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1/*
2 * Code for replacing ftrace calls with jumps.
3 *
4 * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
5 *
6 * Thanks goes to Ingo Molnar, for suggesting the idea.
7 * Mathieu Desnoyers, for suggesting postponing the modifications.
8 * Arjan van de Ven, for keeping me straight, and explaining to me
9 * the dangers of modifying code on the run.
10 */
11
12#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
13
14#include <linux/spinlock.h>
15#include <linux/hardirq.h>
16#include <linux/uaccess.h>
17#include <linux/ftrace.h>
18#include <linux/percpu.h>
19#include <linux/sched.h>
20#include <linux/init.h>
21#include <linux/list.h>
22#include <linux/module.h>
23
24#include <trace/syscall.h>
25
26#include <asm/cacheflush.h>
27#include <asm/ftrace.h>
28#include <asm/nops.h>
29#include <asm/nmi.h>
30
31
32#ifdef CONFIG_DYNAMIC_FTRACE
33
34/*
35 * modifying_code is set to notify NMIs that they need to use
36 * memory barriers when entering or exiting. But we don't want
37 * to burden NMIs with unnecessary memory barriers when code
38 * modification is not being done (which is most of the time).
39 *
40 * A mutex is already held when ftrace_arch_code_modify_prepare
41 * and post_process are called. No locks need to be taken here.
42 *
43 * Stop machine will make sure currently running NMIs are done
44 * and new NMIs will see the updated variable before we need
45 * to worry about NMIs doing memory barriers.
46 */
47static int modifying_code __read_mostly;
48static DEFINE_PER_CPU(int, save_modifying_code);
49
50int ftrace_arch_code_modify_prepare(void)
51{
52 set_kernel_text_rw();
53 set_all_modules_text_rw();
54 modifying_code = 1;
55 return 0;
56}
57
58int ftrace_arch_code_modify_post_process(void)
59{
60 modifying_code = 0;
61 set_all_modules_text_ro();
62 set_kernel_text_ro();
63 return 0;
64}
65
66union ftrace_code_union {
67 char code[MCOUNT_INSN_SIZE];
68 struct {
69 char e8;
70 int offset;
71 } __attribute__((packed));
72};
73
74static int ftrace_calc_offset(long ip, long addr)
75{
76 return (int)(addr - ip);
77}
78
79static unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
80{
81 static union ftrace_code_union calc;
82
83 calc.e8 = 0xe8;
84 calc.offset = ftrace_calc_offset(ip + MCOUNT_INSN_SIZE, addr);
85
86 /*
87 * No locking needed, this must be called via kstop_machine
88 * which in essence is like running on a uniprocessor machine.
89 */
90 return calc.code;
91}
92
93/*
94 * Modifying code must take extra care. On an SMP machine, if
95 * the code being modified is also being executed on another CPU
96 * that CPU will have undefined results and possibly take a GPF.
97 * We use kstop_machine to stop other CPUS from exectuing code.
98 * But this does not stop NMIs from happening. We still need
99 * to protect against that. We separate out the modification of
100 * the code to take care of this.
101 *
102 * Two buffers are added: An IP buffer and a "code" buffer.
103 *
104 * 1) Put the instruction pointer into the IP buffer
105 * and the new code into the "code" buffer.
106 * 2) Wait for any running NMIs to finish and set a flag that says
107 * we are modifying code, it is done in an atomic operation.
108 * 3) Write the code
109 * 4) clear the flag.
110 * 5) Wait for any running NMIs to finish.
111 *
112 * If an NMI is executed, the first thing it does is to call
113 * "ftrace_nmi_enter". This will check if the flag is set to write
114 * and if it is, it will write what is in the IP and "code" buffers.
115 *
116 * The trick is, it does not matter if everyone is writing the same
117 * content to the code location. Also, if a CPU is executing code
118 * it is OK to write to that code location if the contents being written
119 * are the same as what exists.
120 */
121
122#define MOD_CODE_WRITE_FLAG (1 << 31) /* set when NMI should do the write */
123static atomic_t nmi_running = ATOMIC_INIT(0);
124static int mod_code_status; /* holds return value of text write */
125static void *mod_code_ip; /* holds the IP to write to */
126static const void *mod_code_newcode; /* holds the text to write to the IP */
127
128static unsigned nmi_wait_count;
129static atomic_t nmi_update_count = ATOMIC_INIT(0);
130
131int ftrace_arch_read_dyn_info(char *buf, int size)
132{
133 int r;
134
135 r = snprintf(buf, size, "%u %u",
136 nmi_wait_count,
137 atomic_read(&nmi_update_count));
138 return r;
139}
140
141static void clear_mod_flag(void)
142{
143 int old = atomic_read(&nmi_running);
144
145 for (;;) {
146 int new = old & ~MOD_CODE_WRITE_FLAG;
147
148 if (old == new)
149 break;
150
151 old = atomic_cmpxchg(&nmi_running, old, new);
152 }
153}
154
155static void ftrace_mod_code(void)
156{
157 /*
158 * Yes, more than one CPU process can be writing to mod_code_status.
159 * (and the code itself)
160 * But if one were to fail, then they all should, and if one were
161 * to succeed, then they all should.
162 */
163 mod_code_status = probe_kernel_write(mod_code_ip, mod_code_newcode,
164 MCOUNT_INSN_SIZE);
165
166 /* if we fail, then kill any new writers */
167 if (mod_code_status)
168 clear_mod_flag();
169}
170
171void ftrace_nmi_enter(void)
172{
173 __this_cpu_write(save_modifying_code, modifying_code);
174
175 if (!__this_cpu_read(save_modifying_code))
176 return;
177
178 if (atomic_inc_return(&nmi_running) & MOD_CODE_WRITE_FLAG) {
179 smp_rmb();
180 ftrace_mod_code();
181 atomic_inc(&nmi_update_count);
182 }
183 /* Must have previous changes seen before executions */
184 smp_mb();
185}
186
187void ftrace_nmi_exit(void)
188{
189 if (!__this_cpu_read(save_modifying_code))
190 return;
191
192 /* Finish all executions before clearing nmi_running */
193 smp_mb();
194 atomic_dec(&nmi_running);
195}
196
197static void wait_for_nmi_and_set_mod_flag(void)
198{
199 if (!atomic_cmpxchg(&nmi_running, 0, MOD_CODE_WRITE_FLAG))
200 return;
201
202 do {
203 cpu_relax();
204 } while (atomic_cmpxchg(&nmi_running, 0, MOD_CODE_WRITE_FLAG));
205
206 nmi_wait_count++;
207}
208
209static void wait_for_nmi(void)
210{
211 if (!atomic_read(&nmi_running))
212 return;
213
214 do {
215 cpu_relax();
216 } while (atomic_read(&nmi_running));
217
218 nmi_wait_count++;
219}
220
221static inline int
222within(unsigned long addr, unsigned long start, unsigned long end)
223{
224 return addr >= start && addr < end;
225}
226
227static int
228do_ftrace_mod_code(unsigned long ip, const void *new_code)
229{
230 /*
231 * On x86_64, kernel text mappings are mapped read-only with
232 * CONFIG_DEBUG_RODATA. So we use the kernel identity mapping instead
233 * of the kernel text mapping to modify the kernel text.
234 *
235 * For 32bit kernels, these mappings are same and we can use
236 * kernel identity mapping to modify code.
237 */
238 if (within(ip, (unsigned long)_text, (unsigned long)_etext))
239 ip = (unsigned long)__va(__pa(ip));
240
241 mod_code_ip = (void *)ip;
242 mod_code_newcode = new_code;
243
244 /* The buffers need to be visible before we let NMIs write them */
245 smp_mb();
246
247 wait_for_nmi_and_set_mod_flag();
248
249 /* Make sure all running NMIs have finished before we write the code */
250 smp_mb();
251
252 ftrace_mod_code();
253
254 /* Make sure the write happens before clearing the bit */
255 smp_mb();
256
257 clear_mod_flag();
258 wait_for_nmi();
259
260 return mod_code_status;
261}
262
263static const unsigned char *ftrace_nop_replace(void)
264{
265 return ideal_nops[NOP_ATOMIC5];
266}
267
268static int
269ftrace_modify_code(unsigned long ip, unsigned const char *old_code,
270 unsigned const char *new_code)
271{
272 unsigned char replaced[MCOUNT_INSN_SIZE];
273
274 /*
275 * Note: Due to modules and __init, code can
276 * disappear and change, we need to protect against faulting
277 * as well as code changing. We do this by using the
278 * probe_kernel_* functions.
279 *
280 * No real locking needed, this code is run through
281 * kstop_machine, or before SMP starts.
282 */
283
284 /* read the text we want to modify */
285 if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
286 return -EFAULT;
287
288 /* Make sure it is what we expect it to be */
289 if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0)
290 return -EINVAL;
291
292 /* replace the text with the new text */
293 if (do_ftrace_mod_code(ip, new_code))
294 return -EPERM;
295
296 sync_core();
297
298 return 0;
299}
300
301int ftrace_make_nop(struct module *mod,
302 struct dyn_ftrace *rec, unsigned long addr)
303{
304 unsigned const char *new, *old;
305 unsigned long ip = rec->ip;
306
307 old = ftrace_call_replace(ip, addr);
308 new = ftrace_nop_replace();
309
310 return ftrace_modify_code(rec->ip, old, new);
311}
312
313int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
314{
315 unsigned const char *new, *old;
316 unsigned long ip = rec->ip;
317
318 old = ftrace_nop_replace();
319 new = ftrace_call_replace(ip, addr);
320
321 return ftrace_modify_code(rec->ip, old, new);
322}
323
324int ftrace_update_ftrace_func(ftrace_func_t func)
325{
326 unsigned long ip = (unsigned long)(&ftrace_call);
327 unsigned char old[MCOUNT_INSN_SIZE], *new;
328 int ret;
329
330 memcpy(old, &ftrace_call, MCOUNT_INSN_SIZE);
331 new = ftrace_call_replace(ip, (unsigned long)func);
332 ret = ftrace_modify_code(ip, old, new);
333
334 return ret;
335}
336
337int __init ftrace_dyn_arch_init(void *data)
338{
339 /* The return code is retured via data */
340 *(unsigned long *)data = 0;
341
342 return 0;
343}
344#endif
345
346#ifdef CONFIG_FUNCTION_GRAPH_TRACER
347
348#ifdef CONFIG_DYNAMIC_FTRACE
349extern void ftrace_graph_call(void);
350
351static int ftrace_mod_jmp(unsigned long ip,
352 int old_offset, int new_offset)
353{
354 unsigned char code[MCOUNT_INSN_SIZE];
355
356 if (probe_kernel_read(code, (void *)ip, MCOUNT_INSN_SIZE))
357 return -EFAULT;
358
359 if (code[0] != 0xe9 || old_offset != *(int *)(&code[1]))
360 return -EINVAL;
361
362 *(int *)(&code[1]) = new_offset;
363
364 if (do_ftrace_mod_code(ip, &code))
365 return -EPERM;
366
367 return 0;
368}
369
370int ftrace_enable_ftrace_graph_caller(void)
371{
372 unsigned long ip = (unsigned long)(&ftrace_graph_call);
373 int old_offset, new_offset;
374
375 old_offset = (unsigned long)(&ftrace_stub) - (ip + MCOUNT_INSN_SIZE);
376 new_offset = (unsigned long)(&ftrace_graph_caller) - (ip + MCOUNT_INSN_SIZE);
377
378 return ftrace_mod_jmp(ip, old_offset, new_offset);
379}
380
381int ftrace_disable_ftrace_graph_caller(void)
382{
383 unsigned long ip = (unsigned long)(&ftrace_graph_call);
384 int old_offset, new_offset;
385
386 old_offset = (unsigned long)(&ftrace_graph_caller) - (ip + MCOUNT_INSN_SIZE);
387 new_offset = (unsigned long)(&ftrace_stub) - (ip + MCOUNT_INSN_SIZE);
388
389 return ftrace_mod_jmp(ip, old_offset, new_offset);
390}
391
392#endif /* !CONFIG_DYNAMIC_FTRACE */
393
394/*
395 * Hook the return address and push it in the stack of return addrs
396 * in current thread info.
397 */
398void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
399 unsigned long frame_pointer)
400{
401 unsigned long old;
402 int faulted;
403 struct ftrace_graph_ent trace;
404 unsigned long return_hooker = (unsigned long)
405 &return_to_handler;
406
407 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
408 return;
409
410 /*
411 * Protect against fault, even if it shouldn't
412 * happen. This tool is too much intrusive to
413 * ignore such a protection.
414 */
415 asm volatile(
416 "1: " _ASM_MOV " (%[parent]), %[old]\n"
417 "2: " _ASM_MOV " %[return_hooker], (%[parent])\n"
418 " movl $0, %[faulted]\n"
419 "3:\n"
420
421 ".section .fixup, \"ax\"\n"
422 "4: movl $1, %[faulted]\n"
423 " jmp 3b\n"
424 ".previous\n"
425
426 _ASM_EXTABLE(1b, 4b)
427 _ASM_EXTABLE(2b, 4b)
428
429 : [old] "=&r" (old), [faulted] "=r" (faulted)
430 : [parent] "r" (parent), [return_hooker] "r" (return_hooker)
431 : "memory"
432 );
433
434 if (unlikely(faulted)) {
435 ftrace_graph_stop();
436 WARN_ON(1);
437 return;
438 }
439
440 trace.func = self_addr;
441 trace.depth = current->curr_ret_stack + 1;
442
443 /* Only trace if the calling function expects to */
444 if (!ftrace_graph_entry(&trace)) {
445 *parent = old;
446 return;
447 }
448
449 if (ftrace_push_return_trace(old, self_addr, &trace.depth,
450 frame_pointer) == -EBUSY) {
451 *parent = old;
452 return;
453 }
454}
455#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
1/*
2 * Code for replacing ftrace calls with jumps.
3 *
4 * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
5 *
6 * Thanks goes to Ingo Molnar, for suggesting the idea.
7 * Mathieu Desnoyers, for suggesting postponing the modifications.
8 * Arjan van de Ven, for keeping me straight, and explaining to me
9 * the dangers of modifying code on the run.
10 */
11
12#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
13
14#include <linux/spinlock.h>
15#include <linux/hardirq.h>
16#include <linux/uaccess.h>
17#include <linux/ftrace.h>
18#include <linux/percpu.h>
19#include <linux/sched.h>
20#include <linux/init.h>
21#include <linux/list.h>
22#include <linux/module.h>
23
24#include <trace/syscall.h>
25
26#include <asm/cacheflush.h>
27#include <asm/kprobes.h>
28#include <asm/ftrace.h>
29#include <asm/nops.h>
30
31#ifdef CONFIG_DYNAMIC_FTRACE
32
33int ftrace_arch_code_modify_prepare(void)
34{
35 set_kernel_text_rw();
36 set_all_modules_text_rw();
37 return 0;
38}
39
40int ftrace_arch_code_modify_post_process(void)
41{
42 set_all_modules_text_ro();
43 set_kernel_text_ro();
44 return 0;
45}
46
47union ftrace_code_union {
48 char code[MCOUNT_INSN_SIZE];
49 struct {
50 char e8;
51 int offset;
52 } __attribute__((packed));
53};
54
55static int ftrace_calc_offset(long ip, long addr)
56{
57 return (int)(addr - ip);
58}
59
60static unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
61{
62 static union ftrace_code_union calc;
63
64 calc.e8 = 0xe8;
65 calc.offset = ftrace_calc_offset(ip + MCOUNT_INSN_SIZE, addr);
66
67 /*
68 * No locking needed, this must be called via kstop_machine
69 * which in essence is like running on a uniprocessor machine.
70 */
71 return calc.code;
72}
73
74static inline int
75within(unsigned long addr, unsigned long start, unsigned long end)
76{
77 return addr >= start && addr < end;
78}
79
80static unsigned long text_ip_addr(unsigned long ip)
81{
82 /*
83 * On x86_64, kernel text mappings are mapped read-only with
84 * CONFIG_DEBUG_RODATA. So we use the kernel identity mapping instead
85 * of the kernel text mapping to modify the kernel text.
86 *
87 * For 32bit kernels, these mappings are same and we can use
88 * kernel identity mapping to modify code.
89 */
90 if (within(ip, (unsigned long)_text, (unsigned long)_etext))
91 ip = (unsigned long)__va(__pa_symbol(ip));
92
93 return ip;
94}
95
96static const unsigned char *ftrace_nop_replace(void)
97{
98 return ideal_nops[NOP_ATOMIC5];
99}
100
101static int
102ftrace_modify_code_direct(unsigned long ip, unsigned const char *old_code,
103 unsigned const char *new_code)
104{
105 unsigned char replaced[MCOUNT_INSN_SIZE];
106
107 /*
108 * Note: Due to modules and __init, code can
109 * disappear and change, we need to protect against faulting
110 * as well as code changing. We do this by using the
111 * probe_kernel_* functions.
112 *
113 * No real locking needed, this code is run through
114 * kstop_machine, or before SMP starts.
115 */
116
117 /* read the text we want to modify */
118 if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
119 return -EFAULT;
120
121 /* Make sure it is what we expect it to be */
122 if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0)
123 return -EINVAL;
124
125 ip = text_ip_addr(ip);
126
127 /* replace the text with the new text */
128 if (probe_kernel_write((void *)ip, new_code, MCOUNT_INSN_SIZE))
129 return -EPERM;
130
131 sync_core();
132
133 return 0;
134}
135
136int ftrace_make_nop(struct module *mod,
137 struct dyn_ftrace *rec, unsigned long addr)
138{
139 unsigned const char *new, *old;
140 unsigned long ip = rec->ip;
141
142 old = ftrace_call_replace(ip, addr);
143 new = ftrace_nop_replace();
144
145 /*
146 * On boot up, and when modules are loaded, the MCOUNT_ADDR
147 * is converted to a nop, and will never become MCOUNT_ADDR
148 * again. This code is either running before SMP (on boot up)
149 * or before the code will ever be executed (module load).
150 * We do not want to use the breakpoint version in this case,
151 * just modify the code directly.
152 */
153 if (addr == MCOUNT_ADDR)
154 return ftrace_modify_code_direct(rec->ip, old, new);
155
156 /* Normal cases use add_brk_on_nop */
157 WARN_ONCE(1, "invalid use of ftrace_make_nop");
158 return -EINVAL;
159}
160
161int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
162{
163 unsigned const char *new, *old;
164 unsigned long ip = rec->ip;
165
166 old = ftrace_nop_replace();
167 new = ftrace_call_replace(ip, addr);
168
169 /* Should only be called when module is loaded */
170 return ftrace_modify_code_direct(rec->ip, old, new);
171}
172
173/*
174 * The modifying_ftrace_code is used to tell the breakpoint
175 * handler to call ftrace_int3_handler(). If it fails to
176 * call this handler for a breakpoint added by ftrace, then
177 * the kernel may crash.
178 *
179 * As atomic_writes on x86 do not need a barrier, we do not
180 * need to add smp_mb()s for this to work. It is also considered
181 * that we can not read the modifying_ftrace_code before
182 * executing the breakpoint. That would be quite remarkable if
183 * it could do that. Here's the flow that is required:
184 *
185 * CPU-0 CPU-1
186 *
187 * atomic_inc(mfc);
188 * write int3s
189 * <trap-int3> // implicit (r)mb
190 * if (atomic_read(mfc))
191 * call ftrace_int3_handler()
192 *
193 * Then when we are finished:
194 *
195 * atomic_dec(mfc);
196 *
197 * If we hit a breakpoint that was not set by ftrace, it does not
198 * matter if ftrace_int3_handler() is called or not. It will
199 * simply be ignored. But it is crucial that a ftrace nop/caller
200 * breakpoint is handled. No other user should ever place a
201 * breakpoint on an ftrace nop/caller location. It must only
202 * be done by this code.
203 */
204atomic_t modifying_ftrace_code __read_mostly;
205
206static int
207ftrace_modify_code(unsigned long ip, unsigned const char *old_code,
208 unsigned const char *new_code);
209
210/*
211 * Should never be called:
212 * As it is only called by __ftrace_replace_code() which is called by
213 * ftrace_replace_code() that x86 overrides, and by ftrace_update_code()
214 * which is called to turn mcount into nops or nops into function calls
215 * but not to convert a function from not using regs to one that uses
216 * regs, which ftrace_modify_call() is for.
217 */
218int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
219 unsigned long addr)
220{
221 WARN_ON(1);
222 return -EINVAL;
223}
224
225static unsigned long ftrace_update_func;
226
227static int update_ftrace_func(unsigned long ip, void *new)
228{
229 unsigned char old[MCOUNT_INSN_SIZE];
230 int ret;
231
232 memcpy(old, (void *)ip, MCOUNT_INSN_SIZE);
233
234 ftrace_update_func = ip;
235 /* Make sure the breakpoints see the ftrace_update_func update */
236 smp_wmb();
237
238 /* See comment above by declaration of modifying_ftrace_code */
239 atomic_inc(&modifying_ftrace_code);
240
241 ret = ftrace_modify_code(ip, old, new);
242
243 atomic_dec(&modifying_ftrace_code);
244
245 return ret;
246}
247
248int ftrace_update_ftrace_func(ftrace_func_t func)
249{
250 unsigned long ip = (unsigned long)(&ftrace_call);
251 unsigned char *new;
252 int ret;
253
254 new = ftrace_call_replace(ip, (unsigned long)func);
255 ret = update_ftrace_func(ip, new);
256
257 /* Also update the regs callback function */
258 if (!ret) {
259 ip = (unsigned long)(&ftrace_regs_call);
260 new = ftrace_call_replace(ip, (unsigned long)func);
261 ret = update_ftrace_func(ip, new);
262 }
263
264 return ret;
265}
266
267static int is_ftrace_caller(unsigned long ip)
268{
269 if (ip == ftrace_update_func)
270 return 1;
271
272 return 0;
273}
274
275/*
276 * A breakpoint was added to the code address we are about to
277 * modify, and this is the handle that will just skip over it.
278 * We are either changing a nop into a trace call, or a trace
279 * call to a nop. While the change is taking place, we treat
280 * it just like it was a nop.
281 */
282int ftrace_int3_handler(struct pt_regs *regs)
283{
284 unsigned long ip;
285
286 if (WARN_ON_ONCE(!regs))
287 return 0;
288
289 ip = regs->ip - 1;
290 if (!ftrace_location(ip) && !is_ftrace_caller(ip))
291 return 0;
292
293 regs->ip += MCOUNT_INSN_SIZE - 1;
294
295 return 1;
296}
297
298static int ftrace_write(unsigned long ip, const char *val, int size)
299{
300 /*
301 * On x86_64, kernel text mappings are mapped read-only with
302 * CONFIG_DEBUG_RODATA. So we use the kernel identity mapping instead
303 * of the kernel text mapping to modify the kernel text.
304 *
305 * For 32bit kernels, these mappings are same and we can use
306 * kernel identity mapping to modify code.
307 */
308 if (within(ip, (unsigned long)_text, (unsigned long)_etext))
309 ip = (unsigned long)__va(__pa_symbol(ip));
310
311 if (probe_kernel_write((void *)ip, val, size))
312 return -EPERM;
313
314 return 0;
315}
316
317static int add_break(unsigned long ip, const char *old)
318{
319 unsigned char replaced[MCOUNT_INSN_SIZE];
320 unsigned char brk = BREAKPOINT_INSTRUCTION;
321
322 if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
323 return -EFAULT;
324
325 /* Make sure it is what we expect it to be */
326 if (memcmp(replaced, old, MCOUNT_INSN_SIZE) != 0)
327 return -EINVAL;
328
329 return ftrace_write(ip, &brk, 1);
330}
331
332static int add_brk_on_call(struct dyn_ftrace *rec, unsigned long addr)
333{
334 unsigned const char *old;
335 unsigned long ip = rec->ip;
336
337 old = ftrace_call_replace(ip, addr);
338
339 return add_break(rec->ip, old);
340}
341
342
343static int add_brk_on_nop(struct dyn_ftrace *rec)
344{
345 unsigned const char *old;
346
347 old = ftrace_nop_replace();
348
349 return add_break(rec->ip, old);
350}
351
352/*
353 * If the record has the FTRACE_FL_REGS set, that means that it
354 * wants to convert to a callback that saves all regs. If FTRACE_FL_REGS
355 * is not not set, then it wants to convert to the normal callback.
356 */
357static unsigned long get_ftrace_addr(struct dyn_ftrace *rec)
358{
359 if (rec->flags & FTRACE_FL_REGS)
360 return (unsigned long)FTRACE_REGS_ADDR;
361 else
362 return (unsigned long)FTRACE_ADDR;
363}
364
365/*
366 * The FTRACE_FL_REGS_EN is set when the record already points to
367 * a function that saves all the regs. Basically the '_EN' version
368 * represents the current state of the function.
369 */
370static unsigned long get_ftrace_old_addr(struct dyn_ftrace *rec)
371{
372 if (rec->flags & FTRACE_FL_REGS_EN)
373 return (unsigned long)FTRACE_REGS_ADDR;
374 else
375 return (unsigned long)FTRACE_ADDR;
376}
377
378static int add_breakpoints(struct dyn_ftrace *rec, int enable)
379{
380 unsigned long ftrace_addr;
381 int ret;
382
383 ret = ftrace_test_record(rec, enable);
384
385 ftrace_addr = get_ftrace_addr(rec);
386
387 switch (ret) {
388 case FTRACE_UPDATE_IGNORE:
389 return 0;
390
391 case FTRACE_UPDATE_MAKE_CALL:
392 /* converting nop to call */
393 return add_brk_on_nop(rec);
394
395 case FTRACE_UPDATE_MODIFY_CALL_REGS:
396 case FTRACE_UPDATE_MODIFY_CALL:
397 ftrace_addr = get_ftrace_old_addr(rec);
398 /* fall through */
399 case FTRACE_UPDATE_MAKE_NOP:
400 /* converting a call to a nop */
401 return add_brk_on_call(rec, ftrace_addr);
402 }
403 return 0;
404}
405
406/*
407 * On error, we need to remove breakpoints. This needs to
408 * be done caefully. If the address does not currently have a
409 * breakpoint, we know we are done. Otherwise, we look at the
410 * remaining 4 bytes of the instruction. If it matches a nop
411 * we replace the breakpoint with the nop. Otherwise we replace
412 * it with the call instruction.
413 */
414static int remove_breakpoint(struct dyn_ftrace *rec)
415{
416 unsigned char ins[MCOUNT_INSN_SIZE];
417 unsigned char brk = BREAKPOINT_INSTRUCTION;
418 const unsigned char *nop;
419 unsigned long ftrace_addr;
420 unsigned long ip = rec->ip;
421
422 /* If we fail the read, just give up */
423 if (probe_kernel_read(ins, (void *)ip, MCOUNT_INSN_SIZE))
424 return -EFAULT;
425
426 /* If this does not have a breakpoint, we are done */
427 if (ins[0] != brk)
428 return 0;
429
430 nop = ftrace_nop_replace();
431
432 /*
433 * If the last 4 bytes of the instruction do not match
434 * a nop, then we assume that this is a call to ftrace_addr.
435 */
436 if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) != 0) {
437 /*
438 * For extra paranoidism, we check if the breakpoint is on
439 * a call that would actually jump to the ftrace_addr.
440 * If not, don't touch the breakpoint, we make just create
441 * a disaster.
442 */
443 ftrace_addr = get_ftrace_addr(rec);
444 nop = ftrace_call_replace(ip, ftrace_addr);
445
446 if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) == 0)
447 goto update;
448
449 /* Check both ftrace_addr and ftrace_old_addr */
450 ftrace_addr = get_ftrace_old_addr(rec);
451 nop = ftrace_call_replace(ip, ftrace_addr);
452
453 if (memcmp(&ins[1], &nop[1], MCOUNT_INSN_SIZE - 1) != 0)
454 return -EINVAL;
455 }
456
457 update:
458 return ftrace_write(ip, nop, 1);
459}
460
461static int add_update_code(unsigned long ip, unsigned const char *new)
462{
463 /* skip breakpoint */
464 ip++;
465 new++;
466 return ftrace_write(ip, new, MCOUNT_INSN_SIZE - 1);
467}
468
469static int add_update_call(struct dyn_ftrace *rec, unsigned long addr)
470{
471 unsigned long ip = rec->ip;
472 unsigned const char *new;
473
474 new = ftrace_call_replace(ip, addr);
475 return add_update_code(ip, new);
476}
477
478static int add_update_nop(struct dyn_ftrace *rec)
479{
480 unsigned long ip = rec->ip;
481 unsigned const char *new;
482
483 new = ftrace_nop_replace();
484 return add_update_code(ip, new);
485}
486
487static int add_update(struct dyn_ftrace *rec, int enable)
488{
489 unsigned long ftrace_addr;
490 int ret;
491
492 ret = ftrace_test_record(rec, enable);
493
494 ftrace_addr = get_ftrace_addr(rec);
495
496 switch (ret) {
497 case FTRACE_UPDATE_IGNORE:
498 return 0;
499
500 case FTRACE_UPDATE_MODIFY_CALL_REGS:
501 case FTRACE_UPDATE_MODIFY_CALL:
502 case FTRACE_UPDATE_MAKE_CALL:
503 /* converting nop to call */
504 return add_update_call(rec, ftrace_addr);
505
506 case FTRACE_UPDATE_MAKE_NOP:
507 /* converting a call to a nop */
508 return add_update_nop(rec);
509 }
510
511 return 0;
512}
513
514static int finish_update_call(struct dyn_ftrace *rec, unsigned long addr)
515{
516 unsigned long ip = rec->ip;
517 unsigned const char *new;
518
519 new = ftrace_call_replace(ip, addr);
520
521 return ftrace_write(ip, new, 1);
522}
523
524static int finish_update_nop(struct dyn_ftrace *rec)
525{
526 unsigned long ip = rec->ip;
527 unsigned const char *new;
528
529 new = ftrace_nop_replace();
530
531 return ftrace_write(ip, new, 1);
532}
533
534static int finish_update(struct dyn_ftrace *rec, int enable)
535{
536 unsigned long ftrace_addr;
537 int ret;
538
539 ret = ftrace_update_record(rec, enable);
540
541 ftrace_addr = get_ftrace_addr(rec);
542
543 switch (ret) {
544 case FTRACE_UPDATE_IGNORE:
545 return 0;
546
547 case FTRACE_UPDATE_MODIFY_CALL_REGS:
548 case FTRACE_UPDATE_MODIFY_CALL:
549 case FTRACE_UPDATE_MAKE_CALL:
550 /* converting nop to call */
551 return finish_update_call(rec, ftrace_addr);
552
553 case FTRACE_UPDATE_MAKE_NOP:
554 /* converting a call to a nop */
555 return finish_update_nop(rec);
556 }
557
558 return 0;
559}
560
561static void do_sync_core(void *data)
562{
563 sync_core();
564}
565
566static void run_sync(void)
567{
568 int enable_irqs = irqs_disabled();
569
570 /* We may be called with interrupts disbled (on bootup). */
571 if (enable_irqs)
572 local_irq_enable();
573 on_each_cpu(do_sync_core, NULL, 1);
574 if (enable_irqs)
575 local_irq_disable();
576}
577
578void ftrace_replace_code(int enable)
579{
580 struct ftrace_rec_iter *iter;
581 struct dyn_ftrace *rec;
582 const char *report = "adding breakpoints";
583 int count = 0;
584 int ret;
585
586 for_ftrace_rec_iter(iter) {
587 rec = ftrace_rec_iter_record(iter);
588
589 ret = add_breakpoints(rec, enable);
590 if (ret)
591 goto remove_breakpoints;
592 count++;
593 }
594
595 run_sync();
596
597 report = "updating code";
598
599 for_ftrace_rec_iter(iter) {
600 rec = ftrace_rec_iter_record(iter);
601
602 ret = add_update(rec, enable);
603 if (ret)
604 goto remove_breakpoints;
605 }
606
607 run_sync();
608
609 report = "removing breakpoints";
610
611 for_ftrace_rec_iter(iter) {
612 rec = ftrace_rec_iter_record(iter);
613
614 ret = finish_update(rec, enable);
615 if (ret)
616 goto remove_breakpoints;
617 }
618
619 run_sync();
620
621 return;
622
623 remove_breakpoints:
624 ftrace_bug(ret, rec ? rec->ip : 0);
625 printk(KERN_WARNING "Failed on %s (%d):\n", report, count);
626 for_ftrace_rec_iter(iter) {
627 rec = ftrace_rec_iter_record(iter);
628 /*
629 * Breakpoints are handled only when this function is in
630 * progress. The system could not work with them.
631 */
632 if (remove_breakpoint(rec))
633 BUG();
634 }
635 run_sync();
636}
637
638static int
639ftrace_modify_code(unsigned long ip, unsigned const char *old_code,
640 unsigned const char *new_code)
641{
642 int ret;
643
644 ret = add_break(ip, old_code);
645 if (ret)
646 goto out;
647
648 run_sync();
649
650 ret = add_update_code(ip, new_code);
651 if (ret)
652 goto fail_update;
653
654 run_sync();
655
656 ret = ftrace_write(ip, new_code, 1);
657 /*
658 * The breakpoint is handled only when this function is in progress.
659 * The system could not work if we could not remove it.
660 */
661 BUG_ON(ret);
662 out:
663 run_sync();
664 return ret;
665
666 fail_update:
667 /* Also here the system could not work with the breakpoint */
668 if (ftrace_write(ip, old_code, 1))
669 BUG();
670 goto out;
671}
672
673void arch_ftrace_update_code(int command)
674{
675 /* See comment above by declaration of modifying_ftrace_code */
676 atomic_inc(&modifying_ftrace_code);
677
678 ftrace_modify_all_code(command);
679
680 atomic_dec(&modifying_ftrace_code);
681}
682
683int __init ftrace_dyn_arch_init(void)
684{
685 return 0;
686}
687#endif
688
689#ifdef CONFIG_FUNCTION_GRAPH_TRACER
690
691#ifdef CONFIG_DYNAMIC_FTRACE
692extern void ftrace_graph_call(void);
693
694static unsigned char *ftrace_jmp_replace(unsigned long ip, unsigned long addr)
695{
696 static union ftrace_code_union calc;
697
698 /* Jmp not a call (ignore the .e8) */
699 calc.e8 = 0xe9;
700 calc.offset = ftrace_calc_offset(ip + MCOUNT_INSN_SIZE, addr);
701
702 /*
703 * ftrace external locks synchronize the access to the static variable.
704 */
705 return calc.code;
706}
707
708static int ftrace_mod_jmp(unsigned long ip, void *func)
709{
710 unsigned char *new;
711
712 new = ftrace_jmp_replace(ip, (unsigned long)func);
713
714 return update_ftrace_func(ip, new);
715}
716
717int ftrace_enable_ftrace_graph_caller(void)
718{
719 unsigned long ip = (unsigned long)(&ftrace_graph_call);
720
721 return ftrace_mod_jmp(ip, &ftrace_graph_caller);
722}
723
724int ftrace_disable_ftrace_graph_caller(void)
725{
726 unsigned long ip = (unsigned long)(&ftrace_graph_call);
727
728 return ftrace_mod_jmp(ip, &ftrace_stub);
729}
730
731#endif /* !CONFIG_DYNAMIC_FTRACE */
732
733/*
734 * Hook the return address and push it in the stack of return addrs
735 * in current thread info.
736 */
737void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
738 unsigned long frame_pointer)
739{
740 unsigned long old;
741 int faulted;
742 struct ftrace_graph_ent trace;
743 unsigned long return_hooker = (unsigned long)
744 &return_to_handler;
745
746 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
747 return;
748
749 /*
750 * Protect against fault, even if it shouldn't
751 * happen. This tool is too much intrusive to
752 * ignore such a protection.
753 */
754 asm volatile(
755 "1: " _ASM_MOV " (%[parent]), %[old]\n"
756 "2: " _ASM_MOV " %[return_hooker], (%[parent])\n"
757 " movl $0, %[faulted]\n"
758 "3:\n"
759
760 ".section .fixup, \"ax\"\n"
761 "4: movl $1, %[faulted]\n"
762 " jmp 3b\n"
763 ".previous\n"
764
765 _ASM_EXTABLE(1b, 4b)
766 _ASM_EXTABLE(2b, 4b)
767
768 : [old] "=&r" (old), [faulted] "=r" (faulted)
769 : [parent] "r" (parent), [return_hooker] "r" (return_hooker)
770 : "memory"
771 );
772
773 if (unlikely(faulted)) {
774 ftrace_graph_stop();
775 WARN_ON(1);
776 return;
777 }
778
779 trace.func = self_addr;
780 trace.depth = current->curr_ret_stack + 1;
781
782 /* Only trace if the calling function expects to */
783 if (!ftrace_graph_entry(&trace)) {
784 *parent = old;
785 return;
786 }
787
788 if (ftrace_push_return_trace(old, self_addr, &trace.depth,
789 frame_pointer) == -EBUSY) {
790 *parent = old;
791 return;
792 }
793}
794#endif /* CONFIG_FUNCTION_GRAPH_TRACER */