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Linux/arch/arm/kernel/ftrace.c

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  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 
 26 #ifdef CONFIG_THUMB2_KERNEL
 27 #define NOP             0xf85deb04      /* pop.w {lr} */
 28 #else
 29 #define NOP             0xe8bd4000      /* pop {lr} */
 30 #endif
 31 
 32 #ifdef CONFIG_DYNAMIC_FTRACE
 33 
 34 static int __ftrace_modify_code(void *data)
 35 {
 36         int *command = data;
 37 
 38         set_kernel_text_rw();
 39         ftrace_modify_all_code(*command);
 40         set_kernel_text_ro();
 41 
 42         return 0;
 43 }
 44 
 45 void arch_ftrace_update_code(int command)
 46 {
 47         stop_machine(__ftrace_modify_code, &command, NULL);
 48 }
 49 
 50 #ifdef CONFIG_OLD_MCOUNT
 51 #define OLD_MCOUNT_ADDR ((unsigned long) mcount)
 52 #define OLD_FTRACE_ADDR ((unsigned long) ftrace_caller_old)
 53 
 54 #define OLD_NOP         0xe1a00000      /* mov r0, r0 */
 55 
 56 static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
 57 {
 58         return rec->arch.old_mcount ? OLD_NOP : NOP;
 59 }
 60 
 61 static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr)
 62 {
 63         if (!rec->arch.old_mcount)
 64                 return addr;
 65 
 66         if (addr == MCOUNT_ADDR)
 67                 addr = OLD_MCOUNT_ADDR;
 68         else if (addr == FTRACE_ADDR)
 69                 addr = OLD_FTRACE_ADDR;
 70 
 71         return addr;
 72 }
 73 #else
 74 static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
 75 {
 76         return NOP;
 77 }
 78 
 79 static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr)
 80 {
 81         return addr;
 82 }
 83 #endif
 84 
 85 int ftrace_arch_code_modify_prepare(void)
 86 {
 87         set_all_modules_text_rw();
 88         return 0;
 89 }
 90 
 91 int ftrace_arch_code_modify_post_process(void)
 92 {
 93         set_all_modules_text_ro();
 94         /* Make sure any TLB misses during machine stop are cleared. */
 95         flush_tlb_all();
 96         return 0;
 97 }
 98 
 99 static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr)
100 {
101         return arm_gen_branch_link(pc, addr);
102 }
103 
104 static int ftrace_modify_code(unsigned long pc, unsigned long old,
105                               unsigned long new, bool validate)
106 {
107         unsigned long replaced;
108 
109         if (IS_ENABLED(CONFIG_THUMB2_KERNEL)) {
110                 old = __opcode_to_mem_thumb32(old);
111                 new = __opcode_to_mem_thumb32(new);
112         } else {
113                 old = __opcode_to_mem_arm(old);
114                 new = __opcode_to_mem_arm(new);
115         }
116 
117         if (validate) {
118                 if (probe_kernel_read(&replaced, (void *)pc, MCOUNT_INSN_SIZE))
119                         return -EFAULT;
120 
121                 if (replaced != old)
122                         return -EINVAL;
123         }
124 
125         if (probe_kernel_write((void *)pc, &new, MCOUNT_INSN_SIZE))
126                 return -EPERM;
127 
128         flush_icache_range(pc, pc + MCOUNT_INSN_SIZE);
129 
130         return 0;
131 }
132 
133 int ftrace_update_ftrace_func(ftrace_func_t func)
134 {
135         unsigned long pc;
136         unsigned long new;
137         int ret;
138 
139         pc = (unsigned long)&ftrace_call;
140         new = ftrace_call_replace(pc, (unsigned long)func);
141 
142         ret = ftrace_modify_code(pc, 0, new, false);
143 
144 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
145         if (!ret) {
146                 pc = (unsigned long)&ftrace_regs_call;
147                 new = ftrace_call_replace(pc, (unsigned long)func);
148 
149                 ret = ftrace_modify_code(pc, 0, new, false);
150         }
151 #endif
152 
153 #ifdef CONFIG_OLD_MCOUNT
154         if (!ret) {
155                 pc = (unsigned long)&ftrace_call_old;
156                 new = ftrace_call_replace(pc, (unsigned long)func);
157 
158                 ret = ftrace_modify_code(pc, 0, new, false);
159         }
160 #endif
161 
162         return ret;
163 }
164 
165 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
166 {
167         unsigned long new, old;
168         unsigned long ip = rec->ip;
169 
170         old = ftrace_nop_replace(rec);
171 
172         new = ftrace_call_replace(ip, adjust_address(rec, addr));
173 
174         return ftrace_modify_code(rec->ip, old, new, true);
175 }
176 
177 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
178 
179 int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
180                                 unsigned long addr)
181 {
182         unsigned long new, old;
183         unsigned long ip = rec->ip;
184 
185         old = ftrace_call_replace(ip, adjust_address(rec, old_addr));
186 
187         new = ftrace_call_replace(ip, adjust_address(rec, addr));
188 
189         return ftrace_modify_code(rec->ip, old, new, true);
190 }
191 
192 #endif
193 
194 int ftrace_make_nop(struct module *mod,
195                     struct dyn_ftrace *rec, unsigned long addr)
196 {
197         unsigned long ip = rec->ip;
198         unsigned long old;
199         unsigned long new;
200         int ret;
201 
202         old = ftrace_call_replace(ip, adjust_address(rec, addr));
203         new = ftrace_nop_replace(rec);
204         ret = ftrace_modify_code(ip, old, new, true);
205 
206 #ifdef CONFIG_OLD_MCOUNT
207         if (ret == -EINVAL && addr == MCOUNT_ADDR) {
208                 rec->arch.old_mcount = true;
209 
210                 old = ftrace_call_replace(ip, adjust_address(rec, addr));
211                 new = ftrace_nop_replace(rec);
212                 ret = ftrace_modify_code(ip, old, new, true);
213         }
214 #endif
215 
216         return ret;
217 }
218 
219 int __init ftrace_dyn_arch_init(void)
220 {
221         return 0;
222 }
223 #endif /* CONFIG_DYNAMIC_FTRACE */
224 
225 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
226 void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
227                            unsigned long frame_pointer)
228 {
229         unsigned long return_hooker = (unsigned long) &return_to_handler;
230         struct ftrace_graph_ent trace;
231         unsigned long old;
232         int err;
233 
234         if (unlikely(atomic_read(&current->tracing_graph_pause)))
235                 return;
236 
237         old = *parent;
238         *parent = return_hooker;
239 
240         trace.func = self_addr;
241         trace.depth = current->curr_ret_stack + 1;
242 
243         /* Only trace if the calling function expects to */
244         if (!ftrace_graph_entry(&trace)) {
245                 *parent = old;
246                 return;
247         }
248 
249         err = ftrace_push_return_trace(old, self_addr, &trace.depth,
250                                        frame_pointer, NULL);
251         if (err == -EBUSY) {
252                 *parent = old;
253                 return;
254         }
255 }
256 
257 #ifdef CONFIG_DYNAMIC_FTRACE
258 extern unsigned long ftrace_graph_call;
259 extern unsigned long ftrace_graph_call_old;
260 extern void ftrace_graph_caller_old(void);
261 extern unsigned long ftrace_graph_regs_call;
262 extern void ftrace_graph_regs_caller(void);
263 
264 static int __ftrace_modify_caller(unsigned long *callsite,
265                                   void (*func) (void), bool enable)
266 {
267         unsigned long caller_fn = (unsigned long) func;
268         unsigned long pc = (unsigned long) callsite;
269         unsigned long branch = arm_gen_branch(pc, caller_fn);
270         unsigned long nop = 0xe1a00000; /* mov r0, r0 */
271         unsigned long old = enable ? nop : branch;
272         unsigned long new = enable ? branch : nop;
273 
274         return ftrace_modify_code(pc, old, new, true);
275 }
276 
277 static int ftrace_modify_graph_caller(bool enable)
278 {
279         int ret;
280 
281         ret = __ftrace_modify_caller(&ftrace_graph_call,
282                                      ftrace_graph_caller,
283                                      enable);
284 
285 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
286         if (!ret)
287                 ret = __ftrace_modify_caller(&ftrace_graph_regs_call,
288                                      ftrace_graph_regs_caller,
289                                      enable);
290 #endif
291 
292 
293 #ifdef CONFIG_OLD_MCOUNT
294         if (!ret)
295                 ret = __ftrace_modify_caller(&ftrace_graph_call_old,
296                                              ftrace_graph_caller_old,
297                                              enable);
298 #endif
299 
300         return ret;
301 }
302 
303 int ftrace_enable_ftrace_graph_caller(void)
304 {
305         return ftrace_modify_graph_caller(true);
306 }
307 
308 int ftrace_disable_ftrace_graph_caller(void)
309 {
310         return ftrace_modify_graph_caller(false);
311 }
312 #endif /* CONFIG_DYNAMIC_FTRACE */
313 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
314 

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