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>
25 #ifdef CONFIG_THUMB2_KERNEL
26 #define NOP 0xf85deb04 /* pop.w {lr} */
28 #define NOP 0xe8bd4000 /* pop {lr} */
31 #ifdef CONFIG_DYNAMIC_FTRACE
33 static int __ftrace_modify_code(void *data)
38 ftrace_modify_all_code(*command);
44 void arch_ftrace_update_code(int command)
46 stop_machine(__ftrace_modify_code, &command, NULL);
49 #ifdef CONFIG_OLD_MCOUNT
50 #define OLD_MCOUNT_ADDR ((unsigned long) mcount)
51 #define OLD_FTRACE_ADDR ((unsigned long) ftrace_caller_old)
53 #define OLD_NOP 0xe1a00000 /* mov r0, r0 */
55 static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
57 return rec->arch.old_mcount ? OLD_NOP : NOP;
60 static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr)
62 if (!rec->arch.old_mcount)
65 if (addr == MCOUNT_ADDR)
66 addr = OLD_MCOUNT_ADDR;
67 else if (addr == FTRACE_ADDR)
68 addr = OLD_FTRACE_ADDR;
73 static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
78 static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr)
84 int ftrace_arch_code_modify_prepare(void)
86 set_all_modules_text_rw();
90 int ftrace_arch_code_modify_post_process(void)
92 set_all_modules_text_ro();
93 /* Make sure any TLB misses during machine stop are cleared. */
98 static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr,
101 return arm_gen_branch_link(pc, addr, warn);
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, true);
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, true);
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;
160 unsigned long aaddr = adjust_address(rec, addr);
161 struct module *mod = NULL;
163 #ifdef CONFIG_ARM_MODULE_PLTS
167 old = ftrace_nop_replace(rec);
168 new = ftrace_call_replace(ip, aaddr, !mod);
169 #ifdef CONFIG_ARM_MODULE_PLTS
171 aaddr = get_module_plt(mod, ip, aaddr);
172 new = ftrace_call_replace(ip, aaddr, true);
176 return ftrace_modify_code(rec->ip, old, new, true);
179 int ftrace_make_nop(struct module *mod,
180 struct dyn_ftrace *rec, unsigned long addr)
182 unsigned long aaddr = adjust_address(rec, addr);
183 unsigned long ip = rec->ip;
188 #ifdef CONFIG_ARM_MODULE_PLTS
189 /* mod is only supplied during module loading */
196 old = ftrace_call_replace(ip, aaddr,
197 !IS_ENABLED(CONFIG_ARM_MODULE_PLTS) || !mod);
198 #ifdef CONFIG_ARM_MODULE_PLTS
200 aaddr = get_module_plt(mod, ip, aaddr);
201 old = ftrace_call_replace(ip, aaddr, true);
205 new = ftrace_nop_replace(rec);
206 ret = ftrace_modify_code(ip, old, new, true);
208 #ifdef CONFIG_OLD_MCOUNT
209 if (ret == -EINVAL && addr == MCOUNT_ADDR) {
210 rec->arch.old_mcount = true;
212 old = ftrace_call_replace(ip, adjust_address(rec, addr),
213 !IS_ENABLED(CONFIG_ARM_MODULE_PLTS) || !mod);
214 new = ftrace_nop_replace(rec);
215 ret = ftrace_modify_code(ip, old, new, true);
222 int __init ftrace_dyn_arch_init(void)
226 #endif /* CONFIG_DYNAMIC_FTRACE */
228 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
229 void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
230 unsigned long frame_pointer)
232 unsigned long return_hooker = (unsigned long) &return_to_handler;
233 struct ftrace_graph_ent trace;
237 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
241 *parent = return_hooker;
243 trace.func = self_addr;
244 trace.depth = current->curr_ret_stack + 1;
246 /* Only trace if the calling function expects to */
247 if (!ftrace_graph_entry(&trace)) {
252 err = ftrace_push_return_trace(old, self_addr, &trace.depth,
253 frame_pointer, NULL);
260 #ifdef CONFIG_DYNAMIC_FTRACE
261 extern unsigned long ftrace_graph_call;
262 extern unsigned long ftrace_graph_call_old;
263 extern void ftrace_graph_caller_old(void);
265 static int __ftrace_modify_caller(unsigned long *callsite,
266 void (*func) (void), bool enable)
268 unsigned long caller_fn = (unsigned long) func;
269 unsigned long pc = (unsigned long) callsite;
270 unsigned long branch = arm_gen_branch(pc, caller_fn);
271 unsigned long nop = 0xe1a00000; /* mov r0, r0 */
272 unsigned long old = enable ? nop : branch;
273 unsigned long new = enable ? branch : nop;
275 return ftrace_modify_code(pc, old, new, true);
278 static int ftrace_modify_graph_caller(bool enable)
282 ret = __ftrace_modify_caller(&ftrace_graph_call,
286 #ifdef CONFIG_OLD_MCOUNT
288 ret = __ftrace_modify_caller(&ftrace_graph_call_old,
289 ftrace_graph_caller_old,
296 int ftrace_enable_ftrace_graph_caller(void)
298 return ftrace_modify_graph_caller(true);
301 int ftrace_disable_ftrace_graph_caller(void)
303 return ftrace_modify_graph_caller(false);
305 #endif /* CONFIG_DYNAMIC_FTRACE */
306 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */