ARM: move signal handlers into a vdso-like page
[linux-3.10.git] / arch / arm / kernel / ftrace.c
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/opcodes.h>
20 #include <asm/ftrace.h>
21
22 #include "insn.h"
23
24 #ifdef CONFIG_THUMB2_KERNEL
25 #define NOP             0xf85deb04      /* pop.w {lr} */
26 #else
27 #define NOP             0xe8bd4000      /* pop {lr} */
28 #endif
29
30 #ifdef CONFIG_DYNAMIC_FTRACE
31 #ifdef CONFIG_OLD_MCOUNT
32 #define OLD_MCOUNT_ADDR ((unsigned long) mcount)
33 #define OLD_FTRACE_ADDR ((unsigned long) ftrace_caller_old)
34
35 #define OLD_NOP         0xe1a00000      /* mov r0, r0 */
36
37 static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
38 {
39         return rec->arch.old_mcount ? OLD_NOP : NOP;
40 }
41
42 static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr)
43 {
44         if (!rec->arch.old_mcount)
45                 return addr;
46
47         if (addr == MCOUNT_ADDR)
48                 addr = OLD_MCOUNT_ADDR;
49         else if (addr == FTRACE_ADDR)
50                 addr = OLD_FTRACE_ADDR;
51
52         return addr;
53 }
54 #else
55 static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
56 {
57         return NOP;
58 }
59
60 static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr)
61 {
62         return addr;
63 }
64 #endif
65
66 static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr)
67 {
68         return arm_gen_branch_link(pc, addr);
69 }
70
71 static int ftrace_modify_code(unsigned long pc, unsigned long old,
72                               unsigned long new, bool validate)
73 {
74         unsigned long replaced;
75
76         if (IS_ENABLED(CONFIG_THUMB2_KERNEL)) {
77                 old = __opcode_to_mem_thumb32(old);
78                 new = __opcode_to_mem_thumb32(new);
79         } else {
80                 old = __opcode_to_mem_arm(old);
81                 new = __opcode_to_mem_arm(new);
82         }
83
84         if (validate) {
85                 if (probe_kernel_read(&replaced, (void *)pc, MCOUNT_INSN_SIZE))
86                         return -EFAULT;
87
88                 if (replaced != old)
89                         return -EINVAL;
90         }
91
92         if (probe_kernel_write((void *)pc, &new, MCOUNT_INSN_SIZE))
93                 return -EPERM;
94
95         flush_icache_range(pc, pc + MCOUNT_INSN_SIZE);
96
97         return 0;
98 }
99
100 int ftrace_update_ftrace_func(ftrace_func_t func)
101 {
102         unsigned long pc;
103         unsigned long new;
104         int ret;
105
106         pc = (unsigned long)&ftrace_call;
107         new = ftrace_call_replace(pc, (unsigned long)func);
108
109         ret = ftrace_modify_code(pc, 0, new, false);
110
111 #ifdef CONFIG_OLD_MCOUNT
112         if (!ret) {
113                 pc = (unsigned long)&ftrace_call_old;
114                 new = ftrace_call_replace(pc, (unsigned long)func);
115
116                 ret = ftrace_modify_code(pc, 0, new, false);
117         }
118 #endif
119
120         return ret;
121 }
122
123 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
124 {
125         unsigned long new, old;
126         unsigned long ip = rec->ip;
127
128         old = ftrace_nop_replace(rec);
129         new = ftrace_call_replace(ip, adjust_address(rec, addr));
130
131         return ftrace_modify_code(rec->ip, old, new, true);
132 }
133
134 int ftrace_make_nop(struct module *mod,
135                     struct dyn_ftrace *rec, unsigned long addr)
136 {
137         unsigned long ip = rec->ip;
138         unsigned long old;
139         unsigned long new;
140         int ret;
141
142         old = ftrace_call_replace(ip, adjust_address(rec, addr));
143         new = ftrace_nop_replace(rec);
144         ret = ftrace_modify_code(ip, old, new, true);
145
146 #ifdef CONFIG_OLD_MCOUNT
147         if (ret == -EINVAL && addr == MCOUNT_ADDR) {
148                 rec->arch.old_mcount = true;
149
150                 old = ftrace_call_replace(ip, adjust_address(rec, addr));
151                 new = ftrace_nop_replace(rec);
152                 ret = ftrace_modify_code(ip, old, new, true);
153         }
154 #endif
155
156         return ret;
157 }
158
159 int __init ftrace_dyn_arch_init(void *data)
160 {
161         *(unsigned long *)data = 0;
162
163         return 0;
164 }
165 #endif /* CONFIG_DYNAMIC_FTRACE */
166
167 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
168 void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
169                            unsigned long frame_pointer)
170 {
171         unsigned long return_hooker = (unsigned long) &return_to_handler;
172         struct ftrace_graph_ent trace;
173         unsigned long old;
174         int err;
175
176         if (unlikely(atomic_read(&current->tracing_graph_pause)))
177                 return;
178
179         old = *parent;
180         *parent = return_hooker;
181
182         trace.func = self_addr;
183         trace.depth = current->curr_ret_stack + 1;
184
185         /* Only trace if the calling function expects to */
186         if (!ftrace_graph_entry(&trace)) {
187                 *parent = old;
188                 return;
189         }
190
191         err = ftrace_push_return_trace(old, self_addr, &trace.depth,
192                                        frame_pointer);
193         if (err == -EBUSY) {
194                 *parent = old;
195                 return;
196         }
197 }
198
199 #ifdef CONFIG_DYNAMIC_FTRACE
200 extern unsigned long ftrace_graph_call;
201 extern unsigned long ftrace_graph_call_old;
202 extern void ftrace_graph_caller_old(void);
203
204 static int __ftrace_modify_caller(unsigned long *callsite,
205                                   void (*func) (void), bool enable)
206 {
207         unsigned long caller_fn = (unsigned long) func;
208         unsigned long pc = (unsigned long) callsite;
209         unsigned long branch = arm_gen_branch(pc, caller_fn);
210         unsigned long nop = 0xe1a00000; /* mov r0, r0 */
211         unsigned long old = enable ? nop : branch;
212         unsigned long new = enable ? branch : nop;
213
214         return ftrace_modify_code(pc, old, new, true);
215 }
216
217 static int ftrace_modify_graph_caller(bool enable)
218 {
219         int ret;
220
221         ret = __ftrace_modify_caller(&ftrace_graph_call,
222                                      ftrace_graph_caller,
223                                      enable);
224
225 #ifdef CONFIG_OLD_MCOUNT
226         if (!ret)
227                 ret = __ftrace_modify_caller(&ftrace_graph_call_old,
228                                              ftrace_graph_caller_old,
229                                              enable);
230 #endif
231
232         return ret;
233 }
234
235 int ftrace_enable_ftrace_graph_caller(void)
236 {
237         return ftrace_modify_graph_caller(true);
238 }
239
240 int ftrace_disable_ftrace_graph_caller(void)
241 {
242         return ftrace_modify_graph_caller(false);
243 }
244 #endif /* CONFIG_DYNAMIC_FTRACE */
245 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */