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
|
/*
* arch/arm/kernel/kprobes-decode.c
*
* Copyright (C) 2006, 2007 Motorola Inc.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*/
/*
* We do not have hardware single-stepping on ARM, This
* effort is further complicated by the ARM not having a
* "next PC" register. Instructions that change the PC
* can't be safely single-stepped in a MP environment, so
* we have a lot of work to do:
*
* In the prepare phase:
* *) If it is an instruction that does anything
* with the CPU mode, we reject it for a kprobe.
* (This is out of laziness rather than need. The
* instructions could be simulated.)
*
* *) Otherwise, decode the instruction rewriting its
* registers to take fixed, ordered registers and
* setting a handler for it to run the instruction.
*
* In the execution phase by an instruction's handler:
*
* *) If the PC is written to by the instruction, the
* instruction must be fully simulated in software.
*
* *) Otherwise, a modified form of the instruction is
* directly executed. Its handler calls the
* instruction in insn[0]. In insn[1] is a
* "mov pc, lr" to return.
*
* Before calling, load up the reordered registers
* from the original instruction's registers. If one
* of the original input registers is the PC, compute
* and adjust the appropriate input register.
*
* After call completes, copy the output registers to
* the original instruction's original registers.
*
* We don't use a real breakpoint instruction since that
* would have us in the kernel go from SVC mode to SVC
* mode losing the link register. Instead we use an
* undefined instruction. To simplify processing, the
* undefined instruction used for kprobes must be reserved
* exclusively for kprobes use.
*
* TODO: ifdef out some instruction decoding based on architecture.
*/
#include <linux/kernel.h>
#include <linux/kprobes.h>
#include <linux/ptrace.h>
#include "kprobes.h"
#include "probes-arm.h"
#if __LINUX_ARM_ARCH__ >= 6
#define BLX(reg) "blx "reg" \n\t"
#else
#define BLX(reg) "mov lr, pc \n\t" \
"mov pc, "reg" \n\t"
#endif
void __kprobes
emulate_ldrdstrd(struct kprobe *p, struct pt_regs *regs)
{
kprobe_opcode_t insn = p->opcode;
unsigned long pc = (unsigned long)p->addr + 8;
int rt = (insn >> 12) & 0xf;
int rn = (insn >> 16) & 0xf;
int rm = insn & 0xf;
register unsigned long rtv asm("r0") = regs->uregs[rt];
register unsigned long rt2v asm("r1") = regs->uregs[rt+1];
register unsigned long rnv asm("r2") = (rn == 15) ? pc
: regs->uregs[rn];
register unsigned long rmv asm("r3") = regs->uregs[rm];
__asm__ __volatile__ (
BLX("%[fn]")
: "=r" (rtv), "=r" (rt2v), "=r" (rnv)
: "0" (rtv), "1" (rt2v), "2" (rnv), "r" (rmv),
[fn] "r" (p->ainsn.insn_fn)
: "lr", "memory", "cc"
);
regs->uregs[rt] = rtv;
regs->uregs[rt+1] = rt2v;
if (is_writeback(insn))
regs->uregs[rn] = rnv;
}
void __kprobes
emulate_ldr(struct kprobe *p, struct pt_regs *regs)
{
kprobe_opcode_t insn = p->opcode;
unsigned long pc = (unsigned long)p->addr + 8;
int rt = (insn >> 12) & 0xf;
int rn = (insn >> 16) & 0xf;
int rm = insn & 0xf;
register unsigned long rtv asm("r0");
register unsigned long rnv asm("r2") = (rn == 15) ? pc
: regs->uregs[rn];
register unsigned long rmv asm("r3") = regs->uregs[rm];
__asm__ __volatile__ (
BLX("%[fn]")
: "=r" (rtv), "=r" (rnv)
: "1" (rnv), "r" (rmv), [fn] "r" (p->ainsn.insn_fn)
: "lr", "memory", "cc"
);
if (rt == 15)
load_write_pc(rtv, regs);
else
regs->uregs[rt] = rtv;
if (is_writeback(insn))
regs->uregs[rn] = rnv;
}
void __kprobes
emulate_str(struct kprobe *p, struct pt_regs *regs)
{
kprobe_opcode_t insn = p->opcode;
unsigned long rtpc = (unsigned long)p->addr + str_pc_offset;
unsigned long rnpc = (unsigned long)p->addr + 8;
int rt = (insn >> 12) & 0xf;
int rn = (insn >> 16) & 0xf;
int rm = insn & 0xf;
register unsigned long rtv asm("r0") = (rt == 15) ? rtpc
: regs->uregs[rt];
register unsigned long rnv asm("r2") = (rn == 15) ? rnpc
: regs->uregs[rn];
register unsigned long rmv asm("r3") = regs->uregs[rm];
__asm__ __volatile__ (
BLX("%[fn]")
: "=r" (rnv)
: "r" (rtv), "0" (rnv), "r" (rmv), [fn] "r" (p->ainsn.insn_fn)
: "lr", "memory", "cc"
);
if (is_writeback(insn))
regs->uregs[rn] = rnv;
}
void __kprobes
emulate_rd12rn16rm0rs8_rwflags(struct kprobe *p, struct pt_regs *regs)
{
kprobe_opcode_t insn = p->opcode;
unsigned long pc = (unsigned long)p->addr + 8;
int rd = (insn >> 12) & 0xf;
int rn = (insn >> 16) & 0xf;
int rm = insn & 0xf;
int rs = (insn >> 8) & 0xf;
register unsigned long rdv asm("r0") = regs->uregs[rd];
register unsigned long rnv asm("r2") = (rn == 15) ? pc
: regs->uregs[rn];
register unsigned long rmv asm("r3") = (rm == 15) ? pc
: regs->uregs[rm];
register unsigned long rsv asm("r1") = regs->uregs[rs];
unsigned long cpsr = regs->ARM_cpsr;
__asm__ __volatile__ (
"msr cpsr_fs, %[cpsr] \n\t"
BLX("%[fn]")
"mrs %[cpsr], cpsr \n\t"
: "=r" (rdv), [cpsr] "=r" (cpsr)
: "0" (rdv), "r" (rnv), "r" (rmv), "r" (rsv),
"1" (cpsr), [fn] "r" (p->ainsn.insn_fn)
: "lr", "memory", "cc"
);
if (rd == 15)
alu_write_pc(rdv, regs);
else
regs->uregs[rd] = rdv;
regs->ARM_cpsr = (regs->ARM_cpsr & ~APSR_MASK) | (cpsr & APSR_MASK);
}
void __kprobes
emulate_rd12rn16rm0_rwflags_nopc(struct kprobe *p, struct pt_regs *regs)
{
kprobe_opcode_t insn = p->opcode;
int rd = (insn >> 12) & 0xf;
int rn = (insn >> 16) & 0xf;
int rm = insn & 0xf;
register unsigned long rdv asm("r0") = regs->uregs[rd];
register unsigned long rnv asm("r2") = regs->uregs[rn];
register unsigned long rmv asm("r3") = regs->uregs[rm];
unsigned long cpsr = regs->ARM_cpsr;
__asm__ __volatile__ (
"msr cpsr_fs, %[cpsr] \n\t"
BLX("%[fn]")
"mrs %[cpsr], cpsr \n\t"
: "=r" (rdv), [cpsr] "=r" (cpsr)
: "0" (rdv), "r" (rnv), "r" (rmv),
"1" (cpsr), [fn] "r" (p->ainsn.insn_fn)
: "lr", "memory", "cc"
);
regs->uregs[rd] = rdv;
regs->ARM_cpsr = (regs->ARM_cpsr & ~APSR_MASK) | (cpsr & APSR_MASK);
}
void __kprobes
emulate_rd16rn12rm0rs8_rwflags_nopc(struct kprobe *p, struct pt_regs *regs)
{
kprobe_opcode_t insn = p->opcode;
int rd = (insn >> 16) & 0xf;
int rn = (insn >> 12) & 0xf;
int rm = insn & 0xf;
int rs = (insn >> 8) & 0xf;
register unsigned long rdv asm("r2") = regs->uregs[rd];
register unsigned long rnv asm("r0") = regs->uregs[rn];
register unsigned long rmv asm("r3") = regs->uregs[rm];
register unsigned long rsv asm("r1") = regs->uregs[rs];
unsigned long cpsr = regs->ARM_cpsr;
__asm__ __volatile__ (
"msr cpsr_fs, %[cpsr] \n\t"
BLX("%[fn]")
"mrs %[cpsr], cpsr \n\t"
: "=r" (rdv), [cpsr] "=r" (cpsr)
: "0" (rdv), "r" (rnv), "r" (rmv), "r" (rsv),
"1" (cpsr), [fn] "r" (p->ainsn.insn_fn)
: "lr", "memory", "cc"
);
regs->uregs[rd] = rdv;
regs->ARM_cpsr = (regs->ARM_cpsr & ~APSR_MASK) | (cpsr & APSR_MASK);
}
void __kprobes
emulate_rd12rm0_noflags_nopc(struct kprobe *p, struct pt_regs *regs)
{
kprobe_opcode_t insn = p->opcode;
int rd = (insn >> 12) & 0xf;
int rm = insn & 0xf;
register unsigned long rdv asm("r0") = regs->uregs[rd];
register unsigned long rmv asm("r3") = regs->uregs[rm];
__asm__ __volatile__ (
BLX("%[fn]")
: "=r" (rdv)
: "0" (rdv), "r" (rmv), [fn] "r" (p->ainsn.insn_fn)
: "lr", "memory", "cc"
);
regs->uregs[rd] = rdv;
}
void __kprobes
emulate_rdlo12rdhi16rn0rm8_rwflags_nopc(struct kprobe *p, struct pt_regs *regs)
{
kprobe_opcode_t insn = p->opcode;
int rdlo = (insn >> 12) & 0xf;
int rdhi = (insn >> 16) & 0xf;
int rn = insn & 0xf;
int rm = (insn >> 8) & 0xf;
register unsigned long rdlov asm("r0") = regs->uregs[rdlo];
register unsigned long rdhiv asm("r2") = regs->uregs[rdhi];
register unsigned long rnv asm("r3") = regs->uregs[rn];
register unsigned long rmv asm("r1") = regs->uregs[rm];
unsigned long cpsr = regs->ARM_cpsr;
__asm__ __volatile__ (
"msr cpsr_fs, %[cpsr] \n\t"
BLX("%[fn]")
"mrs %[cpsr], cpsr \n\t"
: "=r" (rdlov), "=r" (rdhiv), [cpsr] "=r" (cpsr)
: "0" (rdlov), "1" (rdhiv), "r" (rnv), "r" (rmv),
"2" (cpsr), [fn] "r" (p->ainsn.insn_fn)
: "lr", "memory", "cc"
);
regs->uregs[rdlo] = rdlov;
regs->uregs[rdhi] = rdhiv;
regs->ARM_cpsr = (regs->ARM_cpsr & ~APSR_MASK) | (cpsr & APSR_MASK);
}
|
