xref: /openbmc/linux/arch/mips/kernel/ftrace.c (revision b34e08d5)
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() */
34 void 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  */
47 static 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 
65 static unsigned int insn_jal_ftrace_caller __read_mostly;
66 static unsigned int insn_lui_v1_hi16_mcount __read_mostly;
67 static unsigned int insn_j_ftrace_graph_caller __maybe_unused __read_mostly;
68 
69 static 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 
90 static 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
110 static 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 
157 int 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 
182 int 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 
195 int 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 
204 int __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 
220 extern void ftrace_graph_call(void);
221 #define FTRACE_GRAPH_CALL_IP	((unsigned long)(&ftrace_graph_call))
222 
223 int ftrace_enable_ftrace_graph_caller(void)
224 {
225 	return ftrace_modify_code(FTRACE_GRAPH_CALL_IP,
226 			insn_j_ftrace_graph_caller);
227 }
228 
229 int 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 
242 unsigned 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  */
296 void 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(&current->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;
365 out:
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
374 unsigned 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 
382 unsigned 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 */
400