |
| 124 | int kgdb_single_step; |
| 125 | static pid_t kgdb_sstep_pid; |
| 126 | |
| 127 | /* to keep track of the CPU which is doing the single stepping*/ |
| 128 | atomic_t kgdb_cpu_doing_single_step = ATOMIC_INIT(-1); |
| 129 | |
| 130 | /* |
| 131 | * If you are debugging a problem where roundup (the collection of |
| 132 | * all other CPUs) is a problem [this should be extremely rare], |
| 133 | * then use the nokgdbroundup option to avoid roundup. In that case |
| 134 | * the other CPUs might interfere with your debugging context, so |
| 135 | * use this with care: |
| 136 | */ |
| 137 | static int kgdb_do_roundup = 1; |
| 138 | |
| 139 | static int __init opt_nokgdbroundup(char *str) |
| 140 | { |
| 141 | kgdb_do_roundup = 0; |
| 142 | |
| 143 | return 0; |
| 144 | } |
| 145 | |
| 146 | early_param("nokgdbroundup", opt_nokgdbroundup); |
| 147 | |
| 148 | /* |
| 149 | * Finally, some KGDB code :-) |
| 150 | */ |
| 151 | |
| 152 | /* |
| 153 | * Weak aliases for breakpoint management, |
| 154 | * can be overridden by architectures when needed: |
| 155 | */ |
| 156 | int __weak kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt) |
| 157 | { |
| 158 | int err; |
| 159 | |
| 160 | err = copy_from_kernel_nofault(bpt->saved_instr, (char *)bpt->bpt_addr, |
| 161 | BREAK_INSTR_SIZE); |
| 162 | if (err) |
| 163 | return err; |
| 164 | err = copy_to_kernel_nofault((char *)bpt->bpt_addr, |
| 165 | arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE); |
| 166 | return err; |
| 167 | } |
| 168 | NOKPROBE_SYMBOL(kgdb_arch_set_breakpoint); |
| 169 | |
| 170 | int __weak kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt) |
| 171 | { |
| 172 | return copy_to_kernel_nofault((char *)bpt->bpt_addr, |
| 173 | (char *)bpt->saved_instr, BREAK_INSTR_SIZE); |
| 174 | } |
| 175 | NOKPROBE_SYMBOL(kgdb_arch_remove_breakpoint); |
| 176 | |
| 177 | int __weak kgdb_validate_break_address(unsigned long addr) |
| 178 | { |
| 179 | struct kgdb_bkpt tmp; |
| 180 | int err; |
| 181 | |
| 182 | if (kgdb_within_blocklist(addr)) |
| 183 | return -EINVAL; |
| 184 | |
| 185 | /* Validate setting the breakpoint and then removing it. If the |
| 186 | * remove fails, the kernel needs to emit a bad message because we |
| 187 | * are deep trouble not being able to put things back the way we |
| 188 | * found them. |
| 189 | */ |
| 190 | tmp.bpt_addr = addr; |
| 191 | err = kgdb_arch_set_breakpoint(&tmp); |
| 192 | if (err) |
| 193 | return err; |
| 194 | err = kgdb_arch_remove_breakpoint(&tmp); |
| 195 | if (err) |
| 196 | pr_err("Critical breakpoint error, kernel memory destroyed at: %lx\n", |
| 197 | addr); |
| 198 | return err; |
| 199 | } |
| 200 | |
| 201 | unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs) |
| 202 | { |
| 203 | return instruction_pointer(regs); |
| 204 | } |
| 205 | NOKPROBE_SYMBOL(kgdb_arch_pc); |
| 206 | |
| 207 | int __weak kgdb_arch_init(void) |
| 208 | { |
| 209 | return 0; |
| 210 | } |
| 211 | |
| 212 | int __weak kgdb_skipexception(int exception, struct pt_regs *regs) |
| 213 | { |
| 214 | return 0; |
| 215 | } |
| 216 | NOKPROBE_SYMBOL(kgdb_skipexception); |
| 217 | |
| 218 | #ifdef CONFIG_SMP |
| 219 | |
| 220 | /* |
| 221 | * Default (weak) implementation for kgdb_roundup_cpus |
| 222 | */ |
| 223 | |
| 224 | void __weak kgdb_call_nmi_hook(void *ignored) |
| 225 | { |
| 226 | /* |
| 227 | * NOTE: get_irq_regs() is supposed to get the registers from |
| 228 | * before the IPI interrupt happened and so is supposed to |
| 229 | * show where the processor was. In some situations it's |
| 230 | * possible we might be called without an IPI, so it might be |
| 231 | * safer to figure out how to make kgdb_breakpoint() work |
| 232 | * properly here. |
| 233 | */ |
| 234 | kgdb_nmicallback(raw_smp_processor_id(), get_irq_regs()); |
| 235 | } |
| 236 | NOKPROBE_SYMBOL(kgdb_call_nmi_hook); |
| 237 | |
| 238 | static DEFINE_PER_CPU(call_single_data_t, kgdb_roundup_csd) = |
| 239 | CSD_INIT(kgdb_call_nmi_hook, NULL); |
| 240 | |
| 241 | void __weak kgdb_roundup_cpus(void) |
| 242 | { |
| 243 | call_single_data_t *csd; |
| 244 | int this_cpu = raw_smp_processor_id(); |
| 245 | int cpu; |
| 246 | int ret; |
| 247 | |
| 248 | for_each_online_cpu(cpu) { |
| 249 | /* No need to roundup ourselves */ |
| 250 | if (cpu == this_cpu) |
| 251 | continue; |
| 252 | |
| 253 | csd = &per_cpu(kgdb_roundup_csd, cpu); |
| 254 | |
| 255 | /* |
| 256 | * If it didn't round up last time, don't try again |
| 257 | * since smp_call_function_single_async() will block. |
| 258 | * |
| 259 | * If rounding_up is false then we know that the |
| 260 | * previous call must have at least started and that |
| 261 | * means smp_call_function_single_async() won't block. |
| 262 | */ |
| 263 | if (kgdb_info[cpu].rounding_up) |
| 264 | continue; |
| 265 | kgdb_info[cpu].rounding_up = true; |
| 266 | |
| 267 | ret = smp_call_function_single_async(cpu, csd); |
| 268 | if (ret) |
| 269 | kgdb_info[cpu].rounding_up = false; |
| 270 | } |
| 271 | } |
| 272 | NOKPROBE_SYMBOL(kgdb_roundup_cpus); |
| 273 | |
| 274 | #endif |
| 275 | |
| 276 | /* |
| 277 | * Some architectures need cache flushes when we set/clear a |
| 278 | * breakpoint: |
| 279 | */ |
| 280 | static void kgdb_flush_swbreak_addr(unsigned long addr) |
| 281 | { |
| 282 | if (!CACHE_FLUSH_IS_SAFE) |
| 283 | return; |
| 284 | |
| 285 | /* Force flush instruction cache if it was outside the mm */ |
| 286 | flush_icache_range(addr, addr + BREAK_INSTR_SIZE); |
| 287 | } |
| 288 | NOKPROBE_SYMBOL(kgdb_flush_swbreak_addr); |
| 289 | |
| 290 | /* |
| 291 | * SW breakpoint management: |
| 292 | */ |
| 293 | int dbg_activate_sw_breakpoints(void) |
| 294 | { |
| 295 | int error; |
| 296 | int ret = 0; |
| 297 | int i; |
| 298 | |
| 299 | for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { |
| 300 | if (kgdb_break[i].state != BP_SET) |
| 301 | continue; |
| 302 | |
| 303 | error = kgdb_arch_set_breakpoint(&kgdb_break[i]); |
| 304 | if (error) { |
| 305 | ret = error; |
| 306 | pr_info("BP install failed: %lx\n", |
| 307 | kgdb_break[i].bpt_addr); |
| 308 | continue; |
| 309 | } |
| 310 | |
| 311 | kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr); |
| 312 | kgdb_break[i].state = BP_ACTIVE; |
| 313 | } |
| 314 | return ret; |
| 315 | } |
| 316 | NOKPROBE_SYMBOL(dbg_activate_sw_breakpoints); |
| 317 | |
| 318 | int dbg_set_sw_break(unsigned long addr) |
| 319 | { |
| 320 | int err = kgdb_validate_break_address(addr); |
| 321 | int breakno = -1; |
| 322 | int i; |
| 323 | |
| 324 | if (err) |
| 325 | return err; |
| 326 | |
| 327 | for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { |
| 328 | if ((kgdb_break[i].state == BP_SET) && |
| 329 | (kgdb_break[i].bpt_addr == addr)) |
| 330 | return -EEXIST; |
| 331 | } |
| 332 | for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { |
| 333 | if (kgdb_break[i].state == BP_REMOVED && |
| 334 | kgdb_break[i].bpt_addr == addr) { |
| 335 | breakno = i; |
| 336 | break; |
| 337 | } |
| 338 | } |
| 339 | |
| 340 | if (breakno == -1) { |
| 341 | for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { |
| 342 | if (kgdb_break[i].state == BP_UNDEFINED) { |
| 343 | breakno = i; |
| 344 | break; |
| 345 | } |
| 346 | } |
| 347 | } |
| 348 | |
| 349 | if (breakno == -1) |
| 350 | return -E2BIG; |
| 351 | |
| 352 | kgdb_break[breakno].state = BP_SET; |
| 353 | kgdb_break[breakno].type = BP_BREAKPOINT; |
| 354 | kgdb_break[breakno].bpt_addr = addr; |
| 355 | |
| 356 | return 0; |
| 357 | } |
| 358 | |
| 359 | int dbg_deactivate_sw_breakpoints(void) |
| 360 | { |
| 361 | int error; |
| 362 | int ret = 0; |
| 363 | int i; |
| 364 | |
| 365 | for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { |
| 366 | if (kgdb_break[i].state != BP_ACTIVE) |
| 367 | continue; |
| 368 | error = kgdb_arch_remove_breakpoint(&kgdb_break[i]); |
| 369 | if (error) { |
| 370 | pr_info("BP remove failed: %lx\n", |
| 371 | kgdb_break[i].bpt_addr); |
| 372 | ret = error; |
| 373 | } |
| 374 | |
| 375 | kgdb_flush_swbreak_addr(kgdb_break[i].bpt_addr); |
| 376 | kgdb_break[i].state = BP_SET; |
| 377 | } |
| 378 | return ret; |
| 379 | } |
| 380 | NOKPROBE_SYMBOL(dbg_deactivate_sw_breakpoints); |
| 381 | |
| 382 | int dbg_remove_sw_break(unsigned long addr) |
| 383 | { |
| 384 | int i; |
| 385 | |
| 386 | for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { |
| 387 | if ((kgdb_break[i].state == BP_SET) && |
| 388 | (kgdb_break[i].bpt_addr == addr)) { |
| 389 | kgdb_break[i].state = BP_REMOVED; |
| 390 | return 0; |
| 391 | } |
| 392 | } |
| 393 | return -ENOENT; |
| 394 | } |
| 395 | |
| 396 | int kgdb_isremovedbreak(unsigned long addr) |
| 397 | { |
| 398 | int i; |
| 399 | |
| 400 | for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { |
| 401 | if ((kgdb_break[i].state == BP_REMOVED) && |
| 402 | (kgdb_break[i].bpt_addr == addr)) |
| 403 | return 1; |
| 404 | } |
| 405 | return 0; |
| 406 | } |
| 407 | |
| 408 | int kgdb_has_hit_break(unsigned long addr) |
| 409 | { |
| 410 | int i; |
| 411 | |
| 412 | for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { |
| 413 | if (kgdb_break[i].state == BP_ACTIVE && |
| 414 | kgdb_break[i].bpt_addr == addr) |
| 415 | return 1; |
| 416 | } |
| 417 | return 0; |
| 418 | } |
| 419 | |
| 420 | int dbg_remove_all_break(void) |
| 421 | { |
| 422 | int error; |
| 423 | int i; |
| 424 | |
| 425 | /* Clear memory breakpoints. */ |
| 426 | for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { |
| 427 | if (kgdb_break[i].state != BP_ACTIVE) |
| 428 | goto setundefined; |
| 429 | error = kgdb_arch_remove_breakpoint(&kgdb_break[i]); |
| 430 | if (error) |
| 431 | pr_err("breakpoint remove failed: %lx\n", |
| 432 | kgdb_break[i].bpt_addr); |
| 433 | setundefined: |
| 434 | kgdb_break[i].state = BP_UNDEFINED; |
| 435 | } |
| 436 | |
| 437 | /* Clear hardware breakpoints. */ |
| 438 | if (arch_kgdb_ops.remove_all_hw_break) |
| 439 | arch_kgdb_ops.remove_all_hw_break(); |
| 440 | |
| 441 | return 0; |
| 442 | } |
| 443 | |
| 444 | void kgdb_free_init_mem(void) |
| 445 | { |
| 446 | int i; |
| 447 | |
| 448 | /* Clear init memory breakpoints. */ |
| 449 | for (i = 0; i < KGDB_MAX_BREAKPOINTS; i++) { |
| 450 | if (init_section_contains((void *)kgdb_break[i].bpt_addr, 0)) |
| 451 | kgdb_break[i].state = BP_UNDEFINED; |
| 452 | } |
| 453 | } |
| 454 | |
| 455 | #ifdef CONFIG_KGDB_KDB |
| 456 | void kdb_dump_stack_on_cpu(int cpu) |
| 457 | { |
| 458 | if (cpu == raw_smp_processor_id() || !IS_ENABLED(CONFIG_SMP)) { |
| 459 | dump_stack(); |
| 460 | return; |
| 461 | } |
| 462 | |
| 463 | if (!(kgdb_info[cpu].exception_state & DCPU_IS_SLAVE)) { |
| 464 | kdb_printf("ERROR: Task on cpu %d didn't stop in the debugger\n", |
| 465 | cpu); |
| 466 | return; |
| 467 | } |
| 468 | |
| 469 | /* |
| 470 | * In general, architectures don't support dumping the stack of a |
| 471 | * "running" process that's not the current one. From the point of |
| 472 | * view of the Linux, kernel processes that are looping in the kgdb |
| 473 | * slave loop are still "running". There's also no API (that actually |
| 474 | * works across all architectures) that can do a stack crawl based |
| 475 | * on registers passed as a parameter. |
| 476 | * |
| 477 | * Solve this conundrum by asking slave CPUs to do the backtrace |
| 478 | * themselves. |
| 479 | */ |
| 480 | kgdb_info[cpu].exception_state |= DCPU_WANT_BT; |
| 481 | while (kgdb_info[cpu].exception_state & DCPU_WANT_BT) |
| 482 | cpu_relax(); |
| 483 | } |
| 484 | #endif |
| 485 | |
| 486 | /* |
| 487 | * Return true if there is a valid kgdb I/O module. Also if no |
| 488 | * debugger is attached a message can be printed to the console about |
| 489 | * waiting for the debugger to attach. |
| 490 | * |
| 491 | * The print_wait argument is only to be true when called from inside |
| 492 | * the core kgdb_handle_exception, because it will wait for the |
| 493 | * debugger to attach. |
| 494 | */ |
| 495 | static int kgdb_io_ready(int print_wait) |
| 496 | { |
| 497 | if (!dbg_io_ops) |
| 498 | return 0; |
| 499 | if (kgdb_connected) |
| 500 | return 1; |
| 501 | if (atomic_read(&kgdb_setting_breakpoint)) |
| 502 | return 1; |
| 503 | if (print_wait) { |
| 504 | #ifdef CONFIG_KGDB_KDB |
| 505 | if (!dbg_kdb_mode) |
| 506 | pr_crit("waiting... or $3#33 for KDB\n"); |
| 507 | #else |
| 508 | pr_crit("Waiting for remote debugger\n"); |
| 509 | #endif |
| 510 | } |
| 511 | return 1; |
| 512 | } |
| 513 | NOKPROBE_SYMBOL(kgdb_io_ready); |
| 514 | |
| 515 | static int kgdb_reenter_check(struct kgdb_state *ks) |
| 516 | { |
| 517 | unsigned long addr; |
| 518 | |
| 519 | if (atomic_read(&kgdb_active) != raw_smp_processor_id()) |
| 520 | return 0; |
| 521 | |
| 522 | /* Panic on recursive debugger calls: */ |
| 523 | exception_level++; |
| 524 | addr = kgdb_arch_pc(ks->ex_vector, ks->linux_regs); |
| 525 | dbg_deactivate_sw_breakpoints(); |
| 526 | |
| 527 | /* |
| 528 | * If the break point removed ok at the place exception |
| 529 | * occurred, try to recover and print a warning to the end |
| 530 | * user because the user planted a breakpoint in a place that |
| 531 | * KGDB needs in order to function. |
| 532 | */ |
| 533 | if (dbg_remove_sw_break(addr) == 0) { |
| 534 | exception_level = 0; |
| 535 | kgdb_skipexception(ks->ex_vector, ks->linux_regs); |
| 536 | dbg_activate_sw_breakpoints(); |
| 537 | pr_crit("re-enter error: breakpoint removed %lx\n", addr); |
| 538 | WARN_ON_ONCE(1); |
| 539 | |
| 540 | return 1; |
| 541 | } |
| 542 | dbg_remove_all_break(); |
| 543 | kgdb_skipexception(ks->ex_vector, ks->linux_regs); |
| 544 | |
| 545 | if (exception_level > 1) { |
| 546 | dump_stack(); |
| 547 | kgdb_io_module_registered = false; |
| 548 | panic("Recursive entry to debugger"); |
| 549 | } |
| 550 | |
| 551 | pr_crit("re-enter exception: ALL breakpoints killed\n"); |
| 552 | #ifdef CONFIG_KGDB_KDB |
| 553 | /* Allow kdb to debug itself one level */ |
| 554 | return 0; |
| 555 | #endif |
| 556 | dump_stack(); |
| 557 | panic("Recursive entry to debugger"); |
| 558 | |
| 559 | return 1; |
| 560 | } |
| 561 | NOKPROBE_SYMBOL(kgdb_reenter_check); |
| 562 | |
| 563 | static void dbg_touch_watchdogs(void) |
| 564 | { |
| 565 | touch_softlockup_watchdog_sync(); |
| 566 | clocksource_touch_watchdog(); |
| 567 | rcu_cpu_stall_reset(); |
| 568 | } |
| 569 | NOKPROBE_SYMBOL(dbg_touch_watchdogs); |
| 570 | |
| 571 | static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs, |
| 572 | int exception_state) |
| 573 | { |
| 574 | unsigned long flags; |
| 575 | int sstep_tries = 100; |
| 576 | int error; |
| 577 | int cpu; |
| 578 | int trace_on = 0; |
| 579 | int online_cpus = num_online_cpus(); |
| 580 | u64 time_left; |
| 581 | |
| 582 | kgdb_info[ks->cpu].enter_kgdb++; |
| 583 | kgdb_info[ks->cpu].exception_state |= exception_state; |
| 584 | |
| 585 | if (exception_state == DCPU_WANT_MASTER) |
| 586 | atomic_inc(&masters_in_kgdb); |
| 587 | else |
| 588 | atomic_inc(&slaves_in_kgdb); |
| 589 | |
| 590 | if (arch_kgdb_ops.disable_hw_break) |
| 591 | arch_kgdb_ops.disable_hw_break(regs); |
| 592 | |
| 593 | acquirelock: |
| 594 | rcu_read_lock(); |
| 595 | /* |
| 596 | * Interrupts will be restored by the 'trap return' code, except when |
| 597 | * single stepping. |
| 598 | */ |
| 599 | local_irq_save(flags); |
| 600 | |
| 601 | cpu = ks->cpu; |
| 602 | kgdb_info[cpu].debuggerinfo = regs; |
| 603 | kgdb_info[cpu].task = current; |
| 604 | kgdb_info[cpu].ret_state = 0; |
| 605 | kgdb_info[cpu].irq_depth = hardirq_count() >> HARDIRQ_SHIFT; |
| 606 | |
| 607 | /* Make sure the above info reaches the primary CPU */ |
| 608 | smp_mb(); |
| 609 | |
| 610 | if (exception_level == 1) { |
| 611 | if (raw_spin_trylock(&dbg_master_lock)) |
| 612 | atomic_xchg(&kgdb_active, cpu); |
| 613 | goto cpu_master_loop; |
| 614 | } |
| 615 | |
| 616 | /* |
| 617 | * CPU will loop if it is a slave or request to become a kgdb |
| 618 | * master cpu and acquire the kgdb_active lock: |
| 619 | */ |
| 620 | while (1) { |
| 621 | cpu_loop: |
| 622 | if (kgdb_info[cpu].exception_state & DCPU_NEXT_MASTER) { |
| 623 | kgdb_info[cpu].exception_state &= ~DCPU_NEXT_MASTER; |
| 624 | goto cpu_master_loop; |
| 625 | } else if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) { |
| 626 | if (raw_spin_trylock(&dbg_master_lock)) { |
| 627 | atomic_xchg(&kgdb_active, cpu); |
| 628 | break; |
| 629 | } |
| 630 | } else if (kgdb_info[cpu].exception_state & DCPU_WANT_BT) { |
| 631 | dump_stack(); |
| 632 | kgdb_info[cpu].exception_state &= ~DCPU_WANT_BT; |
| 633 | } else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) { |
| 634 | if (!raw_spin_is_locked(&dbg_slave_lock)) |
| 635 | goto return_normal; |
| 636 | } else { |
| 637 | return_normal: |
| 638 | /* Return to normal operation by executing any |
| 639 | * hw breakpoint fixup. |
| 640 | */ |
| 641 | if (arch_kgdb_ops.correct_hw_break) |
| 642 | arch_kgdb_ops.correct_hw_break(); |
| 643 | if (trace_on) |
| 644 | tracing_on(); |
| 645 | kgdb_info[cpu].debuggerinfo = NULL; |
| 646 | kgdb_info[cpu].task = NULL; |
| 647 | kgdb_info[cpu].exception_state &= |
| 648 | ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE); |
| 649 | kgdb_info[cpu].enter_kgdb--; |
| 650 | smp_mb__before_atomic(); |
| 651 | atomic_dec(&slaves_in_kgdb); |
| 652 | dbg_touch_watchdogs(); |
| 653 | local_irq_restore(flags); |
| 654 | rcu_read_unlock(); |
| 655 | return 0; |
| 656 | } |
| 657 | cpu_relax(); |
| 658 | } |
| 659 | |
| 660 | /* |
| 661 | * For single stepping, try to only enter on the processor |
| 662 | * that was single stepping. To guard against a deadlock, the |
| 663 | * kernel will only try for the value of sstep_tries before |
| 664 | * giving up and continuing on. |
| 665 | */ |
| 666 | if (atomic_read(&kgdb_cpu_doing_single_step) != -1 && |
| 667 | (kgdb_info[cpu].task && |
| 668 | kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) { |
| 669 | atomic_set(&kgdb_active, -1); |
| 670 | raw_spin_unlock(&dbg_master_lock); |
| 671 | dbg_touch_watchdogs(); |
| 672 | local_irq_restore(flags); |
| 673 | rcu_read_unlock(); |
| 674 | |
| 675 | goto acquirelock; |
| 676 | } |
| 677 | |
| 678 | if (!kgdb_io_ready(1)) { |
| 679 | kgdb_info[cpu].ret_state = 1; |
| 680 | goto kgdb_restore; /* No I/O connection, resume the system */ |
| 681 | } |
| 682 | |
| 683 | /* |
| 684 | * Don't enter if we have hit a removed breakpoint. |
| 685 | */ |
| 686 | if (kgdb_skipexception(ks->ex_vector, ks->linux_regs)) |
| 687 | goto kgdb_restore; |
| 688 | |
| 689 | atomic_inc(&ignore_console_lock_warning); |
| 690 | |
| 691 | /* Call the I/O driver's pre_exception routine */ |
| 692 | if (dbg_io_ops->pre_exception) |
| 693 | dbg_io_ops->pre_exception(); |
| 694 | |
| 695 | /* |
| 696 | * Get the passive CPU lock which will hold all the non-primary |
| 697 | * CPU in a spin state while the debugger is active |
| 698 | */ |
| 699 | if (!kgdb_single_step) |
| 700 | raw_spin_lock(&dbg_slave_lock); |
| 701 | |
| 702 | #ifdef CONFIG_SMP |
| 703 | /* If send_ready set, slaves are already waiting */ |
| 704 | if (ks->send_ready) |
| 705 | atomic_set(ks->send_ready, 1); |
| 706 | |
| 707 | /* Signal the other CPUs to enter kgdb_wait() */ |
| 708 | else if ((!kgdb_single_step) && kgdb_do_roundup) |
| 709 | kgdb_roundup_cpus(); |
| 710 | #endif |
| 711 | |
| 712 | /* |
| 713 | * Wait for the other CPUs to be notified and be waiting for us: |
| 714 | */ |
| 715 | time_left = MSEC_PER_SEC; |
| 716 | while (kgdb_do_roundup && --time_left && |
| 717 | (atomic_read(&masters_in_kgdb) + atomic_read(&slaves_in_kgdb)) != |
| 718 | online_cpus) |
| 719 | udelay(1000); |
| 720 | if (!time_left) |
| 721 | pr_crit("Timed out waiting for secondary CPUs.\n"); |
| 722 | |
| 723 | /* |
| 724 | * At this point the primary processor is completely |
| 725 | * in the debugger and all secondary CPUs are quiescent |
| 726 | */ |
| 727 | dbg_deactivate_sw_breakpoints(); |
| 728 | kgdb_single_step = 0; |
| 729 | kgdb_contthread = current; |
| 730 | exception_level = 0; |
| 731 | trace_on = tracing_is_on(); |
| 732 | if (trace_on) |
| 733 | tracing_off(); |
| 734 | |
| 735 | while (1) { |
| 736 | cpu_master_loop: |
| 737 | if (dbg_kdb_mode) { |
| 738 | kgdb_connected = 1; |
| 739 | error = kdb_stub(ks); |
| 740 | if (error == -1) |
| 741 | continue; |
| 742 | kgdb_connected = 0; |
| 743 | } else { |
| 744 | /* |
| 745 | * This is a brutal way to interfere with the debugger |
| 746 | * and prevent gdb being used to poke at kernel memory. |
| 747 | * This could cause trouble if lockdown is applied when |
| 748 | * there is already an active gdb session. For now the |
| 749 | * answer is simply "don't do that". Typically lockdown |
| 750 | * *will* be applied before the debug core gets started |
| 751 | * so only developers using kgdb for fairly advanced |
| 752 | * early kernel debug can be biten by this. Hopefully |
| 753 | * they are sophisticated enough to take care of |
| 754 | * themselves, especially with help from the lockdown |
| 755 | * message printed on the console! |
| 756 | */ |
| 757 | if (security_locked_down(LOCKDOWN_DBG_WRITE_KERNEL)) { |
| 758 | if (IS_ENABLED(CONFIG_KGDB_KDB)) { |
| 759 | /* Switch back to kdb if possible... */ |
| 760 | dbg_kdb_mode = 1; |
| 761 | continue; |
| 762 | } else { |
| 763 | /* ... otherwise just bail */ |
| 764 | break; |
| 765 | } |
| 766 | } |
| 767 | error = gdb_serial_stub(ks); |
| 768 | } |
| 769 | |
| 770 | if (error == DBG_PASS_EVENT) { |
| 771 | dbg_kdb_mode = !dbg_kdb_mode; |
| 772 | } else if (error == DBG_SWITCH_CPU_EVENT) { |
| 773 | kgdb_info[dbg_switch_cpu].exception_state |= |
| 774 | DCPU_NEXT_MASTER; |
| 775 | goto cpu_loop; |
| 776 | } else { |
| 777 | kgdb_info[cpu].ret_state = error; |
| 778 | break; |
| 779 | } |
| 780 | } |
| 781 | |
| 782 | dbg_activate_sw_breakpoints(); |
| 783 | |
| 784 | /* Call the I/O driver's post_exception routine */ |
| 785 | if (dbg_io_ops->post_exception) |
| 786 | dbg_io_ops->post_exception(); |
| 787 | |
| 788 | atomic_dec(&ignore_console_lock_warning); |
| 789 | |
| 790 | if (!kgdb_single_step) { |
| 791 | raw_spin_unlock(&dbg_slave_lock); |
| 792 | /* Wait till all the CPUs have quit from the debugger. */ |
| 793 | while (kgdb_do_roundup && atomic_read(&slaves_in_kgdb)) |
| 794 | cpu_relax(); |
| 795 | } |
| 796 | |
| 797 | kgdb_restore: |
| 798 | if (atomic_read(&kgdb_cpu_doing_single_step) != -1) { |
| 799 | int sstep_cpu = atomic_read(&kgdb_cpu_doing_single_step); |
| 800 | if (kgdb_info[sstep_cpu].task) |
| 801 | kgdb_sstep_pid = kgdb_info[sstep_cpu].task->pid; |
| 802 | else |
| 803 | kgdb_sstep_pid = 0; |
| 804 | } |
| 805 | if (arch_kgdb_ops.correct_hw_break) |
| 806 | arch_kgdb_ops.correct_hw_break(); |
| 807 | if (trace_on) |
| 808 | tracing_on(); |
| 809 | |
| 810 | kgdb_info[cpu].debuggerinfo = NULL; |
| 811 | kgdb_info[cpu].task = NULL; |
| 812 | kgdb_info[cpu].exception_state &= |
| 813 | ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE); |
| 814 | kgdb_info[cpu].enter_kgdb--; |
| 815 | smp_mb__before_atomic(); |
| 816 | atomic_dec(&masters_in_kgdb); |
| 817 | /* Free kgdb_active */ |
| 818 | atomic_set(&kgdb_active, -1); |
| 819 | raw_spin_unlock(&dbg_master_lock); |
| 820 | dbg_touch_watchdogs(); |
| 821 | local_irq_restore(flags); |
| 822 | rcu_read_unlock(); |
| 823 | |
| 824 | return kgdb_info[cpu].ret_state; |
| 825 | } |
| 826 | NOKPROBE_SYMBOL(kgdb_cpu_enter); |
| 827 | |
| 828 | /* |
| 829 | * kgdb_handle_exception() - main entry point from a kernel exception |
| 830 | * |
| 831 | * Locking hierarchy: |
| 832 | * interface locks, if any (begin_session) |
| 833 | * kgdb lock (kgdb_active) |
| 834 | */ |
| 835 | int |
| 836 | kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs) |
| 837 | { |
| 838 | struct kgdb_state kgdb_var; |
| 839 | struct kgdb_state *ks = &kgdb_var; |
| 840 | int ret = 0; |
| 841 | |
| 842 | if (arch_kgdb_ops.enable_nmi) |
| 843 | arch_kgdb_ops.enable_nmi(0); |
| 844 | /* |
| 845 | * Avoid entering the debugger if we were triggered due to an oops |
| 846 | * but panic_timeout indicates the system should automatically |
| 847 | * reboot on panic. We don't want to get stuck waiting for input |
| 848 | * on such systems, especially if its "just" an oops. |
| 849 | */ |
| 850 | if (signo != SIGTRAP && panic_timeout) |
| 851 | return 1; |
| 852 | |
| 853 | memset(ks, 0, sizeof(struct kgdb_state)); |
| 854 | ks->cpu = raw_smp_processor_id(); |
| 855 | ks->ex_vector = evector; |
| 856 | ks->signo = signo; |
| 857 | ks->err_code = ecode; |
| 858 | ks->linux_regs = regs; |
| 859 | |
| 860 | if (kgdb_reenter_check(ks)) |
| 861 | goto out; /* Ouch, double exception ! */ |
| 862 | if (kgdb_info[ks->cpu].enter_kgdb != 0) |
| 863 | goto out; |
| 864 | |
| 865 | ret = kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER); |
| 866 | out: |
| 867 | if (arch_kgdb_ops.enable_nmi) |
| 868 | arch_kgdb_ops.enable_nmi(1); |
| 869 | return ret; |
| 870 | } |
| 871 | NOKPROBE_SYMBOL(kgdb_handle_exception); |
| 872 | |
| 873 | /* |
| 874 | * GDB places a breakpoint at this function to know dynamically loaded objects. |
| 875 | */ |
| 876 | static int module_event(struct notifier_block *self, unsigned long val, |
| 877 | void *data) |
| 878 | { |
| 879 | return 0; |
| 880 | } |
| 881 | |
| 882 | static struct notifier_block dbg_module_load_nb = { |
| 883 | .notifier_call = module_event, |
| 884 | }; |
| 885 | |
| 886 | int kgdb_nmicallback(int cpu, void *regs) |
| 887 | { |
| 888 | #ifdef CONFIG_SMP |
| 889 | struct kgdb_state kgdb_var; |
| 890 | struct kgdb_state *ks = &kgdb_var; |
| 891 | |
| 892 | kgdb_info[cpu].rounding_up = false; |
| 893 | |
| 894 | memset(ks, 0, sizeof(struct kgdb_state)); |
| 895 | ks->cpu = cpu; |
| 896 | ks->linux_regs = regs; |
| 897 | |
| 898 | if (kgdb_info[ks->cpu].enter_kgdb == 0 && |
| 899 | raw_spin_is_locked(&dbg_master_lock)) { |
| 900 | kgdb_cpu_enter(ks, regs, DCPU_IS_SLAVE); |
| 901 | return 0; |
| 902 | } |
| 903 | #endif |
| 904 | return 1; |
| 905 | } |
| 906 | NOKPROBE_SYMBOL(kgdb_nmicallback); |
| 907 | |
| 908 | int kgdb_nmicallin(int cpu, int trapnr, void *regs, int err_code, |
| 909 | atomic_t *send_ready) |
| 910 | { |
| 911 | #ifdef CONFIG_SMP |
| 912 | if (!kgdb_io_ready(0) || !send_ready) |
| 913 | return 1; |
| 914 | |
| 915 | if (kgdb_info[cpu].enter_kgdb == 0) { |
| 916 | struct kgdb_state kgdb_var; |
| 917 | struct kgdb_state *ks = &kgdb_var; |
| 918 | |
| 919 | memset(ks, 0, sizeof(struct kgdb_state)); |
| 920 | ks->cpu = cpu; |
| 921 | ks->ex_vector = trapnr; |
| 922 | ks->signo = SIGTRAP; |
| 923 | ks->err_code = err_code; |
| 924 | ks->linux_regs = regs; |
| 925 | ks->send_ready = send_ready; |
| 926 | kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER); |
| 927 | return 0; |
| 928 | } |
| 929 | #endif |
| 930 | return 1; |
| 931 | } |
| 932 | NOKPROBE_SYMBOL(kgdb_nmicallin); |
| 933 | |
| 934 | static void kgdb_console_write(struct console *co, const char *s, |
| 935 | unsigned count) |
| 936 | { |
| 937 | unsigned long flags; |
| 938 | |
| 939 | /* If we're debugging, or KGDB has not connected, don't try |
| 940 | * and print. */ |
| 941 | if (!kgdb_connected || atomic_read(&kgdb_active) != -1 || dbg_kdb_mode) |
| 942 | return; |
| 943 | |
| 944 | local_irq_save(flags); |
| 945 | gdbstub_msg_write(s, count); |
| 946 | local_irq_restore(flags); |
| 947 | } |
| 948 | |
| 949 | static struct console kgdbcons = { |
| 950 | .name = "kgdb", |
| 951 | .write = kgdb_console_write, |
| 952 | .flags = CON_PRINTBUFFER | CON_ENABLED, |
| 953 | .index = -1, |
| 954 | }; |
| 955 | |
| 956 | static int __init opt_kgdb_con(char *str) |
| 957 | { |
| 958 | kgdb_use_con = 1; |
| 959 | |
| 960 | if (kgdb_io_module_registered && !kgdb_con_registered) { |
| 961 | register_console(&kgdbcons); |
| 962 | kgdb_con_registered = 1; |
| 963 | } |
| 964 | |
| 965 | return 0; |
| 966 | } |
| 967 | |
| 968 | early_param("kgdbcon", opt_kgdb_con); |
| 969 | |
| 970 | #ifdef CONFIG_MAGIC_SYSRQ |
| 971 | static void sysrq_handle_dbg(int key) |
| 972 | { |
| 973 | if (!dbg_io_ops) { |
| 974 | pr_crit("ERROR: No KGDB I/O module available\n"); |
| 975 | return; |
| 976 | } |
| 977 | if (!kgdb_connected) { |
| 978 | #ifdef CONFIG_KGDB_KDB |
| 979 | if (!dbg_kdb_mode) |
| 980 | pr_crit("KGDB or $3#33 for KDB\n"); |
| 981 | #else |
| 982 | pr_crit("Entering KGDB\n"); |
| 983 | #endif |
| 984 | } |
| 985 | |
| 986 | kgdb_breakpoint(); |
| 987 | } |
| 988 | |
| 989 | static const struct sysrq_key_op sysrq_dbg_op = { |
| 990 | .handler = sysrq_handle_dbg, |
| 991 | .help_msg = "debug(g)", |
| 992 | .action_msg = "DEBUG", |
| 993 | }; |
| 994 | #endif |
| 995 | |
| 996 | void kgdb_panic(const char *msg) |
| 997 | { |
| 998 | if (!kgdb_io_module_registered) |
| 999 | return; |
| 1000 | |
| 1001 | /* |
| 1002 | * We don't want to get stuck waiting for input from user if |
| 1003 | * "panic_timeout" indicates the system should automatically |
| 1004 | * reboot on panic. |
| 1005 | */ |
| 1006 | if (panic_timeout) |
| 1007 | return; |
| 1008 | |
| 1009 | if (dbg_kdb_mode) |
| 1010 | kdb_printf("PANIC: %s\n", msg); |
| 1011 | |
| 1012 | kgdb_breakpoint(); |
| 1013 | } |
| 1014 | |
| 1015 | static void kgdb_initial_breakpoint(void) |
| 1016 | { |
| 1017 | kgdb_break_asap = 0; |
| 1018 | |
| 1019 | pr_crit("Waiting for connection from remote gdb...\n"); |
| 1020 | kgdb_breakpoint(); |
| 1021 | } |
| 1022 | |
| 1023 | void __weak kgdb_arch_late(void) |
| 1024 | { |
| 1025 | } |
| 1026 | |
| 1027 | void __init dbg_late_init(void) |
| 1028 | { |
| 1029 | dbg_is_early = false; |
| 1030 | if (kgdb_io_module_registered) |
| 1031 | kgdb_arch_late(); |
| 1032 | kdb_init(KDB_INIT_FULL); |
| 1033 | |
| 1034 | if (kgdb_io_module_registered && kgdb_break_asap) |
| 1035 | kgdb_initial_breakpoint(); |
| 1036 | } |
| 1037 | |
| 1038 | static int |
| 1039 | dbg_notify_reboot(struct notifier_block *this, unsigned long code, void *x) |
| 1040 | { |
| 1041 | /* |
| 1042 | * Take the following action on reboot notify depending on value: |
| 1043 | * 1 == Enter debugger |
| 1044 | * 0 == [the default] detach debug client |
| 1045 | * -1 == Do nothing... and use this until the board resets |
| 1046 | */ |
| 1047 | switch (kgdbreboot) { |
| 1048 | case 1: |
| 1049 | kgdb_breakpoint(); |
| 1050 | goto done; |
| 1051 | case -1: |
| 1052 | goto done; |
| 1053 | } |
| 1054 | if (!dbg_kdb_mode) |
| 1055 | gdbstub_exit(code); |
| 1056 | done: |
| 1057 | return NOTIFY_DONE; |
| 1058 | } |
| 1059 | |
| 1060 | static struct notifier_block dbg_reboot_notifier = { |
| 1061 | .notifier_call = dbg_notify_reboot, |
| 1062 | .next = NULL, |
| 1063 | .priority = INT_MAX, |
| 1064 | }; |
| 1065 | |
| 1066 | static void kgdb_register_callbacks(void) |
| 1067 | { |
| 1068 | if (!kgdb_io_module_registered) { |
| 1069 | kgdb_io_module_registered = 1; |
| 1070 | kgdb_arch_init(); |
| 1071 | if (!dbg_is_early) |
| 1072 | kgdb_arch_late(); |
| 1073 | register_module_notifier(&dbg_module_load_nb); |
| 1074 | register_reboot_notifier(&dbg_reboot_notifier); |
| 1075 | #ifdef CONFIG_MAGIC_SYSRQ |
| 1076 | register_sysrq_key('g', &sysrq_dbg_op); |
| 1077 | #endif |
| 1078 | if (kgdb_use_con && !kgdb_con_registered) { |
| 1079 | register_console(&kgdbcons); |
| 1080 | kgdb_con_registered = 1; |
| 1081 | } |
| 1082 | } |
| 1083 | } |
| 1084 | |
| 1085 | static void kgdb_unregister_callbacks(void) |
| 1086 | { |
| 1087 | /* |
| 1088 | * When this routine is called KGDB should unregister from |
| 1089 | * handlers and clean up, making sure it is not handling any |
| 1090 | * break exceptions at the time. |
| 1091 | */ |
| 1092 | if (kgdb_io_module_registered) { |
| 1093 | kgdb_io_module_registered = 0; |
| 1094 | unregister_reboot_notifier(&dbg_reboot_notifier); |
| 1095 | unregister_module_notifier(&dbg_module_load_nb); |
| 1096 | kgdb_arch_exit(); |
| 1097 | #ifdef CONFIG_MAGIC_SYSRQ |
| 1098 | unregister_sysrq_key('g', &sysrq_dbg_op); |
| 1099 | #endif |
| 1100 | if (kgdb_con_registered) { |
| 1101 | unregister_console(&kgdbcons); |
| 1102 | kgdb_con_registered = 0; |
| 1103 | } |
| 1104 | } |
| 1105 | } |
| 1106 | |
| 1107 | /** |
| 1108 | * kgdb_register_io_module - register KGDB IO module |
| 1109 | * @new_dbg_io_ops: the io ops vector |
| 1110 | * |
| 1111 | * Register it with the KGDB core. |
| 1112 | */ |
| 1113 | int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops) |
| 1114 | { |
| 1115 | struct kgdb_io *old_dbg_io_ops; |
| 1116 | int err; |
| 1117 | |
| 1118 | spin_lock(&kgdb_registration_lock); |
| 1119 | |
| 1120 | old_dbg_io_ops = dbg_io_ops; |
| 1121 | if (old_dbg_io_ops) { |
| 1122 | if (!old_dbg_io_ops->deinit) { |
| 1123 | spin_unlock(&kgdb_registration_lock); |
| 1124 | |
| 1125 | pr_err("KGDB I/O driver %s can't replace %s.\n", |
| 1126 | new_dbg_io_ops->name, old_dbg_io_ops->name); |
| 1127 | return -EBUSY; |
| 1128 | } |
| 1129 | pr_info("Replacing I/O driver %s with %s\n", |
| 1130 | old_dbg_io_ops->name, new_dbg_io_ops->name); |
| 1131 | } |
| 1132 | |
| 1133 | if (new_dbg_io_ops->init) { |
| 1134 | err = new_dbg_io_ops->init(); |
| 1135 | if (err) { |
| 1136 | spin_unlock(&kgdb_registration_lock); |
| 1137 | return err; |
| 1138 | } |
| 1139 | } |
| 1140 | |
| 1141 | dbg_io_ops = new_dbg_io_ops; |
| 1142 | |
| 1143 | spin_unlock(&kgdb_registration_lock); |
| 1144 | |
| 1145 | if (old_dbg_io_ops) { |
| 1146 | old_dbg_io_ops->deinit(); |
| 1147 | return 0; |
| 1148 | } |
| 1149 | |
| 1150 | pr_info("Registered I/O driver %s\n", new_dbg_io_ops->name); |
| 1151 | |
| 1152 | /* Arm KGDB now. */ |
| 1153 | kgdb_register_callbacks(); |
| 1154 | |
| 1155 | if (kgdb_break_asap && |
| 1156 | (!dbg_is_early || IS_ENABLED(CONFIG_ARCH_HAS_EARLY_DEBUG))) |
| 1157 | kgdb_initial_breakpoint(); |
| 1158 | |
| 1159 | return 0; |
| 1160 | } |
| 1161 | EXPORT_SYMBOL_GPL(kgdb_register_io_module); |
| 1162 | |
| 1163 | /** |
| 1164 | * kgdb_unregister_io_module - unregister KGDB IO module |
| 1165 | * @old_dbg_io_ops: the io ops vector |
| 1166 | * |
| 1167 | * Unregister it with the KGDB core. |
| 1168 | */ |
| 1169 | void kgdb_unregister_io_module(struct kgdb_io *old_dbg_io_ops) |
| 1170 | { |
| 1171 | BUG_ON(kgdb_connected); |
| 1172 | |
| 1173 | /* |
| 1174 | * KGDB is no longer able to communicate out, so |
| 1175 | * unregister our callbacks and reset state. |
| 1176 | */ |
| 1177 | kgdb_unregister_callbacks(); |
| 1178 | |
| 1179 | spin_lock(&kgdb_registration_lock); |
| 1180 | |
| 1181 | WARN_ON_ONCE(dbg_io_ops != old_dbg_io_ops); |
| 1182 | dbg_io_ops = NULL; |
| 1183 | |
| 1184 | spin_unlock(&kgdb_registration_lock); |
| 1185 | |
| 1186 | if (old_dbg_io_ops->deinit) |
| 1187 | old_dbg_io_ops->deinit(); |
| 1188 | |
| 1189 | pr_info("Unregistered I/O driver %s, debugger disabled\n", |
| 1190 | old_dbg_io_ops->name); |
| 1191 | } |
| 1192 | EXPORT_SYMBOL_GPL(kgdb_unregister_io_module); |
| 1193 | |
| 1194 | int dbg_io_get_char(void) |
| 1195 | { |
| 1196 | int ret = dbg_io_ops->read_char(); |
| 1197 | if (ret == NO_POLL_CHAR) |
| 1198 | return -1; |
| 1199 | if (!dbg_kdb_mode) |
| 1200 | return ret; |
| 1201 | if (ret == 127) |
| 1202 | return 8; |
| 1203 | return ret; |
| 1204 | } |
| 1205 | |
| 1206 | /** |
| 1207 | * kgdb_breakpoint - generate breakpoint exception |
| 1208 | * |
| 1209 | * This function will generate a breakpoint exception. It is used at the |
| 1210 | * beginning of a program to sync up with a debugger and can be used |
| 1211 | * otherwise as a quick means to stop program execution and "break" into |
| 1212 | * the debugger. |
| 1213 | */ |
| 1214 | noinline void kgdb_breakpoint(void) |
| 1215 | { |
| 1216 | atomic_inc(&kgdb_setting_breakpoint); |
| 1217 | wmb(); /* Sync point before breakpoint */ |
| 1218 | arch_kgdb_breakpoint(); |
| 1219 | wmb(); /* Sync point after breakpoint */ |
| 1220 | atomic_dec(&kgdb_setting_breakpoint); |
| 1221 | } |
| 1222 | EXPORT_SYMBOL_GPL(kgdb_breakpoint); |
| 1223 | |
| 1224 | static int __init opt_kgdb_wait(char *str) |
| 1225 | { |
| 1226 | kgdb_break_asap = 1; |
| 1227 | |
| 1228 | kdb_init(KDB_INIT_EARLY); |
| 1229 | if (kgdb_io_module_registered && |
| 1230 | IS_ENABLED(CONFIG_ARCH_HAS_EARLY_DEBUG)) |
| 1231 | kgdb_initial_breakpoint(); |
| 1232 | |
| 1233 | return 0; |
| 1234 | } |
| 1235 | |
| 1236 | early_param("kgdbwait", opt_kgdb_wait); |