summaryrefslogtreecommitdiffstats
path: root/arch/powerpc/kernel/trace/ftrace_entry.S
blob: 40677416d7b2622da03574fdbdbb86057fff95ac (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
/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
 * Split from ftrace_64.S
 */

#include <linux/export.h>
#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/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.
 */
.macro	ftrace_regs_entry allregs
	/* Create a minimal stack frame for representing B */
	PPC_STLU	r1, -STACK_FRAME_MIN_SIZE(r1)

	/* Create our stack frame + pt_regs */
	PPC_STLU	r1,-SWITCH_FRAME_SIZE(r1)

	/* Save all gprs to pt_regs */
	SAVE_GPR(0, r1)
	SAVE_GPRS(3, 10, r1)

#ifdef CONFIG_PPC64
	/* Save the original return address in A's stack frame */
	std	r0, LRSAVE+SWITCH_FRAME_SIZE+STACK_FRAME_MIN_SIZE(r1)
	/* Ok to continue? */
	lbz	r3, PACA_FTRACE_ENABLED(r13)
	cmpdi	r3, 0
	beq	ftrace_no_trace
#endif

	.if \allregs == 1
	SAVE_GPR(2, r1)
	SAVE_GPRS(11, 31, r1)
	.else
#ifdef CONFIG_LIVEPATCH_64
	SAVE_GPR(14, r1)
#endif
	.endif

	/* Save previous stack pointer (r1) */
	addi	r8, r1, SWITCH_FRAME_SIZE+STACK_FRAME_MIN_SIZE
	PPC_STL	r8, GPR1(r1)

	.if \allregs == 1
	/* Load special regs for save below */
	mfmsr   r8
	mfctr   r9
	mfxer   r10
	mfcr	r11
	.else
	/* Clear MSR to flag as ftrace_caller versus frace_regs_caller */
	li	r8, 0
	.endif

	/* Get the _mcount() call site out of LR */
	mflr	r7
	/* Save it as pt_regs->nip */
	PPC_STL	r7, _NIP(r1)
	/* Also save it in B's stackframe header for proper unwind */
	PPC_STL	r7, LRSAVE+SWITCH_FRAME_SIZE(r1)
	/* Save the read LR in pt_regs->link */
	PPC_STL	r0, _LINK(r1)

#ifdef CONFIG_PPC64
	/* Save callee's TOC in the ABI compliant location */
	std	r2, STK_GOT(r1)
	LOAD_PACA_TOC()		/* get kernel TOC in r2 */
	LOAD_REG_ADDR(r3, function_trace_op)
	ld	r5,0(r3)
#else
	lis	r3,function_trace_op@ha
	lwz	r5,function_trace_op@l(r3)
#endif

#ifdef CONFIG_LIVEPATCH_64
	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 */
	PPC_STL	r8, _MSR(r1)
	.if \allregs == 1
	PPC_STL	r9, _CTR(r1)
	PPC_STL	r10, _XER(r1)
	PPC_STL	r11, _CCR(r1)
	.endif

	/* Load &pt_regs in r6 for call below */
	addi    r6, r1, STACK_INT_FRAME_REGS
.endm

.macro	ftrace_regs_exit allregs
	/* Load ctr with the possibly modified NIP */
	PPC_LL	r3, _NIP(r1)
	mtctr	r3

#ifdef CONFIG_LIVEPATCH_64
	cmpd	r14, r3		/* has NIP been altered? */
#endif

	/* Restore gprs */
	.if \allregs == 1
	REST_GPRS(2, 31, r1)
	.else
	REST_GPRS(3, 10, r1)
#ifdef CONFIG_LIVEPATCH_64
	REST_GPR(14, r1)
#endif
	.endif

	/* Restore possibly modified LR */
	PPC_LL	r0, _LINK(r1)
	mtlr	r0

#ifdef CONFIG_PPC64
	/* Restore callee's TOC */
	ld	r2, STK_GOT(r1)
#endif

	/* Pop our stack frame */
	addi r1, r1, SWITCH_FRAME_SIZE+STACK_FRAME_MIN_SIZE

#ifdef CONFIG_LIVEPATCH_64
        /* Based on the cmpd above, if the NIP was altered handle livepatch */
	bne-	livepatch_handler
#endif
	bctr			/* jump after _mcount site */
.endm

_GLOBAL(ftrace_regs_caller)
	ftrace_regs_entry 1
	/* ftrace_call(r3, r4, r5, r6) */
.globl ftrace_regs_call
ftrace_regs_call:
	bl	ftrace_stub
	nop
	ftrace_regs_exit 1

_GLOBAL(ftrace_caller)
	ftrace_regs_entry 0
	/* ftrace_call(r3, r4, r5, r6) */
.globl ftrace_call
ftrace_call:
	bl	ftrace_stub
	nop
	ftrace_regs_exit 0

_GLOBAL(ftrace_stub)
	blr

#ifdef CONFIG_PPC64
ftrace_no_trace:
	mflr	r3
	mtctr	r3
	REST_GPR(3, r1)
	addi	r1, r1, SWITCH_FRAME_SIZE+STACK_FRAME_MIN_SIZE
	mtlr	r0
	bctr
#endif

#ifdef CONFIG_LIVEPATCH_64
	/*
	 * 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:
	ld	r12, PACA_THREAD_INFO(r13)

	/* 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.
	 */

	ld	r12, PACA_THREAD_INFO(r13)

	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 */
	ld	r12, PACA_THREAD_INFO(r13)
	subi	r11, r11, 24
	std	r11, TI_livepatch_sp(r12)

	/* Return to original caller of live patched function */
	blr
#endif /* CONFIG_LIVEPATCH */

#ifndef CONFIG_ARCH_USING_PATCHABLE_FUNCTION_ENTRY
_GLOBAL(mcount)
_GLOBAL(_mcount)
EXPORT_SYMBOL(_mcount)
	mflr	r12
	mtctr	r12
	mtlr	r0
	bctr
#endif

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
_GLOBAL(return_to_handler)
	/* need to save return values */
#ifdef CONFIG_PPC64
	std	r4,  -32(r1)
	std	r3,  -24(r1)
	/* save TOC */
	std	r2,  -16(r1)
	std	r31, -8(r1)
	mr	r31, r1
	stdu	r1, -112(r1)

	/*
	 * We might be called from a module.
	 * Switch to our TOC to run inside the core kernel.
	 */
	LOAD_PACA_TOC()
#else
	stwu	r1, -16(r1)
	stw	r3, 8(r1)
	stw	r4, 12(r1)
#endif

	bl	ftrace_return_to_handler
	nop

	/* return value has real return address */
	mtlr	r3

#ifdef CONFIG_PPC64
	ld	r1, 0(r1)
	ld	r4,  -32(r1)
	ld	r3,  -24(r1)
	ld	r2,  -16(r1)
	ld	r31, -8(r1)
#else
	lwz	r3, 8(r1)
	lwz	r4, 12(r1)
	addi	r1, r1, 16
#endif

	/* Jump back to real return address */
	blr
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */

.pushsection ".tramp.ftrace.text","aw",@progbits;
.globl ftrace_tramp_text
ftrace_tramp_text:
	.space 32
.popsection

.pushsection ".tramp.ftrace.init","aw",@progbits;
.globl ftrace_tramp_init
ftrace_tramp_init:
	.space 32
.popsection