arch/arm/kernel/perf_callchain.c

   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         perf_callchain_store(entry, regs->ARM_pc);
  68
  69         if (!current->mm)
  70                 return;
  71
  72         tail = (struct frame_tail __user *)regs->ARM_fp - 1;
  73
  74         while ((entry->nr < entry->max_stack) &&
  75                tail && !((unsigned long)tail & 0x3))
  76                 tail = user_backtrace(tail, entry);
  77 }
  78
  79 /*
  80  * Gets called by walk_stackframe() for every stackframe. This will be called
  81  * whist unwinding the stackframe and is like a subroutine return so we use
  82  * the PC.
  83  */
  84 static bool
  85 callchain_trace(void *data, unsigned long pc)
  86 {
  87         struct perf_callchain_entry_ctx *entry = data;
  88         return perf_callchain_store(entry, pc) == 0;
  89 }
  90
  91 void
  92 perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
  93 {
  94         struct stackframe fr;
  95
  96         arm_get_current_stackframe(regs, &fr);
  97         walk_stackframe(&fr, callchain_trace, entry);
  98 }