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,
102 return arm_gen_branch_link(pc, addr, warn);
105 static int ftrace_modify_code(unsigned long pc, unsigned long old,
106 unsigned long new, bool validate)
108 unsigned long replaced;
110 if (IS_ENABLED(CONFIG_THUMB2_KERNEL)) {
111 old = __opcode_to_mem_thumb32(old);
112 new = __opcode_to_mem_thumb32(new);
114 old = __opcode_to_mem_arm(old);
115 new = __opcode_to_mem_arm(new);
119 if (probe_kernel_read(&replaced, (void *)pc, MCOUNT_INSN_SIZE))
126 if (probe_kernel_write((void *)pc, &new, MCOUNT_INSN_SIZE))
129 flush_icache_range(pc, pc + MCOUNT_INSN_SIZE);
134 int ftrace_update_ftrace_func(ftrace_func_t func)
140 pc = (unsigned long)&ftrace_call;
141 new = ftrace_call_replace(pc, (unsigned long)func, true);
143 ret = ftrace_modify_code(pc, 0, new, false);
145 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
147 pc = (unsigned long)&ftrace_regs_call;
148 new = ftrace_call_replace(pc, (unsigned long)func, true);
150 ret = ftrace_modify_code(pc, 0, new, false);
154 #ifdef CONFIG_OLD_MCOUNT
156 pc = (unsigned long)&ftrace_call_old;
157 new = ftrace_call_replace(pc, (unsigned long)func, true);
159 ret = ftrace_modify_code(pc, 0, new, false);
166 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
168 unsigned long new, old;
169 unsigned long ip = rec->ip;
170 unsigned long aaddr = adjust_address(rec, addr);
171 struct module *mod = NULL;
173 #ifdef CONFIG_ARM_MODULE_PLTS
177 old = ftrace_nop_replace(rec);
179 new = ftrace_call_replace(ip, aaddr, !mod);
180 #ifdef CONFIG_ARM_MODULE_PLTS
182 aaddr = get_module_plt(mod, ip, aaddr);
183 new = ftrace_call_replace(ip, aaddr, true);
187 return ftrace_modify_code(rec->ip, old, new, true);
190 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
192 int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
195 unsigned long new, old;
196 unsigned long ip = rec->ip;
198 old = ftrace_call_replace(ip, adjust_address(rec, old_addr), true);
200 new = ftrace_call_replace(ip, adjust_address(rec, addr), true);
202 return ftrace_modify_code(rec->ip, old, new, true);
207 int ftrace_make_nop(struct module *mod,
208 struct dyn_ftrace *rec, unsigned long addr)
210 unsigned long aaddr = adjust_address(rec, addr);
211 unsigned long ip = rec->ip;
216 #ifdef CONFIG_ARM_MODULE_PLTS
217 /* mod is only supplied during module loading */
224 old = ftrace_call_replace(ip, aaddr,
225 !IS_ENABLED(CONFIG_ARM_MODULE_PLTS) || !mod);
226 #ifdef CONFIG_ARM_MODULE_PLTS
228 aaddr = get_module_plt(mod, ip, aaddr);
229 old = ftrace_call_replace(ip, aaddr, true);
233 new = ftrace_nop_replace(rec);
234 ret = ftrace_modify_code(ip, old, new, true);
236 #ifdef CONFIG_OLD_MCOUNT
237 if (ret == -EINVAL && addr == MCOUNT_ADDR) {
238 rec->arch.old_mcount = true;
240 old = ftrace_call_replace(ip, adjust_address(rec, addr), true);
241 new = ftrace_nop_replace(rec);
242 ret = ftrace_modify_code(ip, old, new, true);
249 int __init ftrace_dyn_arch_init(void)
253 #endif /* CONFIG_DYNAMIC_FTRACE */
255 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
256 void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
257 unsigned long frame_pointer)
259 unsigned long return_hooker = (unsigned long) &return_to_handler;
260 struct ftrace_graph_ent trace;
264 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
268 *parent = return_hooker;
270 trace.func = self_addr;
271 trace.depth = current->curr_ret_stack + 1;
273 /* Only trace if the calling function expects to */
274 if (!ftrace_graph_entry(&trace)) {
279 err = ftrace_push_return_trace(old, self_addr, &trace.depth,
280 frame_pointer, NULL);
287 #ifdef CONFIG_DYNAMIC_FTRACE
288 extern unsigned long ftrace_graph_call;
289 extern unsigned long ftrace_graph_call_old;
290 extern void ftrace_graph_caller_old(void);
291 extern unsigned long ftrace_graph_regs_call;
292 extern void ftrace_graph_regs_caller(void);
294 static int __ftrace_modify_caller(unsigned long *callsite,
295 void (*func) (void), bool enable)
297 unsigned long caller_fn = (unsigned long) func;
298 unsigned long pc = (unsigned long) callsite;
299 unsigned long branch = arm_gen_branch(pc, caller_fn);
300 unsigned long nop = 0xe1a00000; /* mov r0, r0 */
301 unsigned long old = enable ? nop : branch;
302 unsigned long new = enable ? branch : nop;
304 return ftrace_modify_code(pc, old, new, true);
307 static int ftrace_modify_graph_caller(bool enable)
311 ret = __ftrace_modify_caller(&ftrace_graph_call,
315 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
317 ret = __ftrace_modify_caller(&ftrace_graph_regs_call,
318 ftrace_graph_regs_caller,
323 #ifdef CONFIG_OLD_MCOUNT
325 ret = __ftrace_modify_caller(&ftrace_graph_call_old,
326 ftrace_graph_caller_old,
333 int ftrace_enable_ftrace_graph_caller(void)
335 return ftrace_modify_graph_caller(true);
338 int ftrace_disable_ftrace_graph_caller(void)
340 return ftrace_modify_graph_caller(false);
342 #endif /* CONFIG_DYNAMIC_FTRACE */
343 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */