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cfa4d93b MH |
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 | { | |
229a0dde MH |
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)) | |
cfa4d93b | 19 | return -EPERM; |
229a0dde MH |
20 | |
21 | if (kstack_end((void *)frame->fp) || frame->fp & 0x3) | |
cfa4d93b MH |
22 | return -EPERM; |
23 | ||
24 | *frame = *(struct stackframe *)frame->fp; | |
229a0dde | 25 | |
cfa4d93b MH |
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_frame_tail = (unsigned long *)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 | /* C-SKY does not support virtualization. */ | |
92 | if (perf_guest_cbs && perf_guest_cbs->is_in_guest()) | |
93 | return; | |
94 | ||
95 | fp = regs->regs[4]; | |
96 | perf_callchain_store(entry, regs->pc); | |
97 | ||
98 | /* | |
99 | * While backtrace from leaf function, lr is normally | |
100 | * not saved inside frame on C-SKY, so get lr from pt_regs | |
101 | * at the sample point. However, lr value can be incorrect if | |
102 | * lr is used as temp register | |
103 | */ | |
104 | fp = user_backtrace(entry, fp, regs->lr); | |
105 | ||
106 | while (fp && !(fp & 0x3) && entry->nr < entry->max_stack) | |
107 | fp = user_backtrace(entry, fp, 0); | |
108 | } | |
109 | ||
110 | void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, | |
111 | struct pt_regs *regs) | |
112 | { | |
113 | struct stackframe fr; | |
114 | ||
115 | /* C-SKY does not support virtualization. */ | |
116 | if (perf_guest_cbs && perf_guest_cbs->is_in_guest()) { | |
117 | pr_warn("C-SKY does not support perf in guest mode!"); | |
118 | return; | |
119 | } | |
120 | ||
121 | fr.fp = regs->regs[4]; | |
122 | fr.lr = regs->lr; | |
123 | walk_stackframe(&fr, entry); | |
124 | } |