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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Code for Kernel probes Jump optimization.
4 *
5 * Copyright 2017, Anju T, IBM Corp.
6 */
7
8#include <linux/kprobes.h>
9#include <linux/jump_label.h>
10#include <linux/types.h>
11#include <linux/slab.h>
12#include <linux/list.h>
13#include <asm/kprobes.h>
14#include <asm/ptrace.h>
15#include <asm/cacheflush.h>
16#include <asm/code-patching.h>
17#include <asm/sstep.h>
18#include <asm/ppc-opcode.h>
19#include <asm/inst.h>
20
21#define TMPL_CALL_HDLR_IDX \
22 (optprobe_template_call_handler - optprobe_template_entry)
23#define TMPL_EMULATE_IDX \
24 (optprobe_template_call_emulate - optprobe_template_entry)
25#define TMPL_RET_IDX \
26 (optprobe_template_ret - optprobe_template_entry)
27#define TMPL_OP_IDX \
28 (optprobe_template_op_address - optprobe_template_entry)
29#define TMPL_INSN_IDX \
30 (optprobe_template_insn - optprobe_template_entry)
31#define TMPL_END_IDX \
32 (optprobe_template_end - optprobe_template_entry)
33
34DEFINE_INSN_CACHE_OPS(ppc_optinsn);
35
36static bool insn_page_in_use;
37
38static void *__ppc_alloc_insn_page(void)
39{
40 if (insn_page_in_use)
41 return NULL;
42 insn_page_in_use = true;
43 return &optinsn_slot;
44}
45
46static void __ppc_free_insn_page(void *page __maybe_unused)
47{
48 insn_page_in_use = false;
49}
50
51struct kprobe_insn_cache kprobe_ppc_optinsn_slots = {
52 .mutex = __MUTEX_INITIALIZER(kprobe_ppc_optinsn_slots.mutex),
53 .pages = LIST_HEAD_INIT(kprobe_ppc_optinsn_slots.pages),
54 /* insn_size initialized later */
55 .alloc = __ppc_alloc_insn_page,
56 .free = __ppc_free_insn_page,
57 .nr_garbage = 0,
58};
59
60/*
61 * Check if we can optimize this probe. Returns NIP post-emulation if this can
62 * be optimized and 0 otherwise.
63 */
64static unsigned long can_optimize(struct kprobe *p)
65{
66 struct pt_regs regs;
67 struct instruction_op op;
68 unsigned long nip = 0;
69
70 /*
71 * kprobe placed for kretprobe during boot time
72 * has a 'nop' instruction, which can be emulated.
73 * So further checks can be skipped.
74 */
75 if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline)
76 return (unsigned long)p->addr + sizeof(kprobe_opcode_t);
77
78 /*
79 * We only support optimizing kernel addresses, but not
80 * module addresses.
81 *
82 * FIXME: Optimize kprobes placed in module addresses.
83 */
84 if (!is_kernel_addr((unsigned long)p->addr))
85 return 0;
86
87 memset(®s, 0, sizeof(struct pt_regs));
88 regs.nip = (unsigned long)p->addr;
89 regs.trap = 0x0;
90 regs.msr = MSR_KERNEL;
91
92 /*
93 * Kprobe placed in conditional branch instructions are
94 * not optimized, as we can't predict the nip prior with
95 * dummy pt_regs and can not ensure that the return branch
96 * from detour buffer falls in the range of address (i.e 32MB).
97 * A branch back from trampoline is set up in the detour buffer
98 * to the nip returned by the analyse_instr() here.
99 *
100 * Ensure that the instruction is not a conditional branch,
101 * and that can be emulated.
102 */
103 if (!is_conditional_branch(ppc_inst_read((struct ppc_inst *)p->ainsn.insn)) &&
104 analyse_instr(&op, ®s,
105 ppc_inst_read((struct ppc_inst *)p->ainsn.insn)) == 1) {
106 emulate_update_regs(®s, &op);
107 nip = regs.nip;
108 }
109
110 return nip;
111}
112
113static void optimized_callback(struct optimized_kprobe *op,
114 struct pt_regs *regs)
115{
116 /* This is possible if op is under delayed unoptimizing */
117 if (kprobe_disabled(&op->kp))
118 return;
119
120 preempt_disable();
121
122 if (kprobe_running()) {
123 kprobes_inc_nmissed_count(&op->kp);
124 } else {
125 __this_cpu_write(current_kprobe, &op->kp);
126 regs->nip = (unsigned long)op->kp.addr;
127 get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
128 opt_pre_handler(&op->kp, regs);
129 __this_cpu_write(current_kprobe, NULL);
130 }
131
132 preempt_enable_no_resched();
133}
134NOKPROBE_SYMBOL(optimized_callback);
135
136void arch_remove_optimized_kprobe(struct optimized_kprobe *op)
137{
138 if (op->optinsn.insn) {
139 free_ppc_optinsn_slot(op->optinsn.insn, 1);
140 op->optinsn.insn = NULL;
141 }
142}
143
144/*
145 * emulate_step() requires insn to be emulated as
146 * second parameter. Load register 'r4' with the
147 * instruction.
148 */
149void patch_imm32_load_insns(unsigned int val, kprobe_opcode_t *addr)
150{
151 /* addis r4,0,(insn)@h */
152 patch_instruction((struct ppc_inst *)addr,
153 ppc_inst(PPC_INST_ADDIS | ___PPC_RT(4) |
154 ((val >> 16) & 0xffff)));
155 addr++;
156
157 /* ori r4,r4,(insn)@l */
158 patch_instruction((struct ppc_inst *)addr,
159 ppc_inst(PPC_INST_ORI | ___PPC_RA(4) |
160 ___PPC_RS(4) | (val & 0xffff)));
161}
162
163/*
164 * Generate instructions to load provided immediate 64-bit value
165 * to register 'reg' and patch these instructions at 'addr'.
166 */
167void patch_imm64_load_insns(unsigned long val, int reg, kprobe_opcode_t *addr)
168{
169 /* lis reg,(op)@highest */
170 patch_instruction((struct ppc_inst *)addr,
171 ppc_inst(PPC_INST_ADDIS | ___PPC_RT(reg) |
172 ((val >> 48) & 0xffff)));
173 addr++;
174
175 /* ori reg,reg,(op)@higher */
176 patch_instruction((struct ppc_inst *)addr,
177 ppc_inst(PPC_INST_ORI | ___PPC_RA(reg) |
178 ___PPC_RS(reg) | ((val >> 32) & 0xffff)));
179 addr++;
180
181 /* rldicr reg,reg,32,31 */
182 patch_instruction((struct ppc_inst *)addr,
183 ppc_inst(PPC_INST_RLDICR | ___PPC_RA(reg) |
184 ___PPC_RS(reg) | __PPC_SH64(32) | __PPC_ME64(31)));
185 addr++;
186
187 /* oris reg,reg,(op)@h */
188 patch_instruction((struct ppc_inst *)addr,
189 ppc_inst(PPC_INST_ORIS | ___PPC_RA(reg) |
190 ___PPC_RS(reg) | ((val >> 16) & 0xffff)));
191 addr++;
192
193 /* ori reg,reg,(op)@l */
194 patch_instruction((struct ppc_inst *)addr,
195 ppc_inst(PPC_INST_ORI | ___PPC_RA(reg) |
196 ___PPC_RS(reg) | (val & 0xffff)));
197}
198
199int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p)
200{
201 struct ppc_inst branch_op_callback, branch_emulate_step, temp;
202 kprobe_opcode_t *op_callback_addr, *emulate_step_addr, *buff;
203 long b_offset;
204 unsigned long nip, size;
205 int rc, i;
206
207 kprobe_ppc_optinsn_slots.insn_size = MAX_OPTINSN_SIZE;
208
209 nip = can_optimize(p);
210 if (!nip)
211 return -EILSEQ;
212
213 /* Allocate instruction slot for detour buffer */
214 buff = get_ppc_optinsn_slot();
215 if (!buff)
216 return -ENOMEM;
217
218 /*
219 * OPTPROBE uses 'b' instruction to branch to optinsn.insn.
220 *
221 * The target address has to be relatively nearby, to permit use
222 * of branch instruction in powerpc, because the address is specified
223 * in an immediate field in the instruction opcode itself, ie 24 bits
224 * in the opcode specify the address. Therefore the address should
225 * be within 32MB on either side of the current instruction.
226 */
227 b_offset = (unsigned long)buff - (unsigned long)p->addr;
228 if (!is_offset_in_branch_range(b_offset))
229 goto error;
230
231 /* Check if the return address is also within 32MB range */
232 b_offset = (unsigned long)(buff + TMPL_RET_IDX) -
233 (unsigned long)nip;
234 if (!is_offset_in_branch_range(b_offset))
235 goto error;
236
237 /* Setup template */
238 /* We can optimize this via patch_instruction_window later */
239 size = (TMPL_END_IDX * sizeof(kprobe_opcode_t)) / sizeof(int);
240 pr_devel("Copying template to %p, size %lu\n", buff, size);
241 for (i = 0; i < size; i++) {
242 rc = patch_instruction((struct ppc_inst *)(buff + i),
243 ppc_inst(*(optprobe_template_entry + i)));
244 if (rc < 0)
245 goto error;
246 }
247
248 /*
249 * Fixup the template with instructions to:
250 * 1. load the address of the actual probepoint
251 */
252 patch_imm64_load_insns((unsigned long)op, 3, buff + TMPL_OP_IDX);
253
254 /*
255 * 2. branch to optimized_callback() and emulate_step()
256 */
257 op_callback_addr = (kprobe_opcode_t *)ppc_kallsyms_lookup_name("optimized_callback");
258 emulate_step_addr = (kprobe_opcode_t *)ppc_kallsyms_lookup_name("emulate_step");
259 if (!op_callback_addr || !emulate_step_addr) {
260 WARN(1, "Unable to lookup optimized_callback()/emulate_step()\n");
261 goto error;
262 }
263
264 rc = create_branch(&branch_op_callback,
265 (struct ppc_inst *)(buff + TMPL_CALL_HDLR_IDX),
266 (unsigned long)op_callback_addr,
267 BRANCH_SET_LINK);
268
269 rc |= create_branch(&branch_emulate_step,
270 (struct ppc_inst *)(buff + TMPL_EMULATE_IDX),
271 (unsigned long)emulate_step_addr,
272 BRANCH_SET_LINK);
273
274 if (rc)
275 goto error;
276
277 patch_instruction((struct ppc_inst *)(buff + TMPL_CALL_HDLR_IDX),
278 branch_op_callback);
279 patch_instruction((struct ppc_inst *)(buff + TMPL_EMULATE_IDX),
280 branch_emulate_step);
281
282 /*
283 * 3. load instruction to be emulated into relevant register, and
284 */
285 temp = ppc_inst_read((struct ppc_inst *)p->ainsn.insn);
286 patch_imm64_load_insns(ppc_inst_as_u64(temp), 4, buff + TMPL_INSN_IDX);
287
288 /*
289 * 4. branch back from trampoline
290 */
291 patch_branch((struct ppc_inst *)(buff + TMPL_RET_IDX), (unsigned long)nip, 0);
292
293 flush_icache_range((unsigned long)buff,
294 (unsigned long)(&buff[TMPL_END_IDX]));
295
296 op->optinsn.insn = buff;
297
298 return 0;
299
300error:
301 free_ppc_optinsn_slot(buff, 0);
302 return -ERANGE;
303
304}
305
306int arch_prepared_optinsn(struct arch_optimized_insn *optinsn)
307{
308 return optinsn->insn != NULL;
309}
310
311/*
312 * On powerpc, Optprobes always replaces one instruction (4 bytes
313 * aligned and 4 bytes long). It is impossible to encounter another
314 * kprobe in this address range. So always return 0.
315 */
316int arch_check_optimized_kprobe(struct optimized_kprobe *op)
317{
318 return 0;
319}
320
321void arch_optimize_kprobes(struct list_head *oplist)
322{
323 struct ppc_inst instr;
324 struct optimized_kprobe *op;
325 struct optimized_kprobe *tmp;
326
327 list_for_each_entry_safe(op, tmp, oplist, list) {
328 /*
329 * Backup instructions which will be replaced
330 * by jump address
331 */
332 memcpy(op->optinsn.copied_insn, op->kp.addr,
333 RELATIVEJUMP_SIZE);
334 create_branch(&instr,
335 (struct ppc_inst *)op->kp.addr,
336 (unsigned long)op->optinsn.insn, 0);
337 patch_instruction((struct ppc_inst *)op->kp.addr, instr);
338 list_del_init(&op->list);
339 }
340}
341
342void arch_unoptimize_kprobe(struct optimized_kprobe *op)
343{
344 arch_arm_kprobe(&op->kp);
345}
346
347void arch_unoptimize_kprobes(struct list_head *oplist,
348 struct list_head *done_list)
349{
350 struct optimized_kprobe *op;
351 struct optimized_kprobe *tmp;
352
353 list_for_each_entry_safe(op, tmp, oplist, list) {
354 arch_unoptimize_kprobe(op);
355 list_move(&op->list, done_list);
356 }
357}
358
359int arch_within_optimized_kprobe(struct optimized_kprobe *op,
360 unsigned long addr)
361{
362 return ((unsigned long)op->kp.addr <= addr &&
363 (unsigned long)op->kp.addr + RELATIVEJUMP_SIZE > addr);
364}