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 #include <linux/syscalls.h>
15
16 #include <asm/asm.h>
17 #include <asm/asm-offsets.h>
18 #include <asm/cacheflush.h>
19 #include <asm/syscall.h>
20 #include <asm/uasm.h>
21 #include <asm/unistd.h>
22
23 #include <asm-generic/sections.h>
24
25 #if defined(KBUILD_MCOUNT_RA_ADDRESS) && defined(CONFIG_32BIT)
26 #define MCOUNT_OFFSET_INSNS 5
27 #else
28 #define MCOUNT_OFFSET_INSNS 4
29 #endif
30
31 /*
32 * Check if the address is in kernel space
33 *
34 * Clone core_kernel_text() from kernel/extable.c, but doesn't call
35 * init_kernel_text() for Ftrace doesn't trace functions in init sections.
36 */
in_kernel_space(unsigned long ip)37 static inline int in_kernel_space(unsigned long ip)
38 {
39 if (ip >= (unsigned long)_stext &&
40 ip <= (unsigned long)_etext)
41 return 1;
42 return 0;
43 }
44
45 #ifdef CONFIG_DYNAMIC_FTRACE
46
47 #define JAL 0x0c000000 /* jump & link: ip --> ra, jump to target */
48 #define ADDR_MASK 0x03ffffff /* op_code|addr : 31...26|25 ....0 */
49 #define JUMP_RANGE_MASK ((1UL << 28) - 1)
50
51 #define INSN_NOP 0x00000000 /* nop */
52 #define INSN_JAL(addr) \
53 ((unsigned int)(JAL | (((addr) >> 2) & ADDR_MASK)))
54
55 static unsigned int insn_jal_ftrace_caller __read_mostly;
56 static unsigned int insn_lui_v1_hi16_mcount __read_mostly;
57 static unsigned int insn_j_ftrace_graph_caller __maybe_unused __read_mostly;
58
ftrace_dyn_arch_init_insns(void)59 static inline void ftrace_dyn_arch_init_insns(void)
60 {
61 u32 *buf;
62 unsigned int v1;
63
64 /* lui v1, hi16_mcount */
65 v1 = 3;
66 buf = (u32 *)&insn_lui_v1_hi16_mcount;
67 UASM_i_LA_mostly(&buf, v1, MCOUNT_ADDR);
68
69 /* jal (ftrace_caller + 8), jump over the first two instruction */
70 buf = (u32 *)&insn_jal_ftrace_caller;
71 uasm_i_jal(&buf, (FTRACE_ADDR + 8) & JUMP_RANGE_MASK);
72
73 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
74 /* j ftrace_graph_caller */
75 buf = (u32 *)&insn_j_ftrace_graph_caller;
76 uasm_i_j(&buf, (unsigned long)ftrace_graph_caller & JUMP_RANGE_MASK);
77 #endif
78 }
79
ftrace_modify_code(unsigned long ip,unsigned int new_code)80 static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
81 {
82 int faulted;
83
84 /* *(unsigned int *)ip = new_code; */
85 safe_store_code(new_code, ip, faulted);
86
87 if (unlikely(faulted))
88 return -EFAULT;
89
90 flush_icache_range(ip, ip + 8);
91
92 return 0;
93 }
94
95 /*
96 * The details about the calling site of mcount on MIPS
97 *
98 * 1. For kernel:
99 *
100 * move at, ra
101 * jal _mcount --> nop
102 *
103 * 2. For modules:
104 *
105 * 2.1 For KBUILD_MCOUNT_RA_ADDRESS and CONFIG_32BIT
106 *
107 * lui v1, hi_16bit_of_mcount --> b 1f (0x10000005)
108 * addiu v1, v1, low_16bit_of_mcount
109 * move at, ra
110 * move $12, ra_address
111 * jalr v1
112 * sub sp, sp, 8
113 * 1: offset = 5 instructions
114 * 2.2 For the Other situations
115 *
116 * lui v1, hi_16bit_of_mcount --> b 1f (0x10000004)
117 * addiu v1, v1, low_16bit_of_mcount
118 * move at, ra
119 * jalr v1
120 * nop | move $12, ra_address | sub sp, sp, 8
121 * 1: offset = 4 instructions
122 */
123
124 #define INSN_B_1F (0x10000000 | MCOUNT_OFFSET_INSNS)
125
ftrace_make_nop(struct module * mod,struct dyn_ftrace * rec,unsigned long addr)126 int ftrace_make_nop(struct module *mod,
127 struct dyn_ftrace *rec, unsigned long addr)
128 {
129 unsigned int new;
130 unsigned long ip = rec->ip;
131
132 /*
133 * If ip is in kernel space, no long call, otherwise, long call is
134 * needed.
135 */
136 new = in_kernel_space(ip) ? INSN_NOP : INSN_B_1F;
137
138 return ftrace_modify_code(ip, new);
139 }
140
ftrace_make_call(struct dyn_ftrace * rec,unsigned long addr)141 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
142 {
143 unsigned int new;
144 unsigned long ip = rec->ip;
145
146 new = in_kernel_space(ip) ? insn_jal_ftrace_caller :
147 insn_lui_v1_hi16_mcount;
148
149 return ftrace_modify_code(ip, new);
150 }
151
152 #define FTRACE_CALL_IP ((unsigned long)(&ftrace_call))
153
ftrace_update_ftrace_func(ftrace_func_t func)154 int ftrace_update_ftrace_func(ftrace_func_t func)
155 {
156 unsigned int new;
157
158 new = INSN_JAL((unsigned long)func);
159
160 return ftrace_modify_code(FTRACE_CALL_IP, new);
161 }
162
ftrace_dyn_arch_init(void * data)163 int __init ftrace_dyn_arch_init(void *data)
164 {
165 /* Encode the instructions when booting */
166 ftrace_dyn_arch_init_insns();
167
168 /* Remove "b ftrace_stub" to ensure ftrace_caller() is executed */
169 ftrace_modify_code(MCOUNT_ADDR, INSN_NOP);
170
171 /* The return code is retured via data */
172 *(unsigned long *)data = 0;
173
174 return 0;
175 }
176 #endif /* CONFIG_DYNAMIC_FTRACE */
177
178 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
179
180 #ifdef CONFIG_DYNAMIC_FTRACE
181
182 extern void ftrace_graph_call(void);
183 #define FTRACE_GRAPH_CALL_IP ((unsigned long)(&ftrace_graph_call))
184
ftrace_enable_ftrace_graph_caller(void)185 int ftrace_enable_ftrace_graph_caller(void)
186 {
187 return ftrace_modify_code(FTRACE_GRAPH_CALL_IP,
188 insn_j_ftrace_graph_caller);
189 }
190
ftrace_disable_ftrace_graph_caller(void)191 int ftrace_disable_ftrace_graph_caller(void)
192 {
193 return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, INSN_NOP);
194 }
195
196 #endif /* CONFIG_DYNAMIC_FTRACE */
197
198 #ifndef KBUILD_MCOUNT_RA_ADDRESS
199
200 #define S_RA_SP (0xafbf << 16) /* s{d,w} ra, offset(sp) */
201 #define S_R_SP (0xafb0 << 16) /* s{d,w} R, offset(sp) */
202 #define OFFSET_MASK 0xffff /* stack offset range: 0 ~ PT_SIZE */
203
ftrace_get_parent_ra_addr(unsigned long self_ra,unsigned long old_parent_ra,unsigned long parent_ra_addr,unsigned long fp)204 unsigned long ftrace_get_parent_ra_addr(unsigned long self_ra, unsigned long
205 old_parent_ra, unsigned long parent_ra_addr, unsigned long fp)
206 {
207 unsigned long sp, ip, tmp;
208 unsigned int code;
209 int faulted;
210
211 /*
212 * For module, move the ip from the return address after the
213 * instruction "lui v1, hi_16bit_of_mcount"(offset is 24), but for
214 * kernel, move after the instruction "move ra, at"(offset is 16)
215 */
216 ip = self_ra - (in_kernel_space(self_ra) ? 16 : 24);
217
218 /*
219 * search the text until finding the non-store instruction or "s{d,w}
220 * ra, offset(sp)" instruction
221 */
222 do {
223 /* get the code at "ip": code = *(unsigned int *)ip; */
224 safe_load_code(code, ip, faulted);
225
226 if (unlikely(faulted))
227 return 0;
228 /*
229 * If we hit the non-store instruction before finding where the
230 * ra is stored, then this is a leaf function and it does not
231 * store the ra on the stack
232 */
233 if ((code & S_R_SP) != S_R_SP)
234 return parent_ra_addr;
235
236 /* Move to the next instruction */
237 ip -= 4;
238 } while ((code & S_RA_SP) != S_RA_SP);
239
240 sp = fp + (code & OFFSET_MASK);
241
242 /* tmp = *(unsigned long *)sp; */
243 safe_load_stack(tmp, sp, faulted);
244 if (unlikely(faulted))
245 return 0;
246
247 if (tmp == old_parent_ra)
248 return sp;
249 return 0;
250 }
251
252 #endif /* !KBUILD_MCOUNT_RA_ADDRESS */
253
254 /*
255 * Hook the return address and push it in the stack of return addrs
256 * in current thread info.
257 */
prepare_ftrace_return(unsigned long * parent_ra_addr,unsigned long self_ra,unsigned long fp)258 void prepare_ftrace_return(unsigned long *parent_ra_addr, unsigned long self_ra,
259 unsigned long fp)
260 {
261 unsigned long old_parent_ra;
262 struct ftrace_graph_ent trace;
263 unsigned long return_hooker = (unsigned long)
264 &return_to_handler;
265 int faulted, insns;
266
267 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
268 return;
269
270 /*
271 * "parent_ra_addr" is the stack address saved the return address of
272 * the caller of _mcount.
273 *
274 * if the gcc < 4.5, a leaf function does not save the return address
275 * in the stack address, so, we "emulate" one in _mcount's stack space,
276 * and hijack it directly, but for a non-leaf function, it save the
277 * return address to the its own stack space, we can not hijack it
278 * directly, but need to find the real stack address,
279 * ftrace_get_parent_addr() does it!
280 *
281 * if gcc>= 4.5, with the new -mmcount-ra-address option, for a
282 * non-leaf function, the location of the return address will be saved
283 * to $12 for us, and for a leaf function, only put a zero into $12. we
284 * do it in ftrace_graph_caller of mcount.S.
285 */
286
287 /* old_parent_ra = *parent_ra_addr; */
288 safe_load_stack(old_parent_ra, parent_ra_addr, faulted);
289 if (unlikely(faulted))
290 goto out;
291 #ifndef KBUILD_MCOUNT_RA_ADDRESS
292 parent_ra_addr = (unsigned long *)ftrace_get_parent_ra_addr(self_ra,
293 old_parent_ra, (unsigned long)parent_ra_addr, fp);
294 /*
295 * If fails when getting the stack address of the non-leaf function's
296 * ra, stop function graph tracer and return
297 */
298 if (parent_ra_addr == 0)
299 goto out;
300 #endif
301 /* *parent_ra_addr = return_hooker; */
302 safe_store_stack(return_hooker, parent_ra_addr, faulted);
303 if (unlikely(faulted))
304 goto out;
305
306 if (ftrace_push_return_trace(old_parent_ra, self_ra, &trace.depth, fp)
307 == -EBUSY) {
308 *parent_ra_addr = old_parent_ra;
309 return;
310 }
311
312 /*
313 * Get the recorded ip of the current mcount calling site in the
314 * __mcount_loc section, which will be used to filter the function
315 * entries configured through the tracing/set_graph_function interface.
316 */
317
318 insns = in_kernel_space(self_ra) ? 2 : MCOUNT_OFFSET_INSNS + 1;
319 trace.func = self_ra - (MCOUNT_INSN_SIZE * insns);
320
321 /* Only trace if the calling function expects to */
322 if (!ftrace_graph_entry(&trace)) {
323 current->curr_ret_stack--;
324 *parent_ra_addr = old_parent_ra;
325 }
326 return;
327 out:
328 ftrace_graph_stop();
329 WARN_ON(1);
330 }
331 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
332
333 #ifdef CONFIG_FTRACE_SYSCALLS
334
335 #ifdef CONFIG_32BIT
arch_syscall_addr(int nr)336 unsigned long __init arch_syscall_addr(int nr)
337 {
338 return (unsigned long)sys_call_table[nr - __NR_O32_Linux];
339 }
340 #endif
341
342 #ifdef CONFIG_64BIT
343
arch_syscall_addr(int nr)344 unsigned long __init arch_syscall_addr(int nr)
345 {
346 #ifdef CONFIG_MIPS32_N32
347 if (nr >= __NR_N32_Linux && nr <= __NR_N32_Linux + __NR_N32_Linux_syscalls)
348 return (unsigned long)sysn32_call_table[(nr - __NR_N32_Linux) * 2];
349 #endif
350 if (nr >= __NR_64_Linux && nr <= __NR_64_Linux + __NR_64_Linux_syscalls)
351 return (unsigned long)sys_call_table[nr - __NR_64_Linux];
352 #ifdef CONFIG_MIPS32_O32
353 if (nr >= __NR_O32_Linux && nr <= __NR_O32_Linux + __NR_O32_Linux_syscalls)
354 return (unsigned long)sys32_call_table[nr - __NR_O32_Linux];
355 #endif
356
357 return (unsigned long) &sys_ni_syscall;
358 }
359 #endif
360
361 #endif /* CONFIG_FTRACE_SYSCALLS */
362