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(addr: (void *)frame->fp) || frame->fp & 0x3) |
22 | return -EPERM; |
23 | |
24 | *frame = *(struct stackframe *)frame->fp; |
25 | |
26 | if (__kernel_text_address(addr: frame->lr)) { |
27 | int graph = 0; |
28 | |
29 | frame->lr = ftrace_graph_ret_addr(NULL, idx: &graph, ret: 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(ctx: entry, ip: fr->lr); |
40 | } while (unwind_frame_kernel(frame: 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(to: &buftail, from: user_frame_tail, |
58 | n: 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(ctx: entry, ip: 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(ctx: entry, ip: 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, reg_lr: regs->lr); |
101 | |
102 | while (fp && !(fp & 0x3) && entry->nr < entry->max_stack) |
103 | fp = user_backtrace(entry, fp, reg_lr: 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: &fr, entry); |
114 | } |
115 | |