xref: /linux/arch/mips/kernel/ftrace.c (revision 8be98d2f2a0a262f8bf8a0bc1fdf522b3c7aab17)
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(&current->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