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 11 #define pr_fmt(fmt) "kprobes: " fmt 12 13 #include <linux/extable.h> 14 #include <linux/kasan.h> 15 #include <linux/kernel.h> 16 #include <linux/kprobes.h> 17 #include <linux/sched/debug.h> 18 #include <linux/set_memory.h> 19 #include <linux/slab.h> 20 #include <linux/stop_machine.h> 21 #include <linux/stringify.h> 22 #include <linux/uaccess.h> 23 #include <linux/vmalloc.h> 24 25 #include <asm/cacheflush.h> 26 #include <asm/daifflags.h> 27 #include <asm/debug-monitors.h> 28 #include <asm/insn.h> 29 #include <asm/irq.h> 30 #include <asm/patching.h> 31 #include <asm/ptrace.h> 32 #include <asm/sections.h> 33 #include <asm/system_misc.h> 34 #include <asm/traps.h> 35 36 #include "decode-insn.h" 37 38 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL; 39 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk); 40 41 static void __kprobes 42 post_kprobe_handler(struct kprobe *, struct kprobe_ctlblk *, struct pt_regs *); 43 44 static void __kprobes arch_prepare_ss_slot(struct kprobe *p) 45 { 46 kprobe_opcode_t *addr = p->ainsn.api.insn; 47 void *addrs[] = {addr, addr + 1}; 48 u32 insns[] = {p->opcode, BRK64_OPCODE_KPROBES_SS}; 49 50 /* prepare insn slot */ 51 aarch64_insn_patch_text(addrs, insns, 2); 52 53 flush_icache_range((uintptr_t)addr, (uintptr_t)(addr + MAX_INSN_SIZE)); 54 55 /* 56 * Needs restoring of return address after stepping xol. 57 */ 58 p->ainsn.api.restore = (unsigned long) p->addr + 59 sizeof(kprobe_opcode_t); 60 } 61 62 static void __kprobes arch_prepare_simulate(struct kprobe *p) 63 { 64 /* This instructions is not executed xol. No need to adjust the PC */ 65 p->ainsn.api.restore = 0; 66 } 67 68 static void __kprobes arch_simulate_insn(struct kprobe *p, struct pt_regs *regs) 69 { 70 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); 71 72 if (p->ainsn.api.handler) 73 p->ainsn.api.handler((u32)p->opcode, (long)p->addr, regs); 74 75 /* single step simulated, now go for post processing */ 76 post_kprobe_handler(p, kcb, regs); 77 } 78 79 int __kprobes arch_prepare_kprobe(struct kprobe *p) 80 { 81 unsigned long probe_addr = (unsigned long)p->addr; 82 83 if (probe_addr & 0x3) 84 return -EINVAL; 85 86 /* copy instruction */ 87 p->opcode = le32_to_cpu(*p->addr); 88 89 if (search_exception_tables(probe_addr)) 90 return -EINVAL; 91 92 /* decode instruction */ 93 switch (arm_kprobe_decode_insn(p->addr, &p->ainsn)) { 94 case INSN_REJECTED: /* insn not supported */ 95 return -EINVAL; 96 97 case INSN_GOOD_NO_SLOT: /* insn need simulation */ 98 p->ainsn.api.insn = NULL; 99 break; 100 101 case INSN_GOOD: /* instruction uses slot */ 102 p->ainsn.api.insn = get_insn_slot(); 103 if (!p->ainsn.api.insn) 104 return -ENOMEM; 105 break; 106 } 107 108 /* prepare the instruction */ 109 if (p->ainsn.api.insn) 110 arch_prepare_ss_slot(p); 111 else 112 arch_prepare_simulate(p); 113 114 return 0; 115 } 116 117 void *alloc_insn_page(void) 118 { 119 return __vmalloc_node_range(PAGE_SIZE, 1, VMALLOC_START, VMALLOC_END, 120 GFP_KERNEL, PAGE_KERNEL_ROX, VM_FLUSH_RESET_PERMS, 121 NUMA_NO_NODE, __builtin_return_address(0)); 122 } 123 124 /* arm kprobe: install breakpoint in text */ 125 void __kprobes arch_arm_kprobe(struct kprobe *p) 126 { 127 void *addr = p->addr; 128 u32 insn = BRK64_OPCODE_KPROBES; 129 130 aarch64_insn_patch_text(&addr, &insn, 1); 131 } 132 133 /* disarm kprobe: remove breakpoint from text */ 134 void __kprobes arch_disarm_kprobe(struct kprobe *p) 135 { 136 void *addr = p->addr; 137 138 aarch64_insn_patch_text(&addr, &p->opcode, 1); 139 } 140 141 void __kprobes arch_remove_kprobe(struct kprobe *p) 142 { 143 if (p->ainsn.api.insn) { 144 free_insn_slot(p->ainsn.api.insn, 0); 145 p->ainsn.api.insn = NULL; 146 } 147 } 148 149 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb) 150 { 151 kcb->prev_kprobe.kp = kprobe_running(); 152 kcb->prev_kprobe.status = kcb->kprobe_status; 153 } 154 155 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb) 156 { 157 __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp); 158 kcb->kprobe_status = kcb->prev_kprobe.status; 159 } 160 161 static void __kprobes set_current_kprobe(struct kprobe *p) 162 { 163 __this_cpu_write(current_kprobe, p); 164 } 165 166 /* 167 * Mask all of DAIF while executing the instruction out-of-line, to keep things 168 * simple and avoid nesting exceptions. Interrupts do have to be disabled since 169 * the kprobe state is per-CPU and doesn't get migrated. 170 */ 171 static void __kprobes kprobes_save_local_irqflag(struct kprobe_ctlblk *kcb, 172 struct pt_regs *regs) 173 { 174 kcb->saved_irqflag = regs->pstate & DAIF_MASK; 175 regs->pstate |= DAIF_MASK; 176 } 177 178 static void __kprobes kprobes_restore_local_irqflag(struct kprobe_ctlblk *kcb, 179 struct pt_regs *regs) 180 { 181 regs->pstate &= ~DAIF_MASK; 182 regs->pstate |= kcb->saved_irqflag; 183 } 184 185 static void __kprobes setup_singlestep(struct kprobe *p, 186 struct pt_regs *regs, 187 struct kprobe_ctlblk *kcb, int reenter) 188 { 189 unsigned long slot; 190 191 if (reenter) { 192 save_previous_kprobe(kcb); 193 set_current_kprobe(p); 194 kcb->kprobe_status = KPROBE_REENTER; 195 } else { 196 kcb->kprobe_status = KPROBE_HIT_SS; 197 } 198 199 200 if (p->ainsn.api.insn) { 201 /* prepare for single stepping */ 202 slot = (unsigned long)p->ainsn.api.insn; 203 204 kprobes_save_local_irqflag(kcb, regs); 205 instruction_pointer_set(regs, slot); 206 } else { 207 /* insn simulation */ 208 arch_simulate_insn(p, regs); 209 } 210 } 211 212 static int __kprobes reenter_kprobe(struct kprobe *p, 213 struct pt_regs *regs, 214 struct kprobe_ctlblk *kcb) 215 { 216 switch (kcb->kprobe_status) { 217 case KPROBE_HIT_SSDONE: 218 case KPROBE_HIT_ACTIVE: 219 kprobes_inc_nmissed_count(p); 220 setup_singlestep(p, regs, kcb, 1); 221 break; 222 case KPROBE_HIT_SS: 223 case KPROBE_REENTER: 224 pr_warn("Failed to recover from reentered kprobes.\n"); 225 dump_kprobe(p); 226 BUG(); 227 break; 228 default: 229 WARN_ON(1); 230 return 0; 231 } 232 233 return 1; 234 } 235 236 static void __kprobes 237 post_kprobe_handler(struct kprobe *cur, struct kprobe_ctlblk *kcb, struct pt_regs *regs) 238 { 239 /* return addr restore if non-branching insn */ 240 if (cur->ainsn.api.restore != 0) 241 instruction_pointer_set(regs, cur->ainsn.api.restore); 242 243 /* restore back original saved kprobe variables and continue */ 244 if (kcb->kprobe_status == KPROBE_REENTER) { 245 restore_previous_kprobe(kcb); 246 return; 247 } 248 /* call post handler */ 249 kcb->kprobe_status = KPROBE_HIT_SSDONE; 250 if (cur->post_handler) 251 cur->post_handler(cur, regs, 0); 252 253 reset_current_kprobe(); 254 } 255 256 int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr) 257 { 258 struct kprobe *cur = kprobe_running(); 259 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); 260 261 switch (kcb->kprobe_status) { 262 case KPROBE_HIT_SS: 263 case KPROBE_REENTER: 264 /* 265 * We are here because the instruction being single 266 * stepped caused a page fault. We reset the current 267 * kprobe and the ip points back to the probe address 268 * and allow the page fault handler to continue as a 269 * normal page fault. 270 */ 271 instruction_pointer_set(regs, (unsigned long) cur->addr); 272 BUG_ON(!instruction_pointer(regs)); 273 274 if (kcb->kprobe_status == KPROBE_REENTER) { 275 restore_previous_kprobe(kcb); 276 } else { 277 kprobes_restore_local_irqflag(kcb, regs); 278 reset_current_kprobe(); 279 } 280 281 break; 282 case KPROBE_HIT_ACTIVE: 283 case KPROBE_HIT_SSDONE: 284 /* 285 * In case the user-specified fault handler returned 286 * zero, try to fix up. 287 */ 288 if (fixup_exception(regs)) 289 return 1; 290 } 291 return 0; 292 } 293 294 static void __kprobes kprobe_handler(struct pt_regs *regs) 295 { 296 struct kprobe *p, *cur_kprobe; 297 struct kprobe_ctlblk *kcb; 298 unsigned long addr = instruction_pointer(regs); 299 300 kcb = get_kprobe_ctlblk(); 301 cur_kprobe = kprobe_running(); 302 303 p = get_kprobe((kprobe_opcode_t *) addr); 304 305 if (p) { 306 if (cur_kprobe) { 307 if (reenter_kprobe(p, regs, kcb)) 308 return; 309 } else { 310 /* Probe hit */ 311 set_current_kprobe(p); 312 kcb->kprobe_status = KPROBE_HIT_ACTIVE; 313 314 /* 315 * If we have no pre-handler or it returned 0, we 316 * continue with normal processing. If we have a 317 * pre-handler and it returned non-zero, it will 318 * modify the execution path and no need to single 319 * stepping. Let's just reset current kprobe and exit. 320 */ 321 if (!p->pre_handler || !p->pre_handler(p, regs)) { 322 setup_singlestep(p, regs, kcb, 0); 323 } else 324 reset_current_kprobe(); 325 } 326 } 327 /* 328 * The breakpoint instruction was removed right 329 * after we hit it. Another cpu has removed 330 * either a probepoint or a debugger breakpoint 331 * at this address. In either case, no further 332 * handling of this interrupt is appropriate. 333 * Return back to original instruction, and continue. 334 */ 335 } 336 337 static int __kprobes 338 kprobe_breakpoint_ss_handler(struct pt_regs *regs, unsigned int esr) 339 { 340 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); 341 unsigned long addr = instruction_pointer(regs); 342 struct kprobe *cur = kprobe_running(); 343 344 if (cur && (kcb->kprobe_status & (KPROBE_HIT_SS | KPROBE_REENTER)) && 345 ((unsigned long)&cur->ainsn.api.insn[1] == addr)) { 346 kprobes_restore_local_irqflag(kcb, regs); 347 post_kprobe_handler(cur, kcb, regs); 348 349 return DBG_HOOK_HANDLED; 350 } 351 352 /* not ours, kprobes should ignore it */ 353 return DBG_HOOK_ERROR; 354 } 355 356 static struct break_hook kprobes_break_ss_hook = { 357 .imm = KPROBES_BRK_SS_IMM, 358 .fn = kprobe_breakpoint_ss_handler, 359 }; 360 361 static int __kprobes 362 kprobe_breakpoint_handler(struct pt_regs *regs, unsigned int esr) 363 { 364 kprobe_handler(regs); 365 return DBG_HOOK_HANDLED; 366 } 367 368 static struct break_hook kprobes_break_hook = { 369 .imm = KPROBES_BRK_IMM, 370 .fn = kprobe_breakpoint_handler, 371 }; 372 373 /* 374 * Provide a blacklist of symbols identifying ranges which cannot be kprobed. 375 * This blacklist is exposed to userspace via debugfs (kprobes/blacklist). 376 */ 377 int __init arch_populate_kprobe_blacklist(void) 378 { 379 int ret; 380 381 ret = kprobe_add_area_blacklist((unsigned long)__entry_text_start, 382 (unsigned long)__entry_text_end); 383 if (ret) 384 return ret; 385 ret = kprobe_add_area_blacklist((unsigned long)__irqentry_text_start, 386 (unsigned long)__irqentry_text_end); 387 if (ret) 388 return ret; 389 ret = kprobe_add_area_blacklist((unsigned long)__idmap_text_start, 390 (unsigned long)__idmap_text_end); 391 if (ret) 392 return ret; 393 ret = kprobe_add_area_blacklist((unsigned long)__hyp_text_start, 394 (unsigned long)__hyp_text_end); 395 if (ret || is_kernel_in_hyp_mode()) 396 return ret; 397 ret = kprobe_add_area_blacklist((unsigned long)__hyp_idmap_text_start, 398 (unsigned long)__hyp_idmap_text_end); 399 return ret; 400 } 401 402 void __kprobes __used *trampoline_probe_handler(struct pt_regs *regs) 403 { 404 return (void *)kretprobe_trampoline_handler(regs, (void *)regs->regs[29]); 405 } 406 407 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri, 408 struct pt_regs *regs) 409 { 410 ri->ret_addr = (kprobe_opcode_t *)regs->regs[30]; 411 ri->fp = (void *)regs->regs[29]; 412 413 /* replace return addr (x30) with trampoline */ 414 regs->regs[30] = (long)&__kretprobe_trampoline; 415 } 416 417 int __kprobes arch_trampoline_kprobe(struct kprobe *p) 418 { 419 return 0; 420 } 421 422 int __init arch_init_kprobes(void) 423 { 424 register_kernel_break_hook(&kprobes_break_hook); 425 register_kernel_break_hook(&kprobes_break_ss_hook); 426 427 return 0; 428 } 429