arch/powerpc/perf/callchain.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Performance counter callchain support - powerpc architecture code
   4  *
   5  * Copyright © 2009 Paul Mackerras, IBM Corporation.
   6  */
   7 #include <linux/kernel.h>
   8 #include <linux/sched.h>
   9 #include <linux/perf_event.h>
  10 #include <linux/percpu.h>
  11 #include <linux/uaccess.h>
  12 #include <linux/mm.h>
  13 #include <asm/ptrace.h>
  14 #include <asm/pgtable.h>
  15 #include <asm/sigcontext.h>
  16 #include <asm/ucontext.h>
  17 #include <asm/vdso.h>
  18 #ifdef CONFIG_PPC64
  19 #include "../kernel/ppc32.h"
  20 #endif
  21 #include <asm/pte-walk.h>
  22
  23
  24 /*
  25  * Is sp valid as the address of the next kernel stack frame after prev_sp?
  26  * The next frame may be in a different stack area but should not go
  27  * back down in the same stack area.
  28  */
  29 static int valid_next_sp(unsigned long sp, unsigned long prev_sp)
  30 {
  31         if (sp & 0xf)
  32                 return 0;               /* must be 16-byte aligned */
  33         if (!validate_sp(sp, current, STACK_FRAME_OVERHEAD))
  34                 return 0;
  35         if (sp >= prev_sp + STACK_FRAME_MIN_SIZE)
  36                 return 1;
  37         /*
  38          * sp could decrease when we jump off an interrupt stack
  39          * back to the regular process stack.
  40          */
  41         if ((sp & ~(THREAD_SIZE - 1)) != (prev_sp & ~(THREAD_SIZE - 1)))
  42                 return 1;
  43         return 0;
  44 }
  45
  46 void
  47 perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
  48 {
  49         unsigned long sp, next_sp;
  50         unsigned long next_ip;
  51         unsigned long lr;
  52         long level = 0;
  53         unsigned long *fp;
  54
  55         lr = regs->link;
  56         sp = regs->gpr[1];
  57         perf_callchain_store(entry, perf_instruction_pointer(regs));
  58
  59         if (!validate_sp(sp, current, STACK_FRAME_OVERHEAD))
  60                 return;
  61
  62         for (;;) {
  63                 fp = (unsigned long *) sp;
  64                 next_sp = fp[0];
  65
  66                 if (next_sp == sp + STACK_INT_FRAME_SIZE &&
  67                     fp[STACK_FRAME_MARKER] == STACK_FRAME_REGS_MARKER) {
  68                         /*
  69                          * This looks like an interrupt frame for an
  70                          * interrupt that occurred in the kernel
  71                          */
  72                         regs = (struct pt_regs *)(sp + STACK_FRAME_OVERHEAD);
  73                         next_ip = regs->nip;
  74                         lr = regs->link;
  75                         level = 0;
  76                         perf_callchain_store_context(entry, PERF_CONTEXT_KERNEL);
  77
  78                 } else {
  79                         if (level == 0)
  80                                 next_ip = lr;
  81                         else
  82                                 next_ip = fp[STACK_FRAME_LR_SAVE];
  83
  84                         /*
  85                          * We can't tell which of the first two addresses
  86                          * we get are valid, but we can filter out the
  87                          * obviously bogus ones here.  We replace them
  88                          * with 0 rather than removing them entirely so
  89                          * that userspace can tell which is which.
  90                          */
  91                         if ((level == 1 && next_ip == lr) ||
  92                             (level <= 1 && !kernel_text_address(next_ip)))
  93                                 next_ip = 0;
  94
  95                         ++level;
  96                 }
  97
  98                 perf_callchain_store(entry, next_ip);
  99                 if (!valid_next_sp(next_sp, sp))
 100                         return;
 101                 sp = next_sp;
 102         }
 103 }
 104
 105 #ifdef CONFIG_PPC64
 106 /*
 107  * On 64-bit we don't want to invoke hash_page on user addresses from
 108  * interrupt context, so if the access faults, we read the page tables
 109  * to find which page (if any) is mapped and access it directly.
 110  */
 111 static int read_user_stack_slow(void __user *ptr, void *buf, int nb)
 112 {
 113         int ret = -EFAULT;
 114         pgd_t *pgdir;
 115         pte_t *ptep, pte;
 116         unsigned shift;
 117         unsigned long addr = (unsigned long) ptr;
 118         unsigned long offset;
 119         unsigned long pfn, flags;
 120         void *kaddr;
 121
 122         pgdir = current->mm->pgd;
 123         if (!pgdir)
 124                 return -EFAULT;
 125
 126         local_irq_save(flags);
 127         ptep = find_current_mm_pte(pgdir, addr, NULL, &shift);
 128         if (!ptep)
 129                 goto err_out;
 130         if (!shift)
 131                 shift = PAGE_SHIFT;
 132
 133         /* align address to page boundary */
 134         offset = addr & ((1UL << shift) - 1);
 135
 136         pte = READ_ONCE(*ptep);
 137         if (!pte_present(pte) || !pte_user(pte))
 138                 goto err_out;
 139         pfn = pte_pfn(pte);
 140         if (!page_is_ram(pfn))
 141                 goto err_out;
 142
 143         /* no highmem to worry about here */
 144         kaddr = pfn_to_kaddr(pfn);
 145         memcpy(buf, kaddr + offset, nb);
 146         ret = 0;
 147 err_out:
 148         local_irq_restore(flags);
 149         return ret;
 150 }
 151
 152 static int read_user_stack_64(unsigned long __user *ptr, unsigned long *ret)
 153 {
 154         if ((unsigned long)ptr > TASK_SIZE - sizeof(unsigned long) ||
 155             ((unsigned long)ptr & 7))
 156                 return -EFAULT;
 157
 158         if (!probe_user_read(ret, ptr, sizeof(*ret)))
 159                 return 0;
 160
 161         return read_user_stack_slow(ptr, ret, 8);
 162 }
 163
 164 static int read_user_stack_32(unsigned int __user *ptr, unsigned int *ret)
 165 {
 166         if ((unsigned long)ptr > TASK_SIZE - sizeof(unsigned int) ||
 167             ((unsigned long)ptr & 3))
 168                 return -EFAULT;
 169
 170         if (!probe_user_read(ret, ptr, sizeof(*ret)))
 171                 return 0;
 172
 173         return read_user_stack_slow(ptr, ret, 4);
 174 }
 175
 176 static inline int valid_user_sp(unsigned long sp, int is_64)
 177 {
 178         if (!sp || (sp & 7) || sp > (is_64 ? TASK_SIZE : 0x100000000UL) - 32)
 179                 return 0;
 180         return 1;
 181 }
 182
 183 /*
 184  * 64-bit user processes use the same stack frame for RT and non-RT signals.
 185  */
 186 struct signal_frame_64 {
 187         char            dummy[__SIGNAL_FRAMESIZE];
 188         struct ucontext uc;
 189         unsigned long   unused[2];
 190         unsigned int    tramp[6];
 191         struct siginfo  *pinfo;
 192         void            *puc;
 193         struct siginfo  info;
 194         char            abigap[288];
 195 };
 196
 197 static int is_sigreturn_64_address(unsigned long nip, unsigned long fp)
 198 {
 199         if (nip == fp + offsetof(struct signal_frame_64, tramp))
 200                 return 1;
 201         if (vdso64_rt_sigtramp && current->mm->context.vdso_base &&
 202             nip == current->mm->context.vdso_base + vdso64_rt_sigtramp)
 203                 return 1;
 204         return 0;
 205 }
 206
 207 /*
 208  * Do some sanity checking on the signal frame pointed to by sp.
 209  * We check the pinfo and puc pointers in the frame.
 210  */
 211 static int sane_signal_64_frame(unsigned long sp)
 212 {
 213         struct signal_frame_64 __user *sf;
 214         unsigned long pinfo, puc;
 215
 216         sf = (struct signal_frame_64 __user *) sp;
 217         if (read_user_stack_64((unsigned long __user *) &sf->pinfo, &pinfo) ||
 218             read_user_stack_64((unsigned long __user *) &sf->puc, &puc))
 219                 return 0;
 220         return pinfo == (unsigned long) &sf->info &&
 221                 puc == (unsigned long) &sf->uc;
 222 }
 223
 224 static void perf_callchain_user_64(struct perf_callchain_entry_ctx *entry,
 225                                    struct pt_regs *regs)
 226 {
 227         unsigned long sp, next_sp;
 228         unsigned long next_ip;
 229         unsigned long lr;
 230         long level = 0;
 231         struct signal_frame_64 __user *sigframe;
 232         unsigned long __user *fp, *uregs;
 233
 234         next_ip = perf_instruction_pointer(regs);
 235         lr = regs->link;
 236         sp = regs->gpr[1];
 237         perf_callchain_store(entry, next_ip);
 238
 239         while (entry->nr < entry->max_stack) {
 240                 fp = (unsigned long __user *) sp;
 241                 if (!valid_user_sp(sp, 1) || read_user_stack_64(fp, &next_sp))
 242                         return;
 243                 if (level > 0 && read_user_stack_64(&fp[2], &next_ip))
 244                         return;
 245
 246                 /*
 247                  * Note: the next_sp - sp >= signal frame size check
 248                  * is true when next_sp < sp, which can happen when
 249                  * transitioning from an alternate signal stack to the
 250                  * normal stack.
 251                  */
 252                 if (next_sp - sp >= sizeof(struct signal_frame_64) &&
 253                     (is_sigreturn_64_address(next_ip, sp) ||
 254                      (level <= 1 && is_sigreturn_64_address(lr, sp))) &&
 255                     sane_signal_64_frame(sp)) {
 256                         /*
 257                          * This looks like an signal frame
 258                          */
 259                         sigframe = (struct signal_frame_64 __user *) sp;
 260                         uregs = sigframe->uc.uc_mcontext.gp_regs;
 261                         if (read_user_stack_64(&uregs[PT_NIP], &next_ip) ||
 262                             read_user_stack_64(&uregs[PT_LNK], &lr) ||
 263                             read_user_stack_64(&uregs[PT_R1], &sp))
 264                                 return;
 265                         level = 0;
 266                         perf_callchain_store_context(entry, PERF_CONTEXT_USER);
 267                         perf_callchain_store(entry, next_ip);
 268                         continue;
 269                 }
 270
 271                 if (level == 0)
 272                         next_ip = lr;
 273                 perf_callchain_store(entry, next_ip);
 274                 ++level;
 275                 sp = next_sp;
 276         }
 277 }
 278
 279 #else  /* CONFIG_PPC64 */
 280 /*
 281  * On 32-bit we just access the address and let hash_page create a
 282  * HPTE if necessary, so there is no need to fall back to reading
 283  * the page tables.  Since this is called at interrupt level,
 284  * do_page_fault() won't treat a DSI as a page fault.
 285  */
 286 static int read_user_stack_32(unsigned int __user *ptr, unsigned int *ret)
 287 {
 288         if ((unsigned long)ptr > TASK_SIZE - sizeof(unsigned int) ||
 289             ((unsigned long)ptr & 3))
 290                 return -EFAULT;
 291
 292         return probe_user_read(ret, ptr, sizeof(*ret));
 293 }
 294
 295 static inline void perf_callchain_user_64(struct perf_callchain_entry_ctx *entry,
 296                                           struct pt_regs *regs)
 297 {
 298 }
 299
 300 static inline int valid_user_sp(unsigned long sp, int is_64)
 301 {
 302         if (!sp || (sp & 7) || sp > TASK_SIZE - 32)
 303                 return 0;
 304         return 1;
 305 }
 306
 307 #define __SIGNAL_FRAMESIZE32    __SIGNAL_FRAMESIZE
 308 #define sigcontext32            sigcontext
 309 #define mcontext32              mcontext
 310 #define ucontext32              ucontext
 311 #define compat_siginfo_t        struct siginfo
 312
 313 #endif /* CONFIG_PPC64 */
 314
 315 /*
 316  * Layout for non-RT signal frames
 317  */
 318 struct signal_frame_32 {
 319         char                    dummy[__SIGNAL_FRAMESIZE32];
 320         struct sigcontext32     sctx;
 321         struct mcontext32       mctx;
 322         int                     abigap[56];
 323 };
 324
 325 /*
 326  * Layout for RT signal frames
 327  */
 328 struct rt_signal_frame_32 {
 329         char                    dummy[__SIGNAL_FRAMESIZE32 + 16];
 330         compat_siginfo_t        info;
 331         struct ucontext32       uc;
 332         int                     abigap[56];
 333 };
 334
 335 static int is_sigreturn_32_address(unsigned int nip, unsigned int fp)
 336 {
 337         if (nip == fp + offsetof(struct signal_frame_32, mctx.mc_pad))
 338                 return 1;
 339         if (vdso32_sigtramp && current->mm->context.vdso_base &&
 340             nip == current->mm->context.vdso_base + vdso32_sigtramp)
 341                 return 1;
 342         return 0;
 343 }
 344
 345 static int is_rt_sigreturn_32_address(unsigned int nip, unsigned int fp)
 346 {
 347         if (nip == fp + offsetof(struct rt_signal_frame_32,
 348                                  uc.uc_mcontext.mc_pad))
 349                 return 1;
 350         if (vdso32_rt_sigtramp && current->mm->context.vdso_base &&
 351             nip == current->mm->context.vdso_base + vdso32_rt_sigtramp)
 352                 return 1;
 353         return 0;
 354 }
 355
 356 static int sane_signal_32_frame(unsigned int sp)
 357 {
 358         struct signal_frame_32 __user *sf;
 359         unsigned int regs;
 360
 361         sf = (struct signal_frame_32 __user *) (unsigned long) sp;
 362         if (read_user_stack_32((unsigned int __user *) &sf->sctx.regs, &regs))
 363                 return 0;
 364         return regs == (unsigned long) &sf->mctx;
 365 }
 366
 367 static int sane_rt_signal_32_frame(unsigned int sp)
 368 {
 369         struct rt_signal_frame_32 __user *sf;
 370         unsigned int regs;
 371
 372         sf = (struct rt_signal_frame_32 __user *) (unsigned long) sp;
 373         if (read_user_stack_32((unsigned int __user *) &sf->uc.uc_regs, &regs))
 374                 return 0;
 375         return regs == (unsigned long) &sf->uc.uc_mcontext;
 376 }
 377
 378 static unsigned int __user *signal_frame_32_regs(unsigned int sp,
 379                                 unsigned int next_sp, unsigned int next_ip)
 380 {
 381         struct mcontext32 __user *mctx = NULL;
 382         struct signal_frame_32 __user *sf;
 383         struct rt_signal_frame_32 __user *rt_sf;
 384
 385         /*
 386          * Note: the next_sp - sp >= signal frame size check
 387          * is true when next_sp < sp, for example, when
 388          * transitioning from an alternate signal stack to the
 389          * normal stack.
 390          */
 391         if (next_sp - sp >= sizeof(struct signal_frame_32) &&
 392             is_sigreturn_32_address(next_ip, sp) &&
 393             sane_signal_32_frame(sp)) {
 394                 sf = (struct signal_frame_32 __user *) (unsigned long) sp;
 395                 mctx = &sf->mctx;
 396         }
 397
 398         if (!mctx && next_sp - sp >= sizeof(struct rt_signal_frame_32) &&
 399             is_rt_sigreturn_32_address(next_ip, sp) &&
 400             sane_rt_signal_32_frame(sp)) {
 401                 rt_sf = (struct rt_signal_frame_32 __user *) (unsigned long) sp;
 402                 mctx = &rt_sf->uc.uc_mcontext;
 403         }
 404
 405         if (!mctx)
 406                 return NULL;
 407         return mctx->mc_gregs;
 408 }
 409
 410 static void perf_callchain_user_32(struct perf_callchain_entry_ctx *entry,
 411                                    struct pt_regs *regs)
 412 {
 413         unsigned int sp, next_sp;
 414         unsigned int next_ip;
 415         unsigned int lr;
 416         long level = 0;
 417         unsigned int __user *fp, *uregs;
 418
 419         next_ip = perf_instruction_pointer(regs);
 420         lr = regs->link;
 421         sp = regs->gpr[1];
 422         perf_callchain_store(entry, next_ip);
 423
 424         while (entry->nr < entry->max_stack) {
 425                 fp = (unsigned int __user *) (unsigned long) sp;
 426                 if (!valid_user_sp(sp, 0) || read_user_stack_32(fp, &next_sp))
 427                         return;
 428                 if (level > 0 && read_user_stack_32(&fp[1], &next_ip))
 429                         return;
 430
 431                 uregs = signal_frame_32_regs(sp, next_sp, next_ip);
 432                 if (!uregs && level <= 1)
 433                         uregs = signal_frame_32_regs(sp, next_sp, lr);
 434                 if (uregs) {
 435                         /*
 436                          * This looks like an signal frame, so restart
 437                          * the stack trace with the values in it.
 438                          */
 439                         if (read_user_stack_32(&uregs[PT_NIP], &next_ip) ||
 440                             read_user_stack_32(&uregs[PT_LNK], &lr) ||
 441                             read_user_stack_32(&uregs[PT_R1], &sp))
 442                                 return;
 443                         level = 0;
 444                         perf_callchain_store_context(entry, PERF_CONTEXT_USER);
 445                         perf_callchain_store(entry, next_ip);
 446                         continue;
 447                 }
 448
 449                 if (level == 0)
 450                         next_ip = lr;
 451                 perf_callchain_store(entry, next_ip);
 452                 ++level;
 453                 sp = next_sp;
 454         }
 455 }
 456
 457 void
 458 perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
 459 {
 460         if (!is_32bit_task())
 461                 perf_callchain_user_64(entry, regs);
 462         else
 463                 perf_callchain_user_32(entry, regs);
 464 }