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 */
 22struct 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 */
 32static struct frame_tail __user *
 33user_backtrace(struct frame_tail __user *tail,
 34	       struct perf_callchain_entry *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
 61void
 62perf_callchain_user(struct perf_callchain_entry *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 < PERF_MAX_STACK_DEPTH) &&
 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 */
 88static int
 89callchain_trace(struct stackframe *fr,
 90		void *data)
 91{
 92	struct perf_callchain_entry *entry = data;
 93	perf_callchain_store(entry, fr->pc);
 94	return 0;
 95}
 96
 97void
 98perf_callchain_kernel(struct perf_callchain_entry *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
111unsigned 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
119unsigned 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}