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1/*
2 * Dynamic function tracing support.
3 *
4 * Copyright (C) 2008 Abhishek Sagar <[email protected]>
5 * Copyright (C) 2010 Rabin Vincent <[email protected]>
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#include <asm/stacktrace.h>
26#include <asm/text-patching.h>
27
28/*
29 * The compiler emitted profiling hook consists of
30 *
31 * PUSH {LR}
32 * BL __gnu_mcount_nc
33 *
34 * To turn this combined sequence into a NOP, we need to restore the value of
35 * SP before the PUSH. Let's use an ADD rather than a POP into LR, as LR is not
36 * modified anyway, and reloading LR from memory is highly likely to be less
37 * efficient.
38 */
39#ifdef CONFIG_THUMB2_KERNEL
40#define NOP 0xf10d0d04 /* add.w sp, sp, #4 */
41#else
42#define NOP 0xe28dd004 /* add sp, sp, #4 */
43#endif
44
45#ifdef CONFIG_DYNAMIC_FTRACE
46
47static int __ftrace_modify_code(void *data)
48{
49 int *command = data;
50
51 ftrace_modify_all_code(*command);
52
53 return 0;
54}
55
56void arch_ftrace_update_code(int command)
57{
58 stop_machine(__ftrace_modify_code, &command, NULL);
59}
60
61static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
62{
63 return NOP;
64}
65
66void ftrace_caller_from_init(void);
67void ftrace_regs_caller_from_init(void);
68
69static unsigned long __ref adjust_address(struct dyn_ftrace *rec,
70 unsigned long addr)
71{
72 if (!IS_ENABLED(CONFIG_DYNAMIC_FTRACE) ||
73 system_state >= SYSTEM_FREEING_INITMEM ||
74 likely(!is_kernel_inittext(rec->ip)))
75 return addr;
76 if (!IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_REGS) ||
77 addr == (unsigned long)&ftrace_caller)
78 return (unsigned long)&ftrace_caller_from_init;
79 return (unsigned long)&ftrace_regs_caller_from_init;
80}
81
82void ftrace_arch_code_modify_prepare(void)
83{
84}
85
86void ftrace_arch_code_modify_post_process(void)
87{
88 /* Make sure any TLB misses during machine stop are cleared. */
89 flush_tlb_all();
90}
91
92static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr,
93 bool warn)
94{
95 return arm_gen_branch_link(pc, addr, warn);
96}
97
98static int ftrace_modify_code(unsigned long pc, unsigned long old,
99 unsigned long new, bool validate)
100{
101 unsigned long replaced;
102
103 if (IS_ENABLED(CONFIG_THUMB2_KERNEL))
104 old = __opcode_to_mem_thumb32(old);
105 else
106 old = __opcode_to_mem_arm(old);
107
108 if (validate) {
109 if (copy_from_kernel_nofault(&replaced, (void *)pc,
110 MCOUNT_INSN_SIZE))
111 return -EFAULT;
112
113 if (replaced != old)
114 return -EINVAL;
115 }
116
117 __patch_text((void *)pc, new);
118
119 return 0;
120}
121
122int ftrace_update_ftrace_func(ftrace_func_t func)
123{
124 unsigned long pc;
125 unsigned long new;
126 int ret;
127
128 pc = (unsigned long)&ftrace_call;
129 new = ftrace_call_replace(pc, (unsigned long)func, true);
130
131 ret = ftrace_modify_code(pc, 0, new, false);
132
133#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
134 if (!ret) {
135 pc = (unsigned long)&ftrace_regs_call;
136 new = ftrace_call_replace(pc, (unsigned long)func, true);
137
138 ret = ftrace_modify_code(pc, 0, new, false);
139 }
140#endif
141
142 return ret;
143}
144
145int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
146{
147 unsigned long new, old;
148 unsigned long ip = rec->ip;
149 unsigned long aaddr = adjust_address(rec, addr);
150 struct module *mod = NULL;
151
152#ifdef CONFIG_ARM_MODULE_PLTS
153 mod = rec->arch.mod;
154#endif
155
156 old = ftrace_nop_replace(rec);
157
158 new = ftrace_call_replace(ip, aaddr, !mod);
159#ifdef CONFIG_ARM_MODULE_PLTS
160 if (!new && mod) {
161 aaddr = get_module_plt(mod, ip, aaddr);
162 new = ftrace_call_replace(ip, aaddr, true);
163 }
164#endif
165
166 return ftrace_modify_code(rec->ip, old, new, true);
167}
168
169#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
170
171int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
172 unsigned long addr)
173{
174 unsigned long new, old;
175 unsigned long ip = rec->ip;
176
177 old = ftrace_call_replace(ip, adjust_address(rec, old_addr), true);
178
179 new = ftrace_call_replace(ip, adjust_address(rec, addr), true);
180
181 return ftrace_modify_code(rec->ip, old, new, true);
182}
183
184#endif
185
186int ftrace_make_nop(struct module *mod,
187 struct dyn_ftrace *rec, unsigned long addr)
188{
189 unsigned long aaddr = adjust_address(rec, addr);
190 unsigned long ip = rec->ip;
191 unsigned long old;
192 unsigned long new;
193 int ret;
194
195#ifdef CONFIG_ARM_MODULE_PLTS
196 /* mod is only supplied during module loading */
197 if (!mod)
198 mod = rec->arch.mod;
199 else
200 rec->arch.mod = mod;
201#endif
202
203 old = ftrace_call_replace(ip, aaddr,
204 !IS_ENABLED(CONFIG_ARM_MODULE_PLTS) || !mod);
205#ifdef CONFIG_ARM_MODULE_PLTS
206 if (!old && mod) {
207 aaddr = get_module_plt(mod, ip, aaddr);
208 old = ftrace_call_replace(ip, aaddr, true);
209 }
210#endif
211
212 new = ftrace_nop_replace(rec);
213 /*
214 * Locations in .init.text may call __gnu_mcount_mc via a linker
215 * emitted veneer if they are too far away from its implementation, and
216 * so validation may fail spuriously in such cases. Let's work around
217 * this by omitting those from validation.
218 */
219 ret = ftrace_modify_code(ip, old, new, !is_kernel_inittext(ip));
220
221 return ret;
222}
223#endif /* CONFIG_DYNAMIC_FTRACE */
224
225#ifdef CONFIG_FUNCTION_GRAPH_TRACER
226asmlinkage
227void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
228 unsigned long frame_pointer,
229 unsigned long stack_pointer)
230{
231 unsigned long return_hooker = (unsigned long) &return_to_handler;
232 unsigned long old;
233
234 if (unlikely(atomic_read(&current->tracing_graph_pause)))
235err_out:
236 return;
237
238 if (IS_ENABLED(CONFIG_UNWINDER_FRAME_POINTER)) {
239 /*
240 * Usually, the stack frames are contiguous in memory but cases
241 * have been observed where the next stack frame does not live
242 * at 'frame_pointer + 4' as this code used to assume.
243 *
244 * Instead, dereference the field in the stack frame that
245 * stores the SP of the calling frame: to avoid unbounded
246 * recursion, this cannot involve any ftrace instrumented
247 * functions, so use the __get_kernel_nofault() primitive
248 * directly.
249 */
250 __get_kernel_nofault(&frame_pointer,
251 (unsigned long *)(frame_pointer - 8),
252 unsigned long, err_out);
253 } else {
254 struct stackframe frame = {
255 .fp = frame_pointer,
256 .sp = stack_pointer,
257 .lr = self_addr,
258 .pc = self_addr,
259 };
260 if (unwind_frame(&frame) < 0)
261 return;
262 if (frame.lr != self_addr)
263 parent = frame.lr_addr;
264 frame_pointer = frame.sp;
265 }
266
267 old = *parent;
268 *parent = return_hooker;
269
270 if (function_graph_enter(old, self_addr, frame_pointer, NULL))
271 *parent = old;
272}
273
274#ifdef CONFIG_DYNAMIC_FTRACE
275extern unsigned long ftrace_graph_call;
276extern unsigned long ftrace_graph_call_old;
277extern void ftrace_graph_caller_old(void);
278extern unsigned long ftrace_graph_regs_call;
279extern void ftrace_graph_regs_caller(void);
280
281static int __ftrace_modify_caller(unsigned long *callsite,
282 void (*func) (void), bool enable)
283{
284 unsigned long caller_fn = (unsigned long) func;
285 unsigned long pc = (unsigned long) callsite;
286 unsigned long branch = arm_gen_branch(pc, caller_fn);
287 unsigned long nop = arm_gen_nop();
288 unsigned long old = enable ? nop : branch;
289 unsigned long new = enable ? branch : nop;
290
291 return ftrace_modify_code(pc, old, new, true);
292}
293
294static int ftrace_modify_graph_caller(bool enable)
295{
296 int ret;
297
298 ret = __ftrace_modify_caller(&ftrace_graph_call,
299 ftrace_graph_caller,
300 enable);
301
302#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
303 if (!ret)
304 ret = __ftrace_modify_caller(&ftrace_graph_regs_call,
305 ftrace_graph_regs_caller,
306 enable);
307#endif
308
309
310 return ret;
311}
312
313int ftrace_enable_ftrace_graph_caller(void)
314{
315 return ftrace_modify_graph_caller(true);
316}
317
318int ftrace_disable_ftrace_graph_caller(void)
319{
320 return ftrace_modify_graph_caller(false);
321}
322#endif /* CONFIG_DYNAMIC_FTRACE */
323#endif /* CONFIG_FUNCTION_GRAPH_TRACER */