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
unwind_frame_kernel(struct stackframe * frame)13 static int unwind_frame_kernel(struct stackframe *frame)
14 {
15 if (kstack_end((void *)frame->fp))
16 return -EPERM;
17 if (frame->fp & 0x3 || frame->fp < TASK_SIZE)
18 return -EPERM;
19
20 *frame = *(struct stackframe *)frame->fp;
21 if (__kernel_text_address(frame->lr)) {
22 int graph = 0;
23
24 frame->lr = ftrace_graph_ret_addr(NULL, &graph, frame->lr,
25 NULL);
26 }
27 return 0;
28 }
29
walk_stackframe(struct stackframe * fr,struct perf_callchain_entry_ctx * entry)30 static void notrace walk_stackframe(struct stackframe *fr,
31 struct perf_callchain_entry_ctx *entry)
32 {
33 do {
34 perf_callchain_store(entry, fr->lr);
35 } while (unwind_frame_kernel(fr) >= 0);
36 }
37
38 /*
39 * Get the return address for a single stackframe and return a pointer to the
40 * next frame tail.
41 */
user_backtrace(struct perf_callchain_entry_ctx * entry,unsigned long fp,unsigned long reg_lr)42 static unsigned long user_backtrace(struct perf_callchain_entry_ctx *entry,
43 unsigned long fp, unsigned long reg_lr)
44 {
45 struct stackframe buftail;
46 unsigned long lr = 0;
47 unsigned long *user_frame_tail = (unsigned long *)fp;
48
49 /* Check accessibility of one struct frame_tail beyond */
50 if (!access_ok(user_frame_tail, sizeof(buftail)))
51 return 0;
52 if (__copy_from_user_inatomic(&buftail, user_frame_tail,
53 sizeof(buftail)))
54 return 0;
55
56 if (reg_lr != 0)
57 lr = reg_lr;
58 else
59 lr = buftail.lr;
60
61 fp = buftail.fp;
62 perf_callchain_store(entry, lr);
63
64 return fp;
65 }
66
67 /*
68 * This will be called when the target is in user mode
69 * This function will only be called when we use
70 * "PERF_SAMPLE_CALLCHAIN" in
71 * kernel/events/core.c:perf_prepare_sample()
72 *
73 * How to trigger perf_callchain_[user/kernel] :
74 * $ perf record -e cpu-clock --call-graph fp ./program
75 * $ perf report --call-graph
76 *
77 * On C-SKY platform, the program being sampled and the C library
78 * need to be compiled with * -mbacktrace, otherwise the user
79 * stack will not contain function frame.
80 */
perf_callchain_user(struct perf_callchain_entry_ctx * entry,struct pt_regs * regs)81 void perf_callchain_user(struct perf_callchain_entry_ctx *entry,
82 struct pt_regs *regs)
83 {
84 unsigned long fp = 0;
85
86 /* C-SKY does not support virtualization. */
87 if (perf_guest_cbs && perf_guest_cbs->is_in_guest())
88 return;
89
90 fp = regs->regs[4];
91 perf_callchain_store(entry, regs->pc);
92
93 /*
94 * While backtrace from leaf function, lr is normally
95 * not saved inside frame on C-SKY, so get lr from pt_regs
96 * at the sample point. However, lr value can be incorrect if
97 * lr is used as temp register
98 */
99 fp = user_backtrace(entry, fp, regs->lr);
100
101 while (fp && !(fp & 0x3) && entry->nr < entry->max_stack)
102 fp = user_backtrace(entry, fp, 0);
103 }
104
perf_callchain_kernel(struct perf_callchain_entry_ctx * entry,struct pt_regs * regs)105 void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,
106 struct pt_regs *regs)
107 {
108 struct stackframe fr;
109
110 /* C-SKY does not support virtualization. */
111 if (perf_guest_cbs && perf_guest_cbs->is_in_guest()) {
112 pr_warn("C-SKY does not support perf in guest mode!");
113 return;
114 }
115
116 fr.fp = regs->regs[4];
117 fr.lr = regs->lr;
118 walk_stackframe(&fr, entry);
119 }
120
