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Linux/arch/powerpc/perf/callchain.c

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

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