arch/arm/kernel/perf_callchain.c

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