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() */
arch_ftrace_update_code(int command)35 void 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
48 static unsigned int insn_jal_ftrace_caller __read_mostly;
49 static unsigned int insn_la_mcount[2] __read_mostly;
50 static unsigned int insn_j_ftrace_graph_caller __maybe_unused __read_mostly;
51
ftrace_dyn_arch_init_insns(void)52 static 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
ftrace_modify_code(unsigned long ip,unsigned int new_code)73 static 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
ftrace_modify_code_2(unsigned long ip,unsigned int new_code1,unsigned int new_code2)89 static 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
ftrace_modify_code_2r(unsigned long ip,unsigned int new_code1,unsigned int new_code2)109 static 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
ftrace_make_nop(struct module * mod,struct dyn_ftrace * rec,unsigned long addr)162 int 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
ftrace_make_call(struct dyn_ftrace * rec,unsigned long addr)187 int 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
ftrace_update_ftrace_func(ftrace_func_t func)204 int 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
ftrace_dyn_arch_init(void)213 int __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
229 extern void ftrace_graph_call(void);
230 #define FTRACE_GRAPH_CALL_IP ((unsigned long)(&ftrace_graph_call))
231
ftrace_enable_ftrace_graph_caller(void)232 int ftrace_enable_ftrace_graph_caller(void)
233 {
234 return ftrace_modify_code(FTRACE_GRAPH_CALL_IP,
235 insn_j_ftrace_graph_caller);
236 }
237
ftrace_disable_ftrace_graph_caller(void)238 int 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
ftrace_get_parent_ra_addr(unsigned long self_ra,unsigned long old_parent_ra,unsigned long parent_ra_addr,unsigned long fp)251 unsigned 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 */
prepare_ftrace_return(unsigned long * parent_ra_addr,unsigned long self_ra,unsigned long fp)305 void 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;
368 out:
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
arch_syscall_addr(int nr)377 unsigned 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
arch_syscall_addr(int nr)385 unsigned 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 */
403