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 */
23struct 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 */
33static struct frame_tail __user *
34user_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
62void
63perf_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 */
84static bool
85callchain_trace(void *data, unsigned long pc)
86{
87	struct perf_callchain_entry_ctx *entry = data;
88	perf_callchain_store(entry, pc);
89	return true;
90}
91
92void
93perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
94{
95	struct stackframe fr;
96
97	arm_get_current_stackframe(regs, &fr);
98	walk_stackframe(&fr, callchain_trace, entry);
99}
100
101unsigned long perf_instruction_pointer(struct pt_regs *regs)
102{
103	return instruction_pointer(regs);
104}
105
106unsigned long perf_misc_flags(struct pt_regs *regs)
107{
108	int misc = 0;
109
110	if (user_mode(regs))
111		misc |= PERF_RECORD_MISC_USER;
112	else
113		misc |= PERF_RECORD_MISC_KERNEL;
114
115	return misc;
116}
117