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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 <linux/memory.h>
11#include <asm/cacheflush.h>
12#include <asm/patch.h>
13
14#ifdef CONFIG_DYNAMIC_FTRACE
15int ftrace_arch_code_modify_prepare(void) __acquires(&text_mutex)
16{
17 mutex_lock(&text_mutex);
18 return 0;
19}
20
21int ftrace_arch_code_modify_post_process(void) __releases(&text_mutex)
22{
23 mutex_unlock(&text_mutex);
24 return 0;
25}
26
27static int ftrace_check_current_call(unsigned long hook_pos,
28 unsigned int *expected)
29{
30 unsigned int replaced[2];
31 unsigned int nops[2] = {NOP4, NOP4};
32
33 /* we expect nops at the hook position */
34 if (!expected)
35 expected = nops;
36
37 /*
38 * Read the text we want to modify;
39 * return must be -EFAULT on read error
40 */
41 if (copy_from_kernel_nofault(replaced, (void *)hook_pos,
42 MCOUNT_INSN_SIZE))
43 return -EFAULT;
44
45 /*
46 * Make sure it is what we expect it to be;
47 * return must be -EINVAL on failed comparison
48 */
49 if (memcmp(expected, replaced, sizeof(replaced))) {
50 pr_err("%p: expected (%08x %08x) but got (%08x %08x)\n",
51 (void *)hook_pos, expected[0], expected[1], replaced[0],
52 replaced[1]);
53 return -EINVAL;
54 }
55
56 return 0;
57}
58
59static int __ftrace_modify_call(unsigned long hook_pos, unsigned long target,
60 bool enable)
61{
62 unsigned int call[2];
63 unsigned int nops[2] = {NOP4, NOP4};
64
65 make_call(hook_pos, target, call);
66
67 /* Replace the auipc-jalr pair at once. Return -EPERM on write error. */
68 if (patch_text_nosync
69 ((void *)hook_pos, enable ? call : nops, MCOUNT_INSN_SIZE))
70 return -EPERM;
71
72 return 0;
73}
74
75int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
76{
77 int ret = ftrace_check_current_call(rec->ip, NULL);
78
79 if (ret)
80 return ret;
81
82 return __ftrace_modify_call(rec->ip, addr, true);
83}
84
85int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
86 unsigned long addr)
87{
88 unsigned int call[2];
89 int ret;
90
91 make_call(rec->ip, addr, call);
92 ret = ftrace_check_current_call(rec->ip, call);
93
94 if (ret)
95 return ret;
96
97 return __ftrace_modify_call(rec->ip, addr, false);
98}
99
100
101/*
102 * This is called early on, and isn't wrapped by
103 * ftrace_arch_code_modify_{prepare,post_process}() and therefor doesn't hold
104 * text_mutex, which triggers a lockdep failure. SMP isn't running so we could
105 * just directly poke the text, but it's simpler to just take the lock
106 * ourselves.
107 */
108int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
109{
110 int out;
111
112 ftrace_arch_code_modify_prepare();
113 out = ftrace_make_nop(mod, rec, MCOUNT_ADDR);
114 ftrace_arch_code_modify_post_process();
115
116 return out;
117}
118
119int ftrace_update_ftrace_func(ftrace_func_t func)
120{
121 int ret = __ftrace_modify_call((unsigned long)&ftrace_call,
122 (unsigned long)func, true);
123 if (!ret) {
124 ret = __ftrace_modify_call((unsigned long)&ftrace_regs_call,
125 (unsigned long)func, true);
126 }
127
128 return ret;
129}
130
131int __init ftrace_dyn_arch_init(void)
132{
133 return 0;
134}
135#endif
136
137#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
138int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
139 unsigned long addr)
140{
141 unsigned int call[2];
142 int ret;
143
144 make_call(rec->ip, old_addr, call);
145 ret = ftrace_check_current_call(rec->ip, call);
146
147 if (ret)
148 return ret;
149
150 return __ftrace_modify_call(rec->ip, addr, true);
151}
152#endif
153
154#ifdef CONFIG_FUNCTION_GRAPH_TRACER
155/*
156 * Most of this function is copied from arm64.
157 */
158void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
159 unsigned long frame_pointer)
160{
161 unsigned long return_hooker = (unsigned long)&return_to_handler;
162 unsigned long old;
163
164 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
165 return;
166
167 /*
168 * We don't suffer access faults, so no extra fault-recovery assembly
169 * is needed here.
170 */
171 old = *parent;
172
173 if (!function_graph_enter(old, self_addr, frame_pointer, parent))
174 *parent = return_hooker;
175}
176
177#ifdef CONFIG_DYNAMIC_FTRACE
178extern void ftrace_graph_call(void);
179int ftrace_enable_ftrace_graph_caller(void)
180{
181 unsigned int call[2];
182 static int init_graph = 1;
183 int ret;
184
185 make_call(&ftrace_graph_call, &ftrace_stub, call);
186
187 /*
188 * When enabling graph tracer for the first time, ftrace_graph_call
189 * should contains a call to ftrace_stub. Once it has been disabled,
190 * the 8-bytes at the position becomes NOPs.
191 */
192 if (init_graph) {
193 ret = ftrace_check_current_call((unsigned long)&ftrace_graph_call,
194 call);
195 init_graph = 0;
196 } else {
197 ret = ftrace_check_current_call((unsigned long)&ftrace_graph_call,
198 NULL);
199 }
200
201 if (ret)
202 return ret;
203
204 return __ftrace_modify_call((unsigned long)&ftrace_graph_call,
205 (unsigned long)&prepare_ftrace_return, true);
206}
207
208int ftrace_disable_ftrace_graph_caller(void)
209{
210 unsigned int call[2];
211 int ret;
212
213 make_call(&ftrace_graph_call, &prepare_ftrace_return, call);
214
215 /*
216 * This is to make sure that ftrace_enable_ftrace_graph_caller
217 * did the right thing.
218 */
219 ret = ftrace_check_current_call((unsigned long)&ftrace_graph_call,
220 call);
221
222 if (ret)
223 return ret;
224
225 return __ftrace_modify_call((unsigned long)&ftrace_graph_call,
226 (unsigned long)&prepare_ftrace_return, false);
227}
228#endif /* CONFIG_DYNAMIC_FTRACE */
229#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
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
13static 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 get (%08x %08x)",
36 (void *)hook_pos, expected[0], expected[1], replaced[0],
37 replaced[1]);
38 return -EINVAL;
39 }
40
41 return 0;
42}
43
44static 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
66int 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
76int 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
91int 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
103int __init ftrace_dyn_arch_init(void)
104{
105 return 0;
106}
107#endif
108
109#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
110int 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 */
130void 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 struct ftrace_graph_ent trace;
136 int err;
137
138 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
139 return;
140
141 /*
142 * We don't suffer access faults, so no extra fault-recovery assembly
143 * is needed here.
144 */
145 old = *parent;
146
147 trace.func = self_addr;
148 trace.depth = current->curr_ret_stack + 1;
149
150 if (!ftrace_graph_entry(&trace))
151 return;
152
153 err = ftrace_push_return_trace(old, self_addr, &trace.depth,
154 frame_pointer, parent);
155 if (err == -EBUSY)
156 return;
157 *parent = return_hooker;
158}
159
160#ifdef CONFIG_DYNAMIC_FTRACE
161extern void ftrace_graph_call(void);
162int ftrace_enable_ftrace_graph_caller(void)
163{
164 unsigned int call[2];
165 static int init_graph = 1;
166 int ret;
167
168 make_call(&ftrace_graph_call, &ftrace_stub, call);
169
170 /*
171 * When enabling graph tracer for the first time, ftrace_graph_call
172 * should contains a call to ftrace_stub. Once it has been disabled,
173 * the 8-bytes at the position becomes NOPs.
174 */
175 if (init_graph) {
176 ret = ftrace_check_current_call((unsigned long)&ftrace_graph_call,
177 call);
178 init_graph = 0;
179 } else {
180 ret = ftrace_check_current_call((unsigned long)&ftrace_graph_call,
181 NULL);
182 }
183
184 if (ret)
185 return ret;
186
187 return __ftrace_modify_call((unsigned long)&ftrace_graph_call,
188 (unsigned long)&prepare_ftrace_return, true);
189}
190
191int ftrace_disable_ftrace_graph_caller(void)
192{
193 unsigned int call[2];
194 int ret;
195
196 make_call(&ftrace_graph_call, &prepare_ftrace_return, call);
197
198 /*
199 * This is to make sure that ftrace_enable_ftrace_graph_caller
200 * did the right thing.
201 */
202 ret = ftrace_check_current_call((unsigned long)&ftrace_graph_call,
203 call);
204
205 if (ret)
206 return ret;
207
208 return __ftrace_modify_call((unsigned long)&ftrace_graph_call,
209 (unsigned long)&prepare_ftrace_return, false);
210}
211#endif /* CONFIG_DYNAMIC_FTRACE */
212#endif /* CONFIG_FUNCTION_GRAPH_TRACER */