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 #include <asm/stacktrace.h>
8
9 /*
10 * Get the return address for a single stackframe and return a pointer to the
11 * next frame tail.
12 */
13 static unsigned long user_backtrace(struct perf_callchain_entry_ctx *entry,
14 unsigned long fp, unsigned long reg_ra)
15 {
16 struct stackframe buftail;
17 unsigned long ra = 0;
18 unsigned long __user *user_frame_tail =
19 (unsigned long __user *)(fp - sizeof(struct stackframe));
20
21 /* Check accessibility of one struct frame_tail beyond */
22 if (!access_ok(user_frame_tail, sizeof(buftail)))
23 return 0;
24 if (__copy_from_user_inatomic(&buftail, user_frame_tail,
25 sizeof(buftail)))
26 return 0;
27
28 if (reg_ra != 0)
29 ra = reg_ra;
30 else
31 ra = buftail.ra;
32
33 fp = buftail.fp;
34 if (ra != 0)
35 perf_callchain_store(entry, ra);
36 else
37 return 0;
38
39 return fp;
40 }
41
42 /*
43 * This will be called when the target is in user mode
44 * This function will only be called when we use
45 * "PERF_SAMPLE_CALLCHAIN" in
46 * kernel/events/core.c:perf_prepare_sample()
47 *
48 * How to trigger perf_callchain_[user/kernel] :
49 * $ perf record -e cpu-clock --call-graph fp ./program
50 * $ perf report --call-graph
51 *
52 * On RISC-V platform, the program being sampled and the C library
53 * need to be compiled with -fno-omit-frame-pointer, otherwise
54 * the user stack will not contain function frame.
55 */
56 void perf_callchain_user(struct perf_callchain_entry_ctx *entry,
57 struct pt_regs *regs)
58 {
59 unsigned long fp = 0;
60
61 fp = regs->s0;
62 perf_callchain_store(entry, regs->epc);
63
64 fp = user_backtrace(entry, fp, regs->ra);
65 while (fp && !(fp & 0x7) && entry->nr < entry->max_stack)
66 fp = user_backtrace(entry, fp, 0);
67 }
68
69 static bool fill_callchain(void *entry, unsigned long pc)
70 {
71 return perf_callchain_store(entry, pc) == 0;
72 }
73
74 void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,
75 struct pt_regs *regs)
76 {
77 walk_stackframe(NULL, regs, fill_callchain, entry);
78 }
79
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