arch/powerpc/perf/callchain.c

   1 /*
   2  * Performance counter callchain support - powerpc architecture code
   3  *
   4  * Copyright © 2009 Paul Mackerras, IBM Corporation.
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the License, or (at your option) any later version.
  10  */
  11 #include <linux/kernel.h>
  12 #include <linux/sched.h>
  13 #include <linux/perf_event.h>
  14 #include <linux/percpu.h>
  15 #include <linux/uaccess.h>
  16 #include <linux/mm.h>
  17 #include <asm/ptrace.h>
  18 #include <asm/pgtable.h>
  19 #include <asm/sigcontext.h>
  20 #include <asm/ucontext.h>
  21 #include <asm/vdso.h>
  22 #ifdef CONFIG_PPC64
  23 #include "../kernel/ppc32.h"
  24 #endif
  25 #include <asm/pte-walk.h>
  26
  27
  28 /*
  29  * Is sp valid as the address of the next kernel stack frame after prev_sp?
  30  * The next frame may be in a different stack area but should not go
  31  * back down in the same stack area.
  32  */
  33 static int valid_next_sp(unsigned long sp, unsigned long prev_sp)
  34 {
  35         if (sp & 0xf)
  36                 return 0;               /* must be 16-byte aligned */
  37         if (!validate_sp(sp, current, STACK_FRAME_OVERHEAD))
  38                 return 0;
  39         if (sp >= prev_sp + STACK_FRAME_MIN_SIZE)
  40                 return 1;
  41         /*
  42          * sp could decrease when we jump off an interrupt stack
  43          * back to the regular process stack.
  44          */
  45         if ((sp & ~(THREAD_SIZE - 1)) != (prev_sp & ~(THREAD_SIZE - 1)))
  46                 return 1;
  47         return 0;
  48 }
  49
  50 void
  51 perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
  52 {
  53         unsigned long sp, next_sp;
  54         unsigned long next_ip;
  55         unsigned long lr;
  56         long level = 0;
  57         unsigned long *fp;
  58
  59         lr = regs->link;
  60         sp = regs->gpr[1];
  61         perf_callchain_store(entry, perf_instruction_pointer(regs));
  62
  63         if (!validate_sp(sp, current, STACK_FRAME_OVERHEAD))
  64                 return;
  65
  66         for (;;) {
  67                 fp = (unsigned long *) sp;
  68                 next_sp = fp[0];
  69
  70                 if (next_sp == sp + STACK_INT_FRAME_SIZE &&
  71                     fp[STACK_FRAME_MARKER] == STACK_FRAME_REGS_MARKER) {
  72                         /*
  73                          * This looks like an interrupt frame for an
  74                          * interrupt that occurred in the kernel
  75                          */
  76                         regs = (struct pt_regs *)(sp + STACK_FRAME_OVERHEAD);
  77                         next_ip = regs->nip;
  78                         lr = regs->link;
  79                         level = 0;
  80                         perf_callchain_store_context(entry, PERF_CONTEXT_KERNEL);
  81
  82                 } else {
  83                         if (level == 0)
  84                                 next_ip = lr;
  85                         else
  86                                 next_ip = fp[STACK_FRAME_LR_SAVE];
  87
  88                         /*
  89                          * We can't tell which of the first two addresses
  90                          * we get are valid, but we can filter out the
  91                          * obviously bogus ones here.  We replace them
  92                          * with 0 rather than removing them entirely so
  93                          * that userspace can tell which is which.
  94                          */
  95                         if ((level == 1 && next_ip == lr) ||
  96                             (level <= 1 && !kernel_text_address(next_ip)))
  97                                 next_ip = 0;
  98
  99                         ++level;
 100                 }
 101
 102                 perf_callchain_store(entry, next_ip);
 103                 if (!valid_next_sp(next_sp, sp))
 104                         return;
 105                 sp = next_sp;
 106         }
 107 }
 108
 109 #ifdef CONFIG_PPC64
 110 /*
 111  * On 64-bit we don't want to invoke hash_page on user addresses from
 112  * interrupt context, so if the access faults, we read the page tables
 113  * to find which page (if any) is mapped and access it directly.
 114  */
 115 static int read_user_stack_slow(void __user *ptr, void *buf, int nb)
 116 {
 117         int ret = -EFAULT;
 118         pgd_t *pgdir;
 119         pte_t *ptep, pte;
 120         unsigned shift;
 121         unsigned long addr = (unsigned long) ptr;
 122         unsigned long offset;
 123         unsigned long pfn, flags;
 124         void *kaddr;
 125
 126         pgdir = current->mm->pgd;
 127         if (!pgdir)
 128                 return -EFAULT;
 129
 130         local_irq_save(flags);
 131         ptep = find_current_mm_pte(pgdir, addr, NULL, &shift);
 132         if (!ptep)
 133                 goto err_out;
 134         if (!shift)
 135                 shift = PAGE_SHIFT;
 136
 137         /* align address to page boundary */
 138         offset = addr & ((1UL << shift) - 1);
 139
 140         pte = READ_ONCE(*ptep);
 141         if (!pte_present(pte) || !pte_user(pte))
 142                 goto err_out;
 143         pfn = pte_pfn(pte);
 144         if (!page_is_ram(pfn))
 145                 goto err_out;
 146
 147         /* no highmem to worry about here */
 148         kaddr = pfn_to_kaddr(pfn);
 149         memcpy(buf, kaddr + offset, nb);
 150         ret = 0;
 151 err_out:
 152         local_irq_restore(flags);
 153         return ret;
 154 }
 155
 156 static int read_user_stack_64(unsigned long __user *ptr, unsigned long *ret)
 157 {
 158         if ((unsigned long)ptr > TASK_SIZE - sizeof(unsigned long) ||
 159             ((unsigned long)ptr & 7))
 160                 return -EFAULT;
 161
 162         pagefault_disable();
 163         if (!__get_user_inatomic(*ret, ptr)) {
 164                 pagefault_enable();
 165                 return 0;
 166         }
 167         pagefault_enable();
 168
 169         return read_user_stack_slow(ptr, ret, 8);
 170 }
 171
 172 static int read_user_stack_32(unsigned int __user *ptr, unsigned int *ret)
 173 {
 174         if ((unsigned long)ptr > TASK_SIZE - sizeof(unsigned int) ||
 175             ((unsigned long)ptr & 3))
 176                 return -EFAULT;
 177
 178         pagefault_disable();
 179         if (!__get_user_inatomic(*ret, ptr)) {
 180                 pagefault_enable();
 181                 return 0;
 182         }
 183         pagefault_enable();
 184
 185         return read_user_stack_slow(ptr, ret, 4);
 186 }
 187
 188 static inline int valid_user_sp(unsigned long sp, int is_64)
 189 {
 190         if (!sp || (sp & 7) || sp > (is_64 ? TASK_SIZE : 0x100000000UL) - 32)
 191                 return 0;
 192         return 1;
 193 }
 194
 195 /*
 196  * 64-bit user processes use the same stack frame for RT and non-RT signals.
 197  */
 198 struct signal_frame_64 {
 199         char            dummy[__SIGNAL_FRAMESIZE];
 200         struct ucontext uc;
 201         unsigned long   unused[2];
 202         unsigned int    tramp[6];
 203         struct siginfo  *pinfo;
 204         void            *puc;
 205         struct siginfo  info;
 206         char            abigap[288];
 207 };
 208
 209 static int is_sigreturn_64_address(unsigned long nip, unsigned long fp)
 210 {
 211         if (nip == fp + offsetof(struct signal_frame_64, tramp))
 212                 return 1;
 213         if (vdso64_rt_sigtramp && current->mm->context.vdso_base &&
 214             nip == current->mm->context.vdso_base + vdso64_rt_sigtramp)
 215                 return 1;
 216         return 0;
 217 }
 218
 219 /*
 220  * Do some sanity checking on the signal frame pointed to by sp.
 221  * We check the pinfo and puc pointers in the frame.
 222  */
 223 static int sane_signal_64_frame(unsigned long sp)
 224 {
 225         struct signal_frame_64 __user *sf;
 226         unsigned long pinfo, puc;
 227
 228         sf = (struct signal_frame_64 __user *) sp;
 229         if (read_user_stack_64((unsigned long __user *) &sf->pinfo, &pinfo) ||
 230             read_user_stack_64((unsigned long __user *) &sf->puc, &puc))
 231                 return 0;
 232         return pinfo == (unsigned long) &sf->info &&
 233                 puc == (unsigned long) &sf->uc;
 234 }
 235
 236 static void perf_callchain_user_64(struct perf_callchain_entry_ctx *entry,
 237                                    struct pt_regs *regs)
 238 {
 239         unsigned long sp, next_sp;
 240         unsigned long next_ip;
 241         unsigned long lr;
 242         long level = 0;
 243         struct signal_frame_64 __user *sigframe;
 244         unsigned long __user *fp, *uregs;
 245
 246         next_ip = perf_instruction_pointer(regs);
 247         lr = regs->link;
 248         sp = regs->gpr[1];
 249         perf_callchain_store(entry, next_ip);
 250
 251         while (entry->nr < entry->max_stack) {
 252                 fp = (unsigned long __user *) sp;
 253                 if (!valid_user_sp(sp, 1) || read_user_stack_64(fp, &next_sp))
 254                         return;
 255                 if (level > 0 && read_user_stack_64(&fp[2], &next_ip))
 256                         return;
 257
 258                 /*
 259                  * Note: the next_sp - sp >= signal frame size check
 260                  * is true when next_sp < sp, which can happen when
 261                  * transitioning from an alternate signal stack to the
 262                  * normal stack.
 263                  */
 264                 if (next_sp - sp >= sizeof(struct signal_frame_64) &&
 265                     (is_sigreturn_64_address(next_ip, sp) ||
 266                      (level <= 1 && is_sigreturn_64_address(lr, sp))) &&
 267                     sane_signal_64_frame(sp)) {
 268                         /*
 269                          * This looks like an signal frame
 270                          */
 271                         sigframe = (struct signal_frame_64 __user *) sp;
 272                         uregs = sigframe->uc.uc_mcontext.gp_regs;
 273                         if (read_user_stack_64(&uregs[PT_NIP], &next_ip) ||
 274                             read_user_stack_64(&uregs[PT_LNK], &lr) ||
 275                             read_user_stack_64(&uregs[PT_R1], &sp))
 276                                 return;
 277                         level = 0;
 278                         perf_callchain_store_context(entry, PERF_CONTEXT_USER);
 279                         perf_callchain_store(entry, next_ip);
 280                         continue;
 281                 }
 282
 283                 if (level == 0)
 284                         next_ip = lr;
 285                 perf_callchain_store(entry, next_ip);
 286                 ++level;
 287                 sp = next_sp;
 288         }
 289 }
 290
 291 static inline int current_is_64bit(void)
 292 {
 293         /*
 294          * We can't use test_thread_flag() here because we may be on an
 295          * interrupt stack, and the thread flags don't get copied over
 296          * from the thread_info on the main stack to the interrupt stack.
 297          */
 298         return !test_ti_thread_flag(task_thread_info(current), TIF_32BIT);
 299 }
 300
 301 #else  /* CONFIG_PPC64 */
 302 /*
 303  * On 32-bit we just access the address and let hash_page create a
 304  * HPTE if necessary, so there is no need to fall back to reading
 305  * the page tables.  Since this is called at interrupt level,
 306  * do_page_fault() won't treat a DSI as a page fault.
 307  */
 308 static int read_user_stack_32(unsigned int __user *ptr, unsigned int *ret)
 309 {
 310         int rc;
 311
 312         if ((unsigned long)ptr > TASK_SIZE - sizeof(unsigned int) ||
 313             ((unsigned long)ptr & 3))
 314                 return -EFAULT;
 315
 316         pagefault_disable();
 317         rc = __get_user_inatomic(*ret, ptr);
 318         pagefault_enable();
 319
 320         return rc;
 321 }
 322
 323 static inline void perf_callchain_user_64(struct perf_callchain_entry_ctx *entry,
 324                                           struct pt_regs *regs)
 325 {
 326 }
 327
 328 static inline int current_is_64bit(void)
 329 {
 330         return 0;
 331 }
 332
 333 static inline int valid_user_sp(unsigned long sp, int is_64)
 334 {
 335         if (!sp || (sp & 7) || sp > TASK_SIZE - 32)
 336                 return 0;
 337         return 1;
 338 }
 339
 340 #define __SIGNAL_FRAMESIZE32    __SIGNAL_FRAMESIZE
 341 #define sigcontext32            sigcontext
 342 #define mcontext32              mcontext
 343 #define ucontext32              ucontext
 344 #define compat_siginfo_t        struct siginfo
 345
 346 #endif /* CONFIG_PPC64 */
 347
 348 /*
 349  * Layout for non-RT signal frames
 350  */
 351 struct signal_frame_32 {
 352         char                    dummy[__SIGNAL_FRAMESIZE32];
 353         struct sigcontext32     sctx;
 354         struct mcontext32       mctx;
 355         int                     abigap[56];
 356 };
 357
 358 /*
 359  * Layout for RT signal frames
 360  */
 361 struct rt_signal_frame_32 {
 362         char                    dummy[__SIGNAL_FRAMESIZE32 + 16];
 363         compat_siginfo_t        info;
 364         struct ucontext32       uc;
 365         int                     abigap[56];
 366 };
 367
 368 static int is_sigreturn_32_address(unsigned int nip, unsigned int fp)
 369 {
 370         if (nip == fp + offsetof(struct signal_frame_32, mctx.mc_pad))
 371                 return 1;
 372         if (vdso32_sigtramp && current->mm->context.vdso_base &&
 373             nip == current->mm->context.vdso_base + vdso32_sigtramp)
 374                 return 1;
 375         return 0;
 376 }
 377
 378 static int is_rt_sigreturn_32_address(unsigned int nip, unsigned int fp)
 379 {
 380         if (nip == fp + offsetof(struct rt_signal_frame_32,
 381                                  uc.uc_mcontext.mc_pad))
 382                 return 1;
 383         if (vdso32_rt_sigtramp && current->mm->context.vdso_base &&
 384             nip == current->mm->context.vdso_base + vdso32_rt_sigtramp)
 385                 return 1;
 386         return 0;
 387 }
 388
 389 static int sane_signal_32_frame(unsigned int sp)
 390 {
 391         struct signal_frame_32 __user *sf;
 392         unsigned int regs;
 393
 394         sf = (struct signal_frame_32 __user *) (unsigned long) sp;
 395         if (read_user_stack_32((unsigned int __user *) &sf->sctx.regs, &regs))
 396                 return 0;
 397         return regs == (unsigned long) &sf->mctx;
 398 }
 399
 400 static int sane_rt_signal_32_frame(unsigned int sp)
 401 {
 402         struct rt_signal_frame_32 __user *sf;
 403         unsigned int regs;
 404
 405         sf = (struct rt_signal_frame_32 __user *) (unsigned long) sp;
 406         if (read_user_stack_32((unsigned int __user *) &sf->uc.uc_regs, &regs))
 407                 return 0;
 408         return regs == (unsigned long) &sf->uc.uc_mcontext;
 409 }
 410
 411 static unsigned int __user *signal_frame_32_regs(unsigned int sp,
 412                                 unsigned int next_sp, unsigned int next_ip)
 413 {
 414         struct mcontext32 __user *mctx = NULL;
 415         struct signal_frame_32 __user *sf;
 416         struct rt_signal_frame_32 __user *rt_sf;
 417
 418         /*
 419          * Note: the next_sp - sp >= signal frame size check
 420          * is true when next_sp < sp, for example, when
 421          * transitioning from an alternate signal stack to the
 422          * normal stack.
 423          */
 424         if (next_sp - sp >= sizeof(struct signal_frame_32) &&
 425             is_sigreturn_32_address(next_ip, sp) &&
 426             sane_signal_32_frame(sp)) {
 427                 sf = (struct signal_frame_32 __user *) (unsigned long) sp;
 428                 mctx = &sf->mctx;
 429         }
 430
 431         if (!mctx && next_sp - sp >= sizeof(struct rt_signal_frame_32) &&
 432             is_rt_sigreturn_32_address(next_ip, sp) &&
 433             sane_rt_signal_32_frame(sp)) {
 434                 rt_sf = (struct rt_signal_frame_32 __user *) (unsigned long) sp;
 435                 mctx = &rt_sf->uc.uc_mcontext;
 436         }
 437
 438         if (!mctx)
 439                 return NULL;
 440         return mctx->mc_gregs;
 441 }
 442
 443 static void perf_callchain_user_32(struct perf_callchain_entry_ctx *entry,
 444                                    struct pt_regs *regs)
 445 {
 446         unsigned int sp, next_sp;
 447         unsigned int next_ip;
 448         unsigned int lr;
 449         long level = 0;
 450         unsigned int __user *fp, *uregs;
 451
 452         next_ip = perf_instruction_pointer(regs);
 453         lr = regs->link;
 454         sp = regs->gpr[1];
 455         perf_callchain_store(entry, next_ip);
 456
 457         while (entry->nr < entry->max_stack) {
 458                 fp = (unsigned int __user *) (unsigned long) sp;
 459                 if (!valid_user_sp(sp, 0) || read_user_stack_32(fp, &next_sp))
 460                         return;
 461                 if (level > 0 && read_user_stack_32(&fp[1], &next_ip))
 462                         return;
 463
 464                 uregs = signal_frame_32_regs(sp, next_sp, next_ip);
 465                 if (!uregs && level <= 1)
 466                         uregs = signal_frame_32_regs(sp, next_sp, lr);
 467                 if (uregs) {
 468                         /*
 469                          * This looks like an signal frame, so restart
 470                          * the stack trace with the values in it.
 471                          */
 472                         if (read_user_stack_32(&uregs[PT_NIP], &next_ip) ||
 473                             read_user_stack_32(&uregs[PT_LNK], &lr) ||
 474                             read_user_stack_32(&uregs[PT_R1], &sp))
 475                                 return;
 476                         level = 0;
 477                         perf_callchain_store_context(entry, PERF_CONTEXT_USER);
 478                         perf_callchain_store(entry, next_ip);
 479                         continue;
 480                 }
 481
 482                 if (level == 0)
 483                         next_ip = lr;
 484                 perf_callchain_store(entry, next_ip);
 485                 ++level;
 486                 sp = next_sp;
 487         }
 488 }
 489
 490 void
 491 perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
 492 {
 493         if (current_is_64bit())
 494                 perf_callchain_user_64(entry, regs);
 495         else
 496                 perf_callchain_user_32(entry, regs);
 497 }