2 * Dynamic function tracing support.
4 * Copyright (C) 2008 Abhishek Sagar <sagar.abhishek@gmail.com>
5 * Copyright (C) 2010 Rabin Vincent <rabin@rab.in>
7 * For licencing details, see COPYING.
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().
15 #include <linux/ftrace.h>
16 #include <linux/uaccess.h>
17 #include <linux/module.h>
18 #include <linux/stop_machine.h>
20 #include <asm/cacheflush.h>
21 #include <asm/opcodes.h>
22 #include <asm/ftrace.h>
24 #include <asm/set_memory.h>
26 #ifdef CONFIG_THUMB2_KERNEL
27 #define NOP 0xf85deb04 /* pop.w {lr} */
29 #define NOP 0xe8bd4000 /* pop {lr} */
32 #ifdef CONFIG_DYNAMIC_FTRACE
34 static int __ftrace_modify_code(void *data)
39 ftrace_modify_all_code(*command);
45 void arch_ftrace_update_code(int command)
47 stop_machine(__ftrace_modify_code, &command, NULL);
50 #ifdef CONFIG_OLD_MCOUNT
51 #define OLD_MCOUNT_ADDR ((unsigned long) mcount)
52 #define OLD_FTRACE_ADDR ((unsigned long) ftrace_caller_old)
54 #define OLD_NOP 0xe1a00000 /* mov r0, r0 */
56 static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
58 return rec->arch.old_mcount ? OLD_NOP : NOP;
61 static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr)
63 if (!rec->arch.old_mcount)
66 if (addr == MCOUNT_ADDR)
67 addr = OLD_MCOUNT_ADDR;
68 else if (addr == FTRACE_ADDR)
69 addr = OLD_FTRACE_ADDR;
74 static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
79 static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr)
85 int ftrace_arch_code_modify_prepare(void)
87 set_all_modules_text_rw();
91 int ftrace_arch_code_modify_post_process(void)
93 set_all_modules_text_ro();
94 /* Make sure any TLB misses during machine stop are cleared. */
99 static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr)
101 return arm_gen_branch_link(pc, addr);
104 static int ftrace_modify_code(unsigned long pc, unsigned long old,
105 unsigned long new, bool validate)
107 unsigned long replaced;
109 if (IS_ENABLED(CONFIG_THUMB2_KERNEL)) {
110 old = __opcode_to_mem_thumb32(old);
111 new = __opcode_to_mem_thumb32(new);
113 old = __opcode_to_mem_arm(old);
114 new = __opcode_to_mem_arm(new);
118 if (probe_kernel_read(&replaced, (void *)pc, MCOUNT_INSN_SIZE))
125 if (probe_kernel_write((void *)pc, &new, MCOUNT_INSN_SIZE))
128 flush_icache_range(pc, pc + MCOUNT_INSN_SIZE);
133 int ftrace_update_ftrace_func(ftrace_func_t func)
139 pc = (unsigned long)&ftrace_call;
140 new = ftrace_call_replace(pc, (unsigned long)func);
142 ret = ftrace_modify_code(pc, 0, new, false);
144 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
146 pc = (unsigned long)&ftrace_regs_call;
147 new = ftrace_call_replace(pc, (unsigned long)func);
149 ret = ftrace_modify_code(pc, 0, new, false);
153 #ifdef CONFIG_OLD_MCOUNT
155 pc = (unsigned long)&ftrace_call_old;
156 new = ftrace_call_replace(pc, (unsigned long)func);
158 ret = ftrace_modify_code(pc, 0, new, false);
165 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
167 unsigned long new, old;
168 unsigned long ip = rec->ip;
170 old = ftrace_nop_replace(rec);
172 new = ftrace_call_replace(ip, adjust_address(rec, addr));
174 return ftrace_modify_code(rec->ip, old, new, true);
177 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
179 int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
182 unsigned long new, old;
183 unsigned long ip = rec->ip;
185 old = ftrace_call_replace(ip, adjust_address(rec, old_addr));
187 new = ftrace_call_replace(ip, adjust_address(rec, addr));
189 return ftrace_modify_code(rec->ip, old, new, true);
194 int ftrace_make_nop(struct module *mod,
195 struct dyn_ftrace *rec, unsigned long addr)
197 unsigned long ip = rec->ip;
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);
206 #ifdef CONFIG_OLD_MCOUNT
207 if (ret == -EINVAL && addr == MCOUNT_ADDR) {
208 rec->arch.old_mcount = true;
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);
219 int __init ftrace_dyn_arch_init(void)
223 #endif /* CONFIG_DYNAMIC_FTRACE */
225 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
226 void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
227 unsigned long frame_pointer)
229 unsigned long return_hooker = (unsigned long) &return_to_handler;
230 struct ftrace_graph_ent trace;
234 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
238 *parent = return_hooker;
240 trace.func = self_addr;
241 trace.depth = current->curr_ret_stack + 1;
243 /* Only trace if the calling function expects to */
244 if (!ftrace_graph_entry(&trace)) {
249 err = ftrace_push_return_trace(old, self_addr, &trace.depth,
250 frame_pointer, NULL);
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);
264 static int __ftrace_modify_caller(unsigned long *callsite,
265 void (*func) (void), bool enable)
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;
274 return ftrace_modify_code(pc, old, new, true);
277 static int ftrace_modify_graph_caller(bool enable)
281 ret = __ftrace_modify_caller(&ftrace_graph_call,
285 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
287 ret = __ftrace_modify_caller(&ftrace_graph_regs_call,
288 ftrace_graph_regs_caller,
293 #ifdef CONFIG_OLD_MCOUNT
295 ret = __ftrace_modify_caller(&ftrace_graph_call_old,
296 ftrace_graph_caller_old,
303 int ftrace_enable_ftrace_graph_caller(void)
305 return ftrace_modify_graph_caller(true);
308 int ftrace_disable_ftrace_graph_caller(void)
310 return ftrace_modify_graph_caller(false);
312 #endif /* CONFIG_DYNAMIC_FTRACE */
313 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */