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
  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 long 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 long 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, &kretprobe_trampoline,
 405                                         (void *)kernel_stack_pointer(regs));
 406 }
 407
 408 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 409                                       struct pt_regs *regs)
 410 {
 411         ri->ret_addr = (kprobe_opcode_t *)regs->regs[30];
 412         ri->fp = (void *)kernel_stack_pointer(regs);
 413
 414         /* replace return addr (x30) with trampoline */
 415         regs->regs[30] = (long)&kretprobe_trampoline;
 416 }
 417
 418 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
 419 {
 420         return 0;
 421 }
 422
 423 int __init arch_init_kprobes(void)
 424 {
 425         register_kernel_break_hook(&kprobes_break_hook);
 426         register_kernel_break_hook(&kprobes_break_ss_hook);
 427
 428         return 0;
 429 }