1 // SPDX-License-Identifier: GPL-2.0
2 // Copyright (C) 2019 Hangzhou C-SKY Microsystems co.,ltd.
3
4 #include <linux/perf_event.h>
5 #include <linux/uaccess.h>
6
7 /* Kernel callchain */
8 struct stackframe {
9 unsigned long fp;
10 unsigned long lr;
11 };
12
13 static int unwind_frame_kernel(struct stackframe *frame)
14 {
15 unsigned long low = (unsigned long)task_stack_page(current);
16 unsigned long high = low + THREAD_SIZE;
17
18 if (unlikely(frame->fp < low || frame->fp > high))
19 return -EPERM;
20
21 if (kstack_end((void *)frame->fp) || frame->fp & 0x3)
22 return -EPERM;
23
24 *frame = *(struct stackframe *)frame->fp;
25
26 if (__kernel_text_address(frame->lr)) {
27 int graph = 0;
28
29 frame->lr = ftrace_graph_ret_addr(NULL, &graph, frame->lr,
30 NULL);
31 }
32 return 0;
33 }
34
35 static void notrace walk_stackframe(struct stackframe *fr,
36 struct perf_callchain_entry_ctx *entry)
37 {
38 do {
39 perf_callchain_store(entry, fr->lr);
40 } while (unwind_frame_kernel(fr) >= 0);
41 }
42
43 /*
44 * Get the return address for a single stackframe and return a pointer to the
45 * next frame tail.
46 */
47 static unsigned long user_backtrace(struct perf_callchain_entry_ctx *entry,
48 unsigned long fp, unsigned long reg_lr)
49 {
50 struct stackframe buftail;
51 unsigned long lr = 0;
52 unsigned long __user *user_frame_tail = (unsigned long __user *)fp;
53
54 /* Check accessibility of one struct frame_tail beyond */
55 if (!access_ok(user_frame_tail, sizeof(buftail)))
56 return 0;
57 if (__copy_from_user_inatomic(&buftail, user_frame_tail,
58 sizeof(buftail)))
59 return 0;
60
61 if (reg_lr != 0)
62 lr = reg_lr;
63 else
64 lr = buftail.lr;
65
66 fp = buftail.fp;
67 perf_callchain_store(entry, lr);
68
69 return fp;
70 }
71
72 /*
73 * This will be called when the target is in user mode
74 * This function will only be called when we use
75 * "PERF_SAMPLE_CALLCHAIN" in
76 * kernel/events/core.c:perf_prepare_sample()
77 *
78 * How to trigger perf_callchain_[user/kernel] :
79 * $ perf record -e cpu-clock --call-graph fp ./program
80 * $ perf report --call-graph
81 *
82 * On C-SKY platform, the program being sampled and the C library
83 * need to be compiled with * -mbacktrace, otherwise the user
84 * stack will not contain function frame.
85 */
86 void perf_callchain_user(struct perf_callchain_entry_ctx *entry,
87 struct pt_regs *regs)
88 {
89 unsigned long fp = 0;
90
91 fp = regs->regs[4];
92 perf_callchain_store(entry, regs->pc);
93
94 /*
95 * While backtrace from leaf function, lr is normally
96 * not saved inside frame on C-SKY, so get lr from pt_regs
97 * at the sample point. However, lr value can be incorrect if
98 * lr is used as temp register
99 */
100 fp = user_backtrace(entry, fp, regs->lr);
101
102 while (fp && !(fp & 0x3) && entry->nr < entry->max_stack)
103 fp = user_backtrace(entry, fp, 0);
104 }
105
106 void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,
107 struct pt_regs *regs)
108 {
109 struct stackframe fr;
110
111 fr.fp = regs->regs[4];
112 fr.lr = regs->lr;
113 walk_stackframe(&fr, entry);
114 }
115
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