1 /* 2 * Copyright (C) 1991, 1992 Linus Torvalds 3 * Copyright (C) 2000, 2001, 2002 Andi Kleen, SuSE Labs 4 */ 5 #include <linux/kallsyms.h> 6 #include <linux/kprobes.h> 7 #include <linux/uaccess.h> 8 #include <linux/utsname.h> 9 #include <linux/hardirq.h> 10 #include <linux/kdebug.h> 11 #include <linux/module.h> 12 #include <linux/ptrace.h> 13 #include <linux/sched/debug.h> 14 #include <linux/sched/task_stack.h> 15 #include <linux/ftrace.h> 16 #include <linux/kexec.h> 17 #include <linux/bug.h> 18 #include <linux/nmi.h> 19 #include <linux/sysfs.h> 20 #include <linux/kasan.h> 21 22 #include <asm/cpu_entry_area.h> 23 #include <asm/stacktrace.h> 24 #include <asm/unwind.h> 25 26 int panic_on_unrecovered_nmi; 27 int panic_on_io_nmi; 28 static int die_counter; 29 30 static struct pt_regs exec_summary_regs; 31 32 bool noinstr in_task_stack(unsigned long *stack, struct task_struct *task, 33 struct stack_info *info) 34 { 35 unsigned long *begin = task_stack_page(task); 36 unsigned long *end = task_stack_page(task) + THREAD_SIZE; 37 38 if (stack < begin || stack >= end) 39 return false; 40 41 info->type = STACK_TYPE_TASK; 42 info->begin = begin; 43 info->end = end; 44 info->next_sp = NULL; 45 46 return true; 47 } 48 49 /* Called from get_stack_info_noinstr - so must be noinstr too */ 50 bool noinstr in_entry_stack(unsigned long *stack, struct stack_info *info) 51 { 52 struct entry_stack *ss = cpu_entry_stack(smp_processor_id()); 53 54 void *begin = ss; 55 void *end = ss + 1; 56 57 if ((void *)stack < begin || (void *)stack >= end) 58 return false; 59 60 info->type = STACK_TYPE_ENTRY; 61 info->begin = begin; 62 info->end = end; 63 info->next_sp = NULL; 64 65 return true; 66 } 67 68 static void printk_stack_address(unsigned long address, int reliable, 69 const char *log_lvl) 70 { 71 touch_nmi_watchdog(); 72 printk("%s %s%pB\n", log_lvl, reliable ? "" : "? ", (void *)address); 73 } 74 75 static int copy_code(struct pt_regs *regs, u8 *buf, unsigned long src, 76 unsigned int nbytes) 77 { 78 if (!user_mode(regs)) 79 return copy_from_kernel_nofault(buf, (u8 *)src, nbytes); 80 81 /* The user space code from other tasks cannot be accessed. */ 82 if (regs != task_pt_regs(current)) 83 return -EPERM; 84 /* 85 * Make sure userspace isn't trying to trick us into dumping kernel 86 * memory by pointing the userspace instruction pointer at it. 87 */ 88 if (__chk_range_not_ok(src, nbytes, TASK_SIZE_MAX)) 89 return -EINVAL; 90 91 /* 92 * Even if named copy_from_user_nmi() this can be invoked from 93 * other contexts and will not try to resolve a pagefault, which is 94 * the correct thing to do here as this code can be called from any 95 * context. 96 */ 97 return copy_from_user_nmi(buf, (void __user *)src, nbytes); 98 } 99 100 /* 101 * There are a couple of reasons for the 2/3rd prologue, courtesy of Linus: 102 * 103 * In case where we don't have the exact kernel image (which, if we did, we can 104 * simply disassemble and navigate to the RIP), the purpose of the bigger 105 * prologue is to have more context and to be able to correlate the code from 106 * the different toolchains better. 107 * 108 * In addition, it helps in recreating the register allocation of the failing 109 * kernel and thus make sense of the register dump. 110 * 111 * What is more, the additional complication of a variable length insn arch like 112 * x86 warrants having longer byte sequence before rIP so that the disassembler 113 * can "sync" up properly and find instruction boundaries when decoding the 114 * opcode bytes. 115 * 116 * Thus, the 2/3rds prologue and 64 byte OPCODE_BUFSIZE is just a random 117 * guesstimate in attempt to achieve all of the above. 118 */ 119 void show_opcodes(struct pt_regs *regs, const char *loglvl) 120 { 121 #define PROLOGUE_SIZE 42 122 #define EPILOGUE_SIZE 21 123 #define OPCODE_BUFSIZE (PROLOGUE_SIZE + 1 + EPILOGUE_SIZE) 124 u8 opcodes[OPCODE_BUFSIZE]; 125 unsigned long prologue = regs->ip - PROLOGUE_SIZE; 126 127 switch (copy_code(regs, opcodes, prologue, sizeof(opcodes))) { 128 case 0: 129 printk("%sCode: %" __stringify(PROLOGUE_SIZE) "ph <%02x> %" 130 __stringify(EPILOGUE_SIZE) "ph\n", loglvl, opcodes, 131 opcodes[PROLOGUE_SIZE], opcodes + PROLOGUE_SIZE + 1); 132 break; 133 case -EPERM: 134 /* No access to the user space stack of other tasks. Ignore. */ 135 break; 136 default: 137 printk("%sCode: Unable to access opcode bytes at RIP 0x%lx.\n", 138 loglvl, prologue); 139 break; 140 } 141 } 142 143 void show_ip(struct pt_regs *regs, const char *loglvl) 144 { 145 #ifdef CONFIG_X86_32 146 printk("%sEIP: %pS\n", loglvl, (void *)regs->ip); 147 #else 148 printk("%sRIP: %04x:%pS\n", loglvl, (int)regs->cs, (void *)regs->ip); 149 #endif 150 show_opcodes(regs, loglvl); 151 } 152 153 void show_iret_regs(struct pt_regs *regs, const char *log_lvl) 154 { 155 show_ip(regs, log_lvl); 156 printk("%sRSP: %04x:%016lx EFLAGS: %08lx", log_lvl, (int)regs->ss, 157 regs->sp, regs->flags); 158 } 159 160 static void show_regs_if_on_stack(struct stack_info *info, struct pt_regs *regs, 161 bool partial, const char *log_lvl) 162 { 163 /* 164 * These on_stack() checks aren't strictly necessary: the unwind code 165 * has already validated the 'regs' pointer. The checks are done for 166 * ordering reasons: if the registers are on the next stack, we don't 167 * want to print them out yet. Otherwise they'll be shown as part of 168 * the wrong stack. Later, when show_trace_log_lvl() switches to the 169 * next stack, this function will be called again with the same regs so 170 * they can be printed in the right context. 171 */ 172 if (!partial && on_stack(info, regs, sizeof(*regs))) { 173 __show_regs(regs, SHOW_REGS_SHORT, log_lvl); 174 175 } else if (partial && on_stack(info, (void *)regs + IRET_FRAME_OFFSET, 176 IRET_FRAME_SIZE)) { 177 /* 178 * When an interrupt or exception occurs in entry code, the 179 * full pt_regs might not have been saved yet. In that case 180 * just print the iret frame. 181 */ 182 show_iret_regs(regs, log_lvl); 183 } 184 } 185 186 void show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs, 187 unsigned long *stack, const char *log_lvl) 188 { 189 struct unwind_state state; 190 struct stack_info stack_info = {0}; 191 unsigned long visit_mask = 0; 192 int graph_idx = 0; 193 bool partial = false; 194 195 printk("%sCall Trace:\n", log_lvl); 196 197 unwind_start(&state, task, regs, stack); 198 stack = stack ? : get_stack_pointer(task, regs); 199 regs = unwind_get_entry_regs(&state, &partial); 200 201 /* 202 * Iterate through the stacks, starting with the current stack pointer. 203 * Each stack has a pointer to the next one. 204 * 205 * x86-64 can have several stacks: 206 * - task stack 207 * - interrupt stack 208 * - HW exception stacks (double fault, nmi, debug, mce) 209 * - entry stack 210 * 211 * x86-32 can have up to four stacks: 212 * - task stack 213 * - softirq stack 214 * - hardirq stack 215 * - entry stack 216 */ 217 for ( ; stack; stack = PTR_ALIGN(stack_info.next_sp, sizeof(long))) { 218 const char *stack_name; 219 220 if (get_stack_info(stack, task, &stack_info, &visit_mask)) { 221 /* 222 * We weren't on a valid stack. It's possible that 223 * we overflowed a valid stack into a guard page. 224 * See if the next page up is valid so that we can 225 * generate some kind of backtrace if this happens. 226 */ 227 stack = (unsigned long *)PAGE_ALIGN((unsigned long)stack); 228 if (get_stack_info(stack, task, &stack_info, &visit_mask)) 229 break; 230 } 231 232 stack_name = stack_type_name(stack_info.type); 233 if (stack_name) 234 printk("%s <%s>\n", log_lvl, stack_name); 235 236 if (regs) 237 show_regs_if_on_stack(&stack_info, regs, partial, log_lvl); 238 239 /* 240 * Scan the stack, printing any text addresses we find. At the 241 * same time, follow proper stack frames with the unwinder. 242 * 243 * Addresses found during the scan which are not reported by 244 * the unwinder are considered to be additional clues which are 245 * sometimes useful for debugging and are prefixed with '?'. 246 * This also serves as a failsafe option in case the unwinder 247 * goes off in the weeds. 248 */ 249 for (; stack < stack_info.end; stack++) { 250 unsigned long real_addr; 251 int reliable = 0; 252 unsigned long addr = READ_ONCE_NOCHECK(*stack); 253 unsigned long *ret_addr_p = 254 unwind_get_return_address_ptr(&state); 255 256 if (!__kernel_text_address(addr)) 257 continue; 258 259 /* 260 * Don't print regs->ip again if it was already printed 261 * by show_regs_if_on_stack(). 262 */ 263 if (regs && stack == ®s->ip) 264 goto next; 265 266 if (stack == ret_addr_p) 267 reliable = 1; 268 269 /* 270 * When function graph tracing is enabled for a 271 * function, its return address on the stack is 272 * replaced with the address of an ftrace handler 273 * (return_to_handler). In that case, before printing 274 * the "real" address, we want to print the handler 275 * address as an "unreliable" hint that function graph 276 * tracing was involved. 277 */ 278 real_addr = ftrace_graph_ret_addr(task, &graph_idx, 279 addr, stack); 280 if (real_addr != addr) 281 printk_stack_address(addr, 0, log_lvl); 282 printk_stack_address(real_addr, reliable, log_lvl); 283 284 if (!reliable) 285 continue; 286 287 next: 288 /* 289 * Get the next frame from the unwinder. No need to 290 * check for an error: if anything goes wrong, the rest 291 * of the addresses will just be printed as unreliable. 292 */ 293 unwind_next_frame(&state); 294 295 /* if the frame has entry regs, print them */ 296 regs = unwind_get_entry_regs(&state, &partial); 297 if (regs) 298 show_regs_if_on_stack(&stack_info, regs, partial, log_lvl); 299 } 300 301 if (stack_name) 302 printk("%s </%s>\n", log_lvl, stack_name); 303 } 304 } 305 306 void show_stack(struct task_struct *task, unsigned long *sp, 307 const char *loglvl) 308 { 309 task = task ? : current; 310 311 /* 312 * Stack frames below this one aren't interesting. Don't show them 313 * if we're printing for %current. 314 */ 315 if (!sp && task == current) 316 sp = get_stack_pointer(current, NULL); 317 318 show_trace_log_lvl(task, NULL, sp, loglvl); 319 } 320 321 void show_stack_regs(struct pt_regs *regs) 322 { 323 show_trace_log_lvl(current, regs, NULL, KERN_DEFAULT); 324 } 325 326 static arch_spinlock_t die_lock = __ARCH_SPIN_LOCK_UNLOCKED; 327 static int die_owner = -1; 328 static unsigned int die_nest_count; 329 330 unsigned long oops_begin(void) 331 { 332 int cpu; 333 unsigned long flags; 334 335 oops_enter(); 336 337 /* racy, but better than risking deadlock. */ 338 raw_local_irq_save(flags); 339 cpu = smp_processor_id(); 340 if (!arch_spin_trylock(&die_lock)) { 341 if (cpu == die_owner) 342 /* nested oops. should stop eventually */; 343 else 344 arch_spin_lock(&die_lock); 345 } 346 die_nest_count++; 347 die_owner = cpu; 348 console_verbose(); 349 bust_spinlocks(1); 350 return flags; 351 } 352 NOKPROBE_SYMBOL(oops_begin); 353 354 void __noreturn rewind_stack_do_exit(int signr); 355 356 void oops_end(unsigned long flags, struct pt_regs *regs, int signr) 357 { 358 if (regs && kexec_should_crash(current)) 359 crash_kexec(regs); 360 361 bust_spinlocks(0); 362 die_owner = -1; 363 add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE); 364 die_nest_count--; 365 if (!die_nest_count) 366 /* Nest count reaches zero, release the lock. */ 367 arch_spin_unlock(&die_lock); 368 raw_local_irq_restore(flags); 369 oops_exit(); 370 371 /* Executive summary in case the oops scrolled away */ 372 __show_regs(&exec_summary_regs, SHOW_REGS_ALL, KERN_DEFAULT); 373 374 if (!signr) 375 return; 376 if (in_interrupt()) 377 panic("Fatal exception in interrupt"); 378 if (panic_on_oops) 379 panic("Fatal exception"); 380 381 /* 382 * We're not going to return, but we might be on an IST stack or 383 * have very little stack space left. Rewind the stack and kill 384 * the task. 385 * Before we rewind the stack, we have to tell KASAN that we're going to 386 * reuse the task stack and that existing poisons are invalid. 387 */ 388 kasan_unpoison_task_stack(current); 389 rewind_stack_do_exit(signr); 390 } 391 NOKPROBE_SYMBOL(oops_end); 392 393 static void __die_header(const char *str, struct pt_regs *regs, long err) 394 { 395 const char *pr = ""; 396 397 /* Save the regs of the first oops for the executive summary later. */ 398 if (!die_counter) 399 exec_summary_regs = *regs; 400 401 if (IS_ENABLED(CONFIG_PREEMPTION)) 402 pr = IS_ENABLED(CONFIG_PREEMPT_RT) ? " PREEMPT_RT" : " PREEMPT"; 403 404 printk(KERN_DEFAULT 405 "%s: %04lx [#%d]%s%s%s%s%s\n", str, err & 0xffff, ++die_counter, 406 pr, 407 IS_ENABLED(CONFIG_SMP) ? " SMP" : "", 408 debug_pagealloc_enabled() ? " DEBUG_PAGEALLOC" : "", 409 IS_ENABLED(CONFIG_KASAN) ? " KASAN" : "", 410 IS_ENABLED(CONFIG_PAGE_TABLE_ISOLATION) ? 411 (boot_cpu_has(X86_FEATURE_PTI) ? " PTI" : " NOPTI") : ""); 412 } 413 NOKPROBE_SYMBOL(__die_header); 414 415 static int __die_body(const char *str, struct pt_regs *regs, long err) 416 { 417 show_regs(regs); 418 print_modules(); 419 420 if (notify_die(DIE_OOPS, str, regs, err, 421 current->thread.trap_nr, SIGSEGV) == NOTIFY_STOP) 422 return 1; 423 424 return 0; 425 } 426 NOKPROBE_SYMBOL(__die_body); 427 428 int __die(const char *str, struct pt_regs *regs, long err) 429 { 430 __die_header(str, regs, err); 431 return __die_body(str, regs, err); 432 } 433 NOKPROBE_SYMBOL(__die); 434 435 /* 436 * This is gone through when something in the kernel has done something bad 437 * and is about to be terminated: 438 */ 439 void die(const char *str, struct pt_regs *regs, long err) 440 { 441 unsigned long flags = oops_begin(); 442 int sig = SIGSEGV; 443 444 if (__die(str, regs, err)) 445 sig = 0; 446 oops_end(flags, regs, sig); 447 } 448 449 void die_addr(const char *str, struct pt_regs *regs, long err, long gp_addr) 450 { 451 unsigned long flags = oops_begin(); 452 int sig = SIGSEGV; 453 454 __die_header(str, regs, err); 455 if (gp_addr) 456 kasan_non_canonical_hook(gp_addr); 457 if (__die_body(str, regs, err)) 458 sig = 0; 459 oops_end(flags, regs, sig); 460 } 461 462 void show_regs(struct pt_regs *regs) 463 { 464 enum show_regs_mode print_kernel_regs; 465 466 show_regs_print_info(KERN_DEFAULT); 467 468 print_kernel_regs = user_mode(regs) ? SHOW_REGS_USER : SHOW_REGS_ALL; 469 __show_regs(regs, print_kernel_regs, KERN_DEFAULT); 470 471 /* 472 * When in-kernel, we also print out the stack at the time of the fault.. 473 */ 474 if (!user_mode(regs)) 475 show_trace_log_lvl(current, regs, NULL, KERN_DEFAULT); 476 } 477