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
|
/*
* Split from ftrace_64.S
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#include <linux/magic.h>
#include <asm/ppc_asm.h>
#include <asm/asm-offsets.h>
#include <asm/ftrace.h>
#include <asm/ppc-opcode.h>
#include <asm/export.h>
#include <asm/thread_info.h>
#include <asm/bug.h>
#include <asm/ptrace.h>
/*
*
* ftrace_caller()/ftrace_regs_caller() is the function that replaces _mcount()
* when ftrace is active.
*
* We arrive here after a function A calls function B, and we are the trace
* function for B. When we enter r1 points to A's stack frame, B has not yet
* had a chance to allocate one yet.
*
* Additionally r2 may point either to the TOC for A, or B, depending on
* whether B did a TOC setup sequence before calling us.
*
* On entry the LR points back to the _mcount() call site, and r0 holds the
* saved LR as it was on entry to B, ie. the original return address at the
* call site in A.
*
* Our job is to save the register state into a struct pt_regs (on the stack)
* and then arrange for the ftrace function to be called.
*/
_GLOBAL(ftrace_regs_caller)
/* Save the original return address in A's stack frame */
std r0,LRSAVE(r1)
/* Create our stack frame + pt_regs */
stdu r1,-SWITCH_FRAME_SIZE(r1)
/* Save all gprs to pt_regs */
SAVE_GPR(0, r1)
SAVE_10GPRS(2, r1)
/* Ok to continue? */
lbz r3, PACA_FTRACE_ENABLED(r13)
cmpdi r3, 0
beq ftrace_no_trace
SAVE_10GPRS(12, r1)
SAVE_10GPRS(22, r1)
/* Save previous stack pointer (r1) */
addi r8, r1, SWITCH_FRAME_SIZE
std r8, GPR1(r1)
/* Load special regs for save below */
mfmsr r8
mfctr r9
mfxer r10
mfcr r11
/* Get the _mcount() call site out of LR */
mflr r7
/* Save it as pt_regs->nip */
std r7, _NIP(r1)
/* Save the read LR in pt_regs->link */
std r0, _LINK(r1)
/* Save callee's TOC in the ABI compliant location */
std r2, 24(r1)
ld r2,PACATOC(r13) /* get kernel TOC in r2 */
addis r3,r2,function_trace_op@toc@ha
addi r3,r3,function_trace_op@toc@l
ld r5,0(r3)
#ifdef CONFIG_LIVEPATCH
mr r14,r7 /* remember old NIP */
#endif
/* Calculate ip from nip-4 into r3 for call below */
subi r3, r7, MCOUNT_INSN_SIZE
/* Put the original return address in r4 as parent_ip */
mr r4, r0
/* Save special regs */
std r8, _MSR(r1)
std r9, _CTR(r1)
std r10, _XER(r1)
std r11, _CCR(r1)
/* Load &pt_regs in r6 for call below */
addi r6, r1 ,STACK_FRAME_OVERHEAD
/* ftrace_call(r3, r4, r5, r6) */
.globl ftrace_regs_call
ftrace_regs_call:
bl ftrace_stub
nop
/* Load ctr with the possibly modified NIP */
ld r3, _NIP(r1)
mtctr r3
#ifdef CONFIG_LIVEPATCH
cmpd r14, r3 /* has NIP been altered? */
#endif
/* Restore gprs */
REST_GPR(0,r1)
REST_10GPRS(2,r1)
REST_10GPRS(12,r1)
REST_10GPRS(22,r1)
/* Restore possibly modified LR */
ld r0, _LINK(r1)
mtlr r0
/* Restore callee's TOC */
ld r2, 24(r1)
/* Pop our stack frame */
addi r1, r1, SWITCH_FRAME_SIZE
#ifdef CONFIG_LIVEPATCH
/* Based on the cmpd above, if the NIP was altered handle livepatch */
bne- livepatch_handler
#endif
ftrace_caller_common:
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
.globl ftrace_graph_call
ftrace_graph_call:
b ftrace_graph_stub
_GLOBAL(ftrace_graph_stub)
#endif
bctr /* jump after _mcount site */
_GLOBAL(ftrace_stub)
blr
ftrace_no_trace:
mflr r3
mtctr r3
REST_GPR(3, r1)
addi r1, r1, SWITCH_FRAME_SIZE
mtlr r0
bctr
_GLOBAL(ftrace_caller)
/* Save the original return address in A's stack frame */
std r0, LRSAVE(r1)
/* Create our stack frame + pt_regs */
stdu r1, -SWITCH_FRAME_SIZE(r1)
/* Save all gprs to pt_regs */
SAVE_8GPRS(3, r1)
lbz r3, PACA_FTRACE_ENABLED(r13)
cmpdi r3, 0
beq ftrace_no_trace
/* Get the _mcount() call site out of LR */
mflr r7
std r7, _NIP(r1)
/* Save callee's TOC in the ABI compliant location */
std r2, 24(r1)
ld r2, PACATOC(r13) /* get kernel TOC in r2 */
addis r3, r2, function_trace_op@toc@ha
addi r3, r3, function_trace_op@toc@l
ld r5, 0(r3)
/* Calculate ip from nip-4 into r3 for call below */
subi r3, r7, MCOUNT_INSN_SIZE
/* Put the original return address in r4 as parent_ip */
mr r4, r0
/* Set pt_regs to NULL */
li r6, 0
/* ftrace_call(r3, r4, r5, r6) */
.globl ftrace_call
ftrace_call:
bl ftrace_stub
nop
ld r3, _NIP(r1)
mtctr r3
/* Restore gprs */
REST_8GPRS(3,r1)
/* Restore callee's TOC */
ld r2, 24(r1)
/* Pop our stack frame */
addi r1, r1, SWITCH_FRAME_SIZE
/* Reload original LR */
ld r0, LRSAVE(r1)
mtlr r0
/* Handle function_graph or go back */
b ftrace_caller_common
#ifdef CONFIG_LIVEPATCH
/*
* This function runs in the mcount context, between two functions. As
* such it can only clobber registers which are volatile and used in
* function linkage.
*
* We get here when a function A, calls another function B, but B has
* been live patched with a new function C.
*
* On entry:
* - we have no stack frame and can not allocate one
* - LR points back to the original caller (in A)
* - CTR holds the new NIP in C
* - r0, r11 & r12 are free
*/
livepatch_handler:
CURRENT_THREAD_INFO(r12, r1)
/* Allocate 3 x 8 bytes */
ld r11, TI_livepatch_sp(r12)
addi r11, r11, 24
std r11, TI_livepatch_sp(r12)
/* Save toc & real LR on livepatch stack */
std r2, -24(r11)
mflr r12
std r12, -16(r11)
/* Store stack end marker */
lis r12, STACK_END_MAGIC@h
ori r12, r12, STACK_END_MAGIC@l
std r12, -8(r11)
/* Put ctr in r12 for global entry and branch there */
mfctr r12
bctrl
/*
* Now we are returning from the patched function to the original
* caller A. We are free to use r11, r12 and we can use r2 until we
* restore it.
*/
CURRENT_THREAD_INFO(r12, r1)
ld r11, TI_livepatch_sp(r12)
/* Check stack marker hasn't been trashed */
lis r2, STACK_END_MAGIC@h
ori r2, r2, STACK_END_MAGIC@l
ld r12, -8(r11)
1: tdne r12, r2
EMIT_BUG_ENTRY 1b, __FILE__, __LINE__ - 1, 0
/* Restore LR & toc from livepatch stack */
ld r12, -16(r11)
mtlr r12
ld r2, -24(r11)
/* Pop livepatch stack frame */
CURRENT_THREAD_INFO(r12, r1)
subi r11, r11, 24
std r11, TI_livepatch_sp(r12)
/* Return to original caller of live patched function */
blr
#endif /* CONFIG_LIVEPATCH */
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
_GLOBAL(ftrace_graph_caller)
stdu r1, -112(r1)
/* with -mprofile-kernel, parameter regs are still alive at _mcount */
std r10, 104(r1)
std r9, 96(r1)
std r8, 88(r1)
std r7, 80(r1)
std r6, 72(r1)
std r5, 64(r1)
std r4, 56(r1)
std r3, 48(r1)
/* Save callee's TOC in the ABI compliant location */
std r2, 24(r1)
ld r2, PACATOC(r13) /* get kernel TOC in r2 */
mfctr r4 /* ftrace_caller has moved local addr here */
std r4, 40(r1)
mflr r3 /* ftrace_caller has restored LR from stack */
subi r4, r4, MCOUNT_INSN_SIZE
bl prepare_ftrace_return
nop
/*
* prepare_ftrace_return gives us the address we divert to.
* Change the LR to this.
*/
mtlr r3
ld r0, 40(r1)
mtctr r0
ld r10, 104(r1)
ld r9, 96(r1)
ld r8, 88(r1)
ld r7, 80(r1)
ld r6, 72(r1)
ld r5, 64(r1)
ld r4, 56(r1)
ld r3, 48(r1)
/* Restore callee's TOC */
ld r2, 24(r1)
addi r1, r1, 112
mflr r0
std r0, LRSAVE(r1)
bctr
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
|
