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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 
 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_ctx *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_context(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, NULL, &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_user(pte))
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_ctx *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 < entry->max_stack) {
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_context(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_ctx *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_ctx *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 < entry->max_stack) {
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_context(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_ctx *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 }
497 

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