1 /*
2 * Dynamic function tracing support.
3 *
4 * Copyright (C) 2008 Abhishek Sagar <sagar.abhishek@gmail.com>
5 * Copyright (C) 2010 Rabin Vincent <rabin@rab.in>
6 *
7 * For licencing details, see COPYING.
8 *
9 * Defines low-level handling of mcount calls when the kernel
10 * is compiled with the -pg flag. When using dynamic ftrace, the
11 * mcount call-sites get patched with NOP till they are enabled.
12 * All code mutation routines here are called under stop_machine().
13 */
14
15 #include <linux/ftrace.h>
16 #include <linux/uaccess.h>
17 #include <linux/module.h>
18 #include <linux/stop_machine.h>
19
20 #include <asm/cacheflush.h>
21 #include <asm/opcodes.h>
22 #include <asm/ftrace.h>
23 #include <asm/insn.h>
24 #include <asm/set_memory.h>
25 #include <asm/patch.h>
26
27 #ifdef CONFIG_THUMB2_KERNEL
28 #define NOP 0xf85deb04 /* pop.w {lr} */
29 #else
30 #define NOP 0xe8bd4000 /* pop {lr} */
31 #endif
32
33 #ifdef CONFIG_DYNAMIC_FTRACE
34
__ftrace_modify_code(void * data)35 static int __ftrace_modify_code(void *data)
36 {
37 int *command = data;
38
39 ftrace_modify_all_code(*command);
40
41 return 0;
42 }
43
arch_ftrace_update_code(int command)44 void arch_ftrace_update_code(int command)
45 {
46 stop_machine(__ftrace_modify_code, &command, NULL);
47 }
48
ftrace_nop_replace(struct dyn_ftrace * rec)49 static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
50 {
51 return NOP;
52 }
53
adjust_address(struct dyn_ftrace * rec,unsigned long addr)54 static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr)
55 {
56 return addr;
57 }
58
ftrace_arch_code_modify_prepare(void)59 int ftrace_arch_code_modify_prepare(void)
60 {
61 return 0;
62 }
63
ftrace_arch_code_modify_post_process(void)64 int ftrace_arch_code_modify_post_process(void)
65 {
66 /* Make sure any TLB misses during machine stop are cleared. */
67 flush_tlb_all();
68 return 0;
69 }
70
ftrace_call_replace(unsigned long pc,unsigned long addr,bool warn)71 static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr,
72 bool warn)
73 {
74 return arm_gen_branch_link(pc, addr, warn);
75 }
76
ftrace_modify_code(unsigned long pc,unsigned long old,unsigned long new,bool validate)77 static int ftrace_modify_code(unsigned long pc, unsigned long old,
78 unsigned long new, bool validate)
79 {
80 unsigned long replaced;
81
82 if (IS_ENABLED(CONFIG_THUMB2_KERNEL))
83 old = __opcode_to_mem_thumb32(old);
84 else
85 old = __opcode_to_mem_arm(old);
86
87 if (validate) {
88 if (copy_from_kernel_nofault(&replaced, (void *)pc,
89 MCOUNT_INSN_SIZE))
90 return -EFAULT;
91
92 if (replaced != old)
93 return -EINVAL;
94 }
95
96 __patch_text((void *)pc, new);
97
98 return 0;
99 }
100
ftrace_update_ftrace_func(ftrace_func_t func)101 int ftrace_update_ftrace_func(ftrace_func_t func)
102 {
103 unsigned long pc;
104 unsigned long new;
105 int ret;
106
107 pc = (unsigned long)&ftrace_call;
108 new = ftrace_call_replace(pc, (unsigned long)func, true);
109
110 ret = ftrace_modify_code(pc, 0, new, false);
111
112 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
113 if (!ret) {
114 pc = (unsigned long)&ftrace_regs_call;
115 new = ftrace_call_replace(pc, (unsigned long)func, true);
116
117 ret = ftrace_modify_code(pc, 0, new, false);
118 }
119 #endif
120
121 return ret;
122 }
123
ftrace_make_call(struct dyn_ftrace * rec,unsigned long addr)124 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
125 {
126 unsigned long new, old;
127 unsigned long ip = rec->ip;
128 unsigned long aaddr = adjust_address(rec, addr);
129 struct module *mod = NULL;
130
131 #ifdef CONFIG_ARM_MODULE_PLTS
132 mod = rec->arch.mod;
133 #endif
134
135 old = ftrace_nop_replace(rec);
136
137 new = ftrace_call_replace(ip, aaddr, !mod);
138 #ifdef CONFIG_ARM_MODULE_PLTS
139 if (!new && mod) {
140 aaddr = get_module_plt(mod, ip, aaddr);
141 new = ftrace_call_replace(ip, aaddr, true);
142 }
143 #endif
144
145 return ftrace_modify_code(rec->ip, old, new, true);
146 }
147
148 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
149
ftrace_modify_call(struct dyn_ftrace * rec,unsigned long old_addr,unsigned long addr)150 int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
151 unsigned long addr)
152 {
153 unsigned long new, old;
154 unsigned long ip = rec->ip;
155
156 old = ftrace_call_replace(ip, adjust_address(rec, old_addr), true);
157
158 new = ftrace_call_replace(ip, adjust_address(rec, addr), true);
159
160 return ftrace_modify_code(rec->ip, old, new, true);
161 }
162
163 #endif
164
ftrace_make_nop(struct module * mod,struct dyn_ftrace * rec,unsigned long addr)165 int ftrace_make_nop(struct module *mod,
166 struct dyn_ftrace *rec, unsigned long addr)
167 {
168 unsigned long aaddr = adjust_address(rec, addr);
169 unsigned long ip = rec->ip;
170 unsigned long old;
171 unsigned long new;
172 int ret;
173
174 #ifdef CONFIG_ARM_MODULE_PLTS
175 /* mod is only supplied during module loading */
176 if (!mod)
177 mod = rec->arch.mod;
178 else
179 rec->arch.mod = mod;
180 #endif
181
182 old = ftrace_call_replace(ip, aaddr,
183 !IS_ENABLED(CONFIG_ARM_MODULE_PLTS) || !mod);
184 #ifdef CONFIG_ARM_MODULE_PLTS
185 if (!old && mod) {
186 aaddr = get_module_plt(mod, ip, aaddr);
187 old = ftrace_call_replace(ip, aaddr, true);
188 }
189 #endif
190
191 new = ftrace_nop_replace(rec);
192 ret = ftrace_modify_code(ip, old, new, true);
193
194 return ret;
195 }
196
ftrace_dyn_arch_init(void)197 int __init ftrace_dyn_arch_init(void)
198 {
199 return 0;
200 }
201 #endif /* CONFIG_DYNAMIC_FTRACE */
202
203 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
prepare_ftrace_return(unsigned long * parent,unsigned long self_addr,unsigned long frame_pointer)204 void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
205 unsigned long frame_pointer)
206 {
207 unsigned long return_hooker = (unsigned long) &return_to_handler;
208 unsigned long old;
209
210 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
211 return;
212
213 old = *parent;
214 *parent = return_hooker;
215
216 if (function_graph_enter(old, self_addr, frame_pointer, NULL))
217 *parent = old;
218 }
219
220 #ifdef CONFIG_DYNAMIC_FTRACE
221 extern unsigned long ftrace_graph_call;
222 extern unsigned long ftrace_graph_call_old;
223 extern void ftrace_graph_caller_old(void);
224 extern unsigned long ftrace_graph_regs_call;
225 extern void ftrace_graph_regs_caller(void);
226
__ftrace_modify_caller(unsigned long * callsite,void (* func)(void),bool enable)227 static int __ftrace_modify_caller(unsigned long *callsite,
228 void (*func) (void), bool enable)
229 {
230 unsigned long caller_fn = (unsigned long) func;
231 unsigned long pc = (unsigned long) callsite;
232 unsigned long branch = arm_gen_branch(pc, caller_fn);
233 unsigned long nop = 0xe1a00000; /* mov r0, r0 */
234 unsigned long old = enable ? nop : branch;
235 unsigned long new = enable ? branch : nop;
236
237 return ftrace_modify_code(pc, old, new, true);
238 }
239
ftrace_modify_graph_caller(bool enable)240 static int ftrace_modify_graph_caller(bool enable)
241 {
242 int ret;
243
244 ret = __ftrace_modify_caller(&ftrace_graph_call,
245 ftrace_graph_caller,
246 enable);
247
248 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
249 if (!ret)
250 ret = __ftrace_modify_caller(&ftrace_graph_regs_call,
251 ftrace_graph_regs_caller,
252 enable);
253 #endif
254
255
256 return ret;
257 }
258
ftrace_enable_ftrace_graph_caller(void)259 int ftrace_enable_ftrace_graph_caller(void)
260 {
261 return ftrace_modify_graph_caller(true);
262 }
263
ftrace_disable_ftrace_graph_caller(void)264 int ftrace_disable_ftrace_graph_caller(void)
265 {
266 return ftrace_modify_graph_caller(false);
267 }
268 #endif /* CONFIG_DYNAMIC_FTRACE */
269 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
270