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 /*
  28  * Is sp valid as the address of the next kernel stack frame after prev_sp?
  29  * The next frame may be in a different stack area but should not go
  30  * back down in the same stack area.
  31  */
  32 static int valid_next_sp(unsigned long sp, unsigned long prev_sp)
  33 {
  34         if (sp & 0xf)
  35                 return 0;               /* must be 16-byte aligned */
  36         if (!validate_sp(sp, current, STACK_FRAME_OVERHEAD))
  37                 return 0;
  38         if (sp >= prev_sp + STACK_FRAME_OVERHEAD)
  39                 return 1;
  40         /*
  41          * sp could decrease when we jump off an interrupt stack
  42          * back to the regular process stack.
  43          */
  44         if ((sp & ~(THREAD_SIZE - 1)) != (prev_sp & ~(THREAD_SIZE - 1)))
  45                 return 1;
  46         return 0;
  47 }
  48
  49 void
  50 perf_callchain_kernel(struct perf_callchain_entry *entry, struct pt_regs *regs)
  51 {
  52         unsigned long sp, next_sp;
  53         unsigned long next_ip;
  54         unsigned long lr;
  55         long level = 0;
  56         unsigned long *fp;
  57
  58         lr = regs->link;
  59         sp = regs->gpr[1];
  60         perf_callchain_store(entry, regs->nip);
  61
  62         if (!validate_sp(sp, current, STACK_FRAME_OVERHEAD))
  63                 return;
  64
  65         for (;;) {
  66                 fp = (unsigned long *) sp;
  67                 next_sp = fp[0];
  68
  69                 if (next_sp == sp + STACK_INT_FRAME_SIZE &&
  70                     fp[STACK_FRAME_MARKER] == STACK_FRAME_REGS_MARKER) {
  71                         /*
  72                          * This looks like an interrupt frame for an
  73                          * interrupt that occurred in the kernel
  74                          */
  75                         regs = (struct pt_regs *)(sp + STACK_FRAME_OVERHEAD);
  76                         next_ip = regs->nip;
  77                         lr = regs->link;
  78                         level = 0;
  79                         perf_callchain_store(entry, PERF_CONTEXT_KERNEL);
  80
  81                 } else {
  82                         if (level == 0)
  83                                 next_ip = lr;
  84                         else
  85                                 next_ip = fp[STACK_FRAME_LR_SAVE];
  86
  87                         /*
  88                          * We can't tell which of the first two addresses
  89                          * we get are valid, but we can filter out the
  90                          * obviously bogus ones here.  We replace them
  91                          * with 0 rather than removing them entirely so
  92                          * that userspace can tell which is which.
  93                          */
  94                         if ((level == 1 && next_ip == lr) ||
  95                             (level <= 1 && !kernel_text_address(next_ip)))
  96                                 next_ip = 0;
  97
  98                         ++level;
  99                 }
 100
 101                 perf_callchain_store(entry, next_ip);
 102                 if (!valid_next_sp(next_sp, sp))
 103                         return;
 104                 sp = next_sp;
 105         }
 106 }
 107
 108 #ifdef CONFIG_PPC64
 109 /*
 110  * On 64-bit we don't want to invoke hash_page on user addresses from
 111  * interrupt context, so if the access faults, we read the page tables
 112  * to find which page (if any) is mapped and access it directly.
 113  */
 114 static int read_user_stack_slow(void __user *ptr, void *ret, int nb)
 115 {
 116         pgd_t *pgdir;
 117         pte_t *ptep, pte;
 118         unsigned shift;
 119         unsigned long addr = (unsigned long) ptr;
 120         unsigned long offset;
 121         unsigned long pfn;
 122         void *kaddr;
 123
 124         pgdir = current->mm->pgd;
 125         if (!pgdir)
 126                 return -EFAULT;
 127
 128         ptep = find_linux_pte_or_hugepte(pgdir, addr, &shift);
 129         if (!shift)
 130                 shift = PAGE_SHIFT;
 131
 132         /* align address to page boundary */
 133         offset = addr & ((1UL << shift) - 1);
 134         addr -= offset;
 135
 136         if (ptep == NULL)
 137                 return -EFAULT;
 138         pte = *ptep;
 139         if (!pte_present(pte) || !(pte_val(pte) & _PAGE_USER))
 140                 return -EFAULT;
 141         pfn = pte_pfn(pte);
 142         if (!page_is_ram(pfn))
 143                 return -EFAULT;
 144
 145         /* no highmem to worry about here */
 146         kaddr = pfn_to_kaddr(pfn);
 147         memcpy(ret, kaddr + offset, nb);
 148         return 0;
 149 }
 150
 151 static int read_user_stack_64(unsigned long __user *ptr, unsigned long *ret)
 152 {
 153         if ((unsigned long)ptr > TASK_SIZE - sizeof(unsigned long) ||
 154             ((unsigned long)ptr & 7))
 155                 return -EFAULT;
 156
 157         pagefault_disable();
 158         if (!__get_user_inatomic(*ret, ptr)) {
 159                 pagefault_enable();
 160                 return 0;
 161         }
 162         pagefault_enable();
 163
 164         return read_user_stack_slow(ptr, ret, 8);
 165 }
 166
 167 static int read_user_stack_32(unsigned int __user *ptr, unsigned int *ret)
 168 {
 169         if ((unsigned long)ptr > TASK_SIZE - sizeof(unsigned int) ||
 170             ((unsigned long)ptr & 3))
 171                 return -EFAULT;
 172
 173         pagefault_disable();
 174         if (!__get_user_inatomic(*ret, ptr)) {
 175                 pagefault_enable();
 176                 return 0;
 177         }
 178         pagefault_enable();
 179
 180         return read_user_stack_slow(ptr, ret, 4);
 181 }
 182
 183 static inline int valid_user_sp(unsigned long sp, int is_64)
 184 {
 185         if (!sp || (sp & 7) || sp > (is_64 ? TASK_SIZE : 0x100000000UL) - 32)
 186                 return 0;
 187         return 1;
 188 }
 189
 190 /*
 191  * 64-bit user processes use the same stack frame for RT and non-RT signals.
 192  */
 193 struct signal_frame_64 {
 194         char            dummy[__SIGNAL_FRAMESIZE];
 195         struct ucontext uc;
 196         unsigned long   unused[2];
 197         unsigned int    tramp[6];
 198         struct siginfo  *pinfo;
 199         void            *puc;
 200         struct siginfo  info;
 201         char            abigap[288];
 202 };
 203
 204 static int is_sigreturn_64_address(unsigned long nip, unsigned long fp)
 205 {
 206         if (nip == fp + offsetof(struct signal_frame_64, tramp))
 207                 return 1;
 208         if (vdso64_rt_sigtramp && current->mm->context.vdso_base &&
 209             nip == current->mm->context.vdso_base + vdso64_rt_sigtramp)
 210                 return 1;
 211         return 0;
 212 }
 213
 214 /*
 215  * Do some sanity checking on the signal frame pointed to by sp.
 216  * We check the pinfo and puc pointers in the frame.
 217  */
 218 static int sane_signal_64_frame(unsigned long sp)
 219 {
 220         struct signal_frame_64 __user *sf;
 221         unsigned long pinfo, puc;
 222
 223         sf = (struct signal_frame_64 __user *) sp;
 224         if (read_user_stack_64((unsigned long __user *) &sf->pinfo, &pinfo) ||
 225             read_user_stack_64((unsigned long __user *) &sf->puc, &puc))
 226                 return 0;
 227         return pinfo == (unsigned long) &sf->info &&
 228                 puc == (unsigned long) &sf->uc;
 229 }
 230
 231 static void perf_callchain_user_64(struct perf_callchain_entry *entry,
 232                                    struct pt_regs *regs)
 233 {
 234         unsigned long sp, next_sp;
 235         unsigned long next_ip;
 236         unsigned long lr;
 237         long level = 0;
 238         struct signal_frame_64 __user *sigframe;
 239         unsigned long __user *fp, *uregs;
 240
 241         next_ip = regs->nip;
 242         lr = regs->link;
 243         sp = regs->gpr[1];
 244         perf_callchain_store(entry, next_ip);
 245
 246         for (;;) {
 247                 fp = (unsigned long __user *) sp;
 248                 if (!valid_user_sp(sp, 1) || read_user_stack_64(fp, &next_sp))
 249                         return;
 250                 if (level > 0 && read_user_stack_64(&fp[2], &next_ip))
 251                         return;
 252
 253                 /*
 254                  * Note: the next_sp - sp >= signal frame size check
 255                  * is true when next_sp < sp, which can happen when
 256                  * transitioning from an alternate signal stack to the
 257                  * normal stack.
 258                  */
 259                 if (next_sp - sp >= sizeof(struct signal_frame_64) &&
 260                     (is_sigreturn_64_address(next_ip, sp) ||
 261                      (level <= 1 && is_sigreturn_64_address(lr, sp))) &&
 262                     sane_signal_64_frame(sp)) {
 263                         /*
 264                          * This looks like an signal frame
 265                          */
 266                         sigframe = (struct signal_frame_64 __user *) sp;
 267                         uregs = sigframe->uc.uc_mcontext.gp_regs;
 268                         if (read_user_stack_64(&uregs[PT_NIP], &next_ip) ||
 269                             read_user_stack_64(&uregs[PT_LNK], &lr) ||
 270                             read_user_stack_64(&uregs[PT_R1], &sp))
 271                                 return;
 272                         level = 0;
 273                         perf_callchain_store(entry, PERF_CONTEXT_USER);
 274                         perf_callchain_store(entry, next_ip);
 275                         continue;
 276                 }
 277
 278                 if (level == 0)
 279                         next_ip = lr;
 280                 perf_callchain_store(entry, next_ip);
 281                 ++level;
 282                 sp = next_sp;
 283         }
 284 }
 285
 286 static inline int current_is_64bit(void)
 287 {
 288         /*
 289          * We can't use test_thread_flag() here because we may be on an
 290          * interrupt stack, and the thread flags don't get copied over
 291          * from the thread_info on the main stack to the interrupt stack.
 292          */
 293         return !test_ti_thread_flag(task_thread_info(current), TIF_32BIT);
 294 }
 295
 296 #else  /* CONFIG_PPC64 */
 297 /*
 298  * On 32-bit we just access the address and let hash_page create a
 299  * HPTE if necessary, so there is no need to fall back to reading
 300  * the page tables.  Since this is called at interrupt level,
 301  * do_page_fault() won't treat a DSI as a page fault.
 302  */
 303 static int read_user_stack_32(unsigned int __user *ptr, unsigned int *ret)
 304 {
 305         int rc;
 306
 307         if ((unsigned long)ptr > TASK_SIZE - sizeof(unsigned int) ||
 308             ((unsigned long)ptr & 3))
 309                 return -EFAULT;
 310
 311         pagefault_disable();
 312         rc = __get_user_inatomic(*ret, ptr);
 313         pagefault_enable();
 314
 315         return rc;
 316 }
 317
 318 static inline void perf_callchain_user_64(struct perf_callchain_entry *entry,
 319                                           struct pt_regs *regs)
 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 perf_callchain_entry *entry,
 439                                    struct pt_regs *regs)
 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         perf_callchain_store(entry, next_ip);
 451
 452         while (entry->nr < PERF_MAX_STACK_DEPTH) {
 453                 fp = (unsigned int __user *) (unsigned long) sp;
 454                 if (!valid_user_sp(sp, 0) || read_user_stack_32(fp, &next_sp))
 455                         return;
 456                 if (level > 0 && read_user_stack_32(&fp[1], &next_ip))
 457                         return;
 458
 459                 uregs = signal_frame_32_regs(sp, next_sp, next_ip);
 460                 if (!uregs && level <= 1)
 461                         uregs = signal_frame_32_regs(sp, next_sp, lr);
 462                 if (uregs) {
 463                         /*
 464                          * This looks like an signal frame, so restart
 465                          * the stack trace with the values in it.
 466                          */
 467                         if (read_user_stack_32(&uregs[PT_NIP], &next_ip) ||
 468                             read_user_stack_32(&uregs[PT_LNK], &lr) ||
 469                             read_user_stack_32(&uregs[PT_R1], &sp))
 470                                 return;
 471                         level = 0;
 472                         perf_callchain_store(entry, PERF_CONTEXT_USER);
 473                         perf_callchain_store(entry, next_ip);
 474                         continue;
 475                 }
 476
 477                 if (level == 0)
 478                         next_ip = lr;
 479                 perf_callchain_store(entry, next_ip);
 480                 ++level;
 481                 sp = next_sp;
 482         }
 483 }
 484
 485 void
 486 perf_callchain_user(struct perf_callchain_entry *entry, struct pt_regs *regs)
 487 {
 488         if (current_is_64bit())
 489                 perf_callchain_user_64(entry, regs);
 490         else
 491                 perf_callchain_user_32(entry, regs);
 492 }