1 // SPDX-License-Identifier: GPL-2.0
2 /* Copyright (C) 2019 Hangzhou C-SKY Microsystems co.,ltd. */
4 #include <linux/perf_event.h>
5 #include <linux/uaccess.h>
14 * Get the return address for a single stackframe and return a pointer to the
17 static unsigned long user_backtrace(struct perf_callchain_entry_ctx *entry,
18 unsigned long fp, unsigned long reg_ra)
20 struct stackframe buftail;
22 unsigned long *user_frame_tail =
23 (unsigned long *)(fp - sizeof(struct stackframe));
25 /* Check accessibility of one struct frame_tail beyond */
26 if (!access_ok(user_frame_tail, sizeof(buftail)))
28 if (__copy_from_user_inatomic(&buftail, user_frame_tail,
39 perf_callchain_store(entry, ra);
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()
52 * How to trigger perf_callchain_[user/kernel] :
53 * $ perf record -e cpu-clock --call-graph fp ./program
54 * $ perf report --call-graph
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.
60 void perf_callchain_user(struct perf_callchain_entry_ctx *entry,
65 /* RISC-V does not support perf in guest mode. */
66 if (perf_guest_cbs && perf_guest_cbs->is_in_guest())
70 perf_callchain_store(entry, regs->sepc);
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);
77 bool fill_callchain(unsigned long pc, void *entry)
79 return perf_callchain_store(entry, pc);
82 void notrace walk_stackframe(struct task_struct *task,
83 struct pt_regs *regs, bool (*fn)(unsigned long, void *), void *arg);
84 void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,
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!");
93 walk_stackframe(NULL, regs, fill_callchain, entry);