1 // SPDX-License-Identifier: GPL-2.0
2 // Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd.
3
4 #include <linux/ftrace.h>
5 #include <linux/uaccess.h>
6 #include <linux/stop_machine.h>
7 #include <asm/cacheflush.h>
8
9 #ifdef CONFIG_DYNAMIC_FTRACE
10
11 #define NOP 0x4000
12 #define NOP32_HI 0xc400
13 #define NOP32_LO 0x4820
14 #define PUSH_LR 0x14d0
15 #define MOVIH_LINK 0xea3a
16 #define ORI_LINK 0xef5a
17 #define JSR_LINK 0xe8fa
18 #define BSR_LINK 0xe000
19
20 /*
21 * Gcc-csky with -pg will insert stub in function prologue:
22 * push lr
23 * jbsr _mcount
24 * nop32
25 * nop32
26 *
27 * If the (callee - current_pc) is less then 64MB, we'll use bsr:
28 * push lr
29 * bsr _mcount
30 * nop32
31 * nop32
32 * else we'll use (movih + ori + jsr):
33 * push lr
34 * movih r26, ...
35 * ori r26, ...
36 * jsr r26
37 *
38 * (r26 is our reserved link-reg)
39 *
40 */
41 static inline void make_jbsr(unsigned long callee, unsigned long pc,
42 uint16_t *call, bool nolr)
43 {
44 long offset;
45
46 call[0] = nolr ? NOP : PUSH_LR;
47
48 offset = (long) callee - (long) pc;
49
50 if (unlikely(offset < -67108864 || offset > 67108864)) {
51 call[1] = MOVIH_LINK;
52 call[2] = callee >> 16;
53 call[3] = ORI_LINK;
54 call[4] = callee & 0xffff;
55 call[5] = JSR_LINK;
56 call[6] = 0;
57 } else {
58 offset = offset >> 1;
59
60 call[1] = BSR_LINK |
61 ((uint16_t)((unsigned long) offset >> 16) & 0x3ff);
62 call[2] = (uint16_t)((unsigned long) offset & 0xffff);
63 call[3] = call[5] = NOP32_HI;
64 call[4] = call[6] = NOP32_LO;
65 }
66 }
67
68 static uint16_t nops[7] = {NOP, NOP32_HI, NOP32_LO, NOP32_HI, NOP32_LO,
69 NOP32_HI, NOP32_LO};
70 static int ftrace_check_current_nop(unsigned long hook)
71 {
72 uint16_t olds[7];
73 unsigned long hook_pos = hook - 2;
74
75 if (copy_from_kernel_nofault((void *)olds, (void *)hook_pos,
76 sizeof(nops)))
77 return -EFAULT;
78
79 if (memcmp((void *)nops, (void *)olds, sizeof(nops))) {
80 pr_err("%p: nop but get (%04x %04x %04x %04x %04x %04x %04x)\n",
81 (void *)hook_pos,
82 olds[0], olds[1], olds[2], olds[3], olds[4], olds[5],
83 olds[6]);
84
85 return -EINVAL;
86 }
87
88 return 0;
89 }
90
91 static int ftrace_modify_code(unsigned long hook, unsigned long target,
92 bool enable, bool nolr)
93 {
94 uint16_t call[7];
95
96 unsigned long hook_pos = hook - 2;
97 int ret = 0;
98
99 make_jbsr(target, hook, call, nolr);
100
101 ret = copy_to_kernel_nofault((void *)hook_pos, enable ? call : nops,
102 sizeof(nops));
103 if (ret)
104 return -EPERM;
105
106 flush_icache_range(hook_pos, hook_pos + MCOUNT_INSN_SIZE);
107
108 return 0;
109 }
110
111 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
112 {
113 int ret = ftrace_check_current_nop(rec->ip);
114
115 if (ret)
116 return ret;
117
118 return ftrace_modify_code(rec->ip, addr, true, false);
119 }
120
121 int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
122 unsigned long addr)
123 {
124 return ftrace_modify_code(rec->ip, addr, false, false);
125 }
126
127 int ftrace_update_ftrace_func(ftrace_func_t func)
128 {
129 int ret = ftrace_modify_code((unsigned long)&ftrace_call,
130 (unsigned long)func, true, true);
131 if (!ret)
132 ret = ftrace_modify_code((unsigned long)&ftrace_regs_call,
133 (unsigned long)func, true, true);
134 return ret;
135 }
136 #endif /* CONFIG_DYNAMIC_FTRACE */
137
138 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
139 int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
140 unsigned long addr)
141 {
142 return ftrace_modify_code(rec->ip, addr, true, true);
143 }
144 #endif
145
146 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
147 void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
148 unsigned long frame_pointer)
149 {
150 unsigned long return_hooker = (unsigned long)&return_to_handler;
151 unsigned long old;
152
153 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
154 return;
155
156 old = *parent;
157
158 if (!function_graph_enter(old, self_addr,
159 *(unsigned long *)frame_pointer, parent)) {
160 /*
161 * For csky-gcc function has sub-call:
162 * subi sp, sp, 8
163 * stw r8, (sp, 0)
164 * mov r8, sp
165 * st.w r15, (sp, 0x4)
166 * push r15
167 * jl _mcount
168 * We only need set *parent for resume
169 *
170 * For csky-gcc function has no sub-call:
171 * subi sp, sp, 4
172 * stw r8, (sp, 0)
173 * mov r8, sp
174 * push r15
175 * jl _mcount
176 * We need set *parent and *(frame_pointer + 4) for resume,
177 * because lr is resumed twice.
178 */
179 *parent = return_hooker;
180 frame_pointer += 4;
181 if (*(unsigned long *)frame_pointer == old)
182 *(unsigned long *)frame_pointer = return_hooker;
183 }
184 }
185
186 #ifdef CONFIG_DYNAMIC_FTRACE
187 int ftrace_enable_ftrace_graph_caller(void)
188 {
189 return ftrace_modify_code((unsigned long)&ftrace_graph_call,
190 (unsigned long)&ftrace_graph_caller, true, true);
191 }
192
193 int ftrace_disable_ftrace_graph_caller(void)
194 {
195 return ftrace_modify_code((unsigned long)&ftrace_graph_call,
196 (unsigned long)&ftrace_graph_caller, false, true);
197 }
198 #endif /* CONFIG_DYNAMIC_FTRACE */
199 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
200
201 #ifdef CONFIG_DYNAMIC_FTRACE
202 #ifndef CONFIG_CPU_HAS_ICACHE_INS
203 struct ftrace_modify_param {
204 int command;
205 atomic_t cpu_count;
206 };
207
208 static int __ftrace_modify_code(void *data)
209 {
210 struct ftrace_modify_param *param = data;
211
212 if (atomic_inc_return(¶m->cpu_count) == 1) {
213 ftrace_modify_all_code(param->command);
214 atomic_inc(¶m->cpu_count);
215 } else {
216 while (atomic_read(¶m->cpu_count) <= num_online_cpus())
217 cpu_relax();
218 local_icache_inv_all(NULL);
219 }
220
221 return 0;
222 }
223
224 void arch_ftrace_update_code(int command)
225 {
226 struct ftrace_modify_param param = { command, ATOMIC_INIT(0) };
227
228 stop_machine(__ftrace_modify_code, ¶m, cpu_online_mask);
229 }
230 #endif
231 #endif /* CONFIG_DYNAMIC_FTRACE */
232
233 /* _mcount is defined in abi's mcount.S */
234 EXPORT_SYMBOL(_mcount);
235
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