arch/x86/kernel/dumpstack.c

   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 unsigned int code_bytes = 64;
  28 static int die_counter;
  29
  30 bool in_task_stack(unsigned long *stack, struct task_struct *task,
  31                    struct stack_info *info)
  32 {
  33         unsigned long *begin = task_stack_page(task);
  34         unsigned long *end   = task_stack_page(task) + THREAD_SIZE;
  35
  36         if (stack < begin || stack >= end)
  37                 return false;
  38
  39         info->type      = STACK_TYPE_TASK;
  40         info->begin     = begin;
  41         info->end       = end;
  42         info->next_sp   = NULL;
  43
  44         return true;
  45 }
  46
  47 bool in_entry_stack(unsigned long *stack, struct stack_info *info)
  48 {
  49         struct entry_stack *ss = cpu_entry_stack(smp_processor_id());
  50
  51         void *begin = ss;
  52         void *end = ss + 1;
  53
  54         if ((void *)stack < begin || (void *)stack >= end)
  55                 return false;
  56
  57         info->type      = STACK_TYPE_ENTRY;
  58         info->begin     = begin;
  59         info->end       = end;
  60         info->next_sp   = NULL;
  61
  62         return true;
  63 }
  64
  65 static void printk_stack_address(unsigned long address, int reliable,
  66                                  char *log_lvl)
  67 {
  68         touch_nmi_watchdog();
  69         printk("%s %s%pB\n", log_lvl, reliable ? "" : "? ", (void *)address);
  70 }
  71
  72 void show_iret_regs(struct pt_regs *regs)
  73 {
  74         printk(KERN_DEFAULT "RIP: %04x:%pS\n", (int)regs->cs, (void *)regs->ip);
  75         printk(KERN_DEFAULT "RSP: %04x:%016lx EFLAGS: %08lx", (int)regs->ss,
  76                 regs->sp, regs->flags);
  77 }
  78
  79 static void show_regs_if_on_stack(struct stack_info *info, struct pt_regs *regs,
  80                                   bool partial)
  81 {
  82         /*
  83          * These on_stack() checks aren't strictly necessary: the unwind code
  84          * has already validated the 'regs' pointer.  The checks are done for
  85          * ordering reasons: if the registers are on the next stack, we don't
  86          * want to print them out yet.  Otherwise they'll be shown as part of
  87          * the wrong stack.  Later, when show_trace_log_lvl() switches to the
  88          * next stack, this function will be called again with the same regs so
  89          * they can be printed in the right context.
  90          */
  91         if (!partial && on_stack(info, regs, sizeof(*regs))) {
  92                 __show_regs(regs, 0);
  93
  94         } else if (partial && on_stack(info, (void *)regs + IRET_FRAME_OFFSET,
  95                                        IRET_FRAME_SIZE)) {
  96                 /*
  97                  * When an interrupt or exception occurs in entry code, the
  98                  * full pt_regs might not have been saved yet.  In that case
  99                  * just print the iret frame.
 100                  */
 101                 show_iret_regs(regs);
 102         }
 103 }
 104
 105 void show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs,
 106                         unsigned long *stack, char *log_lvl)
 107 {
 108         struct unwind_state state;
 109         struct stack_info stack_info = {0};
 110         unsigned long visit_mask = 0;
 111         int graph_idx = 0;
 112         bool partial;
 113
 114         printk("%sCall Trace:\n", log_lvl);
 115
 116         unwind_start(&state, task, regs, stack);
 117         stack = stack ? : get_stack_pointer(task, regs);
 118         regs = unwind_get_entry_regs(&state, &partial);
 119
 120         /*
 121          * Iterate through the stacks, starting with the current stack pointer.
 122          * Each stack has a pointer to the next one.
 123          *
 124          * x86-64 can have several stacks:
 125          * - task stack
 126          * - interrupt stack
 127          * - HW exception stacks (double fault, nmi, debug, mce)
 128          * - entry stack
 129          *
 130          * x86-32 can have up to four stacks:
 131          * - task stack
 132          * - softirq stack
 133          * - hardirq stack
 134          * - entry stack
 135          */
 136         for ( ; stack; stack = PTR_ALIGN(stack_info.next_sp, sizeof(long))) {
 137                 const char *stack_name;
 138
 139                 if (get_stack_info(stack, task, &stack_info, &visit_mask)) {
 140                         /*
 141                          * We weren't on a valid stack.  It's possible that
 142                          * we overflowed a valid stack into a guard page.
 143                          * See if the next page up is valid so that we can
 144                          * generate some kind of backtrace if this happens.
 145                          */
 146                         stack = (unsigned long *)PAGE_ALIGN((unsigned long)stack);
 147                         if (get_stack_info(stack, task, &stack_info, &visit_mask))
 148                                 break;
 149                 }
 150
 151                 stack_name = stack_type_name(stack_info.type);
 152                 if (stack_name)
 153                         printk("%s <%s>\n", log_lvl, stack_name);
 154
 155                 if (regs)
 156                         show_regs_if_on_stack(&stack_info, regs, partial);
 157
 158                 /*
 159                  * Scan the stack, printing any text addresses we find.  At the
 160                  * same time, follow proper stack frames with the unwinder.
 161                  *
 162                  * Addresses found during the scan which are not reported by
 163                  * the unwinder are considered to be additional clues which are
 164                  * sometimes useful for debugging and are prefixed with '?'.
 165                  * This also serves as a failsafe option in case the unwinder
 166                  * goes off in the weeds.
 167                  */
 168                 for (; stack < stack_info.end; stack++) {
 169                         unsigned long real_addr;
 170                         int reliable = 0;
 171                         unsigned long addr = READ_ONCE_NOCHECK(*stack);
 172                         unsigned long *ret_addr_p =
 173                                 unwind_get_return_address_ptr(&state);
 174
 175                         if (!__kernel_text_address(addr))
 176                                 continue;
 177
 178                         /*
 179                          * Don't print regs->ip again if it was already printed
 180                          * by show_regs_if_on_stack().
 181                          */
 182                         if (regs && stack == &regs->ip)
 183                                 goto next;
 184
 185                         if (stack == ret_addr_p)
 186                                 reliable = 1;
 187
 188                         /*
 189                          * When function graph tracing is enabled for a
 190                          * function, its return address on the stack is
 191                          * replaced with the address of an ftrace handler
 192                          * (return_to_handler).  In that case, before printing
 193                          * the "real" address, we want to print the handler
 194                          * address as an "unreliable" hint that function graph
 195                          * tracing was involved.
 196                          */
 197                         real_addr = ftrace_graph_ret_addr(task, &graph_idx,
 198                                                           addr, stack);
 199                         if (real_addr != addr)
 200                                 printk_stack_address(addr, 0, log_lvl);
 201                         printk_stack_address(real_addr, reliable, log_lvl);
 202
 203                         if (!reliable)
 204                                 continue;
 205
 206 next:
 207                         /*
 208                          * Get the next frame from the unwinder.  No need to
 209                          * check for an error: if anything goes wrong, the rest
 210                          * of the addresses will just be printed as unreliable.
 211                          */
 212                         unwind_next_frame(&state);
 213
 214                         /* if the frame has entry regs, print them */
 215                         regs = unwind_get_entry_regs(&state, &partial);
 216                         if (regs)
 217                                 show_regs_if_on_stack(&stack_info, regs, partial);
 218                 }
 219
 220                 if (stack_name)
 221                         printk("%s </%s>\n", log_lvl, stack_name);
 222         }
 223 }
 224
 225 void show_stack(struct task_struct *task, unsigned long *sp)
 226 {
 227         task = task ? : current;
 228
 229         /*
 230          * Stack frames below this one aren't interesting.  Don't show them
 231          * if we're printing for %current.
 232          */
 233         if (!sp && task == current)
 234                 sp = get_stack_pointer(current, NULL);
 235
 236         show_trace_log_lvl(task, NULL, sp, KERN_DEFAULT);
 237 }
 238
 239 void show_stack_regs(struct pt_regs *regs)
 240 {
 241         show_trace_log_lvl(current, regs, NULL, KERN_DEFAULT);
 242 }
 243
 244 static arch_spinlock_t die_lock = __ARCH_SPIN_LOCK_UNLOCKED;
 245 static int die_owner = -1;
 246 static unsigned int die_nest_count;
 247
 248 unsigned long oops_begin(void)
 249 {
 250         int cpu;
 251         unsigned long flags;
 252
 253         oops_enter();
 254
 255         /* racy, but better than risking deadlock. */
 256         raw_local_irq_save(flags);
 257         cpu = smp_processor_id();
 258         if (!arch_spin_trylock(&die_lock)) {
 259                 if (cpu == die_owner)
 260                         /* nested oops. should stop eventually */;
 261                 else
 262                         arch_spin_lock(&die_lock);
 263         }
 264         die_nest_count++;
 265         die_owner = cpu;
 266         console_verbose();
 267         bust_spinlocks(1);
 268         return flags;
 269 }
 270 EXPORT_SYMBOL_GPL(oops_begin);
 271 NOKPROBE_SYMBOL(oops_begin);
 272
 273 void __noreturn rewind_stack_do_exit(int signr);
 274
 275 void oops_end(unsigned long flags, struct pt_regs *regs, int signr)
 276 {
 277         if (regs && kexec_should_crash(current))
 278                 crash_kexec(regs);
 279
 280         bust_spinlocks(0);
 281         die_owner = -1;
 282         add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE);
 283         die_nest_count--;
 284         if (!die_nest_count)
 285                 /* Nest count reaches zero, release the lock. */
 286                 arch_spin_unlock(&die_lock);
 287         raw_local_irq_restore(flags);
 288         oops_exit();
 289
 290         if (!signr)
 291                 return;
 292         if (in_interrupt())
 293                 panic("Fatal exception in interrupt");
 294         if (panic_on_oops)
 295                 panic("Fatal exception");
 296
 297         /*
 298          * We're not going to return, but we might be on an IST stack or
 299          * have very little stack space left.  Rewind the stack and kill
 300          * the task.
 301          */
 302         rewind_stack_do_exit(signr);
 303 }
 304 NOKPROBE_SYMBOL(oops_end);
 305
 306 int __die(const char *str, struct pt_regs *regs, long err)
 307 {
 308 #ifdef CONFIG_X86_32
 309         unsigned short ss;
 310         unsigned long sp;
 311 #endif
 312         printk(KERN_DEFAULT
 313                "%s: %04lx [#%d]%s%s%s%s%s\n", str, err & 0xffff, ++die_counter,
 314                IS_ENABLED(CONFIG_PREEMPT) ? " PREEMPT"         : "",
 315                IS_ENABLED(CONFIG_SMP)     ? " SMP"             : "",
 316                debug_pagealloc_enabled()  ? " DEBUG_PAGEALLOC" : "",
 317                IS_ENABLED(CONFIG_KASAN)   ? " KASAN"           : "",
 318                IS_ENABLED(CONFIG_PAGE_TABLE_ISOLATION) ?
 319                (boot_cpu_has(X86_FEATURE_PTI) ? " PTI" : " NOPTI") : "");
 320
 321         if (notify_die(DIE_OOPS, str, regs, err,
 322                         current->thread.trap_nr, SIGSEGV) == NOTIFY_STOP)
 323                 return 1;
 324
 325         print_modules();
 326         show_regs(regs);
 327 #ifdef CONFIG_X86_32
 328         if (user_mode(regs)) {
 329                 sp = regs->sp;
 330                 ss = regs->ss;
 331         } else {
 332                 sp = kernel_stack_pointer(regs);
 333                 savesegment(ss, ss);
 334         }
 335         printk(KERN_EMERG "EIP: %pS SS:ESP: %04x:%08lx\n",
 336                (void *)regs->ip, ss, sp);
 337 #else
 338         /* Executive summary in case the oops scrolled away */
 339         printk(KERN_ALERT "RIP: %pS RSP: %016lx\n", (void *)regs->ip, regs->sp);
 340 #endif
 341         return 0;
 342 }
 343 NOKPROBE_SYMBOL(__die);
 344
 345 /*
 346  * This is gone through when something in the kernel has done something bad
 347  * and is about to be terminated:
 348  */
 349 void die(const char *str, struct pt_regs *regs, long err)
 350 {
 351         unsigned long flags = oops_begin();
 352         int sig = SIGSEGV;
 353
 354         if (__die(str, regs, err))
 355                 sig = 0;
 356         oops_end(flags, regs, sig);
 357 }
 358
 359 static int __init code_bytes_setup(char *s)
 360 {
 361         ssize_t ret;
 362         unsigned long val;
 363
 364         if (!s)
 365                 return -EINVAL;
 366
 367         ret = kstrtoul(s, 0, &val);
 368         if (ret)
 369                 return ret;
 370
 371         code_bytes = val;
 372         if (code_bytes > 8192)
 373                 code_bytes = 8192;
 374
 375         return 1;
 376 }
 377 __setup("code_bytes=", code_bytes_setup);