arch/tile/kernel/stack.c

   1 /*
   2  * Copyright 2010 Tilera Corporation. All Rights Reserved.
   3  *
   4  *   This program is free software; you can redistribute it and/or
   5  *   modify it under the terms of the GNU General Public License
   6  *   as published by the Free Software Foundation, version 2.
   7  *
   8  *   This program is distributed in the hope that it will be useful, but
   9  *   WITHOUT ANY WARRANTY; without even the implied warranty of
  10  *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
  11  *   NON INFRINGEMENT.  See the GNU General Public License for
  12  *   more details.
  13  */
  14
  15 #include <linux/sched.h>
  16 #include <linux/kernel.h>
  17 #include <linux/kprobes.h>
  18 #include <linux/module.h>
  19 #include <linux/pfn.h>
  20 #include <linux/kallsyms.h>
  21 #include <linux/stacktrace.h>
  22 #include <linux/uaccess.h>
  23 #include <linux/mmzone.h>
  24 #include <linux/dcache.h>
  25 #include <linux/fs.h>
  26 #include <asm/backtrace.h>
  27 #include <asm/page.h>
  28 #include <asm/ucontext.h>
  29 #include <asm/switch_to.h>
  30 #include <asm/sigframe.h>
  31 #include <asm/stack.h>
  32 #include <asm/vdso.h>
  33 #include <arch/abi.h>
  34 #include <arch/interrupts.h>
  35
  36 #define KBT_ONGOING     0  /* Backtrace still ongoing */
  37 #define KBT_DONE        1  /* Backtrace cleanly completed */
  38 #define KBT_RUNNING     2  /* Can't run backtrace on a running task */
  39 #define KBT_LOOP        3  /* Backtrace entered a loop */
  40
  41 /* Is address on the specified kernel stack? */
  42 static int in_kernel_stack(struct KBacktraceIterator *kbt, unsigned long sp)
  43 {
  44         ulong kstack_base = (ulong) kbt->task->stack;
  45         if (kstack_base == 0)  /* corrupt task pointer; just follow stack... */
  46                 return sp >= PAGE_OFFSET && sp < (unsigned long)high_memory;
  47         return sp >= kstack_base && sp < kstack_base + THREAD_SIZE;
  48 }
  49
  50 /* Callback for backtracer; basically a glorified memcpy */
  51 static bool read_memory_func(void *result, unsigned long address,
  52                              unsigned int size, void *vkbt)
  53 {
  54         int retval;
  55         struct KBacktraceIterator *kbt = (struct KBacktraceIterator *)vkbt;
  56
  57         if (address == 0)
  58                 return 0;
  59         if (__kernel_text_address(address)) {
  60                 /* OK to read kernel code. */
  61         } else if (address >= PAGE_OFFSET) {
  62                 /* We only tolerate kernel-space reads of this task's stack */
  63                 if (!in_kernel_stack(kbt, address))
  64                         return 0;
  65         } else if (!kbt->is_current) {
  66                 return 0;       /* can't read from other user address spaces */
  67         }
  68         pagefault_disable();
  69         retval = __copy_from_user_inatomic(result,
  70                                            (void __user __force *)address,
  71                                            size);
  72         pagefault_enable();
  73         return (retval == 0);
  74 }
  75
  76 /* Return a pt_regs pointer for a valid fault handler frame */
  77 static struct pt_regs *valid_fault_handler(struct KBacktraceIterator* kbt)
  78 {
  79         const char *fault = NULL;  /* happy compiler */
  80         char fault_buf[64];
  81         unsigned long sp = kbt->it.sp;
  82         struct pt_regs *p;
  83
  84         if (sp % sizeof(long) != 0)
  85                 return NULL;
  86         if (!in_kernel_stack(kbt, sp))
  87                 return NULL;
  88         if (!in_kernel_stack(kbt, sp + C_ABI_SAVE_AREA_SIZE + PTREGS_SIZE-1))
  89                 return NULL;
  90         p = (struct pt_regs *)(sp + C_ABI_SAVE_AREA_SIZE);
  91         if (p->faultnum == INT_SWINT_1 || p->faultnum == INT_SWINT_1_SIGRETURN)
  92                 fault = "syscall";
  93         else {
  94                 if (kbt->verbose) {     /* else we aren't going to use it */
  95                         snprintf(fault_buf, sizeof(fault_buf),
  96                                  "interrupt %ld", p->faultnum);
  97                         fault = fault_buf;
  98                 }
  99         }
 100         if (EX1_PL(p->ex1) == KERNEL_PL &&
 101             __kernel_text_address(p->pc) &&
 102             in_kernel_stack(kbt, p->sp) &&
 103             p->sp >= sp) {
 104                 if (kbt->verbose)
 105                         pr_err("  <%s while in kernel mode>\n", fault);
 106         } else if (EX1_PL(p->ex1) == USER_PL &&
 107                    p->sp < PAGE_OFFSET && p->sp != 0) {
 108                 if (kbt->verbose)
 109                         pr_err("  <%s while in user mode>\n", fault);
 110         } else if (kbt->verbose) {
 111                 pr_err("  (odd fault: pc %#lx, sp %#lx, ex1 %#lx?)\n",
 112                        p->pc, p->sp, p->ex1);
 113                 p = NULL;
 114         }
 115         if (!kbt->profile || ((1ULL << p->faultnum) & QUEUED_INTERRUPTS) == 0)
 116                 return p;
 117         return NULL;
 118 }
 119
 120 /* Is the pc pointing to a sigreturn trampoline? */
 121 static int is_sigreturn(unsigned long pc)
 122 {
 123         return current->mm && (pc == VDSO_SYM(&__vdso_rt_sigreturn));
 124 }
 125
 126 /* Return a pt_regs pointer for a valid signal handler frame */
 127 static struct pt_regs *valid_sigframe(struct KBacktraceIterator* kbt,
 128                                       struct rt_sigframe* kframe)
 129 {
 130         BacktraceIterator *b = &kbt->it;
 131
 132         if (is_sigreturn(b->pc) && b->sp < PAGE_OFFSET &&
 133             b->sp % sizeof(long) == 0) {
 134                 int retval;
 135                 pagefault_disable();
 136                 retval = __copy_from_user_inatomic(
 137                         kframe, (void __user __force *)b->sp,
 138                         sizeof(*kframe));
 139                 pagefault_enable();
 140                 if (retval != 0 ||
 141                     (unsigned int)(kframe->info.si_signo) >= _NSIG)
 142                         return NULL;
 143                 if (kbt->verbose) {
 144                         pr_err("  <received signal %d>\n",
 145                                kframe->info.si_signo);
 146                 }
 147                 return (struct pt_regs *)&kframe->uc.uc_mcontext;
 148         }
 149         return NULL;
 150 }
 151
 152 static int KBacktraceIterator_is_sigreturn(struct KBacktraceIterator *kbt)
 153 {
 154         return is_sigreturn(kbt->it.pc);
 155 }
 156
 157 static int KBacktraceIterator_restart(struct KBacktraceIterator *kbt)
 158 {
 159         struct pt_regs *p;
 160         struct rt_sigframe kframe;
 161
 162         p = valid_fault_handler(kbt);
 163         if (p == NULL)
 164                 p = valid_sigframe(kbt, &kframe);
 165         if (p == NULL)
 166                 return 0;
 167         backtrace_init(&kbt->it, read_memory_func, kbt,
 168                        p->pc, p->lr, p->sp, p->regs[52]);
 169         kbt->new_context = 1;
 170         return 1;
 171 }
 172
 173 /* Find a frame that isn't a sigreturn, if there is one. */
 174 static int KBacktraceIterator_next_item_inclusive(
 175         struct KBacktraceIterator *kbt)
 176 {
 177         for (;;) {
 178                 do {
 179                         if (!KBacktraceIterator_is_sigreturn(kbt))
 180                                 return KBT_ONGOING;
 181                 } while (backtrace_next(&kbt->it));
 182
 183                 if (!KBacktraceIterator_restart(kbt))
 184                         return KBT_DONE;
 185         }
 186 }
 187
 188 /*
 189  * If the current sp is on a page different than what we recorded
 190  * as the top-of-kernel-stack last time we context switched, we have
 191  * probably blown the stack, and nothing is going to work out well.
 192  * If we can at least get out a warning, that may help the debug,
 193  * though we probably won't be able to backtrace into the code that
 194  * actually did the recursive damage.
 195  */
 196 static void validate_stack(struct pt_regs *regs)
 197 {
 198         int cpu = raw_smp_processor_id();
 199         unsigned long ksp0 = get_current_ksp0();
 200         unsigned long ksp0_base = ksp0 - THREAD_SIZE;
 201         unsigned long sp = stack_pointer;
 202
 203         if (EX1_PL(regs->ex1) == KERNEL_PL && regs->sp >= ksp0) {
 204                 pr_err("WARNING: cpu %d: kernel stack page %#lx underrun!\n"
 205                        "  sp %#lx (%#lx in caller), caller pc %#lx, lr %#lx\n",
 206                        cpu, ksp0_base, sp, regs->sp, regs->pc, regs->lr);
 207         }
 208
 209         else if (sp < ksp0_base + sizeof(struct thread_info)) {
 210                 pr_err("WARNING: cpu %d: kernel stack page %#lx overrun!\n"
 211                        "  sp %#lx (%#lx in caller), caller pc %#lx, lr %#lx\n",
 212                        cpu, ksp0_base, sp, regs->sp, regs->pc, regs->lr);
 213         }
 214 }
 215
 216 void KBacktraceIterator_init(struct KBacktraceIterator *kbt,
 217                              struct task_struct *t, struct pt_regs *regs)
 218 {
 219         unsigned long pc, lr, sp, r52;
 220         int is_current;
 221
 222         /*
 223          * Set up callback information.  We grab the kernel stack base
 224          * so we will allow reads of that address range.
 225          */
 226         is_current = (t == NULL || t == current);
 227         kbt->is_current = is_current;
 228         if (is_current)
 229                 t = validate_current();
 230         kbt->task = t;
 231         kbt->verbose = 0;   /* override in caller if desired */
 232         kbt->profile = 0;   /* override in caller if desired */
 233         kbt->end = KBT_ONGOING;
 234         kbt->new_context = 1;
 235         if (is_current)
 236                 validate_stack(regs);
 237
 238         if (regs == NULL) {
 239                 if (is_current || t->state == TASK_RUNNING) {
 240                         /* Can't do this; we need registers */
 241                         kbt->end = KBT_RUNNING;
 242                         return;
 243                 }
 244                 pc = get_switch_to_pc();
 245                 lr = t->thread.pc;
 246                 sp = t->thread.ksp;
 247                 r52 = 0;
 248         } else {
 249                 pc = regs->pc;
 250                 lr = regs->lr;
 251                 sp = regs->sp;
 252                 r52 = regs->regs[52];
 253         }
 254
 255         backtrace_init(&kbt->it, read_memory_func, kbt, pc, lr, sp, r52);
 256         kbt->end = KBacktraceIterator_next_item_inclusive(kbt);
 257 }
 258 EXPORT_SYMBOL(KBacktraceIterator_init);
 259
 260 int KBacktraceIterator_end(struct KBacktraceIterator *kbt)
 261 {
 262         return kbt->end != KBT_ONGOING;
 263 }
 264 EXPORT_SYMBOL(KBacktraceIterator_end);
 265
 266 void KBacktraceIterator_next(struct KBacktraceIterator *kbt)
 267 {
 268         unsigned long old_pc = kbt->it.pc, old_sp = kbt->it.sp;
 269         kbt->new_context = 0;
 270         if (!backtrace_next(&kbt->it) && !KBacktraceIterator_restart(kbt)) {
 271                 kbt->end = KBT_DONE;
 272                 return;
 273         }
 274         kbt->end = KBacktraceIterator_next_item_inclusive(kbt);
 275         if (old_pc == kbt->it.pc && old_sp == kbt->it.sp) {
 276                 /* Trapped in a loop; give up. */
 277                 kbt->end = KBT_LOOP;
 278         }
 279 }
 280 EXPORT_SYMBOL(KBacktraceIterator_next);
 281
 282 static void describe_addr(struct KBacktraceIterator *kbt,
 283                           unsigned long address,
 284                           int have_mmap_sem, char *buf, size_t bufsize)
 285 {
 286         struct vm_area_struct *vma;
 287         size_t namelen, remaining;
 288         unsigned long size, offset, adjust;
 289         char *p, *modname;
 290         const char *name;
 291         int rc;
 292
 293         /*
 294          * Look one byte back for every caller frame (i.e. those that
 295          * aren't a new context) so we look up symbol data for the
 296          * call itself, not the following instruction, which may be on
 297          * a different line (or in a different function).
 298          */
 299         adjust = !kbt->new_context;
 300         address -= adjust;
 301
 302         if (address >= PAGE_OFFSET) {
 303                 /* Handle kernel symbols. */
 304                 BUG_ON(bufsize < KSYM_NAME_LEN);
 305                 name = kallsyms_lookup(address, &size, &offset,
 306                                        &modname, buf);
 307                 if (name == NULL) {
 308                         buf[0] = '\0';
 309                         return;
 310                 }
 311                 namelen = strlen(buf);
 312                 remaining = (bufsize - 1) - namelen;
 313                 p = buf + namelen;
 314                 rc = snprintf(p, remaining, "+%#lx/%#lx ",
 315                               offset + adjust, size);
 316                 if (modname && rc < remaining)
 317                         snprintf(p + rc, remaining - rc, "[%s] ", modname);
 318                 buf[bufsize-1] = '\0';
 319                 return;
 320         }
 321
 322         /* If we don't have the mmap_sem, we can't show any more info. */
 323         buf[0] = '\0';
 324         if (!have_mmap_sem)
 325                 return;
 326
 327         /* Find vma info. */
 328         vma = find_vma(kbt->task->mm, address);
 329         if (vma == NULL || address < vma->vm_start) {
 330                 snprintf(buf, bufsize, "[unmapped address] ");
 331                 return;
 332         }
 333
 334         if (vma->vm_file) {
 335                 char *s;
 336                 p = d_path(&vma->vm_file->f_path, buf, bufsize);
 337                 if (IS_ERR(p))
 338                         p = "?";
 339                 s = strrchr(p, '/');
 340                 if (s)
 341                         p = s+1;
 342         } else {
 343                 p = "anon";
 344         }
 345
 346         /* Generate a string description of the vma info. */
 347         namelen = strlen(p);
 348         remaining = (bufsize - 1) - namelen;
 349         memmove(buf, p, namelen);
 350         snprintf(buf + namelen, remaining, "[%lx+%lx] ",
 351                  vma->vm_start, vma->vm_end - vma->vm_start);
 352 }
 353
 354 /*
 355  * Avoid possible crash recursion during backtrace.  If it happens, it
 356  * makes it easy to lose the actual root cause of the failure, so we
 357  * put a simple guard on all the backtrace loops.
 358  */
 359 static bool start_backtrace(void)
 360 {
 361         if (current->thread.in_backtrace) {
 362                 pr_err("Backtrace requested while in backtrace!\n");
 363                 return false;
 364         }
 365         current->thread.in_backtrace = true;
 366         return true;
 367 }
 368
 369 static void end_backtrace(void)
 370 {
 371         current->thread.in_backtrace = false;
 372 }
 373
 374 /*
 375  * This method wraps the backtracer's more generic support.
 376  * It is only invoked from the architecture-specific code; show_stack()
 377  * and dump_stack() (in entry.S) are architecture-independent entry points.
 378  */
 379 void tile_show_stack(struct KBacktraceIterator *kbt, int headers)
 380 {
 381         int i;
 382         int have_mmap_sem = 0;
 383
 384         if (!start_backtrace())
 385                 return;
 386         if (headers) {
 387                 /*
 388                  * Add a blank line since if we are called from panic(),
 389                  * then bust_spinlocks() spit out a space in front of us
 390                  * and it will mess up our KERN_ERR.
 391                  */
 392                 pr_err("\n");
 393                 pr_err("Starting stack dump of tid %d, pid %d (%s)"
 394                        " on cpu %d at cycle %lld\n",
 395                        kbt->task->pid, kbt->task->tgid, kbt->task->comm,
 396                        raw_smp_processor_id(), get_cycles());
 397         }
 398         kbt->verbose = 1;
 399         i = 0;
 400         for (; !KBacktraceIterator_end(kbt); KBacktraceIterator_next(kbt)) {
 401                 char namebuf[KSYM_NAME_LEN+100];
 402                 unsigned long address = kbt->it.pc;
 403
 404                 /* Try to acquire the mmap_sem as we pass into userspace. */
 405                 if (address < PAGE_OFFSET && !have_mmap_sem && kbt->task->mm)
 406                         have_mmap_sem =
 407                                 down_read_trylock(&kbt->task->mm->mmap_sem);
 408
 409                 describe_addr(kbt, address, have_mmap_sem,
 410                               namebuf, sizeof(namebuf));
 411
 412                 pr_err("  frame %d: 0x%lx %s(sp 0x%lx)\n",
 413                        i++, address, namebuf, (unsigned long)(kbt->it.sp));
 414
 415                 if (i >= 100) {
 416                         pr_err("Stack dump truncated"
 417                                " (%d frames)\n", i);
 418                         break;
 419                 }
 420         }
 421         if (kbt->end == KBT_LOOP)
 422                 pr_err("Stack dump stopped; next frame identical to this one\n");
 423         if (headers)
 424                 pr_err("Stack dump complete\n");
 425         if (have_mmap_sem)
 426                 up_read(&kbt->task->mm->mmap_sem);
 427         end_backtrace();
 428 }
 429 EXPORT_SYMBOL(tile_show_stack);
 430
 431
 432 /* This is called from show_regs() and _dump_stack() */
 433 void dump_stack_regs(struct pt_regs *regs)
 434 {
 435         struct KBacktraceIterator kbt;
 436         KBacktraceIterator_init(&kbt, NULL, regs);
 437         tile_show_stack(&kbt, 1);
 438 }
 439 EXPORT_SYMBOL(dump_stack_regs);
 440
 441 static struct pt_regs *regs_to_pt_regs(struct pt_regs *regs,
 442                                        ulong pc, ulong lr, ulong sp, ulong r52)
 443 {
 444         memset(regs, 0, sizeof(struct pt_regs));
 445         regs->pc = pc;
 446         regs->lr = lr;
 447         regs->sp = sp;
 448         regs->regs[52] = r52;
 449         return regs;
 450 }
 451
 452 /* This is called from dump_stack() and just converts to pt_regs */
 453 void _dump_stack(int dummy, ulong pc, ulong lr, ulong sp, ulong r52)
 454 {
 455         struct pt_regs regs;
 456         dump_stack_regs(regs_to_pt_regs(&regs, pc, lr, sp, r52));
 457 }
 458
 459 /* This is called from KBacktraceIterator_init_current() */
 460 void _KBacktraceIterator_init_current(struct KBacktraceIterator *kbt, ulong pc,
 461                                       ulong lr, ulong sp, ulong r52)
 462 {
 463         struct pt_regs regs;
 464         KBacktraceIterator_init(kbt, NULL,
 465                                 regs_to_pt_regs(&regs, pc, lr, sp, r52));
 466 }
 467
 468 /* This is called only from kernel/sched/core.c, with esp == NULL */
 469 void show_stack(struct task_struct *task, unsigned long *esp)
 470 {
 471         struct KBacktraceIterator kbt;
 472         if (task == NULL || task == current)
 473                 KBacktraceIterator_init_current(&kbt);
 474         else
 475                 KBacktraceIterator_init(&kbt, task, NULL);
 476         tile_show_stack(&kbt, 0);
 477 }
 478
 479 #ifdef CONFIG_STACKTRACE
 480
 481 /* Support generic Linux stack API too */
 482
 483 void save_stack_trace_tsk(struct task_struct *task, struct stack_trace *trace)
 484 {
 485         struct KBacktraceIterator kbt;
 486         int skip = trace->skip;
 487         int i = 0;
 488
 489         if (!start_backtrace())
 490                 goto done;
 491         if (task == NULL || task == current)
 492                 KBacktraceIterator_init_current(&kbt);
 493         else
 494                 KBacktraceIterator_init(&kbt, task, NULL);
 495         for (; !KBacktraceIterator_end(&kbt); KBacktraceIterator_next(&kbt)) {
 496                 if (skip) {
 497                         --skip;
 498                         continue;
 499                 }
 500                 if (i >= trace->max_entries || kbt.it.pc < PAGE_OFFSET)
 501                         break;
 502                 trace->entries[i++] = kbt.it.pc;
 503         }
 504         end_backtrace();
 505 done:
 506         trace->nr_entries = i;
 507 }
 508 EXPORT_SYMBOL(save_stack_trace_tsk);
 509
 510 void save_stack_trace(struct stack_trace *trace)
 511 {
 512         save_stack_trace_tsk(NULL, trace);
 513 }
 514 EXPORT_SYMBOL_GPL(save_stack_trace);
 515
 516 #endif
 517
 518 /* In entry.S */
 519 EXPORT_SYMBOL(KBacktraceIterator_init_current);