root/arch/powerpc/perf/callchain.c

DEFINITIONS

1. valid_next_sp
2. perf_callchain_kernel
3. read_user_stack_slow
4. read_user_stack_64
5. read_user_stack_32
6. valid_user_sp
7. is_sigreturn_64_address
8. sane_signal_64_frame
9. perf_callchain_user_64
10. current_is_64bit
11. read_user_stack_32
12. perf_callchain_user_64
13. current_is_64bit
14. valid_user_sp
15. is_sigreturn_32_address
16. is_rt_sigreturn_32_address
17. sane_signal_32_frame
18. sane_rt_signal_32_frame
19. signal_frame_32_regs
20. perf_callchain_user_32
21. perf_callchain_user

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