root/arch/arm/kernel/perf_callchain.c

DEFINITIONS

1. user_backtrace
2. perf_callchain_user
3. callchain_trace
4. perf_callchain_kernel
5. perf_instruction_pointer
6. perf_misc_flags

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * ARM callchain support
   4  *
   5  * Copyright (C) 2009 picoChip Designs, Ltd., Jamie Iles
   6  * Copyright (C) 2010 ARM Ltd., Will Deacon <will.deacon@arm.com>
   7  *
   8  * This code is based on the ARM OProfile backtrace code.
   9  */
  10 #include <linux/perf_event.h>
  11 #include <linux/uaccess.h>
  12 
  13 #include <asm/stacktrace.h>
  14 
  15 /*
  16  * The registers we're interested in are at the end of the variable
  17  * length saved register structure. The fp points at the end of this
  18  * structure so the address of this struct is:
  19  * (struct frame_tail *)(xxx->fp)-1
  20  *
  21  * This code has been adapted from the ARM OProfile support.
  22  */
  23 struct frame_tail {
  24         struct frame_tail __user *fp;
  25         unsigned long sp;
  26         unsigned long lr;
  27 } __attribute__((packed));
  28 
  29 /*
  30  * Get the return address for a single stackframe and return a pointer to the
  31  * next frame tail.
  32  */
  33 static struct frame_tail __user *
  34 user_backtrace(struct frame_tail __user *tail,
  35                struct perf_callchain_entry_ctx *entry)
  36 {
  37         struct frame_tail buftail;
  38         unsigned long err;
  39 
  40         if (!access_ok(tail, sizeof(buftail)))
  41                 return NULL;
  42 
  43         pagefault_disable();
  44         err = __copy_from_user_inatomic(&buftail, tail, sizeof(buftail));
  45         pagefault_enable();
  46 
  47         if (err)
  48                 return NULL;
  49 
  50         perf_callchain_store(entry, buftail.lr);
  51 
  52         /*
  53          * Frame pointers should strictly progress back up the stack
  54          * (towards higher addresses).
  55          */
  56         if (tail + 1 >= buftail.fp)
  57                 return NULL;
  58 
  59         return buftail.fp - 1;
  60 }
  61 
  62 void
  63 perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
  64 {
  65         struct frame_tail __user *tail;
  66 
  67         if (perf_guest_cbs && perf_guest_cbs->is_in_guest()) {
  68                 /* We don't support guest os callchain now */
  69                 return;
  70         }
  71 
  72         perf_callchain_store(entry, regs->ARM_pc);
  73 
  74         if (!current->mm)
  75                 return;
  76 
  77         tail = (struct frame_tail __user *)regs->ARM_fp - 1;
  78 
  79         while ((entry->nr < entry->max_stack) &&
  80                tail && !((unsigned long)tail & 0x3))
  81                 tail = user_backtrace(tail, entry);
  82 }
  83 
  84 /*
  85  * Gets called by walk_stackframe() for every stackframe. This will be called
  86  * whist unwinding the stackframe and is like a subroutine return so we use
  87  * the PC.
  88  */
  89 static int
  90 callchain_trace(struct stackframe *fr,
  91                 void *data)
  92 {
  93         struct perf_callchain_entry_ctx *entry = data;
  94         perf_callchain_store(entry, fr->pc);
  95         return 0;
  96 }
  97 
  98 void
  99 perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
 100 {
 101         struct stackframe fr;
 102 
 103         if (perf_guest_cbs && perf_guest_cbs->is_in_guest()) {
 104                 /* We don't support guest os callchain now */
 105                 return;
 106         }
 107 
 108         arm_get_current_stackframe(regs, &fr);
 109         walk_stackframe(&fr, callchain_trace, entry);
 110 }
 111 
 112 unsigned long perf_instruction_pointer(struct pt_regs *regs)
 113 {
 114         if (perf_guest_cbs && perf_guest_cbs->is_in_guest())
 115                 return perf_guest_cbs->get_guest_ip();
 116 
 117         return instruction_pointer(regs);
 118 }
 119 
 120 unsigned long perf_misc_flags(struct pt_regs *regs)
 121 {
 122         int misc = 0;
 123 
 124         if (perf_guest_cbs && perf_guest_cbs->is_in_guest()) {
 125                 if (perf_guest_cbs->is_user_mode())
 126                         misc |= PERF_RECORD_MISC_GUEST_USER;
 127                 else
 128                         misc |= PERF_RECORD_MISC_GUEST_KERNEL;
 129         } else {
 130                 if (user_mode(regs))
 131                         misc |= PERF_RECORD_MISC_USER;
 132                 else
 133                         misc |= PERF_RECORD_MISC_KERNEL;
 134         }
 135 
 136         return misc;
 137 }