1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/spinlock.h>
3 #include <linux/hardirq.h>
4 #include <linux/ftrace.h>
5 #include <linux/percpu.h>
6 #include <linux/init.h>
7 #include <linux/list.h>
8 #include <trace/syscall.h>
9
10 #include <asm/ftrace.h>
11
12 #ifdef CONFIG_DYNAMIC_FTRACE
13 static const u32 ftrace_nop = 0x01000000;
14
15 static u32 ftrace_call_replace(unsigned long ip, unsigned long addr)
16 {
17 u32 call;
18 s32 off;
19
20 off = ((s32)addr - (s32)ip);
21 call = 0x40000000 | ((u32)off >> 2);
22
23 return call;
24 }
25
26 static int ftrace_modify_code(unsigned long ip, u32 old, u32 new)
27 {
28 u32 replaced;
29 int faulted;
30
31 __asm__ __volatile__(
32 "1: cas [%[ip]], %[old], %[new]\n"
33 " flush %[ip]\n"
34 " mov 0, %[faulted]\n"
35 "2:\n"
36 " .section .fixup,#alloc,#execinstr\n"
37 " .align 4\n"
38 "3: sethi %%hi(2b), %[faulted]\n"
39 " jmpl %[faulted] + %%lo(2b), %%g0\n"
40 " mov 1, %[faulted]\n"
41 " .previous\n"
42 " .section __ex_table,\"a\"\n"
43 " .align 4\n"
44 " .word 1b, 3b\n"
45 " .previous\n"
46 : "=r" (replaced), [faulted] "=r" (faulted)
47 : [new] "" (new), [old] "r" (old), [ip] "r" (ip)
48 : "memory");
49
50 if (replaced != old && replaced != new)
51 faulted = 2;
52
53 return faulted;
54 }
55
56 int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr)
57 {
58 unsigned long ip = rec->ip;
59 u32 old, new;
60
61 old = ftrace_call_replace(ip, addr);
62 new = ftrace_nop;
63 return ftrace_modify_code(ip, old, new);
64 }
65
66 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
67 {
68 unsigned long ip = rec->ip;
69 u32 old, new;
70
71 old = ftrace_nop;
72 new = ftrace_call_replace(ip, addr);
73 return ftrace_modify_code(ip, old, new);
74 }
75
76 int ftrace_update_ftrace_func(ftrace_func_t func)
77 {
78 unsigned long ip = (unsigned long)(&ftrace_call);
79 u32 old, new;
80
81 old = *(u32 *) &ftrace_call;
82 new = ftrace_call_replace(ip, (unsigned long)func);
83 return ftrace_modify_code(ip, old, new);
84 }
85 #endif
86
87 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
88
89 #ifdef CONFIG_DYNAMIC_FTRACE
90 extern void ftrace_graph_call(void);
91
92 int ftrace_enable_ftrace_graph_caller(void)
93 {
94 unsigned long ip = (unsigned long)(&ftrace_graph_call);
95 u32 old, new;
96
97 old = *(u32 *) &ftrace_graph_call;
98 new = ftrace_call_replace(ip, (unsigned long) &ftrace_graph_caller);
99 return ftrace_modify_code(ip, old, new);
100 }
101
102 int ftrace_disable_ftrace_graph_caller(void)
103 {
104 unsigned long ip = (unsigned long)(&ftrace_graph_call);
105 u32 old, new;
106
107 old = *(u32 *) &ftrace_graph_call;
108 new = ftrace_call_replace(ip, (unsigned long) &ftrace_stub);
109
110 return ftrace_modify_code(ip, old, new);
111 }
112
113 #endif /* !CONFIG_DYNAMIC_FTRACE */
114
115 /*
116 * Hook the return address and push it in the stack of return addrs
117 * in current thread info.
118 */
119 unsigned long prepare_ftrace_return(unsigned long parent,
120 unsigned long self_addr,
121 unsigned long frame_pointer)
122 {
123 unsigned long return_hooker = (unsigned long) &return_to_handler;
124
125 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
126 return parent + 8UL;
127
128 if (function_graph_enter(parent, self_addr, frame_pointer, NULL))
129 return parent + 8UL;
130
131 return return_hooker;
132 }
133 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
134
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