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
27 static 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
49 void 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(¤t->tracing_graph_pause)))
59 return;
60
61 if (ftrace_get_parent_ra_addr(self_addr, &ra_off))
62 goto out;
63
64 if (!function_graph_enter(old, self_addr, 0, NULL))
65 *(unsigned long *)(callsite_sp + ra_off) = return_hooker;
66
67 return;
68
69 out:
70 ftrace_graph_stop();
71 WARN_ON(1);
72 }
73 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
74
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