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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#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 */
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
18#include <asm/cacheflush.h>
19#include <asm/ftrace.h>
20
21#ifdef CONFIG_THUMB2_KERNEL
22#define NOP 0xeb04f85d /* pop.w {lr} */
23#else
24#define NOP 0xe8bd4000 /* pop {lr} */
25#endif
26
27#ifdef CONFIG_DYNAMIC_FTRACE
28#ifdef CONFIG_OLD_MCOUNT
29#define OLD_MCOUNT_ADDR ((unsigned long) mcount)
30#define OLD_FTRACE_ADDR ((unsigned long) ftrace_caller_old)
31
32#define OLD_NOP 0xe1a00000 /* mov r0, r0 */
33
34static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
35{
36 return rec->arch.old_mcount ? OLD_NOP : NOP;
37}
38
39static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr)
40{
41 if (!rec->arch.old_mcount)
42 return addr;
43
44 if (addr == MCOUNT_ADDR)
45 addr = OLD_MCOUNT_ADDR;
46 else if (addr == FTRACE_ADDR)
47 addr = OLD_FTRACE_ADDR;
48
49 return addr;
50}
51#else
52static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
53{
54 return NOP;
55}
56
57static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr)
58{
59 return addr;
60}
61#endif
62
63#ifdef CONFIG_THUMB2_KERNEL
64static unsigned long ftrace_gen_branch(unsigned long pc, unsigned long addr,
65 bool link)
66{
67 unsigned long s, j1, j2, i1, i2, imm10, imm11;
68 unsigned long first, second;
69 long offset;
70
71 offset = (long)addr - (long)(pc + 4);
72 if (offset < -16777216 || offset > 16777214) {
73 WARN_ON_ONCE(1);
74 return 0;
75 }
76
77 s = (offset >> 24) & 0x1;
78 i1 = (offset >> 23) & 0x1;
79 i2 = (offset >> 22) & 0x1;
80 imm10 = (offset >> 12) & 0x3ff;
81 imm11 = (offset >> 1) & 0x7ff;
82
83 j1 = (!i1) ^ s;
84 j2 = (!i2) ^ s;
85
86 first = 0xf000 | (s << 10) | imm10;
87 second = 0x9000 | (j1 << 13) | (j2 << 11) | imm11;
88 if (link)
89 second |= 1 << 14;
90
91 return (second << 16) | first;
92}
93#else
94static unsigned long ftrace_gen_branch(unsigned long pc, unsigned long addr,
95 bool link)
96{
97 unsigned long opcode = 0xea000000;
98 long offset;
99
100 if (link)
101 opcode |= 1 << 24;
102
103 offset = (long)addr - (long)(pc + 8);
104 if (unlikely(offset < -33554432 || offset > 33554428)) {
105 /* Can't generate branches that far (from ARM ARM). Ftrace
106 * doesn't generate branches outside of kernel text.
107 */
108 WARN_ON_ONCE(1);
109 return 0;
110 }
111
112 offset = (offset >> 2) & 0x00ffffff;
113
114 return opcode | offset;
115}
116#endif
117
118static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr)
119{
120 return ftrace_gen_branch(pc, addr, true);
121}
122
123static int ftrace_modify_code(unsigned long pc, unsigned long old,
124 unsigned long new)
125{
126 unsigned long replaced;
127
128 if (probe_kernel_read(&replaced, (void *)pc, MCOUNT_INSN_SIZE))
129 return -EFAULT;
130
131 if (replaced != old)
132 return -EINVAL;
133
134 if (probe_kernel_write((void *)pc, &new, MCOUNT_INSN_SIZE))
135 return -EPERM;
136
137 flush_icache_range(pc, pc + MCOUNT_INSN_SIZE);
138
139 return 0;
140}
141
142int ftrace_update_ftrace_func(ftrace_func_t func)
143{
144 unsigned long pc, old;
145 unsigned long new;
146 int ret;
147
148 pc = (unsigned long)&ftrace_call;
149 memcpy(&old, &ftrace_call, MCOUNT_INSN_SIZE);
150 new = ftrace_call_replace(pc, (unsigned long)func);
151
152 ret = ftrace_modify_code(pc, old, new);
153
154#ifdef CONFIG_OLD_MCOUNT
155 if (!ret) {
156 pc = (unsigned long)&ftrace_call_old;
157 memcpy(&old, &ftrace_call_old, MCOUNT_INSN_SIZE);
158 new = ftrace_call_replace(pc, (unsigned long)func);
159
160 ret = ftrace_modify_code(pc, old, new);
161 }
162#endif
163
164 return ret;
165}
166
167int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
168{
169 unsigned long new, old;
170 unsigned long ip = rec->ip;
171
172 old = ftrace_nop_replace(rec);
173 new = ftrace_call_replace(ip, adjust_address(rec, addr));
174
175 return ftrace_modify_code(rec->ip, old, new);
176}
177
178int ftrace_make_nop(struct module *mod,
179 struct dyn_ftrace *rec, unsigned long addr)
180{
181 unsigned long ip = rec->ip;
182 unsigned long old;
183 unsigned long new;
184 int ret;
185
186 old = ftrace_call_replace(ip, adjust_address(rec, addr));
187 new = ftrace_nop_replace(rec);
188 ret = ftrace_modify_code(ip, old, new);
189
190#ifdef CONFIG_OLD_MCOUNT
191 if (ret == -EINVAL && addr == MCOUNT_ADDR) {
192 rec->arch.old_mcount = true;
193
194 old = ftrace_call_replace(ip, adjust_address(rec, addr));
195 new = ftrace_nop_replace(rec);
196 ret = ftrace_modify_code(ip, old, new);
197 }
198#endif
199
200 return ret;
201}
202
203int __init ftrace_dyn_arch_init(void *data)
204{
205 *(unsigned long *)data = 0;
206
207 return 0;
208}
209#endif /* CONFIG_DYNAMIC_FTRACE */
210
211#ifdef CONFIG_FUNCTION_GRAPH_TRACER
212void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
213 unsigned long frame_pointer)
214{
215 unsigned long return_hooker = (unsigned long) &return_to_handler;
216 struct ftrace_graph_ent trace;
217 unsigned long old;
218 int err;
219
220 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
221 return;
222
223 old = *parent;
224 *parent = return_hooker;
225
226 err = ftrace_push_return_trace(old, self_addr, &trace.depth,
227 frame_pointer);
228 if (err == -EBUSY) {
229 *parent = old;
230 return;
231 }
232
233 trace.func = self_addr;
234
235 /* Only trace if the calling function expects to */
236 if (!ftrace_graph_entry(&trace)) {
237 current->curr_ret_stack--;
238 *parent = old;
239 }
240}
241
242#ifdef CONFIG_DYNAMIC_FTRACE
243extern unsigned long ftrace_graph_call;
244extern unsigned long ftrace_graph_call_old;
245extern void ftrace_graph_caller_old(void);
246
247static int __ftrace_modify_caller(unsigned long *callsite,
248 void (*func) (void), bool enable)
249{
250 unsigned long caller_fn = (unsigned long) func;
251 unsigned long pc = (unsigned long) callsite;
252 unsigned long branch = ftrace_gen_branch(pc, caller_fn, false);
253 unsigned long nop = 0xe1a00000; /* mov r0, r0 */
254 unsigned long old = enable ? nop : branch;
255 unsigned long new = enable ? branch : nop;
256
257 return ftrace_modify_code(pc, old, new);
258}
259
260static int ftrace_modify_graph_caller(bool enable)
261{
262 int ret;
263
264 ret = __ftrace_modify_caller(&ftrace_graph_call,
265 ftrace_graph_caller,
266 enable);
267
268#ifdef CONFIG_OLD_MCOUNT
269 if (!ret)
270 ret = __ftrace_modify_caller(&ftrace_graph_call_old,
271 ftrace_graph_caller_old,
272 enable);
273#endif
274
275 return ret;
276}
277
278int ftrace_enable_ftrace_graph_caller(void)
279{
280 return ftrace_modify_graph_caller(true);
281}
282
283int ftrace_disable_ftrace_graph_caller(void)
284{
285 return ftrace_modify_graph_caller(false);
286}
287#endif /* CONFIG_DYNAMIC_FTRACE */
288#endif /* CONFIG_FUNCTION_GRAPH_TRACER */