arch/arm64/kernel/probes/kprobes.c

   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 }