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_OLD_MCOUNT
146 pc = (unsigned long)&ftrace_call_old;
147 new = ftrace_call_replace(pc, (unsigned long)func);
149 ret = ftrace_modify_code(pc, 0, new, false);
156 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
158 unsigned long new, old;
159 unsigned long ip = rec->ip;
161 old = ftrace_nop_replace(rec);
162 new = ftrace_call_replace(ip, adjust_address(rec, addr));
164 return ftrace_modify_code(rec->ip, old, new, true);
167 int ftrace_make_nop(struct module *mod,
168 struct dyn_ftrace *rec, unsigned long addr)
170 unsigned long ip = rec->ip;
175 old = ftrace_call_replace(ip, adjust_address(rec, addr));
176 new = ftrace_nop_replace(rec);
177 ret = ftrace_modify_code(ip, old, new, true);
179 #ifdef CONFIG_OLD_MCOUNT
180 if (ret == -EINVAL && addr == MCOUNT_ADDR) {
181 rec->arch.old_mcount = true;
183 old = ftrace_call_replace(ip, adjust_address(rec, addr));
184 new = ftrace_nop_replace(rec);
185 ret = ftrace_modify_code(ip, old, new, true);
192 int __init ftrace_dyn_arch_init(void)
196 #endif /* CONFIG_DYNAMIC_FTRACE */
198 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
199 void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
200 unsigned long frame_pointer)
202 unsigned long return_hooker = (unsigned long) &return_to_handler;
203 struct ftrace_graph_ent trace;
207 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
211 *parent = return_hooker;
213 trace.func = self_addr;
214 trace.depth = current->curr_ret_stack + 1;
216 /* Only trace if the calling function expects to */
217 if (!ftrace_graph_entry(&trace)) {
222 err = ftrace_push_return_trace(old, self_addr, &trace.depth,
223 frame_pointer, NULL);
230 #ifdef CONFIG_DYNAMIC_FTRACE
231 extern unsigned long ftrace_graph_call;
232 extern unsigned long ftrace_graph_call_old;
233 extern void ftrace_graph_caller_old(void);
235 static int __ftrace_modify_caller(unsigned long *callsite,
236 void (*func) (void), bool enable)
238 unsigned long caller_fn = (unsigned long) func;
239 unsigned long pc = (unsigned long) callsite;
240 unsigned long branch = arm_gen_branch(pc, caller_fn);
241 unsigned long nop = 0xe1a00000; /* mov r0, r0 */
242 unsigned long old = enable ? nop : branch;
243 unsigned long new = enable ? branch : nop;
245 return ftrace_modify_code(pc, old, new, true);
248 static int ftrace_modify_graph_caller(bool enable)
252 ret = __ftrace_modify_caller(&ftrace_graph_call,
256 #ifdef CONFIG_OLD_MCOUNT
258 ret = __ftrace_modify_caller(&ftrace_graph_call_old,
259 ftrace_graph_caller_old,
266 int ftrace_enable_ftrace_graph_caller(void)
268 return ftrace_modify_graph_caller(true);
271 int ftrace_disable_ftrace_graph_caller(void)
273 return ftrace_modify_graph_caller(false);
275 #endif /* CONFIG_DYNAMIC_FTRACE */
276 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */