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1/*
2 * This program is free software; you can redistribute it and/or modify
3 * it under the terms of the GNU General Public License version 2 as
4 * published by the Free Software Foundation.
5 */
6
7#include <asm/assembler.h>
8#include <asm/ftrace.h>
9#include <asm/unwind.h>
10
11#include "entry-header.S"
12
13/*
14 * When compiling with -pg, gcc inserts a call to the mcount routine at the
15 * start of every function. In mcount, apart from the function's address (in
16 * lr), we need to get hold of the function's caller's address.
17 *
18 * Older GCCs (pre-4.4) inserted a call to a routine called mcount like this:
19 *
20 * bl mcount
21 *
22 * These versions have the limitation that in order for the mcount routine to
23 * be able to determine the function's caller's address, an APCS-style frame
24 * pointer (which is set up with something like the code below) is required.
25 *
26 * mov ip, sp
27 * push {fp, ip, lr, pc}
28 * sub fp, ip, #4
29 *
30 * With EABI, these frame pointers are not available unless -mapcs-frame is
31 * specified, and if building as Thumb-2, not even then.
32 *
33 * Newer GCCs (4.4+) solve this problem by introducing a new version of mcount,
34 * with call sites like:
35 *
36 * push {lr}
37 * bl __gnu_mcount_nc
38 *
39 * With these compilers, frame pointers are not necessary.
40 *
41 * mcount can be thought of as a function called in the middle of a subroutine
42 * call. As such, it needs to be transparent for both the caller and the
43 * callee: the original lr needs to be restored when leaving mcount, and no
44 * registers should be clobbered. (In the __gnu_mcount_nc implementation, we
45 * clobber the ip register. This is OK because the ARM calling convention
46 * allows it to be clobbered in subroutines and doesn't use it to hold
47 * parameters.)
48 *
49 * When using dynamic ftrace, we patch out the mcount call by a "mov r0, r0"
50 * for the mcount case, and a "pop {lr}" for the __gnu_mcount_nc case (see
51 * arch/arm/kernel/ftrace.c).
52 */
53
54#ifndef CONFIG_OLD_MCOUNT
55#if (__GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 4))
56#error Ftrace requires CONFIG_FRAME_POINTER=y with GCC older than 4.4.0.
57#endif
58#endif
59
60.macro mcount_adjust_addr rd, rn
61 bic \rd, \rn, #1 @ clear the Thumb bit if present
62 sub \rd, \rd, #MCOUNT_INSN_SIZE
63.endm
64
65.macro __mcount suffix
66 mcount_enter
67 ldr r0, =ftrace_trace_function
68 ldr r2, [r0]
69 adr r0, .Lftrace_stub
70 cmp r0, r2
71 bne 1f
72
73#ifdef CONFIG_FUNCTION_GRAPH_TRACER
74 ldr r1, =ftrace_graph_return
75 ldr r2, [r1]
76 cmp r0, r2
77 bne ftrace_graph_caller\suffix
78
79 ldr r1, =ftrace_graph_entry
80 ldr r2, [r1]
81 ldr r0, =ftrace_graph_entry_stub
82 cmp r0, r2
83 bne ftrace_graph_caller\suffix
84#endif
85
86 mcount_exit
87
881: mcount_get_lr r1 @ lr of instrumented func
89 mcount_adjust_addr r0, lr @ instrumented function
90 badr lr, 2f
91 mov pc, r2
922: mcount_exit
93.endm
94
95#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
96
97.macro __ftrace_regs_caller
98
99 sub sp, sp, #8 @ space for PC and CPSR OLD_R0,
100 @ OLD_R0 will overwrite previous LR
101
102 add ip, sp, #12 @ move in IP the value of SP as it was
103 @ before the push {lr} of the mcount mechanism
104
105 str lr, [sp, #0] @ store LR instead of PC
106
107 ldr lr, [sp, #8] @ get previous LR
108
109 str r0, [sp, #8] @ write r0 as OLD_R0 over previous LR
110
111 stmdb sp!, {ip, lr}
112 stmdb sp!, {r0-r11, lr}
113
114 @ stack content at this point:
115 @ 0 4 48 52 56 60 64 68 72
116 @ R0 | R1 | ... | LR | SP + 4 | previous LR | LR | PSR | OLD_R0 |
117
118 mov r3, sp @ struct pt_regs*
119
120 ldr r2, =function_trace_op
121 ldr r2, [r2] @ pointer to the current
122 @ function tracing op
123
124 ldr r1, [sp, #S_LR] @ lr of instrumented func
125
126 ldr lr, [sp, #S_PC] @ get LR
127
128 mcount_adjust_addr r0, lr @ instrumented function
129
130 .globl ftrace_regs_call
131ftrace_regs_call:
132 bl ftrace_stub
133
134#ifdef CONFIG_FUNCTION_GRAPH_TRACER
135 .globl ftrace_graph_regs_call
136ftrace_graph_regs_call:
137 mov r0, r0
138#endif
139
140 @ pop saved regs
141 ldmia sp!, {r0-r12} @ restore r0 through r12
142 ldr ip, [sp, #8] @ restore PC
143 ldr lr, [sp, #4] @ restore LR
144 ldr sp, [sp, #0] @ restore SP
145 mov pc, ip @ return
146.endm
147
148#ifdef CONFIG_FUNCTION_GRAPH_TRACER
149.macro __ftrace_graph_regs_caller
150
151 sub r0, fp, #4 @ lr of instrumented routine (parent)
152
153 @ called from __ftrace_regs_caller
154 ldr r1, [sp, #S_PC] @ instrumented routine (func)
155 mcount_adjust_addr r1, r1
156
157 mov r2, fp @ frame pointer
158 bl prepare_ftrace_return
159
160 @ pop registers saved in ftrace_regs_caller
161 ldmia sp!, {r0-r12} @ restore r0 through r12
162 ldr ip, [sp, #8] @ restore PC
163 ldr lr, [sp, #4] @ restore LR
164 ldr sp, [sp, #0] @ restore SP
165 mov pc, ip @ return
166
167.endm
168#endif
169#endif
170
171.macro __ftrace_caller suffix
172 mcount_enter
173
174 mcount_get_lr r1 @ lr of instrumented func
175 mcount_adjust_addr r0, lr @ instrumented function
176
177#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
178 ldr r2, =function_trace_op
179 ldr r2, [r2] @ pointer to the current
180 @ function tracing op
181 mov r3, #0 @ regs is NULL
182#endif
183
184 .globl ftrace_call\suffix
185ftrace_call\suffix:
186 bl ftrace_stub
187
188#ifdef CONFIG_FUNCTION_GRAPH_TRACER
189 .globl ftrace_graph_call\suffix
190ftrace_graph_call\suffix:
191 mov r0, r0
192#endif
193
194 mcount_exit
195.endm
196
197.macro __ftrace_graph_caller
198 sub r0, fp, #4 @ &lr of instrumented routine (&parent)
199#ifdef CONFIG_DYNAMIC_FTRACE
200 @ called from __ftrace_caller, saved in mcount_enter
201 ldr r1, [sp, #16] @ instrumented routine (func)
202 mcount_adjust_addr r1, r1
203#else
204 @ called from __mcount, untouched in lr
205 mcount_adjust_addr r1, lr @ instrumented routine (func)
206#endif
207 mov r2, fp @ frame pointer
208 bl prepare_ftrace_return
209 mcount_exit
210.endm
211
212#ifdef CONFIG_OLD_MCOUNT
213/*
214 * mcount
215 */
216
217.macro mcount_enter
218 stmdb sp!, {r0-r3, lr}
219.endm
220
221.macro mcount_get_lr reg
222 ldr \reg, [fp, #-4]
223.endm
224
225.macro mcount_exit
226 ldr lr, [fp, #-4]
227 ldmia sp!, {r0-r3, pc}
228.endm
229
230ENTRY(mcount)
231#ifdef CONFIG_DYNAMIC_FTRACE
232 stmdb sp!, {lr}
233 ldr lr, [fp, #-4]
234 ldmia sp!, {pc}
235#else
236 __mcount _old
237#endif
238ENDPROC(mcount)
239
240#ifdef CONFIG_DYNAMIC_FTRACE
241ENTRY(ftrace_caller_old)
242 __ftrace_caller _old
243ENDPROC(ftrace_caller_old)
244#endif
245
246#ifdef CONFIG_FUNCTION_GRAPH_TRACER
247ENTRY(ftrace_graph_caller_old)
248 __ftrace_graph_caller
249ENDPROC(ftrace_graph_caller_old)
250#endif
251
252.purgem mcount_enter
253.purgem mcount_get_lr
254.purgem mcount_exit
255#endif
256
257/*
258 * __gnu_mcount_nc
259 */
260
261.macro mcount_enter
262/*
263 * This pad compensates for the push {lr} at the call site. Note that we are
264 * unable to unwind through a function which does not otherwise save its lr.
265 */
266 UNWIND(.pad #4)
267 stmdb sp!, {r0-r3, lr}
268 UNWIND(.save {r0-r3, lr})
269.endm
270
271.macro mcount_get_lr reg
272 ldr \reg, [sp, #20]
273.endm
274
275.macro mcount_exit
276 ldmia sp!, {r0-r3, ip, lr}
277 ret ip
278.endm
279
280ENTRY(__gnu_mcount_nc)
281UNWIND(.fnstart)
282#ifdef CONFIG_DYNAMIC_FTRACE
283 mov ip, lr
284 ldmia sp!, {lr}
285 ret ip
286#else
287 __mcount
288#endif
289UNWIND(.fnend)
290ENDPROC(__gnu_mcount_nc)
291
292#ifdef CONFIG_DYNAMIC_FTRACE
293ENTRY(ftrace_caller)
294UNWIND(.fnstart)
295 __ftrace_caller
296UNWIND(.fnend)
297ENDPROC(ftrace_caller)
298
299#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
300ENTRY(ftrace_regs_caller)
301UNWIND(.fnstart)
302 __ftrace_regs_caller
303UNWIND(.fnend)
304ENDPROC(ftrace_regs_caller)
305#endif
306
307#endif
308
309#ifdef CONFIG_FUNCTION_GRAPH_TRACER
310ENTRY(ftrace_graph_caller)
311UNWIND(.fnstart)
312 __ftrace_graph_caller
313UNWIND(.fnend)
314ENDPROC(ftrace_graph_caller)
315
316#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
317ENTRY(ftrace_graph_regs_caller)
318UNWIND(.fnstart)
319 __ftrace_graph_regs_caller
320UNWIND(.fnend)
321ENDPROC(ftrace_graph_regs_caller)
322#endif
323#endif
324
325.purgem mcount_enter
326.purgem mcount_get_lr
327.purgem mcount_exit
328
329#ifdef CONFIG_FUNCTION_GRAPH_TRACER
330 .globl return_to_handler
331return_to_handler:
332 stmdb sp!, {r0-r3}
333 mov r0, fp @ frame pointer
334 bl ftrace_return_to_handler
335 mov lr, r0 @ r0 has real ret addr
336 ldmia sp!, {r0-r3}
337 ret lr
338#endif
339
340ENTRY(ftrace_stub)
341.Lftrace_stub:
342 ret lr
343ENDPROC(ftrace_stub)
1/* SPDX-License-Identifier: GPL-2.0-only */
2
3#include <asm/assembler.h>
4#include <asm/ftrace.h>
5#include <asm/unwind.h>
6
7#include "entry-header.S"
8
9/*
10 * When compiling with -pg, gcc inserts a call to the mcount routine at the
11 * start of every function. In mcount, apart from the function's address (in
12 * lr), we need to get hold of the function's caller's address.
13 *
14 * Newer GCCs (4.4+) solve this problem by using a version of mcount with call
15 * sites like:
16 *
17 * push {lr}
18 * bl __gnu_mcount_nc
19 *
20 * With these compilers, frame pointers are not necessary.
21 *
22 * mcount can be thought of as a function called in the middle of a subroutine
23 * call. As such, it needs to be transparent for both the caller and the
24 * callee: the original lr needs to be restored when leaving mcount, and no
25 * registers should be clobbered. (In the __gnu_mcount_nc implementation, we
26 * clobber the ip register. This is OK because the ARM calling convention
27 * allows it to be clobbered in subroutines and doesn't use it to hold
28 * parameters.)
29 *
30 * When using dynamic ftrace, we patch out the mcount call by a "pop {lr}"
31 * instead of the __gnu_mcount_nc call (see arch/arm/kernel/ftrace.c).
32 */
33
34.macro mcount_adjust_addr rd, rn
35 bic \rd, \rn, #1 @ clear the Thumb bit if present
36 sub \rd, \rd, #MCOUNT_INSN_SIZE
37.endm
38
39.macro __mcount suffix
40 mcount_enter
41 ldr r0, =ftrace_trace_function
42 ldr r2, [r0]
43 adr r0, .Lftrace_stub
44 cmp r0, r2
45 bne 1f
46
47#ifdef CONFIG_FUNCTION_GRAPH_TRACER
48 ldr r1, =ftrace_graph_return
49 ldr r2, [r1]
50 cmp r0, r2
51 bne ftrace_graph_caller\suffix
52
53 ldr r1, =ftrace_graph_entry
54 ldr r2, [r1]
55 ldr r0, =ftrace_graph_entry_stub
56 cmp r0, r2
57 bne ftrace_graph_caller\suffix
58#endif
59
60 mcount_exit
61
621: mcount_get_lr r1 @ lr of instrumented func
63 mcount_adjust_addr r0, lr @ instrumented function
64 badr lr, 2f
65 mov pc, r2
662: mcount_exit
67.endm
68
69#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
70
71.macro __ftrace_regs_caller
72
73 sub sp, sp, #8 @ space for PC and CPSR OLD_R0,
74 @ OLD_R0 will overwrite previous LR
75
76 add ip, sp, #12 @ move in IP the value of SP as it was
77 @ before the push {lr} of the mcount mechanism
78
79 str lr, [sp, #0] @ store LR instead of PC
80
81 ldr lr, [sp, #8] @ get previous LR
82
83 str r0, [sp, #8] @ write r0 as OLD_R0 over previous LR
84
85 stmdb sp!, {ip, lr}
86 stmdb sp!, {r0-r11, lr}
87
88 @ stack content at this point:
89 @ 0 4 48 52 56 60 64 68 72
90 @ R0 | R1 | ... | LR | SP + 4 | previous LR | LR | PSR | OLD_R0 |
91
92 mov r3, sp @ struct pt_regs*
93
94 ldr r2, =function_trace_op
95 ldr r2, [r2] @ pointer to the current
96 @ function tracing op
97
98 ldr r1, [sp, #S_LR] @ lr of instrumented func
99
100 ldr lr, [sp, #S_PC] @ get LR
101
102 mcount_adjust_addr r0, lr @ instrumented function
103
104 .globl ftrace_regs_call
105ftrace_regs_call:
106 bl ftrace_stub
107
108#ifdef CONFIG_FUNCTION_GRAPH_TRACER
109 .globl ftrace_graph_regs_call
110ftrace_graph_regs_call:
111 mov r0, r0
112#endif
113
114 @ pop saved regs
115 ldmia sp!, {r0-r12} @ restore r0 through r12
116 ldr ip, [sp, #8] @ restore PC
117 ldr lr, [sp, #4] @ restore LR
118 ldr sp, [sp, #0] @ restore SP
119 mov pc, ip @ return
120.endm
121
122#ifdef CONFIG_FUNCTION_GRAPH_TRACER
123.macro __ftrace_graph_regs_caller
124
125 sub r0, fp, #4 @ lr of instrumented routine (parent)
126
127 @ called from __ftrace_regs_caller
128 ldr r1, [sp, #S_PC] @ instrumented routine (func)
129 mcount_adjust_addr r1, r1
130
131 mov r2, fp @ frame pointer
132 bl prepare_ftrace_return
133
134 @ pop registers saved in ftrace_regs_caller
135 ldmia sp!, {r0-r12} @ restore r0 through r12
136 ldr ip, [sp, #8] @ restore PC
137 ldr lr, [sp, #4] @ restore LR
138 ldr sp, [sp, #0] @ restore SP
139 mov pc, ip @ return
140
141.endm
142#endif
143#endif
144
145.macro __ftrace_caller suffix
146 mcount_enter
147
148 mcount_get_lr r1 @ lr of instrumented func
149 mcount_adjust_addr r0, lr @ instrumented function
150
151#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
152 ldr r2, =function_trace_op
153 ldr r2, [r2] @ pointer to the current
154 @ function tracing op
155 mov r3, #0 @ regs is NULL
156#endif
157
158 .globl ftrace_call\suffix
159ftrace_call\suffix:
160 bl ftrace_stub
161
162#ifdef CONFIG_FUNCTION_GRAPH_TRACER
163 .globl ftrace_graph_call\suffix
164ftrace_graph_call\suffix:
165 mov r0, r0
166#endif
167
168 mcount_exit
169.endm
170
171.macro __ftrace_graph_caller
172 sub r0, fp, #4 @ &lr of instrumented routine (&parent)
173#ifdef CONFIG_DYNAMIC_FTRACE
174 @ called from __ftrace_caller, saved in mcount_enter
175 ldr r1, [sp, #16] @ instrumented routine (func)
176 mcount_adjust_addr r1, r1
177#else
178 @ called from __mcount, untouched in lr
179 mcount_adjust_addr r1, lr @ instrumented routine (func)
180#endif
181 mov r2, fp @ frame pointer
182 bl prepare_ftrace_return
183 mcount_exit
184.endm
185
186/*
187 * __gnu_mcount_nc
188 */
189
190.macro mcount_enter
191/*
192 * This pad compensates for the push {lr} at the call site. Note that we are
193 * unable to unwind through a function which does not otherwise save its lr.
194 */
195 UNWIND(.pad #4)
196 stmdb sp!, {r0-r3, lr}
197 UNWIND(.save {r0-r3, lr})
198.endm
199
200.macro mcount_get_lr reg
201 ldr \reg, [sp, #20]
202.endm
203
204.macro mcount_exit
205 ldmia sp!, {r0-r3, ip, lr}
206 ret ip
207.endm
208
209ENTRY(__gnu_mcount_nc)
210UNWIND(.fnstart)
211#ifdef CONFIG_DYNAMIC_FTRACE
212 mov ip, lr
213 ldmia sp!, {lr}
214 ret ip
215#else
216 __mcount
217#endif
218UNWIND(.fnend)
219ENDPROC(__gnu_mcount_nc)
220
221#ifdef CONFIG_DYNAMIC_FTRACE
222ENTRY(ftrace_caller)
223UNWIND(.fnstart)
224 __ftrace_caller
225UNWIND(.fnend)
226ENDPROC(ftrace_caller)
227
228#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
229ENTRY(ftrace_regs_caller)
230UNWIND(.fnstart)
231 __ftrace_regs_caller
232UNWIND(.fnend)
233ENDPROC(ftrace_regs_caller)
234#endif
235
236#endif
237
238#ifdef CONFIG_FUNCTION_GRAPH_TRACER
239ENTRY(ftrace_graph_caller)
240UNWIND(.fnstart)
241 __ftrace_graph_caller
242UNWIND(.fnend)
243ENDPROC(ftrace_graph_caller)
244
245#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
246ENTRY(ftrace_graph_regs_caller)
247UNWIND(.fnstart)
248 __ftrace_graph_regs_caller
249UNWIND(.fnend)
250ENDPROC(ftrace_graph_regs_caller)
251#endif
252#endif
253
254.purgem mcount_enter
255.purgem mcount_get_lr
256.purgem mcount_exit
257
258#ifdef CONFIG_FUNCTION_GRAPH_TRACER
259 .globl return_to_handler
260return_to_handler:
261 stmdb sp!, {r0-r3}
262 mov r0, fp @ frame pointer
263 bl ftrace_return_to_handler
264 mov lr, r0 @ r0 has real ret addr
265 ldmia sp!, {r0-r3}
266 ret lr
267#endif
268
269ENTRY(ftrace_stub)
270.Lftrace_stub:
271 ret lr
272ENDPROC(ftrace_stub)