arch/powerpc/perf/callchain_64.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/sigcontext.h>
  15 #include <asm/ucontext.h>
  16 #include <asm/vdso.h>
  17 #include <asm/pte-walk.h>
  18
  19 #include "callchain.h"
  20
  21 /*
  22  * On 64-bit we don't want to invoke hash_page on user addresses from
  23  * interrupt context, so if the access faults, we read the page tables
  24  * to find which page (if any) is mapped and access it directly. Radix
  25  * has no need for this so it doesn't use read_user_stack_slow.
  26  */
  27 int read_user_stack_slow(const void __user *ptr, void *buf, int nb)
  28 {
  29
  30         unsigned long addr = (unsigned long) ptr;
  31         unsigned long offset;
  32         struct page *page;
  33         void *kaddr;
  34
  35         if (get_user_page_fast_only(addr, FOLL_WRITE, &page)) {
  36                 kaddr = page_address(page);
  37
  38                 /* align address to page boundary */
  39                 offset = addr & ~PAGE_MASK;
  40
  41                 memcpy(buf, kaddr + offset, nb);
  42                 put_page(page);
  43                 return 0;
  44         }
  45         return -EFAULT;
  46 }
  47
  48 static int read_user_stack_64(const unsigned long __user *ptr, unsigned long *ret)
  49 {
  50         return __read_user_stack(ptr, ret, sizeof(*ret));
  51 }
  52
  53 /*
  54  * 64-bit user processes use the same stack frame for RT and non-RT signals.
  55  */
  56 struct signal_frame_64 {
  57         char            dummy[__SIGNAL_FRAMESIZE];
  58         struct ucontext uc;
  59         unsigned long   unused[2];
  60         unsigned int    tramp[6];
  61         struct siginfo  *pinfo;
  62         void            *puc;
  63         struct siginfo  info;
  64         char            abigap[288];
  65 };
  66
  67 static int is_sigreturn_64_address(unsigned long nip, unsigned long fp)
  68 {
  69         if (nip == fp + offsetof(struct signal_frame_64, tramp))
  70                 return 1;
  71         if (current->mm->context.vdso &&
  72             nip == VDSO64_SYMBOL(current->mm->context.vdso, sigtramp_rt64))
  73                 return 1;
  74         return 0;
  75 }
  76
  77 /*
  78  * Do some sanity checking on the signal frame pointed to by sp.
  79  * We check the pinfo and puc pointers in the frame.
  80  */
  81 static int sane_signal_64_frame(unsigned long sp)
  82 {
  83         struct signal_frame_64 __user *sf;
  84         unsigned long pinfo, puc;
  85
  86         sf = (struct signal_frame_64 __user *) sp;
  87         if (read_user_stack_64((unsigned long __user *) &sf->pinfo, &pinfo) ||
  88             read_user_stack_64((unsigned long __user *) &sf->puc, &puc))
  89                 return 0;
  90         return pinfo == (unsigned long) &sf->info &&
  91                 puc == (unsigned long) &sf->uc;
  92 }
  93
  94 void perf_callchain_user_64(struct perf_callchain_entry_ctx *entry,
  95                             struct pt_regs *regs)
  96 {
  97         unsigned long sp, next_sp;
  98         unsigned long next_ip;
  99         unsigned long lr;
 100         long level = 0;
 101         struct signal_frame_64 __user *sigframe;
 102         unsigned long __user *fp, *uregs;
 103
 104         next_ip = perf_instruction_pointer(regs);
 105         lr = regs->link;
 106         sp = regs->gpr[1];
 107         perf_callchain_store(entry, next_ip);
 108
 109         while (entry->nr < entry->max_stack) {
 110                 fp = (unsigned long __user *) sp;
 111                 if (invalid_user_sp(sp) || read_user_stack_64(fp, &next_sp))
 112                         return;
 113                 if (level > 0 && read_user_stack_64(&fp[2], &next_ip))
 114                         return;
 115
 116                 /*
 117                  * Note: the next_sp - sp >= signal frame size check
 118                  * is true when next_sp < sp, which can happen when
 119                  * transitioning from an alternate signal stack to the
 120                  * normal stack.
 121                  */
 122                 if (next_sp - sp >= sizeof(struct signal_frame_64) &&
 123                     (is_sigreturn_64_address(next_ip, sp) ||
 124                      (level <= 1 && is_sigreturn_64_address(lr, sp))) &&
 125                     sane_signal_64_frame(sp)) {
 126                         /*
 127                          * This looks like an signal frame
 128                          */
 129                         sigframe = (struct signal_frame_64 __user *) sp;
 130                         uregs = sigframe->uc.uc_mcontext.gp_regs;
 131                         if (read_user_stack_64(&uregs[PT_NIP], &next_ip) ||
 132                             read_user_stack_64(&uregs[PT_LNK], &lr) ||
 133                             read_user_stack_64(&uregs[PT_R1], &sp))
 134                                 return;
 135                         level = 0;
 136                         perf_callchain_store_context(entry, PERF_CONTEXT_USER);
 137                         perf_callchain_store(entry, next_ip);
 138                         continue;
 139                 }
 140
 141                 if (level == 0)
 142                         next_ip = lr;
 143                 perf_callchain_store(entry, next_ip);
 144                 ++level;
 145                 sp = next_sp;
 146         }
 147 }