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 }
99
100 unsigned long perf_instruction_pointer(struct pt_regs *regs)
101 {
102 return instruction_pointer(regs);
103 }
104
105 unsigned long perf_misc_flags(struct pt_regs *regs)
106 {
107 int misc = 0;
108
109 if (user_mode(regs))
110 misc |= PERF_RECORD_MISC_USER;
111 else
112 misc |= PERF_RECORD_MISC_KERNEL;
113
114 return misc;
115 }
116
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.