kernel/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
  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_MIN_SIZE)
  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, perf_instruction_pointer(regs));
  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 *buf, int nb)
 115 {
 116         int ret = -EFAULT;
 117         pgd_t *pgdir;
 118         pte_t *ptep, pte;
 119         unsigned shift;
 120         unsigned long addr = (unsigned long) ptr;
 121         unsigned long offset;
 122         unsigned long pfn, flags;
 123         void *kaddr;
 124
 125         pgdir = current->mm->pgd;
 126         if (!pgdir)
 127                 return -EFAULT;
 128
 129         local_irq_save(flags);
 130         ptep = find_linux_pte_or_hugepte(pgdir, addr, &shift);
 131         if (!ptep)
 132                 goto err_out;
 133         if (!shift)
 134                 shift = PAGE_SHIFT;
 135
 136         /* align address to page boundary */
 137         offset = addr & ((1UL << shift) - 1);
 138
 139         pte = READ_ONCE(*ptep);
 140         if (!pte_present(pte) || !(pte_val(pte) & _PAGE_USER))
 141                 goto err_out;
 142         pfn = pte_pfn(pte);
 143         if (!page_is_ram(pfn))
 144                 goto err_out;
 145
 146         /* no highmem to worry about here */
 147         kaddr = pfn_to_kaddr(pfn);
 148         memcpy(buf, kaddr + offset, nb);
 149         ret = 0;
 150 err_out:
 151         local_irq_restore(flags);
 152         return ret;
 153 }
 154
 155 static int read_user_stack_64(unsigned long __user *ptr, unsigned long *ret)
 156 {
 157         if ((unsigned long)ptr > TASK_SIZE - sizeof(unsigned long) ||
 158             ((unsigned long)ptr & 7))
 159                 return -EFAULT;
 160
 161         pagefault_disable();
 162         if (!__get_user_inatomic(*ret, ptr)) {
 163                 pagefault_enable();
 164                 return 0;
 165         }
 166         pagefault_enable();
 167
 168         return read_user_stack_slow(ptr, ret, 8);
 169 }
 170
 171 static int read_user_stack_32(unsigned int __user *ptr, unsigned int *ret)
 172 {
 173         if ((unsigned long)ptr > TASK_SIZE - sizeof(unsigned int) ||
 174             ((unsigned long)ptr & 3))
 175                 return -EFAULT;
 176
 177         pagefault_disable();
 178         if (!__get_user_inatomic(*ret, ptr)) {
 179                 pagefault_enable();
 180                 return 0;
 181         }
 182         pagefault_enable();
 183
 184         return read_user_stack_slow(ptr, ret, 4);
 185 }
 186
 187 static inline int valid_user_sp(unsigned long sp, int is_64)
 188 {
 189         if (!sp || (sp & 7) || sp > (is_64 ? TASK_SIZE : 0x100000000UL) - 32)
 190                 return 0;
 191         return 1;
 192 }
 193
 194 /*
 195  * 64-bit user processes use the same stack frame for RT and non-RT signals.
 196  */
 197 struct signal_frame_64 {
 198         char            dummy[__SIGNAL_FRAMESIZE];
 199         struct ucontext uc;
 200         unsigned long   unused[2];
 201         unsigned int    tramp[6];
 202         struct siginfo  *pinfo;
 203         void            *puc;
 204         struct siginfo  info;
 205         char            abigap[288];
 206 };
 207
 208 static int is_sigreturn_64_address(unsigned long nip, unsigned long fp)
 209 {
 210         if (nip == fp + offsetof(struct signal_frame_64, tramp))
 211                 return 1;
 212         if (vdso64_rt_sigtramp && current->mm->context.vdso_base &&
 213             nip == current->mm->context.vdso_base + vdso64_rt_sigtramp)
 214                 return 1;
 215         return 0;
 216 }
 217
 218 /*
 219  * Do some sanity checking on the signal frame pointed to by sp.
 220  * We check the pinfo and puc pointers in the frame.
 221  */
 222 static int sane_signal_64_frame(unsigned long sp)
 223 {
 224         struct signal_frame_64 __user *sf;
 225         unsigned long pinfo, puc;
 226
 227         sf = (struct signal_frame_64 __user *) sp;
 228         if (read_user_stack_64((unsigned long __user *) &sf->pinfo, &pinfo) ||
 229             read_user_stack_64((unsigned long __user *) &sf->puc, &puc))
 230                 return 0;
 231         return pinfo == (unsigned long) &sf->info &&
 232                 puc == (unsigned long) &sf->uc;
 233 }
 234
 235 static void perf_callchain_user_64(struct perf_callchain_entry *entry,
 236                                    struct pt_regs *regs)
 237 {
 238         unsigned long sp, next_sp;
 239         unsigned long next_ip;
 240         unsigned long lr;
 241         long level = 0;
 242         struct signal_frame_64 __user *sigframe;
 243         unsigned long __user *fp, *uregs;
 244
 245         next_ip = perf_instruction_pointer(regs);
 246         lr = regs->link;
 247         sp = regs->gpr[1];
 248         perf_callchain_store(entry, next_ip);
 249
 250         while (entry->nr < PERF_MAX_STACK_DEPTH) {
 251                 fp = (unsigned long __user *) sp;
 252                 if (!valid_user_sp(sp, 1) || read_user_stack_64(fp, &next_sp))
 253                         return;
 254                 if (level > 0 && read_user_stack_64(&fp[2], &next_ip))
 255                         return;
 256
 257                 /*
 258                  * Note: the next_sp - sp >= signal frame size check
 259                  * is true when next_sp < sp, which can happen when
 260                  * transitioning from an alternate signal stack to the
 261                  * normal stack.
 262                  */
 263                 if (next_sp - sp >= sizeof(struct signal_frame_64) &&
 264                     (is_sigreturn_64_address(next_ip, sp) ||
 265                      (level <= 1 && is_sigreturn_64_address(lr, sp))) &&
 266                     sane_signal_64_frame(sp)) {
 267                         /*
 268                          * This looks like an signal frame
 269                          */
 270                         sigframe = (struct signal_frame_64 __user *) sp;
 271                         uregs = sigframe->uc.uc_mcontext.gp_regs;
 272                         if (read_user_stack_64(&uregs[PT_NIP], &next_ip) ||
 273                             read_user_stack_64(&uregs[PT_LNK], &lr) ||
 274                             read_user_stack_64(&uregs[PT_R1], &sp))
 275                                 return;
 276                         level = 0;
 277                         perf_callchain_store(entry, PERF_CONTEXT_USER);
 278                         perf_callchain_store(entry, next_ip);
 279                         continue;
 280                 }
 281
 282                 if (level == 0)
 283                         next_ip = lr;
 284                 perf_callchain_store(entry, next_ip);
 285                 ++level;
 286                 sp = next_sp;
 287         }
 288 }
 289
 290 static inline int current_is_64bit(void)
 291 {
 292         /*
 293          * We can't use test_thread_flag() here because we may be on an
 294          * interrupt stack, and the thread flags don't get copied over
 295          * from the thread_info on the main stack to the interrupt stack.
 296          */
 297         return !test_ti_thread_flag(task_thread_info(current), TIF_32BIT);
 298 }
 299
 300 #else  /* CONFIG_PPC64 */
 301 /*
 302  * On 32-bit we just access the address and let hash_page create a
 303  * HPTE if necessary, so there is no need to fall back to reading
 304  * the page tables.  Since this is called at interrupt level,
 305  * do_page_fault() won't treat a DSI as a page fault.
 306  */
 307 static int read_user_stack_32(unsigned int __user *ptr, unsigned int *ret)
 308 {
 309         int rc;
 310
 311         if ((unsigned long)ptr > TASK_SIZE - sizeof(unsigned int) ||
 312             ((unsigned long)ptr & 3))
 313                 return -EFAULT;
 314
 315         pagefault_disable();
 316         rc = __get_user_inatomic(*ret, ptr);
 317         pagefault_enable();
 318
 319         return rc;
 320 }
 321
 322 static inline void perf_callchain_user_64(struct perf_callchain_entry *entry,
 323                                           struct pt_regs *regs)
 324 {
 325 }
 326
 327 static inline int current_is_64bit(void)
 328 {
 329         return 0;
 330 }
 331
 332 static inline int valid_user_sp(unsigned long sp, int is_64)
 333 {
 334         if (!sp || (sp & 7) || sp > TASK_SIZE - 32)
 335                 return 0;
 336         return 1;
 337 }
 338
 339 #define __SIGNAL_FRAMESIZE32    __SIGNAL_FRAMESIZE
 340 #define sigcontext32            sigcontext
 341 #define mcontext32              mcontext
 342 #define ucontext32              ucontext
 343 #define compat_siginfo_t        struct siginfo
 344
 345 #endif /* CONFIG_PPC64 */
 346
 347 /*
 348  * Layout for non-RT signal frames
 349  */
 350 struct signal_frame_32 {
 351         char                    dummy[__SIGNAL_FRAMESIZE32];
 352         struct sigcontext32     sctx;
 353         struct mcontext32       mctx;
 354         int                     abigap[56];
 355 };
 356
 357 /*
 358  * Layout for RT signal frames
 359  */
 360 struct rt_signal_frame_32 {
 361         char                    dummy[__SIGNAL_FRAMESIZE32 + 16];
 362         compat_siginfo_t        info;
 363         struct ucontext32       uc;
 364         int                     abigap[56];
 365 };
 366
 367 static int is_sigreturn_32_address(unsigned int nip, unsigned int fp)
 368 {
 369         if (nip == fp + offsetof(struct signal_frame_32, mctx.mc_pad))
 370                 return 1;
 371         if (vdso32_sigtramp && current->mm->context.vdso_base &&
 372             nip == current->mm->context.vdso_base + vdso32_sigtramp)
 373                 return 1;
 374         return 0;
 375 }
 376
 377 static int is_rt_sigreturn_32_address(unsigned int nip, unsigned int fp)
 378 {
 379         if (nip == fp + offsetof(struct rt_signal_frame_32,
 380                                  uc.uc_mcontext.mc_pad))
 381                 return 1;
 382         if (vdso32_rt_sigtramp && current->mm->context.vdso_base &&
 383             nip == current->mm->context.vdso_base + vdso32_rt_sigtramp)
 384                 return 1;
 385         return 0;
 386 }
 387
 388 static int sane_signal_32_frame(unsigned int sp)
 389 {
 390         struct signal_frame_32 __user *sf;
 391         unsigned int regs;
 392
 393         sf = (struct signal_frame_32 __user *) (unsigned long) sp;
 394         if (read_user_stack_32((unsigned int __user *) &sf->sctx.regs, &regs))
 395                 return 0;
 396         return regs == (unsigned long) &sf->mctx;
 397 }
 398
 399 static int sane_rt_signal_32_frame(unsigned int sp)
 400 {
 401         struct rt_signal_frame_32 __user *sf;
 402         unsigned int regs;
 403
 404         sf = (struct rt_signal_frame_32 __user *) (unsigned long) sp;
 405         if (read_user_stack_32((unsigned int __user *) &sf->uc.uc_regs, &regs))
 406                 return 0;
 407         return regs == (unsigned long) &sf->uc.uc_mcontext;
 408 }
 409
 410 static unsigned int __user *signal_frame_32_regs(unsigned int sp,
 411                                 unsigned int next_sp, unsigned int next_ip)
 412 {
 413         struct mcontext32 __user *mctx = NULL;
 414         struct signal_frame_32 __user *sf;
 415         struct rt_signal_frame_32 __user *rt_sf;
 416
 417         /*
 418          * Note: the next_sp - sp >= signal frame size check
 419          * is true when next_sp < sp, for example, when
 420          * transitioning from an alternate signal stack to the
 421          * normal stack.
 422          */
 423         if (next_sp - sp >= sizeof(struct signal_frame_32) &&
 424             is_sigreturn_32_address(next_ip, sp) &&
 425             sane_signal_32_frame(sp)) {
 426                 sf = (struct signal_frame_32 __user *) (unsigned long) sp;
 427                 mctx = &sf->mctx;
 428         }
 429
 430         if (!mctx && next_sp - sp >= sizeof(struct rt_signal_frame_32) &&
 431             is_rt_sigreturn_32_address(next_ip, sp) &&
 432             sane_rt_signal_32_frame(sp)) {
 433                 rt_sf = (struct rt_signal_frame_32 __user *) (unsigned long) sp;
 434                 mctx = &rt_sf->uc.uc_mcontext;
 435         }
 436
 437         if (!mctx)
 438                 return NULL;
 439         return mctx->mc_gregs;
 440 }
 441
 442 static void perf_callchain_user_32(struct perf_callchain_entry *entry,
 443                                    struct pt_regs *regs)
 444 {
 445         unsigned int sp, next_sp;
 446         unsigned int next_ip;
 447         unsigned int lr;
 448         long level = 0;
 449         unsigned int __user *fp, *uregs;
 450
 451         next_ip = perf_instruction_pointer(regs);
 452         lr = regs->link;
 453         sp = regs->gpr[1];
 454         perf_callchain_store(entry, next_ip);
 455
 456         while (entry->nr < PERF_MAX_STACK_DEPTH) {
 457                 fp = (unsigned int __user *) (unsigned long) sp;
 458                 if (!valid_user_sp(sp, 0) || read_user_stack_32(fp, &next_sp))
 459                         return;
 460                 if (level > 0 && read_user_stack_32(&fp[1], &next_ip))
 461                         return;
 462
 463                 uregs = signal_frame_32_regs(sp, next_sp, next_ip);
 464                 if (!uregs && level <= 1)
 465                         uregs = signal_frame_32_regs(sp, next_sp, lr);
 466                 if (uregs) {
 467                         /*
 468                          * This looks like an signal frame, so restart
 469                          * the stack trace with the values in it.
 470                          */
 471                         if (read_user_stack_32(&uregs[PT_NIP], &next_ip) ||
 472                             read_user_stack_32(&uregs[PT_LNK], &lr) ||
 473                             read_user_stack_32(&uregs[PT_R1], &sp))
 474                                 return;
 475                         level = 0;
 476                         perf_callchain_store(entry, PERF_CONTEXT_USER);
 477                         perf_callchain_store(entry, next_ip);
 478                         continue;
 479                 }
 480
 481                 if (level == 0)
 482                         next_ip = lr;
 483                 perf_callchain_store(entry, next_ip);
 484                 ++level;
 485                 sp = next_sp;
 486         }
 487 }
 488
 489 void
 490 perf_callchain_user(struct perf_callchain_entry *entry, struct pt_regs *regs)
 491 {
 492         if (current_is_64bit())
 493                 perf_callchain_user_64(entry, regs);
 494         else
 495                 perf_callchain_user_32(entry, regs);
 496 }