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1/*
2 * Dynamic function tracing support.
3 *
4 * Copyright (C) 2008 Abhishek Sagar <sagar.abhishek@gmail.com>
5 * Copyright (C) 2010 Rabin Vincent <rabin@rab.in>
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
25#ifdef CONFIG_THUMB2_KERNEL
26#define NOP 0xf85deb04 /* pop.w {lr} */
27#else
28#define NOP 0xe8bd4000 /* pop {lr} */
29#endif
30
31#ifdef CONFIG_DYNAMIC_FTRACE
32#ifdef CONFIG_OLD_MCOUNT
33#define OLD_MCOUNT_ADDR ((unsigned long) mcount)
34#define OLD_FTRACE_ADDR ((unsigned long) ftrace_caller_old)
35
36#define OLD_NOP 0xe1a00000 /* mov r0, r0 */
37
38static int __ftrace_modify_code(void *data)
39{
40 int *command = data;
41
42 set_kernel_text_rw();
43 ftrace_modify_all_code(*command);
44 set_kernel_text_ro();
45
46 return 0;
47}
48
49void arch_ftrace_update_code(int command)
50{
51 stop_machine(__ftrace_modify_code, &command, NULL);
52}
53
54static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
55{
56 return rec->arch.old_mcount ? OLD_NOP : NOP;
57}
58
59static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr)
60{
61 if (!rec->arch.old_mcount)
62 return addr;
63
64 if (addr == MCOUNT_ADDR)
65 addr = OLD_MCOUNT_ADDR;
66 else if (addr == FTRACE_ADDR)
67 addr = OLD_FTRACE_ADDR;
68
69 return addr;
70}
71#else
72static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
73{
74 return NOP;
75}
76
77static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr)
78{
79 return addr;
80}
81#endif
82
83int ftrace_arch_code_modify_prepare(void)
84{
85 set_all_modules_text_rw();
86 return 0;
87}
88
89int ftrace_arch_code_modify_post_process(void)
90{
91 set_all_modules_text_ro();
92 /* Make sure any TLB misses during machine stop are cleared. */
93 flush_tlb_all();
94 return 0;
95}
96
97static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr)
98{
99 return arm_gen_branch_link(pc, addr);
100}
101
102static int ftrace_modify_code(unsigned long pc, unsigned long old,
103 unsigned long new, bool validate)
104{
105 unsigned long replaced;
106
107 if (IS_ENABLED(CONFIG_THUMB2_KERNEL)) {
108 old = __opcode_to_mem_thumb32(old);
109 new = __opcode_to_mem_thumb32(new);
110 } else {
111 old = __opcode_to_mem_arm(old);
112 new = __opcode_to_mem_arm(new);
113 }
114
115 if (validate) {
116 if (probe_kernel_read(&replaced, (void *)pc, MCOUNT_INSN_SIZE))
117 return -EFAULT;
118
119 if (replaced != old)
120 return -EINVAL;
121 }
122
123 if (probe_kernel_write((void *)pc, &new, MCOUNT_INSN_SIZE))
124 return -EPERM;
125
126 flush_icache_range(pc, pc + MCOUNT_INSN_SIZE);
127
128 return 0;
129}
130
131int ftrace_update_ftrace_func(ftrace_func_t func)
132{
133 unsigned long pc;
134 unsigned long new;
135 int ret;
136
137 pc = (unsigned long)&ftrace_call;
138 new = ftrace_call_replace(pc, (unsigned long)func);
139
140 ret = ftrace_modify_code(pc, 0, new, false);
141
142#ifdef CONFIG_OLD_MCOUNT
143 if (!ret) {
144 pc = (unsigned long)&ftrace_call_old;
145 new = ftrace_call_replace(pc, (unsigned long)func);
146
147 ret = ftrace_modify_code(pc, 0, new, false);
148 }
149#endif
150
151 return ret;
152}
153
154int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
155{
156 unsigned long new, old;
157 unsigned long ip = rec->ip;
158
159 old = ftrace_nop_replace(rec);
160 new = ftrace_call_replace(ip, adjust_address(rec, addr));
161
162 return ftrace_modify_code(rec->ip, old, new, true);
163}
164
165int ftrace_make_nop(struct module *mod,
166 struct dyn_ftrace *rec, unsigned long addr)
167{
168 unsigned long ip = rec->ip;
169 unsigned long old;
170 unsigned long new;
171 int ret;
172
173 old = ftrace_call_replace(ip, adjust_address(rec, addr));
174 new = ftrace_nop_replace(rec);
175 ret = ftrace_modify_code(ip, old, new, true);
176
177#ifdef CONFIG_OLD_MCOUNT
178 if (ret == -EINVAL && addr == MCOUNT_ADDR) {
179 rec->arch.old_mcount = true;
180
181 old = ftrace_call_replace(ip, adjust_address(rec, addr));
182 new = ftrace_nop_replace(rec);
183 ret = ftrace_modify_code(ip, old, new, true);
184 }
185#endif
186
187 return ret;
188}
189
190int __init ftrace_dyn_arch_init(void)
191{
192 return 0;
193}
194#endif /* CONFIG_DYNAMIC_FTRACE */
195
196#ifdef CONFIG_FUNCTION_GRAPH_TRACER
197void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
198 unsigned long frame_pointer)
199{
200 unsigned long return_hooker = (unsigned long) &return_to_handler;
201 struct ftrace_graph_ent trace;
202 unsigned long old;
203 int err;
204
205 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
206 return;
207
208 old = *parent;
209 *parent = return_hooker;
210
211 trace.func = self_addr;
212 trace.depth = current->curr_ret_stack + 1;
213
214 /* Only trace if the calling function expects to */
215 if (!ftrace_graph_entry(&trace)) {
216 *parent = old;
217 return;
218 }
219
220 err = ftrace_push_return_trace(old, self_addr, &trace.depth,
221 frame_pointer);
222 if (err == -EBUSY) {
223 *parent = old;
224 return;
225 }
226}
227
228#ifdef CONFIG_DYNAMIC_FTRACE
229extern unsigned long ftrace_graph_call;
230extern unsigned long ftrace_graph_call_old;
231extern void ftrace_graph_caller_old(void);
232
233static int __ftrace_modify_caller(unsigned long *callsite,
234 void (*func) (void), bool enable)
235{
236 unsigned long caller_fn = (unsigned long) func;
237 unsigned long pc = (unsigned long) callsite;
238 unsigned long branch = arm_gen_branch(pc, caller_fn);
239 unsigned long nop = 0xe1a00000; /* mov r0, r0 */
240 unsigned long old = enable ? nop : branch;
241 unsigned long new = enable ? branch : nop;
242
243 return ftrace_modify_code(pc, old, new, true);
244}
245
246static int ftrace_modify_graph_caller(bool enable)
247{
248 int ret;
249
250 ret = __ftrace_modify_caller(&ftrace_graph_call,
251 ftrace_graph_caller,
252 enable);
253
254#ifdef CONFIG_OLD_MCOUNT
255 if (!ret)
256 ret = __ftrace_modify_caller(&ftrace_graph_call_old,
257 ftrace_graph_caller_old,
258 enable);
259#endif
260
261 return ret;
262}
263
264int ftrace_enable_ftrace_graph_caller(void)
265{
266 return ftrace_modify_graph_caller(true);
267}
268
269int ftrace_disable_ftrace_graph_caller(void)
270{
271 return ftrace_modify_graph_caller(false);
272}
273#endif /* CONFIG_DYNAMIC_FTRACE */
274#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
1/*
2 * Dynamic function tracing support.
3 *
4 * Copyright (C) 2008 Abhishek Sagar <sagar.abhishek@gmail.com>
5 * Copyright (C) 2010 Rabin Vincent <rabin@rab.in>
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(¤t->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 */