1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 2022 Loongson Technology Corporation Limited
4 */
5
6#include <linux/init.h>
7#include <linux/ftrace.h>
8#include <linux/syscalls.h>
9#include <linux/uaccess.h>
10
11#include <asm/asm.h>
12#include <asm/asm-offsets.h>
13#include <asm/cacheflush.h>
14#include <asm/inst.h>
15#include <asm/loongarch.h>
16#include <asm/syscall.h>
17
18#include <asm-generic/sections.h>
19
20#ifdef CONFIG_FUNCTION_GRAPH_TRACER
21
22/*
23 * As `call _mcount` follows LoongArch psABI, ra-saved operation and
24 * stack operation can be found before this insn.
25 */
26
27static int ftrace_get_parent_ra_addr(unsigned long insn_addr, int *ra_off)
28{
29 int limit = 32;
30 union loongarch_instruction *insn;
31
32 insn = (union loongarch_instruction *)insn_addr;
33
34 do {
35 insn--;
36 limit--;
37
38 if (is_ra_save_ins(insn))
39 *ra_off = -((1 << 12) - insn->reg2i12_format.immediate);
40
41 } while (!is_stack_alloc_ins(insn) && limit);
42
43 if (!limit)
44 return -EINVAL;
45
46 return 0;
47}
48
49void prepare_ftrace_return(unsigned long self_addr,
50 unsigned long callsite_sp, unsigned long old)
51{
52 int ra_off;
53 unsigned long return_hooker = (unsigned long)&return_to_handler;
54
55 if (unlikely(ftrace_graph_is_dead()))
56 return;
57
58 if (unlikely(atomic_read(&current->tracing_graph_pause)))
59 return;
60
61 if (ftrace_get_parent_ra_addr(insn_addr: self_addr, ra_off: &ra_off))
62 goto out;
63
64 if (!function_graph_enter(ret: old, func: self_addr, fp: 0, NULL))
65 *(unsigned long *)(callsite_sp + ra_off) = return_hooker;
66
67 return;
68
69out:
70 ftrace_graph_stop();
71 WARN_ON(1);
72}
73#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
74

source code of linux/arch/loongarch/kernel/ftrace.c