1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * arch/arm64/kernel/probes/kprobes.c 4 * 5 * Kprobes support for ARM64 6 * 7 * Copyright (C) 2013 Linaro Limited. 8 * Author: Sandeepa Prabhu <sandeepa.prabhu@linaro.org> 9 */ 10 #include <linux/extable.h> 11 #include <linux/kasan.h> 12 #include <linux/kernel.h> 13 #include <linux/kprobes.h> 14 #include <linux/sched/debug.h> 15 #include <linux/set_memory.h> 16 #include <linux/slab.h> 17 #include <linux/stop_machine.h> 18 #include <linux/stringify.h> 19 #include <linux/uaccess.h> 20 #include <linux/vmalloc.h> 21 22 #include <asm/cacheflush.h> 23 #include <asm/daifflags.h> 24 #include <asm/debug-monitors.h> 25 #include <asm/insn.h> 26 #include <asm/irq.h> 27 #include <asm/patching.h> 28 #include <asm/ptrace.h> 29 #include <asm/sections.h> 30 #include <asm/system_misc.h> 31 #include <asm/traps.h> 32 33 #include "decode-insn.h" 34 35 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL; 36 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk); 37 38 static void __kprobes 39 post_kprobe_handler(struct kprobe *, struct kprobe_ctlblk *, struct pt_regs *); 40 41 static void __kprobes arch_prepare_ss_slot(struct kprobe *p) 42 { 43 kprobe_opcode_t *addr = p->ainsn.api.insn; 44 void *addrs[] = {addr, addr + 1}; 45 u32 insns[] = {p->opcode, BRK64_OPCODE_KPROBES_SS}; 46 47 /* prepare insn slot */ 48 aarch64_insn_patch_text(addrs, insns, 2); 49 50 flush_icache_range((uintptr_t)addr, (uintptr_t)(addr + MAX_INSN_SIZE)); 51 52 /* 53 * Needs restoring of return address after stepping xol. 54 */ 55 p->ainsn.api.restore = (unsigned long) p->addr + 56 sizeof(kprobe_opcode_t); 57 } 58 59 static void __kprobes arch_prepare_simulate(struct kprobe *p) 60 { 61 /* This instructions is not executed xol. No need to adjust the PC */ 62 p->ainsn.api.restore = 0; 63 } 64 65 static void __kprobes arch_simulate_insn(struct kprobe *p, struct pt_regs *regs) 66 { 67 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); 68 69 if (p->ainsn.api.handler) 70 p->ainsn.api.handler((u32)p->opcode, (long)p->addr, regs); 71 72 /* single step simulated, now go for post processing */ 73 post_kprobe_handler(p, kcb, regs); 74 } 75 76 int __kprobes arch_prepare_kprobe(struct kprobe *p) 77 { 78 unsigned long probe_addr = (unsigned long)p->addr; 79 80 if (probe_addr & 0x3) 81 return -EINVAL; 82 83 /* copy instruction */ 84 p->opcode = le32_to_cpu(*p->addr); 85 86 if (search_exception_tables(probe_addr)) 87 return -EINVAL; 88 89 /* decode instruction */ 90 switch (arm_kprobe_decode_insn(p->addr, &p->ainsn)) { 91 case INSN_REJECTED: /* insn not supported */ 92 return -EINVAL; 93 94 case INSN_GOOD_NO_SLOT: /* insn need simulation */ 95 p->ainsn.api.insn = NULL; 96 break; 97 98 case INSN_GOOD: /* instruction uses slot */ 99 p->ainsn.api.insn = get_insn_slot(); 100 if (!p->ainsn.api.insn) 101 return -ENOMEM; 102 break; 103 } 104 105 /* prepare the instruction */ 106 if (p->ainsn.api.insn) 107 arch_prepare_ss_slot(p); 108 else 109 arch_prepare_simulate(p); 110 111 return 0; 112 } 113 114 void *alloc_insn_page(void) 115 { 116 return __vmalloc_node_range(PAGE_SIZE, 1, VMALLOC_START, VMALLOC_END, 117 GFP_KERNEL, PAGE_KERNEL_ROX, VM_FLUSH_RESET_PERMS, 118 NUMA_NO_NODE, __builtin_return_address(0)); 119 } 120 121 /* arm kprobe: install breakpoint in text */ 122 void __kprobes arch_arm_kprobe(struct kprobe *p) 123 { 124 void *addr = p->addr; 125 u32 insn = BRK64_OPCODE_KPROBES; 126 127 aarch64_insn_patch_text(&addr, &insn, 1); 128 } 129 130 /* disarm kprobe: remove breakpoint from text */ 131 void __kprobes arch_disarm_kprobe(struct kprobe *p) 132 { 133 void *addr = p->addr; 134 135 aarch64_insn_patch_text(&addr, &p->opcode, 1); 136 } 137 138 void __kprobes arch_remove_kprobe(struct kprobe *p) 139 { 140 if (p->ainsn.api.insn) { 141 free_insn_slot(p->ainsn.api.insn, 0); 142 p->ainsn.api.insn = NULL; 143 } 144 } 145 146 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb) 147 { 148 kcb->prev_kprobe.kp = kprobe_running(); 149 kcb->prev_kprobe.status = kcb->kprobe_status; 150 } 151 152 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb) 153 { 154 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp); 155 kcb->kprobe_status = kcb->prev_kprobe.status; 156 } 157 158 static void __kprobes set_current_kprobe(struct kprobe *p) 159 { 160 __this_cpu_write(current_kprobe, p); 161 } 162 163 /* 164 * Mask all of DAIF while executing the instruction out-of-line, to keep things 165 * simple and avoid nesting exceptions. Interrupts do have to be disabled since 166 * the kprobe state is per-CPU and doesn't get migrated. 167 */ 168 static void __kprobes kprobes_save_local_irqflag(struct kprobe_ctlblk *kcb, 169 struct pt_regs *regs) 170 { 171 kcb->saved_irqflag = regs->pstate & DAIF_MASK; 172 regs->pstate |= DAIF_MASK; 173 } 174 175 static void __kprobes kprobes_restore_local_irqflag(struct kprobe_ctlblk *kcb, 176 struct pt_regs *regs) 177 { 178 regs->pstate &= ~DAIF_MASK; 179 regs->pstate |= kcb->saved_irqflag; 180 } 181 182 static void __kprobes setup_singlestep(struct kprobe *p, 183 struct pt_regs *regs, 184 struct kprobe_ctlblk *kcb, int reenter) 185 { 186 unsigned long slot; 187 188 if (reenter) { 189 save_previous_kprobe(kcb); 190 set_current_kprobe(p); 191 kcb->kprobe_status = KPROBE_REENTER; 192 } else { 193 kcb->kprobe_status = KPROBE_HIT_SS; 194 } 195 196 197 if (p->ainsn.api.insn) { 198 /* prepare for single stepping */ 199 slot = (unsigned long)p->ainsn.api.insn; 200 201 kprobes_save_local_irqflag(kcb, regs); 202 instruction_pointer_set(regs, slot); 203 } else { 204 /* insn simulation */ 205 arch_simulate_insn(p, regs); 206 } 207 } 208 209 static int __kprobes reenter_kprobe(struct kprobe *p, 210 struct pt_regs *regs, 211 struct kprobe_ctlblk *kcb) 212 { 213 switch (kcb->kprobe_status) { 214 case KPROBE_HIT_SSDONE: 215 case KPROBE_HIT_ACTIVE: 216 kprobes_inc_nmissed_count(p); 217 setup_singlestep(p, regs, kcb, 1); 218 break; 219 case KPROBE_HIT_SS: 220 case KPROBE_REENTER: 221 pr_warn("Unrecoverable kprobe detected.\n"); 222 dump_kprobe(p); 223 BUG(); 224 break; 225 default: 226 WARN_ON(1); 227 return 0; 228 } 229 230 return 1; 231 } 232 233 static void __kprobes 234 post_kprobe_handler(struct kprobe *cur, struct kprobe_ctlblk *kcb, struct pt_regs *regs) 235 { 236 /* return addr restore if non-branching insn */ 237 if (cur->ainsn.api.restore != 0) 238 instruction_pointer_set(regs, cur->ainsn.api.restore); 239 240 /* restore back original saved kprobe variables and continue */ 241 if (kcb->kprobe_status == KPROBE_REENTER) { 242 restore_previous_kprobe(kcb); 243 return; 244 } 245 /* call post handler */ 246 kcb->kprobe_status = KPROBE_HIT_SSDONE; 247 if (cur->post_handler) 248 cur->post_handler(cur, regs, 0); 249 250 reset_current_kprobe(); 251 } 252 253 int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr) 254 { 255 struct kprobe *cur = kprobe_running(); 256 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); 257 258 switch (kcb->kprobe_status) { 259 case KPROBE_HIT_SS: 260 case KPROBE_REENTER: 261 /* 262 * We are here because the instruction being single 263 * stepped caused a page fault. We reset the current 264 * kprobe and the ip points back to the probe address 265 * and allow the page fault handler to continue as a 266 * normal page fault. 267 */ 268 instruction_pointer_set(regs, (unsigned long) cur->addr); 269 BUG_ON(!instruction_pointer(regs)); 270 271 if (kcb->kprobe_status == KPROBE_REENTER) { 272 restore_previous_kprobe(kcb); 273 } else { 274 kprobes_restore_local_irqflag(kcb, regs); 275 reset_current_kprobe(); 276 } 277 278 break; 279 case KPROBE_HIT_ACTIVE: 280 case KPROBE_HIT_SSDONE: 281 /* 282 * In case the user-specified fault handler returned 283 * zero, try to fix up. 284 */ 285 if (fixup_exception(regs)) 286 return 1; 287 } 288 return 0; 289 } 290 291 static void __kprobes kprobe_handler(struct pt_regs *regs) 292 { 293 struct kprobe *p, *cur_kprobe; 294 struct kprobe_ctlblk *kcb; 295 unsigned long addr = instruction_pointer(regs); 296 297 kcb = get_kprobe_ctlblk(); 298 cur_kprobe = kprobe_running(); 299 300 p = get_kprobe((kprobe_opcode_t *) addr); 301 302 if (p) { 303 if (cur_kprobe) { 304 if (reenter_kprobe(p, regs, kcb)) 305 return; 306 } else { 307 /* Probe hit */ 308 set_current_kprobe(p); 309 kcb->kprobe_status = KPROBE_HIT_ACTIVE; 310 311 /* 312 * If we have no pre-handler or it returned 0, we 313 * continue with normal processing. If we have a 314 * pre-handler and it returned non-zero, it will 315 * modify the execution path and no need to single 316 * stepping. Let's just reset current kprobe and exit. 317 */ 318 if (!p->pre_handler || !p->pre_handler(p, regs)) { 319 setup_singlestep(p, regs, kcb, 0); 320 } else 321 reset_current_kprobe(); 322 } 323 } 324 /* 325 * The breakpoint instruction was removed right 326 * after we hit it. Another cpu has removed 327 * either a probepoint or a debugger breakpoint 328 * at this address. In either case, no further 329 * handling of this interrupt is appropriate. 330 * Return back to original instruction, and continue. 331 */ 332 } 333 334 static int __kprobes 335 kprobe_breakpoint_ss_handler(struct pt_regs *regs, unsigned int esr) 336 { 337 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); 338 unsigned long addr = instruction_pointer(regs); 339 struct kprobe *cur = kprobe_running(); 340 341 if (cur && (kcb->kprobe_status & (KPROBE_HIT_SS | KPROBE_REENTER)) && 342 ((unsigned long)&cur->ainsn.api.insn[1] == addr)) { 343 kprobes_restore_local_irqflag(kcb, regs); 344 post_kprobe_handler(cur, kcb, regs); 345 346 return DBG_HOOK_HANDLED; 347 } 348 349 /* not ours, kprobes should ignore it */ 350 return DBG_HOOK_ERROR; 351 } 352 353 static struct break_hook kprobes_break_ss_hook = { 354 .imm = KPROBES_BRK_SS_IMM, 355 .fn = kprobe_breakpoint_ss_handler, 356 }; 357 358 static int __kprobes 359 kprobe_breakpoint_handler(struct pt_regs *regs, unsigned int esr) 360 { 361 kprobe_handler(regs); 362 return DBG_HOOK_HANDLED; 363 } 364 365 static struct break_hook kprobes_break_hook = { 366 .imm = KPROBES_BRK_IMM, 367 .fn = kprobe_breakpoint_handler, 368 }; 369 370 /* 371 * Provide a blacklist of symbols identifying ranges which cannot be kprobed. 372 * This blacklist is exposed to userspace via debugfs (kprobes/blacklist). 373 */ 374 int __init arch_populate_kprobe_blacklist(void) 375 { 376 int ret; 377 378 ret = kprobe_add_area_blacklist((unsigned long)__entry_text_start, 379 (unsigned long)__entry_text_end); 380 if (ret) 381 return ret; 382 ret = kprobe_add_area_blacklist((unsigned long)__irqentry_text_start, 383 (unsigned long)__irqentry_text_end); 384 if (ret) 385 return ret; 386 ret = kprobe_add_area_blacklist((unsigned long)__idmap_text_start, 387 (unsigned long)__idmap_text_end); 388 if (ret) 389 return ret; 390 ret = kprobe_add_area_blacklist((unsigned long)__hyp_text_start, 391 (unsigned long)__hyp_text_end); 392 if (ret || is_kernel_in_hyp_mode()) 393 return ret; 394 ret = kprobe_add_area_blacklist((unsigned long)__hyp_idmap_text_start, 395 (unsigned long)__hyp_idmap_text_end); 396 return ret; 397 } 398 399 void __kprobes __used *trampoline_probe_handler(struct pt_regs *regs) 400 { 401 return (void *)kretprobe_trampoline_handler(regs, &kretprobe_trampoline, 402 (void *)kernel_stack_pointer(regs)); 403 } 404 405 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri, 406 struct pt_regs *regs) 407 { 408 ri->ret_addr = (kprobe_opcode_t *)regs->regs[30]; 409 ri->fp = (void *)kernel_stack_pointer(regs); 410 411 /* replace return addr (x30) with trampoline */ 412 regs->regs[30] = (long)&kretprobe_trampoline; 413 } 414 415 int __kprobes arch_trampoline_kprobe(struct kprobe *p) 416 { 417 return 0; 418 } 419 420 int __init arch_init_kprobes(void) 421 { 422 register_kernel_break_hook(&kprobes_break_hook); 423 register_kernel_break_hook(&kprobes_break_ss_hook); 424 425 return 0; 426 } 427