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