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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#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// SPDX-License-Identifier: GPL-2.0
2/*
3 * Code for replacing ftrace calls with jumps.
4 *
5 * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
6 * Copyright (C) 2009, 2010 DSLab, Lanzhou University, China
7 * Author: Wu Zhangjin <wuzhangjin@gmail.com>
8 *
9 * Thanks goes to Steven Rostedt for writing the original x86 version.
10 */
11
12#include <linux/uaccess.h>
13#include <linux/init.h>
14#include <linux/ftrace.h>
15#include <linux/syscalls.h>
16
17#include <asm/asm.h>
18#include <asm/asm-offsets.h>
19#include <asm/cacheflush.h>
20#include <asm/syscall.h>
21#include <asm/uasm.h>
22#include <asm/unistd.h>
23
24#include <asm-generic/sections.h>
25
26#if defined(KBUILD_MCOUNT_RA_ADDRESS) && defined(CONFIG_32BIT)
27#define MCOUNT_OFFSET_INSNS 5
28#else
29#define MCOUNT_OFFSET_INSNS 4
30#endif
31
32#ifdef CONFIG_DYNAMIC_FTRACE
33
34/* Arch override because MIPS doesn't need to run this from stop_machine() */
35void arch_ftrace_update_code(int command)
36{
37 ftrace_modify_all_code(command);
38}
39
40#define JAL 0x0c000000 /* jump & link: ip --> ra, jump to target */
41#define ADDR_MASK 0x03ffffff /* op_code|addr : 31...26|25 ....0 */
42#define JUMP_RANGE_MASK ((1UL << 28) - 1)
43
44#define INSN_NOP 0x00000000 /* nop */
45#define INSN_JAL(addr) \
46 ((unsigned int)(JAL | (((addr) >> 2) & ADDR_MASK)))
47
48static unsigned int insn_jal_ftrace_caller __read_mostly;
49static unsigned int insn_la_mcount[2] __read_mostly;
50static unsigned int insn_j_ftrace_graph_caller __maybe_unused __read_mostly;
51
52static inline void ftrace_dyn_arch_init_insns(void)
53{
54 u32 *buf;
55 unsigned int v1;
56
57 /* la v1, _mcount */
58 v1 = 3;
59 buf = (u32 *)&insn_la_mcount[0];
60 UASM_i_LA(&buf, v1, MCOUNT_ADDR);
61
62 /* jal (ftrace_caller + 8), jump over the first two instruction */
63 buf = (u32 *)&insn_jal_ftrace_caller;
64 uasm_i_jal(&buf, (FTRACE_ADDR + 8) & JUMP_RANGE_MASK);
65
66#ifdef CONFIG_FUNCTION_GRAPH_TRACER
67 /* j ftrace_graph_caller */
68 buf = (u32 *)&insn_j_ftrace_graph_caller;
69 uasm_i_j(&buf, (unsigned long)ftrace_graph_caller & JUMP_RANGE_MASK);
70#endif
71}
72
73static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
74{
75 int faulted;
76
77 /* *(unsigned int *)ip = new_code; */
78 safe_store_code(new_code, ip, faulted);
79
80 if (unlikely(faulted))
81 return -EFAULT;
82
83 flush_icache_range(ip, ip + 8);
84
85 return 0;
86}
87
88#ifndef CONFIG_64BIT
89static int ftrace_modify_code_2(unsigned long ip, unsigned int new_code1,
90 unsigned int new_code2)
91{
92 int faulted;
93
94 safe_store_code(new_code1, ip, faulted);
95 if (unlikely(faulted))
96 return -EFAULT;
97
98 ip += 4;
99 safe_store_code(new_code2, ip, faulted);
100 if (unlikely(faulted))
101 return -EFAULT;
102
103 ip -= 4;
104 flush_icache_range(ip, ip + 8);
105
106 return 0;
107}
108
109static int ftrace_modify_code_2r(unsigned long ip, unsigned int new_code1,
110 unsigned int new_code2)
111{
112 int faulted;
113
114 ip += 4;
115 safe_store_code(new_code2, ip, faulted);
116 if (unlikely(faulted))
117 return -EFAULT;
118
119 ip -= 4;
120 safe_store_code(new_code1, ip, faulted);
121 if (unlikely(faulted))
122 return -EFAULT;
123
124 flush_icache_range(ip, ip + 8);
125
126 return 0;
127}
128#endif
129
130/*
131 * The details about the calling site of mcount on MIPS
132 *
133 * 1. For kernel:
134 *
135 * move at, ra
136 * jal _mcount --> nop
137 * sub sp, sp, 8 --> nop (CONFIG_32BIT)
138 *
139 * 2. For modules:
140 *
141 * 2.1 For KBUILD_MCOUNT_RA_ADDRESS and CONFIG_32BIT
142 *
143 * lui v1, hi_16bit_of_mcount --> b 1f (0x10000005)
144 * addiu v1, v1, low_16bit_of_mcount --> nop (CONFIG_32BIT)
145 * move at, ra
146 * move $12, ra_address
147 * jalr v1
148 * sub sp, sp, 8
149 * 1: offset = 5 instructions
150 * 2.2 For the Other situations
151 *
152 * lui v1, hi_16bit_of_mcount --> b 1f (0x10000004)
153 * addiu v1, v1, low_16bit_of_mcount --> nop (CONFIG_32BIT)
154 * move at, ra
155 * jalr v1
156 * nop | move $12, ra_address | sub sp, sp, 8
157 * 1: offset = 4 instructions
158 */
159
160#define INSN_B_1F (0x10000000 | MCOUNT_OFFSET_INSNS)
161
162int ftrace_make_nop(struct module *mod,
163 struct dyn_ftrace *rec, unsigned long addr)
164{
165 unsigned int new;
166 unsigned long ip = rec->ip;
167
168 /*
169 * If ip is in kernel space, no long call, otherwise, long call is
170 * needed.
171 */
172 new = core_kernel_text(ip) ? INSN_NOP : INSN_B_1F;
173#ifdef CONFIG_64BIT
174 return ftrace_modify_code(ip, new);
175#else
176 /*
177 * On 32 bit MIPS platforms, gcc adds a stack adjust
178 * instruction in the delay slot after the branch to
179 * mcount and expects mcount to restore the sp on return.
180 * This is based on a legacy API and does nothing but
181 * waste instructions so it's being removed at runtime.
182 */
183 return ftrace_modify_code_2(ip, new, INSN_NOP);
184#endif
185}
186
187int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
188{
189 unsigned int new;
190 unsigned long ip = rec->ip;
191
192 new = core_kernel_text(ip) ? insn_jal_ftrace_caller : insn_la_mcount[0];
193
194#ifdef CONFIG_64BIT
195 return ftrace_modify_code(ip, new);
196#else
197 return ftrace_modify_code_2r(ip, new, core_kernel_text(ip) ?
198 INSN_NOP : insn_la_mcount[1]);
199#endif
200}
201
202#define FTRACE_CALL_IP ((unsigned long)(&ftrace_call))
203
204int ftrace_update_ftrace_func(ftrace_func_t func)
205{
206 unsigned int new;
207
208 new = INSN_JAL((unsigned long)func);
209
210 return ftrace_modify_code(FTRACE_CALL_IP, new);
211}
212
213int __init ftrace_dyn_arch_init(void)
214{
215 /* Encode the instructions when booting */
216 ftrace_dyn_arch_init_insns();
217
218 /* Remove "b ftrace_stub" to ensure ftrace_caller() is executed */
219 ftrace_modify_code(MCOUNT_ADDR, INSN_NOP);
220
221 return 0;
222}
223#endif /* CONFIG_DYNAMIC_FTRACE */
224
225#ifdef CONFIG_FUNCTION_GRAPH_TRACER
226
227#ifdef CONFIG_DYNAMIC_FTRACE
228
229extern void ftrace_graph_call(void);
230#define FTRACE_GRAPH_CALL_IP ((unsigned long)(&ftrace_graph_call))
231
232int ftrace_enable_ftrace_graph_caller(void)
233{
234 return ftrace_modify_code(FTRACE_GRAPH_CALL_IP,
235 insn_j_ftrace_graph_caller);
236}
237
238int ftrace_disable_ftrace_graph_caller(void)
239{
240 return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, INSN_NOP);
241}
242
243#endif /* CONFIG_DYNAMIC_FTRACE */
244
245#ifndef KBUILD_MCOUNT_RA_ADDRESS
246
247#define S_RA_SP (0xafbf << 16) /* s{d,w} ra, offset(sp) */
248#define S_R_SP (0xafb0 << 16) /* s{d,w} R, offset(sp) */
249#define OFFSET_MASK 0xffff /* stack offset range: 0 ~ PT_SIZE */
250
251unsigned long ftrace_get_parent_ra_addr(unsigned long self_ra, unsigned long
252 old_parent_ra, unsigned long parent_ra_addr, unsigned long fp)
253{
254 unsigned long sp, ip, tmp;
255 unsigned int code;
256 int faulted;
257
258 /*
259 * For module, move the ip from the return address after the
260 * instruction "lui v1, hi_16bit_of_mcount"(offset is 24), but for
261 * kernel, move after the instruction "move ra, at"(offset is 16)
262 */
263 ip = self_ra - (core_kernel_text(self_ra) ? 16 : 24);
264
265 /*
266 * search the text until finding the non-store instruction or "s{d,w}
267 * ra, offset(sp)" instruction
268 */
269 do {
270 /* get the code at "ip": code = *(unsigned int *)ip; */
271 safe_load_code(code, ip, faulted);
272
273 if (unlikely(faulted))
274 return 0;
275 /*
276 * If we hit the non-store instruction before finding where the
277 * ra is stored, then this is a leaf function and it does not
278 * store the ra on the stack
279 */
280 if ((code & S_R_SP) != S_R_SP)
281 return parent_ra_addr;
282
283 /* Move to the next instruction */
284 ip -= 4;
285 } while ((code & S_RA_SP) != S_RA_SP);
286
287 sp = fp + (code & OFFSET_MASK);
288
289 /* tmp = *(unsigned long *)sp; */
290 safe_load_stack(tmp, sp, faulted);
291 if (unlikely(faulted))
292 return 0;
293
294 if (tmp == old_parent_ra)
295 return sp;
296 return 0;
297}
298
299#endif /* !KBUILD_MCOUNT_RA_ADDRESS */
300
301/*
302 * Hook the return address and push it in the stack of return addrs
303 * in current thread info.
304 */
305void prepare_ftrace_return(unsigned long *parent_ra_addr, unsigned long self_ra,
306 unsigned long fp)
307{
308 unsigned long old_parent_ra;
309 unsigned long return_hooker = (unsigned long)
310 &return_to_handler;
311 int faulted, insns;
312
313 if (unlikely(ftrace_graph_is_dead()))
314 return;
315
316 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
317 return;
318
319 /*
320 * "parent_ra_addr" is the stack address where the return address of
321 * the caller of _mcount is saved.
322 *
323 * If gcc < 4.5, a leaf function does not save the return address
324 * in the stack address, so we "emulate" one in _mcount's stack space,
325 * and hijack it directly.
326 * For a non-leaf function, it does save the return address to its own
327 * stack space, so we can not hijack it directly, but need to find the
328 * real stack address, which is done by ftrace_get_parent_addr().
329 *
330 * If gcc >= 4.5, with the new -mmcount-ra-address option, for a
331 * non-leaf function, the location of the return address will be saved
332 * to $12 for us.
333 * For a leaf function, it just puts a zero into $12, so we handle
334 * it in ftrace_graph_caller() of mcount.S.
335 */
336
337 /* old_parent_ra = *parent_ra_addr; */
338 safe_load_stack(old_parent_ra, parent_ra_addr, faulted);
339 if (unlikely(faulted))
340 goto out;
341#ifndef KBUILD_MCOUNT_RA_ADDRESS
342 parent_ra_addr = (unsigned long *)ftrace_get_parent_ra_addr(self_ra,
343 old_parent_ra, (unsigned long)parent_ra_addr, fp);
344 /*
345 * If fails when getting the stack address of the non-leaf function's
346 * ra, stop function graph tracer and return
347 */
348 if (parent_ra_addr == NULL)
349 goto out;
350#endif
351 /* *parent_ra_addr = return_hooker; */
352 safe_store_stack(return_hooker, parent_ra_addr, faulted);
353 if (unlikely(faulted))
354 goto out;
355
356 /*
357 * Get the recorded ip of the current mcount calling site in the
358 * __mcount_loc section, which will be used to filter the function
359 * entries configured through the tracing/set_graph_function interface.
360 */
361
362 insns = core_kernel_text(self_ra) ? 2 : MCOUNT_OFFSET_INSNS + 1;
363 self_ra -= (MCOUNT_INSN_SIZE * insns);
364
365 if (function_graph_enter(old_parent_ra, self_ra, fp, NULL))
366 *parent_ra_addr = old_parent_ra;
367 return;
368out:
369 ftrace_graph_stop();
370 WARN_ON(1);
371}
372#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
373
374#ifdef CONFIG_FTRACE_SYSCALLS
375
376#ifdef CONFIG_32BIT
377unsigned long __init arch_syscall_addr(int nr)
378{
379 return (unsigned long)sys_call_table[nr - __NR_O32_Linux];
380}
381#endif
382
383#ifdef CONFIG_64BIT
384
385unsigned long __init arch_syscall_addr(int nr)
386{
387#ifdef CONFIG_MIPS32_N32
388 if (nr >= __NR_N32_Linux && nr < __NR_N32_Linux + __NR_N32_Linux_syscalls)
389 return (unsigned long)sysn32_call_table[nr - __NR_N32_Linux];
390#endif
391 if (nr >= __NR_64_Linux && nr < __NR_64_Linux + __NR_64_Linux_syscalls)
392 return (unsigned long)sys_call_table[nr - __NR_64_Linux];
393#ifdef CONFIG_MIPS32_O32
394 if (nr >= __NR_O32_Linux && nr < __NR_O32_Linux + __NR_O32_Linux_syscalls)
395 return (unsigned long)sys32_call_table[nr - __NR_O32_Linux];
396#endif
397
398 return (unsigned long) &sys_ni_syscall;
399}
400#endif
401
402#endif /* CONFIG_FTRACE_SYSCALLS */