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 <arch/abi.h>
  33 #include <arch/interrupts.h>
  34
  35 #define KBT_ONGOING     0  /* Backtrace still ongoing */
  36 #define KBT_DONE        1  /* Backtrace cleanly completed */
  37 #define KBT_RUNNING     2  /* Can't run backtrace on a running task */
  38 #define KBT_LOOP        3  /* Backtrace entered a loop */
  39
  40 /* Is address on the specified kernel stack? */
  41 static int in_kernel_stack(struct KBacktraceIterator *kbt, unsigned long sp)
  42 {
  43         ulong kstack_base = (ulong) kbt->task->stack;
  44         if (kstack_base == 0)  /* corrupt task pointer; just follow stack... */
  45                 return sp >= PAGE_OFFSET && sp < (unsigned long)high_memory;
  46         return sp >= kstack_base && sp < kstack_base + THREAD_SIZE;
  47 }
  48
  49 /* Callback for backtracer; basically a glorified memcpy */
  50 static bool read_memory_func(void *result, unsigned long address,
  51                              unsigned int size, void *vkbt)
  52 {
  53         int retval;
  54         struct KBacktraceIterator *kbt = (struct KBacktraceIterator *)vkbt;
  55
  56         if (address == 0)
  57                 return 0;
  58         if (__kernel_text_address(address)) {
  59                 /* OK to read kernel code. */
  60         } else if (address >= PAGE_OFFSET) {
  61                 /* We only tolerate kernel-space reads of this task's stack */
  62                 if (!in_kernel_stack(kbt, address))
  63                         return 0;
  64         } else if (!kbt->is_current) {
  65                 return 0;       /* can't read from other user address spaces */
  66         }
  67         pagefault_disable();
  68         retval = __copy_from_user_inatomic(result,
  69                                            (void __user __force *)address,
  70                                            size);
  71         pagefault_enable();
  72         return (retval == 0);
  73 }
  74
  75 /* Return a pt_regs pointer for a valid fault handler frame */
  76 static struct pt_regs *valid_fault_handler(struct KBacktraceIterator* kbt)
  77 {
  78         const char *fault = NULL;  /* happy compiler */
  79         char fault_buf[64];
  80         unsigned long sp = kbt->it.sp;
  81         struct pt_regs *p;
  82
  83         if (sp % sizeof(long) != 0)
  84                 return NULL;
  85         if (!in_kernel_stack(kbt, sp))
  86                 return NULL;
  87         if (!in_kernel_stack(kbt, sp + C_ABI_SAVE_AREA_SIZE + PTREGS_SIZE-1))
  88                 return NULL;
  89         p = (struct pt_regs *)(sp + C_ABI_SAVE_AREA_SIZE);
  90         if (p->faultnum == INT_SWINT_1 || p->faultnum == INT_SWINT_1_SIGRETURN)
  91                 fault = "syscall";
  92         else {
  93                 if (kbt->verbose) {     /* else we aren't going to use it */
  94                         snprintf(fault_buf, sizeof(fault_buf),
  95                                  "interrupt %ld", p->faultnum);
  96                         fault = fault_buf;
  97                 }
  98         }
  99         if (EX1_PL(p->ex1) == KERNEL_PL &&
 100             __kernel_text_address(p->pc) &&
 101             in_kernel_stack(kbt, p->sp) &&
 102             p->sp >= sp) {
 103                 if (kbt->verbose)
 104                         pr_err("  <%s while in kernel mode>\n", fault);
 105         } else if (EX1_PL(p->ex1) == USER_PL &&
 106             p->pc < PAGE_OFFSET &&
 107             p->sp < PAGE_OFFSET) {
 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 (pc == VDSO_BASE);
 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 (b->pc == VDSO_BASE && 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 = 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  * This method wraps the backtracer's more generic support.
 356  * It is only invoked from the architecture-specific code; show_stack()
 357  * and dump_stack() (in entry.S) are architecture-independent entry points.
 358  */
 359 void tile_show_stack(struct KBacktraceIterator *kbt, int headers)
 360 {
 361         int i;
 362         int have_mmap_sem = 0;
 363
 364         if (headers) {
 365                 /*
 366                  * Add a blank line since if we are called from panic(),
 367                  * then bust_spinlocks() spit out a space in front of us
 368                  * and it will mess up our KERN_ERR.
 369                  */
 370                 pr_err("\n");
 371                 pr_err("Starting stack dump of tid %d, pid %d (%s)"
 372                        " on cpu %d at cycle %lld\n",
 373                        kbt->task->pid, kbt->task->tgid, kbt->task->comm,
 374                        smp_processor_id(), get_cycles());
 375         }
 376         kbt->verbose = 1;
 377         i = 0;
 378         for (; !KBacktraceIterator_end(kbt); KBacktraceIterator_next(kbt)) {
 379                 char namebuf[KSYM_NAME_LEN+100];
 380                 unsigned long address = kbt->it.pc;
 381
 382                 /* Try to acquire the mmap_sem as we pass into userspace. */
 383                 if (address < PAGE_OFFSET && !have_mmap_sem && kbt->task->mm)
 384                         have_mmap_sem =
 385                                 down_read_trylock(&kbt->task->mm->mmap_sem);
 386
 387                 describe_addr(kbt, address, have_mmap_sem,
 388                               namebuf, sizeof(namebuf));
 389
 390                 pr_err("  frame %d: 0x%lx %s(sp 0x%lx)\n",
 391                        i++, address, namebuf, (unsigned long)(kbt->it.sp));
 392
 393                 if (i >= 100) {
 394                         pr_err("Stack dump truncated"
 395                                " (%d frames)\n", i);
 396                         break;
 397                 }
 398         }
 399         if (kbt->end == KBT_LOOP)
 400                 pr_err("Stack dump stopped; next frame identical to this one\n");
 401         if (headers)
 402                 pr_err("Stack dump complete\n");
 403         if (have_mmap_sem)
 404                 up_read(&kbt->task->mm->mmap_sem);
 405 }
 406 EXPORT_SYMBOL(tile_show_stack);
 407
 408
 409 /* This is called from show_regs() and _dump_stack() */
 410 void dump_stack_regs(struct pt_regs *regs)
 411 {
 412         struct KBacktraceIterator kbt;
 413         KBacktraceIterator_init(&kbt, NULL, regs);
 414         tile_show_stack(&kbt, 1);
 415 }
 416 EXPORT_SYMBOL(dump_stack_regs);
 417
 418 static struct pt_regs *regs_to_pt_regs(struct pt_regs *regs,
 419                                        ulong pc, ulong lr, ulong sp, ulong r52)
 420 {
 421         memset(regs, 0, sizeof(struct pt_regs));
 422         regs->pc = pc;
 423         regs->lr = lr;
 424         regs->sp = sp;
 425         regs->regs[52] = r52;
 426         return regs;
 427 }
 428
 429 /* This is called from dump_stack() and just converts to pt_regs */
 430 void _dump_stack(int dummy, ulong pc, ulong lr, ulong sp, ulong r52)
 431 {
 432         struct pt_regs regs;
 433         dump_stack_regs(regs_to_pt_regs(&regs, pc, lr, sp, r52));
 434 }
 435
 436 /* This is called from KBacktraceIterator_init_current() */
 437 void _KBacktraceIterator_init_current(struct KBacktraceIterator *kbt, ulong pc,
 438                                       ulong lr, ulong sp, ulong r52)
 439 {
 440         struct pt_regs regs;
 441         KBacktraceIterator_init(kbt, NULL,
 442                                 regs_to_pt_regs(&regs, pc, lr, sp, r52));
 443 }
 444
 445 /* This is called only from kernel/sched.c, with esp == NULL */
 446 void show_stack(struct task_struct *task, unsigned long *esp)
 447 {
 448         struct KBacktraceIterator kbt;
 449         if (task == NULL || task == current)
 450                 KBacktraceIterator_init_current(&kbt);
 451         else
 452                 KBacktraceIterator_init(&kbt, task, NULL);
 453         tile_show_stack(&kbt, 0);
 454 }
 455
 456 #ifdef CONFIG_STACKTRACE
 457
 458 /* Support generic Linux stack API too */
 459
 460 void save_stack_trace_tsk(struct task_struct *task, struct stack_trace *trace)
 461 {
 462         struct KBacktraceIterator kbt;
 463         int skip = trace->skip;
 464         int i = 0;
 465
 466         if (task == NULL || task == current)
 467                 KBacktraceIterator_init_current(&kbt);
 468         else
 469                 KBacktraceIterator_init(&kbt, task, NULL);
 470         for (; !KBacktraceIterator_end(&kbt); KBacktraceIterator_next(&kbt)) {
 471                 if (skip) {
 472                         --skip;
 473                         continue;
 474                 }
 475                 if (i >= trace->max_entries || kbt.it.pc < PAGE_OFFSET)
 476                         break;
 477                 trace->entries[i++] = kbt.it.pc;
 478         }
 479         trace->nr_entries = i;
 480 }
 481 EXPORT_SYMBOL(save_stack_trace_tsk);
 482
 483 void save_stack_trace(struct stack_trace *trace)
 484 {
 485         save_stack_trace_tsk(NULL, trace);
 486 }
 487 EXPORT_SYMBOL_GPL(save_stack_trace);
 488
 489 #endif
 490
 491 /* In entry.S */
 492 EXPORT_SYMBOL(KBacktraceIterator_init_current);