summaryrefslogtreecommitdiff
path: root/arch/x86/kernel/mcount_64.S
blob: 09284cfab86fb3f1cf26ee68335d5061e495a1dc (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
328
329
330
331
332
333
334
/*
 *  linux/arch/x86_64/mcount_64.S
 *
 *  Copyright (C) 2014  Steven Rostedt, Red Hat Inc
 */

#include <linux/linkage.h>
#include <asm/ptrace.h>
#include <asm/ftrace.h>
#include <asm/nospec-branch.h>

	.code64
	.section .entry.text, "ax"


#ifdef CONFIG_FUNCTION_TRACER

#ifdef CC_USING_FENTRY
# define function_hook	__fentry__
#else
# define function_hook	mcount
#endif

/* All cases save the original rbp (8 bytes) */
#ifdef CONFIG_FRAME_POINTER
# ifdef CC_USING_FENTRY
/* Save parent and function stack frames (rip and rbp) */
#  define MCOUNT_FRAME_SIZE	(8+16*2)
# else
/* Save just function stack frame (rip and rbp) */
#  define MCOUNT_FRAME_SIZE	(8+16)
# endif
#else
/* No need to save a stack frame */
# define MCOUNT_FRAME_SIZE	8
#endif /* CONFIG_FRAME_POINTER */

/* Size of stack used to save mcount regs in save_mcount_regs */
#define MCOUNT_REG_SIZE		(SS+8 + MCOUNT_FRAME_SIZE)

/*
 * gcc -pg option adds a call to 'mcount' in most functions.
 * When -mfentry is used, the call is to 'fentry' and not 'mcount'
 * and is done before the function's stack frame is set up.
 * They both require a set of regs to be saved before calling
 * any C code and restored before returning back to the function.
 *
 * On boot up, all these calls are converted into nops. When tracing
 * is enabled, the call can jump to either ftrace_caller or
 * ftrace_regs_caller. Callbacks (tracing functions) that require
 * ftrace_regs_caller (like kprobes) need to have pt_regs passed to
 * it. For this reason, the size of the pt_regs structure will be
 * allocated on the stack and the required mcount registers will
 * be saved in the locations that pt_regs has them in.
 */

/*
 * @added: the amount of stack added before calling this
 *
 * After this is called, the following registers contain:
 *
 *  %rdi - holds the address that called the trampoline
 *  %rsi - holds the parent function (traced function's return address)
 *  %rdx - holds the original %rbp
 */
.macro save_mcount_regs added=0

	/* Always save the original rbp */
	pushq %rbp

#ifdef CONFIG_FRAME_POINTER
	/*
	 * Stack traces will stop at the ftrace trampoline if the frame pointer
	 * is not set up properly. If fentry is used, we need to save a frame
	 * pointer for the parent as well as the function traced, because the
	 * fentry is called before the stack frame is set up, where as mcount
	 * is called afterward.
	 */
#ifdef CC_USING_FENTRY
	/* Save the parent pointer (skip orig rbp and our return address) */
	pushq \added+8*2(%rsp)
	pushq %rbp
	movq %rsp, %rbp
	/* Save the return address (now skip orig rbp, rbp and parent) */
	pushq \added+8*3(%rsp)
#else
	/* Can't assume that rip is before this (unless added was zero) */
	pushq \added+8(%rsp)
#endif
	pushq %rbp
	movq %rsp, %rbp
#endif /* CONFIG_FRAME_POINTER */

	/*
	 * We add enough stack to save all regs.
	 */
	subq $(MCOUNT_REG_SIZE - MCOUNT_FRAME_SIZE), %rsp
	movq %rax, RAX(%rsp)
	movq %rcx, RCX(%rsp)
	movq %rdx, RDX(%rsp)
	movq %rsi, RSI(%rsp)
	movq %rdi, RDI(%rsp)
	movq %r8, R8(%rsp)
	movq %r9, R9(%rsp)
	/*
	 * Save the original RBP. Even though the mcount ABI does not
	 * require this, it helps out callers.
	 */
	movq MCOUNT_REG_SIZE-8(%rsp), %rdx
	movq %rdx, RBP(%rsp)

	/* Copy the parent address into %rsi (second parameter) */
#ifdef CC_USING_FENTRY
	movq MCOUNT_REG_SIZE+8+\added(%rsp), %rsi
#else
	/* %rdx contains original %rbp */
	movq 8(%rdx), %rsi
#endif

	 /* Move RIP to its proper location */
	movq MCOUNT_REG_SIZE+\added(%rsp), %rdi
	movq %rdi, RIP(%rsp)

	/*
	 * Now %rdi (the first parameter) has the return address of
	 * where ftrace_call returns. But the callbacks expect the
	 * address of the call itself.
	 */
	subq $MCOUNT_INSN_SIZE, %rdi
	.endm

.macro restore_mcount_regs
	movq R9(%rsp), %r9
	movq R8(%rsp), %r8
	movq RDI(%rsp), %rdi
	movq RSI(%rsp), %rsi
	movq RDX(%rsp), %rdx
	movq RCX(%rsp), %rcx
	movq RAX(%rsp), %rax

	/* ftrace_regs_caller can modify %rbp */
	movq RBP(%rsp), %rbp

	addq $MCOUNT_REG_SIZE, %rsp

	.endm

#ifdef CONFIG_DYNAMIC_FTRACE

ENTRY(function_hook)
	retq
END(function_hook)

ENTRY(ftrace_caller)
	/* save_mcount_regs fills in first two parameters */
	save_mcount_regs

GLOBAL(ftrace_caller_op_ptr)
	/* Load the ftrace_ops into the 3rd parameter */
	movq function_trace_op(%rip), %rdx

	/* regs go into 4th parameter (but make it NULL) */
	movq $0, %rcx

GLOBAL(ftrace_call)
	call ftrace_stub

	restore_mcount_regs

	/*
	 * The copied trampoline must call ftrace_return as it
	 * still may need to call the function graph tracer.
	 */
GLOBAL(ftrace_caller_end)

GLOBAL(ftrace_return)

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
GLOBAL(ftrace_graph_call)
	jmp ftrace_stub
#endif

/* This is weak to keep gas from relaxing the jumps */
WEAK(ftrace_stub)
	retq
END(ftrace_caller)

ENTRY(ftrace_regs_caller)
	/* Save the current flags before any operations that can change them */
	pushfq

	/* added 8 bytes to save flags */
	save_mcount_regs 8
	/* save_mcount_regs fills in first two parameters */

GLOBAL(ftrace_regs_caller_op_ptr)
	/* Load the ftrace_ops into the 3rd parameter */
	movq function_trace_op(%rip), %rdx

	/* Save the rest of pt_regs */
	movq %r15, R15(%rsp)
	movq %r14, R14(%rsp)
	movq %r13, R13(%rsp)
	movq %r12, R12(%rsp)
	movq %r11, R11(%rsp)
	movq %r10, R10(%rsp)
	movq %rbx, RBX(%rsp)
	/* Copy saved flags */
	movq MCOUNT_REG_SIZE(%rsp), %rcx
	movq %rcx, EFLAGS(%rsp)
	/* Kernel segments */
	movq $__KERNEL_DS, %rcx
	movq %rcx, SS(%rsp)
	movq $__KERNEL_CS, %rcx
	movq %rcx, CS(%rsp)
	/* Stack - skipping return address and flags */
	leaq MCOUNT_REG_SIZE+8*2(%rsp), %rcx
	movq %rcx, RSP(%rsp)

	/* regs go into 4th parameter */
	leaq (%rsp), %rcx

GLOBAL(ftrace_regs_call)
	call ftrace_stub

	/* Copy flags back to SS, to restore them */
	movq EFLAGS(%rsp), %rax
	movq %rax, MCOUNT_REG_SIZE(%rsp)

	/* Handlers can change the RIP */
	movq RIP(%rsp), %rax
	movq %rax, MCOUNT_REG_SIZE+8(%rsp)

	/* restore the rest of pt_regs */
	movq R15(%rsp), %r15
	movq R14(%rsp), %r14
	movq R13(%rsp), %r13
	movq R12(%rsp), %r12
	movq R10(%rsp), %r10
	movq RBX(%rsp), %rbx

	restore_mcount_regs

	/* Restore flags */
	popfq

	/*
	 * As this jmp to ftrace_return can be a short jump
	 * it must not be copied into the trampoline.
	 * The trampoline will add the code to jump
	 * to the return.
	 */
GLOBAL(ftrace_regs_caller_end)

	jmp ftrace_return

END(ftrace_regs_caller)


#else /* ! CONFIG_DYNAMIC_FTRACE */

ENTRY(function_hook)
	cmpq $ftrace_stub, ftrace_trace_function
	jnz trace

fgraph_trace:
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
	cmpq $ftrace_stub, ftrace_graph_return
	jnz ftrace_graph_caller

	cmpq $ftrace_graph_entry_stub, ftrace_graph_entry
	jnz ftrace_graph_caller
#endif

GLOBAL(ftrace_stub)
	retq

trace:
	/* save_mcount_regs fills in first two parameters */
	save_mcount_regs

	/*
	 * When DYNAMIC_FTRACE is not defined, ARCH_SUPPORTS_FTRACE_OPS is not
	 * set (see include/asm/ftrace.h and include/linux/ftrace.h).  Only the
	 * ip and parent ip are used and the list function is called when
	 * function tracing is enabled.
	 */

	movq ftrace_trace_function, %r8
	CALL_NOSPEC %r8
	restore_mcount_regs

	jmp fgraph_trace
END(function_hook)
#endif /* CONFIG_DYNAMIC_FTRACE */
#endif /* CONFIG_FUNCTION_TRACER */

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
ENTRY(ftrace_graph_caller)
	/* Saves rbp into %rdx and fills first parameter  */
	save_mcount_regs

#ifdef CC_USING_FENTRY
	leaq MCOUNT_REG_SIZE+8(%rsp), %rsi
	movq $0, %rdx	/* No framepointers needed */
#else
	/* Save address of the return address of traced function */
	leaq 8(%rdx), %rsi
	/* ftrace does sanity checks against frame pointers */
	movq (%rdx), %rdx
#endif
	call	prepare_ftrace_return

	restore_mcount_regs

	retq
END(ftrace_graph_caller)

GLOBAL(return_to_handler)
	subq  $24, %rsp

	/* Save the return values */
	movq %rax, (%rsp)
	movq %rdx, 8(%rsp)
	movq %rbp, %rdi

	call ftrace_return_to_handler

	movq %rax, %rdi
	movq 8(%rsp), %rdx
	movq (%rsp), %rax
	addq $24, %rsp
	JMP_NOSPEC %rdi
#endif