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 *
user_backtrace(struct frame_tail __user * tail,struct perf_callchain_entry_ctx * entry)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
perf_callchain_user(struct perf_callchain_entry_ctx * entry,struct pt_regs * regs)63 perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
64 {
65 struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
66 struct frame_tail __user *tail;
67
68 if (guest_cbs && guest_cbs->is_in_guest()) {
69 /* We don't support guest os callchain now */
70 return;
71 }
72
73 perf_callchain_store(entry, regs->ARM_pc);
74
75 if (!current->mm)
76 return;
77
78 tail = (struct frame_tail __user *)regs->ARM_fp - 1;
79
80 while ((entry->nr < entry->max_stack) &&
81 tail && !((unsigned long)tail & 0x3))
82 tail = user_backtrace(tail, entry);
83 }
84
85 /*
86 * Gets called by walk_stackframe() for every stackframe. This will be called
87 * whist unwinding the stackframe and is like a subroutine return so we use
88 * the PC.
89 */
90 static int
callchain_trace(struct stackframe * fr,void * data)91 callchain_trace(struct stackframe *fr,
92 void *data)
93 {
94 struct perf_callchain_entry_ctx *entry = data;
95 perf_callchain_store(entry, fr->pc);
96 return 0;
97 }
98
99 void
perf_callchain_kernel(struct perf_callchain_entry_ctx * entry,struct pt_regs * regs)100 perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
101 {
102 struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
103 struct stackframe fr;
104
105 if (guest_cbs && guest_cbs->is_in_guest()) {
106 /* We don't support guest os callchain now */
107 return;
108 }
109
110 arm_get_current_stackframe(regs, &fr);
111 walk_stackframe(&fr, callchain_trace, entry);
112 }
113
perf_instruction_pointer(struct pt_regs * regs)114 unsigned long perf_instruction_pointer(struct pt_regs *regs)
115 {
116 struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
117
118 if (guest_cbs && guest_cbs->is_in_guest())
119 return guest_cbs->get_guest_ip();
120
121 return instruction_pointer(regs);
122 }
123
perf_misc_flags(struct pt_regs * regs)124 unsigned long perf_misc_flags(struct pt_regs *regs)
125 {
126 struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
127 int misc = 0;
128
129 if (guest_cbs && guest_cbs->is_in_guest()) {
130 if (guest_cbs->is_user_mode())
131 misc |= PERF_RECORD_MISC_GUEST_USER;
132 else
133 misc |= PERF_RECORD_MISC_GUEST_KERNEL;
134 } else {
135 if (user_mode(regs))
136 misc |= PERF_RECORD_MISC_USER;
137 else
138 misc |= PERF_RECORD_MISC_KERNEL;
139 }
140
141 return misc;
142 }
143