aboutsummaryrefslogtreecommitdiffstats
path: root/arch/mips/kernel/ftrace.c
blob: feb8021a305f49a4e6f366183e27626316398ed3 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
/*
 * Code for replacing ftrace calls with jumps.
 *
 * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
 * Copyright (C) 2009, 2010 DSLab, Lanzhou University, China
 * Author: Wu Zhangjin <wuzhangjin@gmail.com>
 *
 * Thanks goes to Steven Rostedt for writing the original x86 version.
 */

#include <linux/uaccess.h>
#include <linux/init.h>
#include <linux/ftrace.h>

#include <asm/asm.h>
#include <asm/asm-offsets.h>
#include <asm/cacheflush.h>
#include <asm/uasm.h>

#include <asm-generic/sections.h>

#ifdef CONFIG_DYNAMIC_FTRACE

#define JAL 0x0c000000		/* jump & link: ip --> ra, jump to target */
#define ADDR_MASK 0x03ffffff	/*  op_code|addr : 31...26|25 ....0 */
#define JUMP_RANGE_MASK ((1UL << 28) - 1)

#define INSN_NOP 0x00000000	/* nop */
#define INSN_JAL(addr)	\
	((unsigned int)(JAL | (((addr) >> 2) & ADDR_MASK)))

static unsigned int insn_jal_ftrace_caller __read_mostly;
static unsigned int insn_lui_v1_hi16_mcount __read_mostly;
static unsigned int insn_j_ftrace_graph_caller __maybe_unused __read_mostly;

static inline void ftrace_dyn_arch_init_insns(void)
{
	u32 *buf;
	unsigned int v1;

	/* lui v1, hi16_mcount */
	v1 = 3;
	buf = (u32 *)&insn_lui_v1_hi16_mcount;
	UASM_i_LA_mostly(&buf, v1, MCOUNT_ADDR);

	/* jal (ftrace_caller + 8), jump over the first two instruction */
	buf = (u32 *)&insn_jal_ftrace_caller;
	uasm_i_jal(&buf, (FTRACE_ADDR + 8) & JUMP_RANGE_MASK);

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
	/* j ftrace_graph_caller */
	buf = (u32 *)&insn_j_ftrace_graph_caller;
	uasm_i_j(&buf, (unsigned long)ftrace_graph_caller & JUMP_RANGE_MASK);
#endif
}

/*
 * Check if the address is in kernel space
 *
 * Clone core_kernel_text() from kernel/extable.c, but doesn't call
 * init_kernel_text() for Ftrace doesn't trace functions in init sections.
 */
static inline int in_kernel_space(unsigned long ip)
{
	if (ip >= (unsigned long)_stext &&
	    ip <= (unsigned long)_etext)
		return 1;
	return 0;
}

static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
{
	int faulted;

	/* *(unsigned int *)ip = new_code; */
	safe_store_code(new_code, ip, faulted);

	if (unlikely(faulted))
		return -EFAULT;

	flush_icache_range(ip, ip + 8);

	return 0;
}

/*
 * The details about the calling site of mcount on MIPS
 *
 * 1. For kernel:
 *
 * move at, ra
 * jal _mcount		--> nop
 *
 * 2. For modules:
 *
 * 2.1 For KBUILD_MCOUNT_RA_ADDRESS and CONFIG_32BIT
 *
 * lui v1, hi_16bit_of_mcount        --> b 1f (0x10000005)
 * addiu v1, v1, low_16bit_of_mcount
 * move at, ra
 * move $12, ra_address
 * jalr v1
 *  sub sp, sp, 8
 *                                  1: offset = 5 instructions
 * 2.2 For the Other situations
 *
 * lui v1, hi_16bit_of_mcount        --> b 1f (0x10000004)
 * addiu v1, v1, low_16bit_of_mcount
 * move at, ra
 * jalr v1
 *  nop | move $12, ra_address | sub sp, sp, 8
 *                                  1: offset = 4 instructions
 */

#if defined(KBUILD_MCOUNT_RA_ADDRESS) && defined(CONFIG_32BIT)
#define MCOUNT_OFFSET_INSNS 5
#else
#define MCOUNT_OFFSET_INSNS 4
#endif
#define INSN_B_1F (0x10000000 | MCOUNT_OFFSET_INSNS)

int ftrace_make_nop(struct module *mod,
		    struct dyn_ftrace *rec, unsigned long addr)
{
	unsigned int new;
	unsigned long ip = rec->ip;

	/*
	 * If ip is in kernel space, no long call, otherwise, long call is
	 * needed.
	 */
	new = in_kernel_space(ip) ? INSN_NOP : INSN_B_1F;

	return ftrace_modify_code(ip, new);
}

int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
	unsigned int new;
	unsigned long ip = rec->ip;

	new = in_kernel_space(ip) ? insn_jal_ftrace_caller :
		insn_lui_v1_hi16_mcount;

	return ftrace_modify_code(ip, new);
}

#define FTRACE_CALL_IP ((unsigned long)(&ftrace_call))

int ftrace_update_ftrace_func(ftrace_func_t func)
{
	unsigned int new;

	new = INSN_JAL((unsigned long)func);

	return ftrace_modify_code(FTRACE_CALL_IP, new);
}

int __init ftrace_dyn_arch_init(void *data)
{
	/* Encode the instructions when booting */
	ftrace_dyn_arch_init_insns();

	/* Remove "b ftrace_stub" to ensure ftrace_caller() is executed */
	ftrace_modify_code(MCOUNT_ADDR, INSN_NOP);

	/* The return code is retured via data */
	*(unsigned long *)data = 0;

	return 0;
}
#endif	/* CONFIG_DYNAMIC_FTRACE */

#ifdef CONFIG_FUNCTION_GRAPH_TRACER

#ifdef CONFIG_DYNAMIC_FTRACE

extern void ftrace_graph_call(void);
#define FTRACE_GRAPH_CALL_IP	((unsigned long)(&ftrace_graph_call))

int ftrace_enable_ftrace_graph_caller(void)
{
	return ftrace_modify_code(FTRACE_GRAPH_CALL_IP,
			insn_j_ftrace_graph_caller);
}

int ftrace_disable_ftrace_graph_caller(void)
{
	return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, INSN_NOP);
}

#endif	/* CONFIG_DYNAMIC_FTRACE */

#ifndef KBUILD_MCOUNT_RA_ADDRESS

#define S_RA_SP	(0xafbf << 16)	/* s{d,w} ra, offset(sp) */
#define S_R_SP	(0xafb0 << 16)  /* s{d,w} R, offset(sp) */
#define OFFSET_MASK	0xffff	/* stack offset range: 0 ~ PT_SIZE */

unsigned long ftrace_get_parent_ra_addr(unsigned long self_ra, unsigned long
		old_parent_ra, unsigned long parent_ra_addr, unsigned long fp)
{
	unsigned long sp, ip, tmp;
	unsigned int code;
	int faulted;

	/*
	 * For module, move the ip from the return address after the
	 * instruction "lui v1, hi_16bit_of_mcount"(offset is 24), but for
	 * kernel, move after the instruction "move ra, at"(offset is 16)
	 */
	ip = self_ra - (in_kernel_space(self_ra) ? 16 : 24);

	/*
	 * search the text until finding the non-store instruction or "s{d,w}
	 * ra, offset(sp)" instruction
	 */
	do {
		/* get the code at "ip": code = *(unsigned int *)ip; */
		safe_load_code(code, ip, faulted);

		if (unlikely(faulted))
			return 0;
		/*
		 * If we hit the non-store instruction before finding where the
		 * ra is stored, then this is a leaf function and it does not
		 * store the ra on the stack
		 */
		if ((code & S_R_SP) != S_R_SP)
			return parent_ra_addr;

		/* Move to the next instruction */
		ip -= 4;
	} while ((code & S_RA_SP) != S_RA_SP);

	sp = fp + (code & OFFSET_MASK);

	/* tmp = *(unsigned long *)sp; */
	safe_load_stack(tmp, sp, faulted);
	if (unlikely(faulted))
		return 0;

	if (tmp == old_parent_ra)
		return sp;
	return 0;
}

#endif	/* !KBUILD_MCOUNT_RA_ADDRESS */

/*
 * Hook the return address and push it in the stack of return addrs
 * in current thread info.
 */
void prepare_ftrace_return(unsigned long *parent_ra_addr, unsigned long self_ra,
			   unsigned long fp)
{
	unsigned long old_parent_ra;
	struct ftrace_graph_ent trace;
	unsigned long return_hooker = (unsigned long)
	    &return_to_handler;
	int faulted, insns;

	if (unlikely(atomic_read(&current->tracing_graph_pause)))
		return;

	/*
	 * "parent_ra_addr" is the stack address saved the return address of
	 * the caller of _mcount.
	 *
	 * if the gcc < 4.5, a leaf function does not save the return address
	 * in the stack address, so, we "emulate" one in _mcount's stack space,
	 * and hijack it directly, but for a non-leaf function, it save the
	 * return address to the its own stack space, we can not hijack it
	 * directly, but need to find the real stack address,
	 * ftrace_get_parent_addr() does it!
	 *
	 * if gcc>= 4.5, with the new -mmcount-ra-address option, for a
	 * non-leaf function, the location of the return address will be saved
	 * to $12 for us, and for a leaf function, only put a zero into $12. we
	 * do it in ftrace_graph_caller of mcount.S.
	 */

	/* old_parent_ra = *parent_ra_addr; */
	safe_load_stack(old_parent_ra, parent_ra_addr, faulted);
	if (unlikely(faulted))
		goto out;
#ifndef KBUILD_MCOUNT_RA_ADDRESS
	parent_ra_addr = (unsigned long *)ftrace_get_parent_ra_addr(self_ra,
			old_parent_ra, (unsigned long)parent_ra_addr, fp);
	/*
	 * If fails when getting the stack address of the non-leaf function's
	 * ra, stop function graph tracer and return
	 */
	if (parent_ra_addr == 0)
		goto out;
#endif
	/* *parent_ra_addr = return_hooker; */
	safe_store_stack(return_hooker, parent_ra_addr, faulted);
	if (unlikely(faulted))
		goto out;

	if (ftrace_push_return_trace(old_parent_ra, self_ra, &trace.depth, fp)
	    == -EBUSY) {
		*parent_ra_addr = old_parent_ra;
		return;
	}

	/*
	 * Get the recorded ip of the current mcount calling site in the
	 * __mcount_loc section, which will be used to filter the function
	 * entries configured through the tracing/set_graph_function interface.
	 */

	insns = in_kernel_space(self_ra) ? 2 : MCOUNT_OFFSET_INSNS + 1;
	trace.func = self_ra - (MCOUNT_INSN_SIZE * insns);

	/* Only trace if the calling function expects to */
	if (!ftrace_graph_entry(&trace)) {
		current->curr_ret_stack--;
		*parent_ra_addr = old_parent_ra;
	}
	return;
out:
	ftrace_graph_stop();
	WARN_ON(1);
}
#endif	/* CONFIG_FUNCTION_GRAPH_TRACER */

Privacy Policy