arch/powerpc/kernel/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 "ppc32.h"
  24 #endif
  25
  26 /*
  27  * Store another value in a callchain_entry.
  28  */
  29 static inline void callchain_store(struct perf_callchain_entry *entry, u64 ip)
  30 {
  31         unsigned int nr = entry->nr;
  32
  33         if (nr < PERF_MAX_STACK_DEPTH) {
  34                 entry->ip[nr] = ip;
  35                 entry->nr = nr + 1;
  36         }
  37 }
  38
  39 /*
  40  * Is sp valid as the address of the next kernel stack frame after prev_sp?
  41  * The next frame may be in a different stack area but should not go
  42  * back down in the same stack area.
  43  */
  44 static int valid_next_sp(unsigned long sp, unsigned long prev_sp)
  45 {
  46         if (sp & 0xf)
  47                 return 0;               /* must be 16-byte aligned */
  48         if (!validate_sp(sp, current, STACK_FRAME_OVERHEAD))
  49                 return 0;
  50         if (sp >= prev_sp + STACK_FRAME_OVERHEAD)
  51                 return 1;
  52         /*
  53          * sp could decrease when we jump off an interrupt stack
  54          * back to the regular process stack.
  55          */
  56         if ((sp & ~(THREAD_SIZE - 1)) != (prev_sp & ~(THREAD_SIZE - 1)))
  57                 return 1;
  58         return 0;
  59 }
  60
  61 static void perf_callchain_kernel(struct pt_regs *regs,
  62                                   struct perf_callchain_entry *entry)
  63 {
  64         unsigned long sp, next_sp;
  65         unsigned long next_ip;
  66         unsigned long lr;
  67         long level = 0;
  68         unsigned long *fp;
  69
  70         lr = regs->link;
  71         sp = regs->gpr[1];
  72         callchain_store(entry, PERF_CONTEXT_KERNEL);
  73         callchain_store(entry, regs->nip);
  74
  75         if (!validate_sp(sp, current, STACK_FRAME_OVERHEAD))
  76                 return;
  77
  78         for (;;) {
  79                 fp = (unsigned long *) sp;
  80                 next_sp = fp[0];
  81
  82                 if (next_sp == sp + STACK_INT_FRAME_SIZE &&
  83                     fp[STACK_FRAME_MARKER] == STACK_FRAME_REGS_MARKER) {
  84                         /*
  85                          * This looks like an interrupt frame for an
  86                          * interrupt that occurred in the kernel
  87                          */
  88                         regs = (struct pt_regs *)(sp + STACK_FRAME_OVERHEAD);
  89                         next_ip = regs->nip;
  90                         lr = regs->link;
  91                         level = 0;
  92                         callchain_store(entry, PERF_CONTEXT_KERNEL);
  93
  94                 } else {
  95                         if (level == 0)
  96                                 next_ip = lr;
  97                         else
  98                                 next_ip = fp[STACK_FRAME_LR_SAVE];
  99
 100                         /*
 101                          * We can't tell which of the first two addresses
 102                          * we get are valid, but we can filter out the
 103                          * obviously bogus ones here.  We replace them
 104                          * with 0 rather than removing them entirely so
 105                          * that userspace can tell which is which.
 106                          */
 107                         if ((level == 1 && next_ip == lr) ||
 108                             (level <= 1 && !kernel_text_address(next_ip)))
 109                                 next_ip = 0;
 110
 111                         ++level;
 112                 }
 113
 114                 callchain_store(entry, next_ip);
 115                 if (!valid_next_sp(next_sp, sp))
 116                         return;
 117                 sp = next_sp;
 118         }
 119 }
 120
 121 #ifdef CONFIG_PPC64
 122 /*
 123  * On 64-bit we don't want to invoke hash_page on user addresses from
 124  * interrupt context, so if the access faults, we read the page tables
 125  * to find which page (if any) is mapped and access it directly.
 126  */
 127 static int read_user_stack_slow(void __user *ptr, void *ret, int nb)
 128 {
 129         pgd_t *pgdir;
 130         pte_t *ptep, pte;
 131         unsigned shift;
 132         unsigned long addr = (unsigned long) ptr;
 133         unsigned long offset;
 134         unsigned long pfn;
 135         void *kaddr;
 136
 137         pgdir = current->mm->pgd;
 138         if (!pgdir)
 139                 return -EFAULT;
 140
 141         ptep = find_linux_pte_or_hugepte(pgdir, addr, &shift);
 142         if (!shift)
 143                 shift = PAGE_SHIFT;
 144
 145         /* align address to page boundary */
 146         offset = addr & ((1UL << shift) - 1);
 147         addr -= offset;
 148
 149         if (ptep == NULL)
 150                 return -EFAULT;
 151         pte = *ptep;
 152         if (!pte_present(pte) || !(pte_val(pte) & _PAGE_USER))
 153                 return -EFAULT;
 154         pfn = pte_pfn(pte);
 155         if (!page_is_ram(pfn))
 156                 return -EFAULT;
 157
 158         /* no highmem to worry about here */
 159         kaddr = pfn_to_kaddr(pfn);
 160         memcpy(ret, kaddr + offset, nb);
 161         return 0;
 162 }
 163
 164 static int read_user_stack_64(unsigned long __user *ptr, unsigned long *ret)
 165 {
 166         if ((unsigned long)ptr > TASK_SIZE - sizeof(unsigned long) ||
 167             ((unsigned long)ptr & 7))
 168                 return -EFAULT;
 169
 170         if (!__get_user_inatomic(*ret, ptr))
 171                 return 0;
 172
 173         return read_user_stack_slow(ptr, ret, 8);
 174 }
 175
 176 static int read_user_stack_32(unsigned int __user *ptr, unsigned int *ret)
 177 {
 178         if ((unsigned long)ptr > TASK_SIZE - sizeof(unsigned int) ||
 179             ((unsigned long)ptr & 3))
 180                 return -EFAULT;
 181
 182         if (!__get_user_inatomic(*ret, ptr))
 183                 return 0;
 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 pt_regs *regs,
 237                                    struct perf_callchain_entry *entry)
 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 = regs->nip;
 247         lr = regs->link;
 248         sp = regs->gpr[1];
 249         callchain_store(entry, PERF_CONTEXT_USER);
 250         callchain_store(entry, next_ip);
 251
 252         for (;;) {
 253                 fp = (unsigned long __user *) sp;
 254                 if (!valid_user_sp(sp, 1) || read_user_stack_64(fp, &next_sp))
 255                         return;
 256                 if (level > 0 && read_user_stack_64(&fp[2], &next_ip))
 257                         return;
 258
 259                 /*
 260                  * Note: the next_sp - sp >= signal frame size check
 261                  * is true when next_sp < sp, which can happen when
 262                  * transitioning from an alternate signal stack to the
 263                  * normal stack.
 264                  */
 265                 if (next_sp - sp >= sizeof(struct signal_frame_64) &&
 266                     (is_sigreturn_64_address(next_ip, sp) ||
 267                      (level <= 1 && is_sigreturn_64_address(lr, sp))) &&
 268                     sane_signal_64_frame(sp)) {
 269                         /*
 270                          * This looks like an signal frame
 271                          */
 272                         sigframe = (struct signal_frame_64 __user *) sp;
 273                         uregs = sigframe->uc.uc_mcontext.gp_regs;
 274                         if (read_user_stack_64(&uregs[PT_NIP], &next_ip) ||
 275                             read_user_stack_64(&uregs[PT_LNK], &lr) ||
 276                             read_user_stack_64(&uregs[PT_R1], &sp))
 277                                 return;
 278                         level = 0;
 279                         callchain_store(entry, PERF_CONTEXT_USER);
 280                         callchain_store(entry, next_ip);
 281                         continue;
 282                 }
 283
 284                 if (level == 0)
 285                         next_ip = lr;
 286                 callchain_store(entry, next_ip);
 287                 ++level;
 288                 sp = next_sp;
 289         }
 290 }
 291
 292 static inline int current_is_64bit(void)
 293 {
 294         /*
 295          * We can't use test_thread_flag() here because we may be on an
 296          * interrupt stack, and the thread flags don't get copied over
 297          * from the thread_info on the main stack to the interrupt stack.
 298          */
 299         return !test_ti_thread_flag(task_thread_info(current), TIF_32BIT);
 300 }
 301
 302 #else  /* CONFIG_PPC64 */
 303 /*
 304  * On 32-bit we just access the address and let hash_page create a
 305  * HPTE if necessary, so there is no need to fall back to reading
 306  * the page tables.  Since this is called at interrupt level,
 307  * do_page_fault() won't treat a DSI as a page fault.
 308  */
 309 static int read_user_stack_32(unsigned int __user *ptr, unsigned int *ret)
 310 {
 311         if ((unsigned long)ptr > TASK_SIZE - sizeof(unsigned int) ||
 312             ((unsigned long)ptr & 3))
 313                 return -EFAULT;
 314
 315         return __get_user_inatomic(*ret, ptr);
 316 }
 317
 318 static inline void perf_callchain_user_64(struct pt_regs *regs,
 319                                           struct perf_callchain_entry *entry)
 320 {
 321 }
 322
 323 static inline int current_is_64bit(void)
 324 {
 325         return 0;
 326 }
 327
 328 static inline int valid_user_sp(unsigned long sp, int is_64)
 329 {
 330         if (!sp || (sp & 7) || sp > TASK_SIZE - 32)
 331                 return 0;
 332         return 1;
 333 }
 334
 335 #define __SIGNAL_FRAMESIZE32    __SIGNAL_FRAMESIZE
 336 #define sigcontext32            sigcontext
 337 #define mcontext32              mcontext
 338 #define ucontext32              ucontext
 339 #define compat_siginfo_t        struct siginfo
 340
 341 #endif /* CONFIG_PPC64 */
 342
 343 /*
 344  * Layout for non-RT signal frames
 345  */
 346 struct signal_frame_32 {
 347         char                    dummy[__SIGNAL_FRAMESIZE32];
 348         struct sigcontext32     sctx;
 349         struct mcontext32       mctx;
 350         int                     abigap[56];
 351 };
 352
 353 /*
 354  * Layout for RT signal frames
 355  */
 356 struct rt_signal_frame_32 {
 357         char                    dummy[__SIGNAL_FRAMESIZE32 + 16];
 358         compat_siginfo_t        info;
 359         struct ucontext32       uc;
 360         int                     abigap[56];
 361 };
 362
 363 static int is_sigreturn_32_address(unsigned int nip, unsigned int fp)
 364 {
 365         if (nip == fp + offsetof(struct signal_frame_32, mctx.mc_pad))
 366                 return 1;
 367         if (vdso32_sigtramp && current->mm->context.vdso_base &&
 368             nip == current->mm->context.vdso_base + vdso32_sigtramp)
 369                 return 1;
 370         return 0;
 371 }
 372
 373 static int is_rt_sigreturn_32_address(unsigned int nip, unsigned int fp)
 374 {
 375         if (nip == fp + offsetof(struct rt_signal_frame_32,
 376                                  uc.uc_mcontext.mc_pad))
 377                 return 1;
 378         if (vdso32_rt_sigtramp && current->mm->context.vdso_base &&
 379             nip == current->mm->context.vdso_base + vdso32_rt_sigtramp)
 380                 return 1;
 381         return 0;
 382 }
 383
 384 static int sane_signal_32_frame(unsigned int sp)
 385 {
 386         struct signal_frame_32 __user *sf;
 387         unsigned int regs;
 388
 389         sf = (struct signal_frame_32 __user *) (unsigned long) sp;
 390         if (read_user_stack_32((unsigned int __user *) &sf->sctx.regs, &regs))
 391                 return 0;
 392         return regs == (unsigned long) &sf->mctx;
 393 }
 394
 395 static int sane_rt_signal_32_frame(unsigned int sp)
 396 {
 397         struct rt_signal_frame_32 __user *sf;
 398         unsigned int regs;
 399
 400         sf = (struct rt_signal_frame_32 __user *) (unsigned long) sp;
 401         if (read_user_stack_32((unsigned int __user *) &sf->uc.uc_regs, &regs))
 402                 return 0;
 403         return regs == (unsigned long) &sf->uc.uc_mcontext;
 404 }
 405
 406 static unsigned int __user *signal_frame_32_regs(unsigned int sp,
 407                                 unsigned int next_sp, unsigned int next_ip)
 408 {
 409         struct mcontext32 __user *mctx = NULL;
 410         struct signal_frame_32 __user *sf;
 411         struct rt_signal_frame_32 __user *rt_sf;
 412
 413         /*
 414          * Note: the next_sp - sp >= signal frame size check
 415          * is true when next_sp < sp, for example, when
 416          * transitioning from an alternate signal stack to the
 417          * normal stack.
 418          */
 419         if (next_sp - sp >= sizeof(struct signal_frame_32) &&
 420             is_sigreturn_32_address(next_ip, sp) &&
 421             sane_signal_32_frame(sp)) {
 422                 sf = (struct signal_frame_32 __user *) (unsigned long) sp;
 423                 mctx = &sf->mctx;
 424         }
 425
 426         if (!mctx && next_sp - sp >= sizeof(struct rt_signal_frame_32) &&
 427             is_rt_sigreturn_32_address(next_ip, sp) &&
 428             sane_rt_signal_32_frame(sp)) {
 429                 rt_sf = (struct rt_signal_frame_32 __user *) (unsigned long) sp;
 430                 mctx = &rt_sf->uc.uc_mcontext;
 431         }
 432
 433         if (!mctx)
 434                 return NULL;
 435         return mctx->mc_gregs;
 436 }
 437
 438 static void perf_callchain_user_32(struct pt_regs *regs,
 439                                    struct perf_callchain_entry *entry)
 440 {
 441         unsigned int sp, next_sp;
 442         unsigned int next_ip;
 443         unsigned int lr;
 444         long level = 0;
 445         unsigned int __user *fp, *uregs;
 446
 447         next_ip = regs->nip;
 448         lr = regs->link;
 449         sp = regs->gpr[1];
 450         callchain_store(entry, PERF_CONTEXT_USER);
 451         callchain_store(entry, next_ip);
 452
 453         while (entry->nr < PERF_MAX_STACK_DEPTH) {
 454                 fp = (unsigned int __user *) (unsigned long) sp;
 455                 if (!valid_user_sp(sp, 0) || read_user_stack_32(fp, &next_sp))
 456                         return;
 457                 if (level > 0 && read_user_stack_32(&fp[1], &next_ip))
 458                         return;
 459
 460                 uregs = signal_frame_32_regs(sp, next_sp, next_ip);
 461                 if (!uregs && level <= 1)
 462                         uregs = signal_frame_32_regs(sp, next_sp, lr);
 463                 if (uregs) {
 464                         /*
 465                          * This looks like an signal frame, so restart
 466                          * the stack trace with the values in it.
 467                          */
 468                         if (read_user_stack_32(&uregs[PT_NIP], &next_ip) ||
 469                             read_user_stack_32(&uregs[PT_LNK], &lr) ||
 470                             read_user_stack_32(&uregs[PT_R1], &sp))
 471                                 return;
 472                         level = 0;
 473                         callchain_store(entry, PERF_CONTEXT_USER);
 474                         callchain_store(entry, next_ip);
 475                         continue;
 476                 }
 477
 478                 if (level == 0)
 479                         next_ip = lr;
 480                 callchain_store(entry, next_ip);
 481                 ++level;
 482                 sp = next_sp;
 483         }
 484 }
 485
 486 /*
 487  * Since we can't get PMU interrupts inside a PMU interrupt handler,
 488  * we don't need separate irq and nmi entries here.
 489  */
 490 static DEFINE_PER_CPU(struct perf_callchain_entry, cpu_perf_callchain);
 491
 492 struct perf_callchain_entry *perf_callchain(struct pt_regs *regs)
 493 {
 494         struct perf_callchain_entry *entry = &__get_cpu_var(cpu_perf_callchain);
 495
 496         entry->nr = 0;
 497
 498         if (!user_mode(regs)) {
 499                 perf_callchain_kernel(regs, entry);
 500                 if (current->mm)
 501                         regs = task_pt_regs(current);
 502                 else
 503                         regs = NULL;
 504         }
 505
 506         if (regs) {
 507                 if (current_is_64bit())
 508                         perf_callchain_user_64(regs, entry);
 509                 else
 510                         perf_callchain_user_32(regs, entry);
 511         }
 512
 513         return entry;
 514 }