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 <linux/hardirq.h>
  27 #include <linux/string.h>
  28 #include <asm/backtrace.h>
  29 #include <asm/page.h>
  30 #include <asm/ucontext.h>
  31 #include <asm/switch_to.h>
  32 #include <asm/sigframe.h>
  33 #include <asm/stack.h>
  34 #include <asm/vdso.h>
  35 #include <arch/abi.h>
  36 #include <arch/interrupts.h>
  37
  38 #define KBT_ONGOING     0  /* Backtrace still ongoing */
  39 #define KBT_DONE        1  /* Backtrace cleanly completed */
  40 #define KBT_RUNNING     2  /* Can't run backtrace on a running task */
  41 #define KBT_LOOP        3  /* Backtrace entered a loop */
  42
  43 /* Is address on the specified kernel stack? */
  44 static int in_kernel_stack(struct KBacktraceIterator *kbt, unsigned long sp)
  45 {
  46         ulong kstack_base = (ulong) kbt->task->stack;
  47         if (kstack_base == 0)  /* corrupt task pointer; just follow stack... */
  48                 return sp >= PAGE_OFFSET && sp < (unsigned long)high_memory;
  49         return sp >= kstack_base && sp < kstack_base + THREAD_SIZE;
  50 }
  51
  52 /* Callback for backtracer; basically a glorified memcpy */
  53 static bool read_memory_func(void *result, unsigned long address,
  54                              unsigned int size, void *vkbt)
  55 {
  56         int retval;
  57         struct KBacktraceIterator *kbt = (struct KBacktraceIterator *)vkbt;
  58
  59         if (address == 0)
  60                 return 0;
  61         if (__kernel_text_address(address)) {
  62                 /* OK to read kernel code. */
  63         } else if (address >= PAGE_OFFSET) {
  64                 /* We only tolerate kernel-space reads of this task's stack */
  65                 if (!in_kernel_stack(kbt, address))
  66                         return 0;
  67         } else if (!kbt->is_current) {
  68                 return 0;       /* can't read from other user address spaces */
  69         }
  70         pagefault_disable();
  71         retval = __copy_from_user_inatomic(result,
  72                                            (void __user __force *)address,
  73                                            size);
  74         pagefault_enable();
  75         return (retval == 0);
  76 }
  77
  78 /* Return a pt_regs pointer for a valid fault handler frame */
  79 static struct pt_regs *valid_fault_handler(struct KBacktraceIterator* kbt)
  80 {
  81         const char *fault = NULL;  /* happy compiler */
  82         char fault_buf[64];
  83         unsigned long sp = kbt->it.sp;
  84         struct pt_regs *p;
  85
  86         if (sp % sizeof(long) != 0)
  87                 return NULL;
  88         if (!in_kernel_stack(kbt, sp))
  89                 return NULL;
  90         if (!in_kernel_stack(kbt, sp + C_ABI_SAVE_AREA_SIZE + PTREGS_SIZE-1))
  91                 return NULL;
  92         p = (struct pt_regs *)(sp + C_ABI_SAVE_AREA_SIZE);
  93         if (p->faultnum == INT_SWINT_1 || p->faultnum == INT_SWINT_1_SIGRETURN)
  94                 fault = "syscall";
  95         else {
  96                 if (kbt->verbose) {     /* else we aren't going to use it */
  97                         snprintf(fault_buf, sizeof(fault_buf),
  98                                  "interrupt %ld", p->faultnum);
  99                         fault = fault_buf;
 100                 }
 101         }
 102         if (EX1_PL(p->ex1) == KERNEL_PL &&
 103             __kernel_text_address(p->pc) &&
 104             in_kernel_stack(kbt, p->sp) &&
 105             p->sp >= sp) {
 106                 if (kbt->verbose)
 107                         pr_err("  <%s while in kernel mode>\n", fault);
 108         } else if (user_mode(p) &&
 109                    p->sp < PAGE_OFFSET && p->sp != 0) {
 110                 if (kbt->verbose)
 111                         pr_err("  <%s while in user mode>\n", fault);
 112         } else {
 113                 if (kbt->verbose && (p->pc != 0 || p->sp != 0 || p->ex1 != 0))
 114                         pr_err("  (odd fault: pc %#lx, sp %#lx, ex1 %#lx?)\n",
 115                                p->pc, p->sp, p->ex1);
 116                 return NULL;
 117         }
 118         if (kbt->profile && ((1ULL << p->faultnum) & QUEUED_INTERRUPTS) != 0)
 119                 return NULL;
 120         return p;
 121 }
 122
 123 /* Is the iterator pointing to a sigreturn trampoline? */
 124 static int is_sigreturn(struct KBacktraceIterator *kbt)
 125 {
 126         return kbt->task->mm &&
 127                 (kbt->it.pc == ((ulong)kbt->task->mm->context.vdso_base +
 128                                 (ulong)&__vdso_rt_sigreturn));
 129 }
 130
 131 /* Return a pt_regs pointer for a valid signal handler frame */
 132 static struct pt_regs *valid_sigframe(struct KBacktraceIterator* kbt,
 133                                       struct rt_sigframe* kframe)
 134 {
 135         BacktraceIterator *b = &kbt->it;
 136
 137         if (is_sigreturn(kbt) && b->sp < PAGE_OFFSET &&
 138             b->sp % sizeof(long) == 0) {
 139                 int retval;
 140                 pagefault_disable();
 141                 retval = __copy_from_user_inatomic(
 142                         kframe, (void __user __force *)b->sp,
 143                         sizeof(*kframe));
 144                 pagefault_enable();
 145                 if (retval != 0 ||
 146                     (unsigned int)(kframe->info.si_signo) >= _NSIG)
 147                         return NULL;
 148                 if (kbt->verbose) {
 149                         pr_err("  <received signal %d>\n",
 150                                kframe->info.si_signo);
 151                 }
 152                 return (struct pt_regs *)&kframe->uc.uc_mcontext;
 153         }
 154         return NULL;
 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 (!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 %#lx..%#lx underrun!\n"
 205                        "  sp %#lx (%#lx in caller), caller pc %#lx, lr %#lx\n",
 206                        cpu, ksp0_base, ksp0, 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 %#lx..%#lx overrun!\n"
 211                        "  sp %#lx (%#lx in caller), caller pc %#lx, lr %#lx\n",
 212                        cpu, ksp0_base, ksp0, 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                 p = file_path(vma->vm_file, buf, bufsize);
 336                 if (IS_ERR(p))
 337                         p = "?";
 338                 name = kbasename(p);
 339         } else {
 340                 name = "anon";
 341         }
 342
 343         /* Generate a string description of the vma info. */
 344         namelen = strlen(name);
 345         remaining = (bufsize - 1) - namelen;
 346         memmove(buf, name, namelen);
 347         snprintf(buf + namelen, remaining, "[%lx+%lx] ",
 348                  vma->vm_start, vma->vm_end - vma->vm_start);
 349 }
 350
 351 /*
 352  * Avoid possible crash recursion during backtrace.  If it happens, it
 353  * makes it easy to lose the actual root cause of the failure, so we
 354  * put a simple guard on all the backtrace loops.
 355  */
 356 static bool start_backtrace(void)
 357 {
 358         if (current_thread_info()->in_backtrace) {
 359                 pr_err("Backtrace requested while in backtrace!\n");
 360                 return false;
 361         }
 362         current_thread_info()->in_backtrace = true;
 363         return true;
 364 }
 365
 366 static void end_backtrace(void)
 367 {
 368         current_thread_info()->in_backtrace = false;
 369 }
 370
 371 /*
 372  * This method wraps the backtracer's more generic support.
 373  * It is only invoked from the architecture-specific code; show_stack()
 374  * and dump_stack() are architecture-independent entry points.
 375  */
 376 void tile_show_stack(struct KBacktraceIterator *kbt)
 377 {
 378         int i;
 379         int have_mmap_sem = 0;
 380
 381         if (!start_backtrace())
 382                 return;
 383         kbt->verbose = 1;
 384         i = 0;
 385         for (; !KBacktraceIterator_end(kbt); KBacktraceIterator_next(kbt)) {
 386                 char namebuf[KSYM_NAME_LEN+100];
 387                 unsigned long address = kbt->it.pc;
 388
 389                 /*
 390                  * Try to acquire the mmap_sem as we pass into userspace.
 391                  * If we're in an interrupt context, don't even try, since
 392                  * it's not safe to call e.g. d_path() from an interrupt,
 393                  * since it uses spin locks without disabling interrupts.
 394                  * Note we test "kbt->task == current", not "kbt->is_current",
 395                  * since we're checking that "current" will work in d_path().
 396                  */
 397                 if (kbt->task == current && address < PAGE_OFFSET &&
 398                     !have_mmap_sem && kbt->task->mm && !in_interrupt()) {
 399                         have_mmap_sem =
 400                                 down_read_trylock(&kbt->task->mm->mmap_sem);
 401                 }
 402
 403                 describe_addr(kbt, address, have_mmap_sem,
 404                               namebuf, sizeof(namebuf));
 405
 406                 pr_err("  frame %d: 0x%lx %s(sp 0x%lx)\n",
 407                        i++, address, namebuf, (unsigned long)(kbt->it.sp));
 408
 409                 if (i >= 100) {
 410                         pr_err("Stack dump truncated (%d frames)\n", i);
 411                         break;
 412                 }
 413         }
 414         if (kbt->end == KBT_LOOP)
 415                 pr_err("Stack dump stopped; next frame identical to this one\n");
 416         if (have_mmap_sem)
 417                 up_read(&kbt->task->mm->mmap_sem);
 418         end_backtrace();
 419 }
 420 EXPORT_SYMBOL(tile_show_stack);
 421
 422 static struct pt_regs *regs_to_pt_regs(struct pt_regs *regs,
 423                                        ulong pc, ulong lr, ulong sp, ulong r52)
 424 {
 425         memset(regs, 0, sizeof(struct pt_regs));
 426         regs->pc = pc;
 427         regs->lr = lr;
 428         regs->sp = sp;
 429         regs->regs[52] = r52;
 430         return regs;
 431 }
 432
 433 /* Deprecated function currently only used by kernel_double_fault(). */
 434 void _dump_stack(int dummy, ulong pc, ulong lr, ulong sp, ulong r52)
 435 {
 436         struct KBacktraceIterator kbt;
 437         struct pt_regs regs;
 438
 439         regs_to_pt_regs(&regs, pc, lr, sp, r52);
 440         KBacktraceIterator_init(&kbt, NULL, &regs);
 441         tile_show_stack(&kbt);
 442 }
 443
 444 /* This is called from KBacktraceIterator_init_current() */
 445 void _KBacktraceIterator_init_current(struct KBacktraceIterator *kbt, ulong pc,
 446                                       ulong lr, ulong sp, ulong r52)
 447 {
 448         struct pt_regs regs;
 449         KBacktraceIterator_init(kbt, NULL,
 450                                 regs_to_pt_regs(&regs, pc, lr, sp, r52));
 451 }
 452
 453 /*
 454  * Called from sched_show_task() with task != NULL, or dump_stack()
 455  * with task == NULL.  The esp argument is always NULL.
 456  */
 457 void show_stack(struct task_struct *task, unsigned long *esp)
 458 {
 459         struct KBacktraceIterator kbt;
 460         if (task == NULL || task == current) {
 461                 KBacktraceIterator_init_current(&kbt);
 462                 KBacktraceIterator_next(&kbt);  /* don't show first frame */
 463         } else {
 464                 KBacktraceIterator_init(&kbt, task, NULL);
 465         }
 466         tile_show_stack(&kbt);
 467 }
 468
 469 #ifdef CONFIG_STACKTRACE
 470
 471 /* Support generic Linux stack API too */
 472
 473 static void save_stack_trace_common(struct task_struct *task,
 474                                     struct pt_regs *regs,
 475                                     bool user,
 476                                     struct stack_trace *trace)
 477 {
 478         struct KBacktraceIterator kbt;
 479         int skip = trace->skip;
 480         int i = 0;
 481
 482         if (!start_backtrace())
 483                 goto done;
 484         if (regs != NULL) {
 485                 KBacktraceIterator_init(&kbt, NULL, regs);
 486         } else if (task == NULL || task == current) {
 487                 KBacktraceIterator_init_current(&kbt);
 488                 skip++;  /* don't show KBacktraceIterator_init_current */
 489         } else {
 490                 KBacktraceIterator_init(&kbt, task, NULL);
 491         }
 492         for (; !KBacktraceIterator_end(&kbt); KBacktraceIterator_next(&kbt)) {
 493                 if (skip) {
 494                         --skip;
 495                         continue;
 496                 }
 497                 if (i >= trace->max_entries ||
 498                     (!user && kbt.it.pc < PAGE_OFFSET))
 499                         break;
 500                 trace->entries[i++] = kbt.it.pc;
 501         }
 502         end_backtrace();
 503 done:
 504         if (i < trace->max_entries)
 505                 trace->entries[i++] = ULONG_MAX;
 506         trace->nr_entries = i;
 507 }
 508
 509 void save_stack_trace_tsk(struct task_struct *task, struct stack_trace *trace)
 510 {
 511         save_stack_trace_common(task, NULL, false, trace);
 512 }
 513 EXPORT_SYMBOL(save_stack_trace_tsk);
 514
 515 void save_stack_trace(struct stack_trace *trace)
 516 {
 517         save_stack_trace_common(NULL, NULL, false, trace);
 518 }
 519 EXPORT_SYMBOL_GPL(save_stack_trace);
 520
 521 void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
 522 {
 523         save_stack_trace_common(NULL, regs, false, trace);
 524 }
 525
 526 void save_stack_trace_user(struct stack_trace *trace)
 527 {
 528         /* Trace user stack if we are not a kernel thread. */
 529         if (current->mm)
 530                 save_stack_trace_common(NULL, task_pt_regs(current),
 531                                         true, trace);
 532         else if (trace->nr_entries < trace->max_entries)
 533                 trace->entries[trace->nr_entries++] = ULONG_MAX;
 534 }
 535 #endif
 536
 537 /* In entry.S */
 538 EXPORT_SYMBOL(KBacktraceIterator_init_current);