Loading...
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#ifdef CONFIG_DYNAMIC_FTRACE
32
33/* Arch override because MIPS doesn't need to run this from stop_machine() */
34void arch_ftrace_update_code(int command)
35{
36 ftrace_modify_all_code(command);
37}
38
39#endif
40
41/*
42 * Check if the address is in kernel space
43 *
44 * Clone core_kernel_text() from kernel/extable.c, but doesn't call
45 * init_kernel_text() for Ftrace doesn't trace functions in init sections.
46 */
47static inline int in_kernel_space(unsigned long ip)
48{
49 if (ip >= (unsigned long)_stext &&
50 ip <= (unsigned long)_etext)
51 return 1;
52 return 0;
53}
54
55#ifdef CONFIG_DYNAMIC_FTRACE
56
57#define JAL 0x0c000000 /* jump & link: ip --> ra, jump to target */
58#define ADDR_MASK 0x03ffffff /* op_code|addr : 31...26|25 ....0 */
59#define JUMP_RANGE_MASK ((1UL << 28) - 1)
60
61#define INSN_NOP 0x00000000 /* nop */
62#define INSN_JAL(addr) \
63 ((unsigned int)(JAL | (((addr) >> 2) & ADDR_MASK)))
64
65static unsigned int insn_jal_ftrace_caller __read_mostly;
66static unsigned int insn_la_mcount[2] __read_mostly;
67static unsigned int insn_j_ftrace_graph_caller __maybe_unused __read_mostly;
68
69static inline void ftrace_dyn_arch_init_insns(void)
70{
71 u32 *buf;
72 unsigned int v1;
73
74 /* la v1, _mcount */
75 v1 = 3;
76 buf = (u32 *)&insn_la_mcount[0];
77 UASM_i_LA(&buf, v1, MCOUNT_ADDR);
78
79 /* jal (ftrace_caller + 8), jump over the first two instruction */
80 buf = (u32 *)&insn_jal_ftrace_caller;
81 uasm_i_jal(&buf, (FTRACE_ADDR + 8) & JUMP_RANGE_MASK);
82
83#ifdef CONFIG_FUNCTION_GRAPH_TRACER
84 /* j ftrace_graph_caller */
85 buf = (u32 *)&insn_j_ftrace_graph_caller;
86 uasm_i_j(&buf, (unsigned long)ftrace_graph_caller & JUMP_RANGE_MASK);
87#endif
88}
89
90static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
91{
92 int faulted;
93 mm_segment_t old_fs;
94
95 /* *(unsigned int *)ip = new_code; */
96 safe_store_code(new_code, ip, faulted);
97
98 if (unlikely(faulted))
99 return -EFAULT;
100
101 old_fs = get_fs();
102 set_fs(get_ds());
103 flush_icache_range(ip, ip + 8);
104 set_fs(old_fs);
105
106 return 0;
107}
108
109#ifndef CONFIG_64BIT
110static int ftrace_modify_code_2(unsigned long ip, unsigned int new_code1,
111 unsigned int new_code2)
112{
113 int faulted;
114 mm_segment_t old_fs;
115
116 safe_store_code(new_code1, ip, faulted);
117 if (unlikely(faulted))
118 return -EFAULT;
119
120 ip += 4;
121 safe_store_code(new_code2, ip, faulted);
122 if (unlikely(faulted))
123 return -EFAULT;
124
125 ip -= 4;
126 old_fs = get_fs();
127 set_fs(get_ds());
128 flush_icache_range(ip, ip + 8);
129 set_fs(old_fs);
130
131 return 0;
132}
133
134static int ftrace_modify_code_2r(unsigned long ip, unsigned int new_code1,
135 unsigned int new_code2)
136{
137 int faulted;
138 mm_segment_t old_fs;
139
140 ip += 4;
141 safe_store_code(new_code2, ip, faulted);
142 if (unlikely(faulted))
143 return -EFAULT;
144
145 ip -= 4;
146 safe_store_code(new_code1, ip, faulted);
147 if (unlikely(faulted))
148 return -EFAULT;
149
150 old_fs = get_fs();
151 set_fs(get_ds());
152 flush_icache_range(ip, ip + 8);
153 set_fs(old_fs);
154
155 return 0;
156}
157#endif
158
159/*
160 * The details about the calling site of mcount on MIPS
161 *
162 * 1. For kernel:
163 *
164 * move at, ra
165 * jal _mcount --> nop
166 * sub sp, sp, 8 --> nop (CONFIG_32BIT)
167 *
168 * 2. For modules:
169 *
170 * 2.1 For KBUILD_MCOUNT_RA_ADDRESS and CONFIG_32BIT
171 *
172 * lui v1, hi_16bit_of_mcount --> b 1f (0x10000005)
173 * addiu v1, v1, low_16bit_of_mcount --> nop (CONFIG_32BIT)
174 * move at, ra
175 * move $12, ra_address
176 * jalr v1
177 * sub sp, sp, 8
178 * 1: offset = 5 instructions
179 * 2.2 For the Other situations
180 *
181 * lui v1, hi_16bit_of_mcount --> b 1f (0x10000004)
182 * addiu v1, v1, low_16bit_of_mcount --> nop (CONFIG_32BIT)
183 * move at, ra
184 * jalr v1
185 * nop | move $12, ra_address | sub sp, sp, 8
186 * 1: offset = 4 instructions
187 */
188
189#define INSN_B_1F (0x10000000 | MCOUNT_OFFSET_INSNS)
190
191int ftrace_make_nop(struct module *mod,
192 struct dyn_ftrace *rec, unsigned long addr)
193{
194 unsigned int new;
195 unsigned long ip = rec->ip;
196
197 /*
198 * If ip is in kernel space, no long call, otherwise, long call is
199 * needed.
200 */
201 new = in_kernel_space(ip) ? INSN_NOP : INSN_B_1F;
202#ifdef CONFIG_64BIT
203 return ftrace_modify_code(ip, new);
204#else
205 /*
206 * On 32 bit MIPS platforms, gcc adds a stack adjust
207 * instruction in the delay slot after the branch to
208 * mcount and expects mcount to restore the sp on return.
209 * This is based on a legacy API and does nothing but
210 * waste instructions so it's being removed at runtime.
211 */
212 return ftrace_modify_code_2(ip, new, INSN_NOP);
213#endif
214}
215
216int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
217{
218 unsigned int new;
219 unsigned long ip = rec->ip;
220
221 new = in_kernel_space(ip) ? insn_jal_ftrace_caller : insn_la_mcount[0];
222
223#ifdef CONFIG_64BIT
224 return ftrace_modify_code(ip, new);
225#else
226 return ftrace_modify_code_2r(ip, new, in_kernel_space(ip) ?
227 INSN_NOP : insn_la_mcount[1]);
228#endif
229}
230
231#define FTRACE_CALL_IP ((unsigned long)(&ftrace_call))
232
233int ftrace_update_ftrace_func(ftrace_func_t func)
234{
235 unsigned int new;
236
237 new = INSN_JAL((unsigned long)func);
238
239 return ftrace_modify_code(FTRACE_CALL_IP, new);
240}
241
242int __init ftrace_dyn_arch_init(void)
243{
244 /* Encode the instructions when booting */
245 ftrace_dyn_arch_init_insns();
246
247 /* Remove "b ftrace_stub" to ensure ftrace_caller() is executed */
248 ftrace_modify_code(MCOUNT_ADDR, INSN_NOP);
249
250 return 0;
251}
252#endif /* CONFIG_DYNAMIC_FTRACE */
253
254#ifdef CONFIG_FUNCTION_GRAPH_TRACER
255
256#ifdef CONFIG_DYNAMIC_FTRACE
257
258extern void ftrace_graph_call(void);
259#define FTRACE_GRAPH_CALL_IP ((unsigned long)(&ftrace_graph_call))
260
261int ftrace_enable_ftrace_graph_caller(void)
262{
263 return ftrace_modify_code(FTRACE_GRAPH_CALL_IP,
264 insn_j_ftrace_graph_caller);
265}
266
267int ftrace_disable_ftrace_graph_caller(void)
268{
269 return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, INSN_NOP);
270}
271
272#endif /* CONFIG_DYNAMIC_FTRACE */
273
274#ifndef KBUILD_MCOUNT_RA_ADDRESS
275
276#define S_RA_SP (0xafbf << 16) /* s{d,w} ra, offset(sp) */
277#define S_R_SP (0xafb0 << 16) /* s{d,w} R, offset(sp) */
278#define OFFSET_MASK 0xffff /* stack offset range: 0 ~ PT_SIZE */
279
280unsigned long ftrace_get_parent_ra_addr(unsigned long self_ra, unsigned long
281 old_parent_ra, unsigned long parent_ra_addr, unsigned long fp)
282{
283 unsigned long sp, ip, tmp;
284 unsigned int code;
285 int faulted;
286
287 /*
288 * For module, move the ip from the return address after the
289 * instruction "lui v1, hi_16bit_of_mcount"(offset is 24), but for
290 * kernel, move after the instruction "move ra, at"(offset is 16)
291 */
292 ip = self_ra - (in_kernel_space(self_ra) ? 16 : 24);
293
294 /*
295 * search the text until finding the non-store instruction or "s{d,w}
296 * ra, offset(sp)" instruction
297 */
298 do {
299 /* get the code at "ip": code = *(unsigned int *)ip; */
300 safe_load_code(code, ip, faulted);
301
302 if (unlikely(faulted))
303 return 0;
304 /*
305 * If we hit the non-store instruction before finding where the
306 * ra is stored, then this is a leaf function and it does not
307 * store the ra on the stack
308 */
309 if ((code & S_R_SP) != S_R_SP)
310 return parent_ra_addr;
311
312 /* Move to the next instruction */
313 ip -= 4;
314 } while ((code & S_RA_SP) != S_RA_SP);
315
316 sp = fp + (code & OFFSET_MASK);
317
318 /* tmp = *(unsigned long *)sp; */
319 safe_load_stack(tmp, sp, faulted);
320 if (unlikely(faulted))
321 return 0;
322
323 if (tmp == old_parent_ra)
324 return sp;
325 return 0;
326}
327
328#endif /* !KBUILD_MCOUNT_RA_ADDRESS */
329
330/*
331 * Hook the return address and push it in the stack of return addrs
332 * in current thread info.
333 */
334void prepare_ftrace_return(unsigned long *parent_ra_addr, unsigned long self_ra,
335 unsigned long fp)
336{
337 unsigned long old_parent_ra;
338 struct ftrace_graph_ent trace;
339 unsigned long return_hooker = (unsigned long)
340 &return_to_handler;
341 int faulted, insns;
342
343 if (unlikely(ftrace_graph_is_dead()))
344 return;
345
346 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
347 return;
348
349 /*
350 * "parent_ra_addr" is the stack address saved the return address of
351 * the caller of _mcount.
352 *
353 * if the gcc < 4.5, a leaf function does not save the return address
354 * in the stack address, so, we "emulate" one in _mcount's stack space,
355 * and hijack it directly, but for a non-leaf function, it save the
356 * return address to the its own stack space, we can not hijack it
357 * directly, but need to find the real stack address,
358 * ftrace_get_parent_addr() does it!
359 *
360 * if gcc>= 4.5, with the new -mmcount-ra-address option, for a
361 * non-leaf function, the location of the return address will be saved
362 * to $12 for us, and for a leaf function, only put a zero into $12. we
363 * do it in ftrace_graph_caller of mcount.S.
364 */
365
366 /* old_parent_ra = *parent_ra_addr; */
367 safe_load_stack(old_parent_ra, parent_ra_addr, faulted);
368 if (unlikely(faulted))
369 goto out;
370#ifndef KBUILD_MCOUNT_RA_ADDRESS
371 parent_ra_addr = (unsigned long *)ftrace_get_parent_ra_addr(self_ra,
372 old_parent_ra, (unsigned long)parent_ra_addr, fp);
373 /*
374 * If fails when getting the stack address of the non-leaf function's
375 * ra, stop function graph tracer and return
376 */
377 if (parent_ra_addr == 0)
378 goto out;
379#endif
380 /* *parent_ra_addr = return_hooker; */
381 safe_store_stack(return_hooker, parent_ra_addr, faulted);
382 if (unlikely(faulted))
383 goto out;
384
385 if (ftrace_push_return_trace(old_parent_ra, self_ra, &trace.depth, fp)
386 == -EBUSY) {
387 *parent_ra_addr = old_parent_ra;
388 return;
389 }
390
391 /*
392 * Get the recorded ip of the current mcount calling site in the
393 * __mcount_loc section, which will be used to filter the function
394 * entries configured through the tracing/set_graph_function interface.
395 */
396
397 insns = in_kernel_space(self_ra) ? 2 : MCOUNT_OFFSET_INSNS + 1;
398 trace.func = self_ra - (MCOUNT_INSN_SIZE * insns);
399
400 /* Only trace if the calling function expects to */
401 if (!ftrace_graph_entry(&trace)) {
402 current->curr_ret_stack--;
403 *parent_ra_addr = old_parent_ra;
404 }
405 return;
406out:
407 ftrace_graph_stop();
408 WARN_ON(1);
409}
410#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
411
412#ifdef CONFIG_FTRACE_SYSCALLS
413
414#ifdef CONFIG_32BIT
415unsigned long __init arch_syscall_addr(int nr)
416{
417 return (unsigned long)sys_call_table[nr - __NR_O32_Linux];
418}
419#endif
420
421#ifdef CONFIG_64BIT
422
423unsigned long __init arch_syscall_addr(int nr)
424{
425#ifdef CONFIG_MIPS32_N32
426 if (nr >= __NR_N32_Linux && nr <= __NR_N32_Linux + __NR_N32_Linux_syscalls)
427 return (unsigned long)sysn32_call_table[nr - __NR_N32_Linux];
428#endif
429 if (nr >= __NR_64_Linux && nr <= __NR_64_Linux + __NR_64_Linux_syscalls)
430 return (unsigned long)sys_call_table[nr - __NR_64_Linux];
431#ifdef CONFIG_MIPS32_O32
432 if (nr >= __NR_O32_Linux && nr <= __NR_O32_Linux + __NR_O32_Linux_syscalls)
433 return (unsigned long)sys32_call_table[nr - __NR_O32_Linux];
434#endif
435
436 return (unsigned long) &sys_ni_syscall;
437}
438#endif
439
440#endif /* CONFIG_FTRACE_SYSCALLS */
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#ifdef CONFIG_DYNAMIC_FTRACE
32
33/* Arch override because MIPS doesn't need to run this from stop_machine() */
34void arch_ftrace_update_code(int command)
35{
36 ftrace_modify_all_code(command);
37}
38
39#endif
40
41/*
42 * Check if the address is in kernel space
43 *
44 * Clone core_kernel_text() from kernel/extable.c, but doesn't call
45 * init_kernel_text() for Ftrace doesn't trace functions in init sections.
46 */
47static inline int in_kernel_space(unsigned long ip)
48{
49 if (ip >= (unsigned long)_stext &&
50 ip <= (unsigned long)_etext)
51 return 1;
52 return 0;
53}
54
55#ifdef CONFIG_DYNAMIC_FTRACE
56
57#define JAL 0x0c000000 /* jump & link: ip --> ra, jump to target */
58#define ADDR_MASK 0x03ffffff /* op_code|addr : 31...26|25 ....0 */
59#define JUMP_RANGE_MASK ((1UL << 28) - 1)
60
61#define INSN_NOP 0x00000000 /* nop */
62#define INSN_JAL(addr) \
63 ((unsigned int)(JAL | (((addr) >> 2) & ADDR_MASK)))
64
65static unsigned int insn_jal_ftrace_caller __read_mostly;
66static unsigned int insn_lui_v1_hi16_mcount __read_mostly;
67static unsigned int insn_j_ftrace_graph_caller __maybe_unused __read_mostly;
68
69static inline void ftrace_dyn_arch_init_insns(void)
70{
71 u32 *buf;
72 unsigned int v1;
73
74 /* lui v1, hi16_mcount */
75 v1 = 3;
76 buf = (u32 *)&insn_lui_v1_hi16_mcount;
77 UASM_i_LA_mostly(&buf, v1, MCOUNT_ADDR);
78
79 /* jal (ftrace_caller + 8), jump over the first two instruction */
80 buf = (u32 *)&insn_jal_ftrace_caller;
81 uasm_i_jal(&buf, (FTRACE_ADDR + 8) & JUMP_RANGE_MASK);
82
83#ifdef CONFIG_FUNCTION_GRAPH_TRACER
84 /* j ftrace_graph_caller */
85 buf = (u32 *)&insn_j_ftrace_graph_caller;
86 uasm_i_j(&buf, (unsigned long)ftrace_graph_caller & JUMP_RANGE_MASK);
87#endif
88}
89
90static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
91{
92 int faulted;
93 mm_segment_t old_fs;
94
95 /* *(unsigned int *)ip = new_code; */
96 safe_store_code(new_code, ip, faulted);
97
98 if (unlikely(faulted))
99 return -EFAULT;
100
101 old_fs = get_fs();
102 set_fs(get_ds());
103 flush_icache_range(ip, ip + 8);
104 set_fs(old_fs);
105
106 return 0;
107}
108
109#ifndef CONFIG_64BIT
110static int ftrace_modify_code_2(unsigned long ip, unsigned int new_code1,
111 unsigned int new_code2)
112{
113 int faulted;
114
115 safe_store_code(new_code1, ip, faulted);
116 if (unlikely(faulted))
117 return -EFAULT;
118 safe_store_code(new_code2, ip + 4, faulted);
119 if (unlikely(faulted))
120 return -EFAULT;
121 flush_icache_range(ip, ip + 8);
122 return 0;
123}
124#endif
125
126/*
127 * The details about the calling site of mcount on MIPS
128 *
129 * 1. For kernel:
130 *
131 * move at, ra
132 * jal _mcount --> nop
133 *
134 * 2. For modules:
135 *
136 * 2.1 For KBUILD_MCOUNT_RA_ADDRESS and CONFIG_32BIT
137 *
138 * lui v1, hi_16bit_of_mcount --> b 1f (0x10000005)
139 * addiu v1, v1, low_16bit_of_mcount
140 * move at, ra
141 * move $12, ra_address
142 * jalr v1
143 * sub sp, sp, 8
144 * 1: offset = 5 instructions
145 * 2.2 For the Other situations
146 *
147 * lui v1, hi_16bit_of_mcount --> b 1f (0x10000004)
148 * addiu v1, v1, low_16bit_of_mcount
149 * move at, ra
150 * jalr v1
151 * nop | move $12, ra_address | sub sp, sp, 8
152 * 1: offset = 4 instructions
153 */
154
155#define INSN_B_1F (0x10000000 | MCOUNT_OFFSET_INSNS)
156
157int ftrace_make_nop(struct module *mod,
158 struct dyn_ftrace *rec, unsigned long addr)
159{
160 unsigned int new;
161 unsigned long ip = rec->ip;
162
163 /*
164 * If ip is in kernel space, no long call, otherwise, long call is
165 * needed.
166 */
167 new = in_kernel_space(ip) ? INSN_NOP : INSN_B_1F;
168#ifdef CONFIG_64BIT
169 return ftrace_modify_code(ip, new);
170#else
171 /*
172 * On 32 bit MIPS platforms, gcc adds a stack adjust
173 * instruction in the delay slot after the branch to
174 * mcount and expects mcount to restore the sp on return.
175 * This is based on a legacy API and does nothing but
176 * waste instructions so it's being removed at runtime.
177 */
178 return ftrace_modify_code_2(ip, new, INSN_NOP);
179#endif
180}
181
182int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
183{
184 unsigned int new;
185 unsigned long ip = rec->ip;
186
187 new = in_kernel_space(ip) ? insn_jal_ftrace_caller :
188 insn_lui_v1_hi16_mcount;
189
190 return ftrace_modify_code(ip, new);
191}
192
193#define FTRACE_CALL_IP ((unsigned long)(&ftrace_call))
194
195int ftrace_update_ftrace_func(ftrace_func_t func)
196{
197 unsigned int new;
198
199 new = INSN_JAL((unsigned long)func);
200
201 return ftrace_modify_code(FTRACE_CALL_IP, new);
202}
203
204int __init ftrace_dyn_arch_init(void)
205{
206 /* Encode the instructions when booting */
207 ftrace_dyn_arch_init_insns();
208
209 /* Remove "b ftrace_stub" to ensure ftrace_caller() is executed */
210 ftrace_modify_code(MCOUNT_ADDR, INSN_NOP);
211
212 return 0;
213}
214#endif /* CONFIG_DYNAMIC_FTRACE */
215
216#ifdef CONFIG_FUNCTION_GRAPH_TRACER
217
218#ifdef CONFIG_DYNAMIC_FTRACE
219
220extern void ftrace_graph_call(void);
221#define FTRACE_GRAPH_CALL_IP ((unsigned long)(&ftrace_graph_call))
222
223int ftrace_enable_ftrace_graph_caller(void)
224{
225 return ftrace_modify_code(FTRACE_GRAPH_CALL_IP,
226 insn_j_ftrace_graph_caller);
227}
228
229int ftrace_disable_ftrace_graph_caller(void)
230{
231 return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, INSN_NOP);
232}
233
234#endif /* CONFIG_DYNAMIC_FTRACE */
235
236#ifndef KBUILD_MCOUNT_RA_ADDRESS
237
238#define S_RA_SP (0xafbf << 16) /* s{d,w} ra, offset(sp) */
239#define S_R_SP (0xafb0 << 16) /* s{d,w} R, offset(sp) */
240#define OFFSET_MASK 0xffff /* stack offset range: 0 ~ PT_SIZE */
241
242unsigned long ftrace_get_parent_ra_addr(unsigned long self_ra, unsigned long
243 old_parent_ra, unsigned long parent_ra_addr, unsigned long fp)
244{
245 unsigned long sp, ip, tmp;
246 unsigned int code;
247 int faulted;
248
249 /*
250 * For module, move the ip from the return address after the
251 * instruction "lui v1, hi_16bit_of_mcount"(offset is 24), but for
252 * kernel, move after the instruction "move ra, at"(offset is 16)
253 */
254 ip = self_ra - (in_kernel_space(self_ra) ? 16 : 24);
255
256 /*
257 * search the text until finding the non-store instruction or "s{d,w}
258 * ra, offset(sp)" instruction
259 */
260 do {
261 /* get the code at "ip": code = *(unsigned int *)ip; */
262 safe_load_code(code, ip, faulted);
263
264 if (unlikely(faulted))
265 return 0;
266 /*
267 * If we hit the non-store instruction before finding where the
268 * ra is stored, then this is a leaf function and it does not
269 * store the ra on the stack
270 */
271 if ((code & S_R_SP) != S_R_SP)
272 return parent_ra_addr;
273
274 /* Move to the next instruction */
275 ip -= 4;
276 } while ((code & S_RA_SP) != S_RA_SP);
277
278 sp = fp + (code & OFFSET_MASK);
279
280 /* tmp = *(unsigned long *)sp; */
281 safe_load_stack(tmp, sp, faulted);
282 if (unlikely(faulted))
283 return 0;
284
285 if (tmp == old_parent_ra)
286 return sp;
287 return 0;
288}
289
290#endif /* !KBUILD_MCOUNT_RA_ADDRESS */
291
292/*
293 * Hook the return address and push it in the stack of return addrs
294 * in current thread info.
295 */
296void prepare_ftrace_return(unsigned long *parent_ra_addr, unsigned long self_ra,
297 unsigned long fp)
298{
299 unsigned long old_parent_ra;
300 struct ftrace_graph_ent trace;
301 unsigned long return_hooker = (unsigned long)
302 &return_to_handler;
303 int faulted, insns;
304
305 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
306 return;
307
308 /*
309 * "parent_ra_addr" is the stack address saved the return address of
310 * the caller of _mcount.
311 *
312 * if the gcc < 4.5, a leaf function does not save the return address
313 * in the stack address, so, we "emulate" one in _mcount's stack space,
314 * and hijack it directly, but for a non-leaf function, it save the
315 * return address to the its own stack space, we can not hijack it
316 * directly, but need to find the real stack address,
317 * ftrace_get_parent_addr() does it!
318 *
319 * if gcc>= 4.5, with the new -mmcount-ra-address option, for a
320 * non-leaf function, the location of the return address will be saved
321 * to $12 for us, and for a leaf function, only put a zero into $12. we
322 * do it in ftrace_graph_caller of mcount.S.
323 */
324
325 /* old_parent_ra = *parent_ra_addr; */
326 safe_load_stack(old_parent_ra, parent_ra_addr, faulted);
327 if (unlikely(faulted))
328 goto out;
329#ifndef KBUILD_MCOUNT_RA_ADDRESS
330 parent_ra_addr = (unsigned long *)ftrace_get_parent_ra_addr(self_ra,
331 old_parent_ra, (unsigned long)parent_ra_addr, fp);
332 /*
333 * If fails when getting the stack address of the non-leaf function's
334 * ra, stop function graph tracer and return
335 */
336 if (parent_ra_addr == 0)
337 goto out;
338#endif
339 /* *parent_ra_addr = return_hooker; */
340 safe_store_stack(return_hooker, parent_ra_addr, faulted);
341 if (unlikely(faulted))
342 goto out;
343
344 if (ftrace_push_return_trace(old_parent_ra, self_ra, &trace.depth, fp)
345 == -EBUSY) {
346 *parent_ra_addr = old_parent_ra;
347 return;
348 }
349
350 /*
351 * Get the recorded ip of the current mcount calling site in the
352 * __mcount_loc section, which will be used to filter the function
353 * entries configured through the tracing/set_graph_function interface.
354 */
355
356 insns = in_kernel_space(self_ra) ? 2 : MCOUNT_OFFSET_INSNS + 1;
357 trace.func = self_ra - (MCOUNT_INSN_SIZE * insns);
358
359 /* Only trace if the calling function expects to */
360 if (!ftrace_graph_entry(&trace)) {
361 current->curr_ret_stack--;
362 *parent_ra_addr = old_parent_ra;
363 }
364 return;
365out:
366 ftrace_graph_stop();
367 WARN_ON(1);
368}
369#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
370
371#ifdef CONFIG_FTRACE_SYSCALLS
372
373#ifdef CONFIG_32BIT
374unsigned long __init arch_syscall_addr(int nr)
375{
376 return (unsigned long)sys_call_table[nr - __NR_O32_Linux];
377}
378#endif
379
380#ifdef CONFIG_64BIT
381
382unsigned long __init arch_syscall_addr(int nr)
383{
384#ifdef CONFIG_MIPS32_N32
385 if (nr >= __NR_N32_Linux && nr <= __NR_N32_Linux + __NR_N32_Linux_syscalls)
386 return (unsigned long)sysn32_call_table[nr - __NR_N32_Linux];
387#endif
388 if (nr >= __NR_64_Linux && nr <= __NR_64_Linux + __NR_64_Linux_syscalls)
389 return (unsigned long)sys_call_table[nr - __NR_64_Linux];
390#ifdef CONFIG_MIPS32_O32
391 if (nr >= __NR_O32_Linux && nr <= __NR_O32_Linux + __NR_O32_Linux_syscalls)
392 return (unsigned long)sys32_call_table[nr - __NR_O32_Linux];
393#endif
394
395 return (unsigned long) &sys_ni_syscall;
396}
397#endif
398
399#endif /* CONFIG_FTRACE_SYSCALLS */