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 ra;
11 };
12
13 /*
14 * Get the return address for a single stackframe and return a pointer to the
15 * next frame tail.
16 */
user_backtrace(struct perf_callchain_entry_ctx * entry,unsigned long fp,unsigned long reg_ra)17 static unsigned long user_backtrace(struct perf_callchain_entry_ctx *entry,
18 unsigned long fp, unsigned long reg_ra)
19 {
20 struct stackframe buftail;
21 unsigned long ra = 0;
22 unsigned long *user_frame_tail =
23 (unsigned long *)(fp - sizeof(struct stackframe));
24
25 /* Check accessibility of one struct frame_tail beyond */
26 if (!access_ok(user_frame_tail, sizeof(buftail)))
27 return 0;
28 if (__copy_from_user_inatomic(&buftail, user_frame_tail,
29 sizeof(buftail)))
30 return 0;
31
32 if (reg_ra != 0)
33 ra = reg_ra;
34 else
35 ra = buftail.ra;
36
37 fp = buftail.fp;
38 if (ra != 0)
39 perf_callchain_store(entry, ra);
40 else
41 return 0;
42
43 return fp;
44 }
45
46 /*
47 * This will be called when the target is in user mode
48 * This function will only be called when we use
49 * "PERF_SAMPLE_CALLCHAIN" in
50 * kernel/events/core.c:perf_prepare_sample()
51 *
52 * How to trigger perf_callchain_[user/kernel] :
53 * $ perf record -e cpu-clock --call-graph fp ./program
54 * $ perf report --call-graph
55 *
56 * On RISC-V platform, the program being sampled and the C library
57 * need to be compiled with -fno-omit-frame-pointer, otherwise
58 * the user stack will not contain function frame.
59 */
perf_callchain_user(struct perf_callchain_entry_ctx * entry,struct pt_regs * regs)60 void perf_callchain_user(struct perf_callchain_entry_ctx *entry,
61 struct pt_regs *regs)
62 {
63 unsigned long fp = 0;
64
65 /* RISC-V does not support perf in guest mode. */
66 if (perf_guest_cbs && perf_guest_cbs->is_in_guest())
67 return;
68
69 fp = regs->s0;
70 perf_callchain_store(entry, regs->sepc);
71
72 fp = user_backtrace(entry, fp, regs->ra);
73 while (fp && !(fp & 0x3) && entry->nr < entry->max_stack)
74 fp = user_backtrace(entry, fp, 0);
75 }
76
fill_callchain(unsigned long pc,void * entry)77 bool fill_callchain(unsigned long pc, void *entry)
78 {
79 return perf_callchain_store(entry, pc);
80 }
81
82 void notrace walk_stackframe(struct task_struct *task,
83 struct pt_regs *regs, bool (*fn)(unsigned long, void *), void *arg);
perf_callchain_kernel(struct perf_callchain_entry_ctx * entry,struct pt_regs * regs)84 void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,
85 struct pt_regs *regs)
86 {
87 /* RISC-V does not support perf in guest mode. */
88 if (perf_guest_cbs && perf_guest_cbs->is_in_guest()) {
89 pr_warn("RISC-V does not support perf in guest mode!");
90 return;
91 }
92
93 walk_stackframe(NULL, regs, fill_callchain, entry);
94 }
95
