1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*
3 * Copyright (C) 2013 Linaro Limited
4 * Author: AKASHI Takahiro <takahiro.akashi@linaro.org>
5 * Copyright (C) 2017 Andes Technology Corporation
6 */
7
8 #include <linux/ftrace.h>
9 #include <linux/uaccess.h>
10 #include <asm/cacheflush.h>
11
12 #ifdef CONFIG_DYNAMIC_FTRACE
ftrace_check_current_call(unsigned long hook_pos,unsigned int * expected)13 static int ftrace_check_current_call(unsigned long hook_pos,
14 unsigned int *expected)
15 {
16 unsigned int replaced[2];
17 unsigned int nops[2] = {NOP4, NOP4};
18
19 /* we expect nops at the hook position */
20 if (!expected)
21 expected = nops;
22
23 /*
24 * Read the text we want to modify;
25 * return must be -EFAULT on read error
26 */
27 if (probe_kernel_read(replaced, (void *)hook_pos, MCOUNT_INSN_SIZE))
28 return -EFAULT;
29
30 /*
31 * Make sure it is what we expect it to be;
32 * return must be -EINVAL on failed comparison
33 */
34 if (memcmp(expected, replaced, sizeof(replaced))) {
35 pr_err("%p: expected (%08x %08x) but got (%08x %08x)\n",
36 (void *)hook_pos, expected[0], expected[1], replaced[0],
37 replaced[1]);
38 return -EINVAL;
39 }
40
41 return 0;
42 }
43
__ftrace_modify_call(unsigned long hook_pos,unsigned long target,bool enable)44 static int __ftrace_modify_call(unsigned long hook_pos, unsigned long target,
45 bool enable)
46 {
47 unsigned int call[2];
48 unsigned int nops[2] = {NOP4, NOP4};
49 int ret = 0;
50
51 make_call(hook_pos, target, call);
52
53 /* replace the auipc-jalr pair at once */
54 ret = probe_kernel_write((void *)hook_pos, enable ? call : nops,
55 MCOUNT_INSN_SIZE);
56 /* return must be -EPERM on write error */
57 if (ret)
58 return -EPERM;
59
60 smp_mb();
61 flush_icache_range((void *)hook_pos, (void *)hook_pos + MCOUNT_INSN_SIZE);
62
63 return 0;
64 }
65
ftrace_make_call(struct dyn_ftrace * rec,unsigned long addr)66 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
67 {
68 int ret = ftrace_check_current_call(rec->ip, NULL);
69
70 if (ret)
71 return ret;
72
73 return __ftrace_modify_call(rec->ip, addr, true);
74 }
75
ftrace_make_nop(struct module * mod,struct dyn_ftrace * rec,unsigned long addr)76 int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
77 unsigned long addr)
78 {
79 unsigned int call[2];
80 int ret;
81
82 make_call(rec->ip, addr, call);
83 ret = ftrace_check_current_call(rec->ip, call);
84
85 if (ret)
86 return ret;
87
88 return __ftrace_modify_call(rec->ip, addr, false);
89 }
90
ftrace_update_ftrace_func(ftrace_func_t func)91 int ftrace_update_ftrace_func(ftrace_func_t func)
92 {
93 int ret = __ftrace_modify_call((unsigned long)&ftrace_call,
94 (unsigned long)func, true);
95 if (!ret) {
96 ret = __ftrace_modify_call((unsigned long)&ftrace_regs_call,
97 (unsigned long)func, true);
98 }
99
100 return ret;
101 }
102
ftrace_dyn_arch_init(void)103 int __init ftrace_dyn_arch_init(void)
104 {
105 return 0;
106 }
107 #endif
108
109 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
ftrace_modify_call(struct dyn_ftrace * rec,unsigned long old_addr,unsigned long addr)110 int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
111 unsigned long addr)
112 {
113 unsigned int call[2];
114 int ret;
115
116 make_call(rec->ip, old_addr, call);
117 ret = ftrace_check_current_call(rec->ip, call);
118
119 if (ret)
120 return ret;
121
122 return __ftrace_modify_call(rec->ip, addr, true);
123 }
124 #endif
125
126 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
127 /*
128 * Most of this function is copied from arm64.
129 */
prepare_ftrace_return(unsigned long * parent,unsigned long self_addr,unsigned long frame_pointer)130 void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
131 unsigned long frame_pointer)
132 {
133 unsigned long return_hooker = (unsigned long)&return_to_handler;
134 unsigned long old;
135
136 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
137 return;
138
139 /*
140 * We don't suffer access faults, so no extra fault-recovery assembly
141 * is needed here.
142 */
143 old = *parent;
144
145 if (!function_graph_enter(old, self_addr, frame_pointer, parent))
146 *parent = return_hooker;
147 }
148
149 #ifdef CONFIG_DYNAMIC_FTRACE
150 extern void ftrace_graph_call(void);
ftrace_enable_ftrace_graph_caller(void)151 int ftrace_enable_ftrace_graph_caller(void)
152 {
153 unsigned int call[2];
154 static int init_graph = 1;
155 int ret;
156
157 make_call(&ftrace_graph_call, &ftrace_stub, call);
158
159 /*
160 * When enabling graph tracer for the first time, ftrace_graph_call
161 * should contains a call to ftrace_stub. Once it has been disabled,
162 * the 8-bytes at the position becomes NOPs.
163 */
164 if (init_graph) {
165 ret = ftrace_check_current_call((unsigned long)&ftrace_graph_call,
166 call);
167 init_graph = 0;
168 } else {
169 ret = ftrace_check_current_call((unsigned long)&ftrace_graph_call,
170 NULL);
171 }
172
173 if (ret)
174 return ret;
175
176 return __ftrace_modify_call((unsigned long)&ftrace_graph_call,
177 (unsigned long)&prepare_ftrace_return, true);
178 }
179
ftrace_disable_ftrace_graph_caller(void)180 int ftrace_disable_ftrace_graph_caller(void)
181 {
182 unsigned int call[2];
183 int ret;
184
185 make_call(&ftrace_graph_call, &prepare_ftrace_return, call);
186
187 /*
188 * This is to make sure that ftrace_enable_ftrace_graph_caller
189 * did the right thing.
190 */
191 ret = ftrace_check_current_call((unsigned long)&ftrace_graph_call,
192 call);
193
194 if (ret)
195 return ret;
196
197 return __ftrace_modify_call((unsigned long)&ftrace_graph_call,
198 (unsigned long)&prepare_ftrace_return, false);
199 }
200 #endif /* CONFIG_DYNAMIC_FTRACE */
201 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
202