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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 * Copyright (C) 2009, 2010 DSLab, Lanzhou University, China
6 * Author: Wu Zhangjin <wuzhangjin@gmail.com>
7 *
8 * Thanks goes to Steven Rostedt for writing the original x86 version.
9 */
10
11 #include <linux/uaccess.h>
12 #include <linux/init.h>
13 #include <linux/ftrace.h>
14
15 #include <asm/asm.h>
16 #include <asm/asm-offsets.h>
17 #include <asm/cacheflush.h>
18 #include <asm/uasm.h>
19
20 /*
21 * If the Instruction Pointer is in module space (0xc0000000), return true;
22 * otherwise, it is in kernel space (0x80000000), return false.
23 *
24 * FIXME: This will not work when the kernel space and module space are the
25 * same. If they are the same, we need to modify scripts/recordmcount.pl,
26 * ftrace_make_nop/call() and the other related parts to ensure the
27 * enabling/disabling of the calling site to _mcount is right for both kernel
28 * and module.
29 */
30
31 static inline int in_module(unsigned long ip)
32 {
33 return ip & 0x40000000;
34 }
35
36 #ifdef CONFIG_DYNAMIC_FTRACE
37
38 #define JAL 0x0c000000 /* jump & link: ip --> ra, jump to target */
39 #define ADDR_MASK 0x03ffffff /* op_code|addr : 31...26|25 ....0 */
40
41 #define INSN_B_1F_4 0x10000004 /* b 1f; offset = 4 */
42 #define INSN_B_1F_5 0x10000005 /* b 1f; offset = 5 */
43 #define INSN_NOP 0x00000000 /* nop */
44 #define INSN_JAL(addr) \
45 ((unsigned int)(JAL | (((addr) >> 2) & ADDR_MASK)))
46
47 static unsigned int insn_jal_ftrace_caller __read_mostly;
48 static unsigned int insn_lui_v1_hi16_mcount __read_mostly;
49 static unsigned int insn_j_ftrace_graph_caller __maybe_unused __read_mostly;
50
51 static inline void ftrace_dyn_arch_init_insns(void)
52 {
53 u32 *buf;
54 unsigned int v1;
55
56 /* lui v1, hi16_mcount */
57 v1 = 3;
58 buf = (u32 *)&insn_lui_v1_hi16_mcount;
59 UASM_i_LA_mostly(&buf, v1, MCOUNT_ADDR);
60
61 /* jal (ftrace_caller + 8), jump over the first two instruction */
62 buf = (u32 *)&insn_jal_ftrace_caller;
63 uasm_i_jal(&buf, (FTRACE_ADDR + 8));
64
65 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
66 /* j ftrace_graph_caller */
67 buf = (u32 *)&insn_j_ftrace_graph_caller;
68 uasm_i_j(&buf, (unsigned long)ftrace_graph_caller);
69 #endif
70 }
71
72 static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
73 {
74 int faulted;
75
76 /* *(unsigned int *)ip = new_code; */
77 safe_store_code(new_code, ip, faulted);
78
79 if (unlikely(faulted))
80 return -EFAULT;
81
82 flush_icache_range(ip, ip + 8);
83
84 return 0;
85 }
86
87 int ftrace_make_nop(struct module *mod,
88 struct dyn_ftrace *rec, unsigned long addr)
89 {
90 unsigned int new;
91 unsigned long ip = rec->ip;
92
93 /*
94 * We have compiled module with -mlong-calls, but compiled the kernel
95 * without it, we need to cope with them respectively.
96 */
97 if (in_module(ip)) {
98 #if defined(KBUILD_MCOUNT_RA_ADDRESS) && defined(CONFIG_32BIT)
99 /*
100 * lui v1, hi_16bit_of_mcount --> b 1f (0x10000005)
101 * addiu v1, v1, low_16bit_of_mcount
102 * move at, ra
103 * move $12, ra_address
104 * jalr v1
105 * sub sp, sp, 8
106 * 1: offset = 5 instructions
107 */
108 new = INSN_B_1F_5;
109 #else
110 /*
111 * lui v1, hi_16bit_of_mcount --> b 1f (0x10000004)
112 * addiu v1, v1, low_16bit_of_mcount
113 * move at, ra
114 * jalr v1
115 * nop | move $12, ra_address | sub sp, sp, 8
116 * 1: offset = 4 instructions
117 */
118 new = INSN_B_1F_4;
119 #endif
120 } else {
121 /*
122 * move at, ra
123 * jal _mcount --> nop
124 */
125 new = INSN_NOP;
126 }
127 return ftrace_modify_code(ip, new);
128 }
129
130 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
131 {
132 unsigned int new;
133 unsigned long ip = rec->ip;
134
135 /* ip, module: 0xc0000000, kernel: 0x80000000 */
136 new = in_module(ip) ? insn_lui_v1_hi16_mcount : insn_jal_ftrace_caller;
137
138 return ftrace_modify_code(ip, new);
139 }
140
141 #define FTRACE_CALL_IP ((unsigned long)(&ftrace_call))
142
143 int ftrace_update_ftrace_func(ftrace_func_t func)
144 {
145 unsigned int new;
146
147 new = INSN_JAL((unsigned long)func);
148
149 return ftrace_modify_code(FTRACE_CALL_IP, new);
150 }
151
152 int __init ftrace_dyn_arch_init(void *data)
153 {
154 /* Encode the instructions when booting */
155 ftrace_dyn_arch_init_insns();
156
157 /* Remove "b ftrace_stub" to ensure ftrace_caller() is executed */
158 ftrace_modify_code(MCOUNT_ADDR, INSN_NOP);
159
160 /* The return code is retured via data */
161 *(unsigned long *)data = 0;
162
163 return 0;
164 }
165 #endif /* CONFIG_DYNAMIC_FTRACE */
166
167 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
168
169 #ifdef CONFIG_DYNAMIC_FTRACE
170
171 extern void ftrace_graph_call(void);
172 #define FTRACE_GRAPH_CALL_IP ((unsigned long)(&ftrace_graph_call))
173
174 int ftrace_enable_ftrace_graph_caller(void)
175 {
176 return ftrace_modify_code(FTRACE_GRAPH_CALL_IP,
177 insn_j_ftrace_graph_caller);
178 }
179
180 int ftrace_disable_ftrace_graph_caller(void)
181 {
182 return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, INSN_NOP);
183 }
184
185 #endif /* CONFIG_DYNAMIC_FTRACE */
186
187 #ifndef KBUILD_MCOUNT_RA_ADDRESS
188
189 #define S_RA_SP (0xafbf << 16) /* s{d,w} ra, offset(sp) */
190 #define S_R_SP (0xafb0 << 16) /* s{d,w} R, offset(sp) */
191 #define OFFSET_MASK 0xffff /* stack offset range: 0 ~ PT_SIZE */
192
193 unsigned long ftrace_get_parent_addr(unsigned long self_addr,
194 unsigned long parent,
195 unsigned long parent_addr,
196 unsigned long fp)
197 {
198 unsigned long sp, ip, ra;
199 unsigned int code;
200 int faulted;
201
202 /*
203 * For module, move the ip from calling site of mcount to the
204 * instruction "lui v1, hi_16bit_of_mcount"(offset is 20), but for
205 * kernel, move to the instruction "move ra, at"(offset is 12)
206 */
207 ip = self_addr - (in_module(self_addr) ? 20 : 12);
208
209 /*
210 * search the text until finding the non-store instruction or "s{d,w}
211 * ra, offset(sp)" instruction
212 */
213 do {
214 ip -= 4;
215
216 /* get the code at "ip": code = *(unsigned int *)ip; */
217 safe_load_code(code, ip, faulted);
218
219 if (unlikely(faulted))
220 return 0;
221 /*
222 * If we hit the non-store instruction before finding where the
223 * ra is stored, then this is a leaf function and it does not
224 * store the ra on the stack
225 */
226 if ((code & S_R_SP) != S_R_SP)
227 return parent_addr;
228
229 } while (((code & S_RA_SP) != S_RA_SP));
230
231 sp = fp + (code & OFFSET_MASK);
232
233 /* ra = *(unsigned long *)sp; */
234 safe_load_stack(ra, sp, faulted);
235 if (unlikely(faulted))
236 return 0;
237
238 if (ra == parent)
239 return sp;
240 return 0;
241 }
242
243 #endif /* !KBUILD_MCOUNT_RA_ADDRESS */
244
245 /*
246 * Hook the return address and push it in the stack of return addrs
247 * in current thread info.
248 */
249 void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
250 unsigned long fp)
251 {
252 unsigned long old;
253 struct ftrace_graph_ent trace;
254 unsigned long return_hooker = (unsigned long)
255 &return_to_handler;
256 int faulted;
257
258 if (unlikely(atomic_read(&current->tracing_graph_pause)))
259 return;
260
261 /*
262 * "parent" is the stack address saved the return address of the caller
263 * of _mcount.
264 *
265 * if the gcc < 4.5, a leaf function does not save the return address
266 * in the stack address, so, we "emulate" one in _mcount's stack space,
267 * and hijack it directly, but for a non-leaf function, it save the
268 * return address to the its own stack space, we can not hijack it
269 * directly, but need to find the real stack address,
270 * ftrace_get_parent_addr() does it!
271 *
272 * if gcc>= 4.5, with the new -mmcount-ra-address option, for a
273 * non-leaf function, the location of the return address will be saved
274 * to $12 for us, and for a leaf function, only put a zero into $12. we
275 * do it in ftrace_graph_caller of mcount.S.
276 */
277
278 /* old = *parent; */
279 safe_load_stack(old, parent, faulted);
280 if (unlikely(faulted))
281 goto out;
282 #ifndef KBUILD_MCOUNT_RA_ADDRESS
283 parent = (unsigned long *)ftrace_get_parent_addr(self_addr, old,
284 (unsigned long)parent, fp);
285 /*
286 * If fails when getting the stack address of the non-leaf function's
287 * ra, stop function graph tracer and return
288 */
289 if (parent == 0)
290 goto out;
291 #endif
292 /* *parent = return_hooker; */
293 safe_store_stack(return_hooker, parent, faulted);
294 if (unlikely(faulted))
295 goto out;
296
297 if (ftrace_push_return_trace(old, self_addr, &trace.depth, fp) ==
298 -EBUSY) {
299 *parent = old;
300 return;
301 }
302
303 trace.func = self_addr;
304
305 /* Only trace if the calling function expects to */
306 if (!ftrace_graph_entry(&trace)) {
307 current->curr_ret_stack--;
308 *parent = old;
309 }
310 return;
311 out:
312 ftrace_graph_stop();
313 WARN_ON(1);
314 }
315 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */