arch/riscv/kernel/probes/kprobes.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2
   3 #include <linux/kprobes.h>
   4 #include <linux/extable.h>
   5 #include <linux/slab.h>
   6 #include <linux/stop_machine.h>
   7 #include <asm/ptrace.h>
   8 #include <linux/uaccess.h>
   9 #include <asm/sections.h>
  10 #include <asm/cacheflush.h>
  11 #include <asm/bug.h>
  12 #include <asm/patch.h>
  13
  14 #include "decode-insn.h"
  15
  16 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
  17 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
  18
  19 static void __kprobes
  20 post_kprobe_handler(struct kprobe_ctlblk *, struct pt_regs *);
  21
  22 static void __kprobes arch_prepare_ss_slot(struct kprobe *p)
  23 {
  24         unsigned long offset = GET_INSN_LENGTH(p->opcode);
  25
  26         p->ainsn.api.restore = (unsigned long)p->addr + offset;
  27
  28         patch_text(p->ainsn.api.insn, p->opcode);
  29         patch_text((void *)((unsigned long)(p->ainsn.api.insn) + offset),
  30                    __BUG_INSN_32);
  31 }
  32
  33 static void __kprobes arch_prepare_simulate(struct kprobe *p)
  34 {
  35         p->ainsn.api.restore = 0;
  36 }
  37
  38 static void __kprobes arch_simulate_insn(struct kprobe *p, struct pt_regs *regs)
  39 {
  40         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
  41
  42         if (p->ainsn.api.handler)
  43                 p->ainsn.api.handler((u32)p->opcode,
  44                                         (unsigned long)p->addr, regs);
  45
  46         post_kprobe_handler(kcb, regs);
  47 }
  48
  49 int __kprobes arch_prepare_kprobe(struct kprobe *p)
  50 {
  51         unsigned long probe_addr = (unsigned long)p->addr;
  52
  53         if (probe_addr & 0x1) {
  54                 pr_warn("Address not aligned.\n");
  55
  56                 return -EINVAL;
  57         }
  58
  59         /* copy instruction */
  60         p->opcode = *p->addr;
  61
  62         /* decode instruction */
  63         switch (riscv_probe_decode_insn(p->addr, &p->ainsn.api)) {
  64         case INSN_REJECTED:     /* insn not supported */
  65                 return -EINVAL;
  66
  67         case INSN_GOOD_NO_SLOT: /* insn need simulation */
  68                 p->ainsn.api.insn = NULL;
  69                 break;
  70
  71         case INSN_GOOD: /* instruction uses slot */
  72                 p->ainsn.api.insn = get_insn_slot();
  73                 if (!p->ainsn.api.insn)
  74                         return -ENOMEM;
  75                 break;
  76         }
  77
  78         /* prepare the instruction */
  79         if (p->ainsn.api.insn)
  80                 arch_prepare_ss_slot(p);
  81         else
  82                 arch_prepare_simulate(p);
  83
  84         return 0;
  85 }
  86
  87 void *alloc_insn_page(void)
  88 {
  89         return  __vmalloc_node_range(PAGE_SIZE, 1, VMALLOC_START, VMALLOC_END,
  90                                      GFP_KERNEL, PAGE_KERNEL_READ_EXEC,
  91                                      VM_FLUSH_RESET_PERMS, NUMA_NO_NODE,
  92                                      __builtin_return_address(0));
  93 }
  94
  95 /* install breakpoint in text */
  96 void __kprobes arch_arm_kprobe(struct kprobe *p)
  97 {
  98         if ((p->opcode & __INSN_LENGTH_MASK) == __INSN_LENGTH_32)
  99                 patch_text(p->addr, __BUG_INSN_32);
 100         else
 101                 patch_text(p->addr, __BUG_INSN_16);
 102 }
 103
 104 /* remove breakpoint from text */
 105 void __kprobes arch_disarm_kprobe(struct kprobe *p)
 106 {
 107         patch_text(p->addr, p->opcode);
 108 }
 109
 110 void __kprobes arch_remove_kprobe(struct kprobe *p)
 111 {
 112 }
 113
 114 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
 115 {
 116         kcb->prev_kprobe.kp = kprobe_running();
 117         kcb->prev_kprobe.status = kcb->kprobe_status;
 118 }
 119
 120 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
 121 {
 122         __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
 123         kcb->kprobe_status = kcb->prev_kprobe.status;
 124 }
 125
 126 static void __kprobes set_current_kprobe(struct kprobe *p)
 127 {
 128         __this_cpu_write(current_kprobe, p);
 129 }
 130
 131 /*
 132  * Interrupts need to be disabled before single-step mode is set, and not
 133  * reenabled until after single-step mode ends.
 134  * Without disabling interrupt on local CPU, there is a chance of
 135  * interrupt occurrence in the period of exception return and  start of
 136  * out-of-line single-step, that result in wrongly single stepping
 137  * into the interrupt handler.
 138  */
 139 static void __kprobes kprobes_save_local_irqflag(struct kprobe_ctlblk *kcb,
 140                                                 struct pt_regs *regs)
 141 {
 142         kcb->saved_status = regs->status;
 143         regs->status &= ~SR_SPIE;
 144 }
 145
 146 static void __kprobes kprobes_restore_local_irqflag(struct kprobe_ctlblk *kcb,
 147                                                 struct pt_regs *regs)
 148 {
 149         regs->status = kcb->saved_status;
 150 }
 151
 152 static void __kprobes
 153 set_ss_context(struct kprobe_ctlblk *kcb, unsigned long addr, struct kprobe *p)
 154 {
 155         unsigned long offset = GET_INSN_LENGTH(p->opcode);
 156
 157         kcb->ss_ctx.ss_pending = true;
 158         kcb->ss_ctx.match_addr = addr + offset;
 159 }
 160
 161 static void __kprobes clear_ss_context(struct kprobe_ctlblk *kcb)
 162 {
 163         kcb->ss_ctx.ss_pending = false;
 164         kcb->ss_ctx.match_addr = 0;
 165 }
 166
 167 static void __kprobes setup_singlestep(struct kprobe *p,
 168                                        struct pt_regs *regs,
 169                                        struct kprobe_ctlblk *kcb, int reenter)
 170 {
 171         unsigned long slot;
 172
 173         if (reenter) {
 174                 save_previous_kprobe(kcb);
 175                 set_current_kprobe(p);
 176                 kcb->kprobe_status = KPROBE_REENTER;
 177         } else {
 178                 kcb->kprobe_status = KPROBE_HIT_SS;
 179         }
 180
 181         if (p->ainsn.api.insn) {
 182                 /* prepare for single stepping */
 183                 slot = (unsigned long)p->ainsn.api.insn;
 184
 185                 set_ss_context(kcb, slot, p);   /* mark pending ss */
 186
 187                 /* IRQs and single stepping do not mix well. */
 188                 kprobes_save_local_irqflag(kcb, regs);
 189
 190                 instruction_pointer_set(regs, slot);
 191         } else {
 192                 /* insn simulation */
 193                 arch_simulate_insn(p, regs);
 194         }
 195 }
 196
 197 static int __kprobes reenter_kprobe(struct kprobe *p,
 198                                     struct pt_regs *regs,
 199                                     struct kprobe_ctlblk *kcb)
 200 {
 201         switch (kcb->kprobe_status) {
 202         case KPROBE_HIT_SSDONE:
 203         case KPROBE_HIT_ACTIVE:
 204                 kprobes_inc_nmissed_count(p);
 205                 setup_singlestep(p, regs, kcb, 1);
 206                 break;
 207         case KPROBE_HIT_SS:
 208         case KPROBE_REENTER:
 209                 pr_warn("Unrecoverable kprobe detected.\n");
 210                 dump_kprobe(p);
 211                 BUG();
 212                 break;
 213         default:
 214                 WARN_ON(1);
 215                 return 0;
 216         }
 217
 218         return 1;
 219 }
 220
 221 static void __kprobes
 222 post_kprobe_handler(struct kprobe_ctlblk *kcb, struct pt_regs *regs)
 223 {
 224         struct kprobe *cur = kprobe_running();
 225
 226         if (!cur)
 227                 return;
 228
 229         /* return addr restore if non-branching insn */
 230         if (cur->ainsn.api.restore != 0)
 231                 regs->epc = cur->ainsn.api.restore;
 232
 233         /* restore back original saved kprobe variables and continue */
 234         if (kcb->kprobe_status == KPROBE_REENTER) {
 235                 restore_previous_kprobe(kcb);
 236                 return;
 237         }
 238
 239         /* call post handler */
 240         kcb->kprobe_status = KPROBE_HIT_SSDONE;
 241         if (cur->post_handler)  {
 242                 /* post_handler can hit breakpoint and single step
 243                  * again, so we enable D-flag for recursive exception.
 244                  */
 245                 cur->post_handler(cur, regs, 0);
 246         }
 247
 248         reset_current_kprobe();
 249 }
 250
 251 int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int trapnr)
 252 {
 253         struct kprobe *cur = kprobe_running();
 254         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 255
 256         switch (kcb->kprobe_status) {
 257         case KPROBE_HIT_SS:
 258         case KPROBE_REENTER:
 259                 /*
 260                  * We are here because the instruction being single
 261                  * stepped caused a page fault. We reset the current
 262                  * kprobe and the ip points back to the probe address
 263                  * and allow the page fault handler to continue as a
 264                  * normal page fault.
 265                  */
 266                 regs->epc = (unsigned long) cur->addr;
 267                 BUG_ON(!instruction_pointer(regs));
 268
 269                 if (kcb->kprobe_status == KPROBE_REENTER)
 270                         restore_previous_kprobe(kcb);
 271                 else {
 272                         kprobes_restore_local_irqflag(kcb, regs);
 273                         reset_current_kprobe();
 274                 }
 275
 276                 break;
 277         case KPROBE_HIT_ACTIVE:
 278         case KPROBE_HIT_SSDONE:
 279                 /*
 280                  * We increment the nmissed count for accounting,
 281                  * we can also use npre/npostfault count for accounting
 282                  * these specific fault cases.
 283                  */
 284                 kprobes_inc_nmissed_count(cur);
 285
 286                 /*
 287                  * We come here because instructions in the pre/post
 288                  * handler caused the page_fault, this could happen
 289                  * if handler tries to access user space by
 290                  * copy_from_user(), get_user() etc. Let the
 291                  * user-specified handler try to fix it first.
 292                  */
 293                 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
 294                         return 1;
 295
 296                 /*
 297                  * In case the user-specified fault handler returned
 298                  * zero, try to fix up.
 299                  */
 300                 if (fixup_exception(regs))
 301                         return 1;
 302         }
 303         return 0;
 304 }
 305
 306 bool __kprobes
 307 kprobe_breakpoint_handler(struct pt_regs *regs)
 308 {
 309         struct kprobe *p, *cur_kprobe;
 310         struct kprobe_ctlblk *kcb;
 311         unsigned long addr = instruction_pointer(regs);
 312
 313         kcb = get_kprobe_ctlblk();
 314         cur_kprobe = kprobe_running();
 315
 316         p = get_kprobe((kprobe_opcode_t *) addr);
 317
 318         if (p) {
 319                 if (cur_kprobe) {
 320                         if (reenter_kprobe(p, regs, kcb))
 321                                 return true;
 322                 } else {
 323                         /* Probe hit */
 324                         set_current_kprobe(p);
 325                         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 326
 327                         /*
 328                          * If we have no pre-handler or it returned 0, we
 329                          * continue with normal processing.  If we have a
 330                          * pre-handler and it returned non-zero, it will
 331                          * modify the execution path and no need to single
 332                          * stepping. Let's just reset current kprobe and exit.
 333                          *
 334                          * pre_handler can hit a breakpoint and can step thru
 335                          * before return.
 336                          */
 337                         if (!p->pre_handler || !p->pre_handler(p, regs))
 338                                 setup_singlestep(p, regs, kcb, 0);
 339                         else
 340                                 reset_current_kprobe();
 341                 }
 342                 return true;
 343         }
 344
 345         /*
 346          * The breakpoint instruction was removed right
 347          * after we hit it.  Another cpu has removed
 348          * either a probepoint or a debugger breakpoint
 349          * at this address.  In either case, no further
 350          * handling of this interrupt is appropriate.
 351          * Return back to original instruction, and continue.
 352          */
 353         return false;
 354 }
 355
 356 bool __kprobes
 357 kprobe_single_step_handler(struct pt_regs *regs)
 358 {
 359         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 360
 361         if ((kcb->ss_ctx.ss_pending)
 362             && (kcb->ss_ctx.match_addr == instruction_pointer(regs))) {
 363                 clear_ss_context(kcb);  /* clear pending ss */
 364
 365                 kprobes_restore_local_irqflag(kcb, regs);
 366
 367                 post_kprobe_handler(kcb, regs);
 368                 return true;
 369         }
 370         return false;
 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)__irqentry_text_start,
 382                                         (unsigned long)__irqentry_text_end);
 383         return ret;
 384 }
 385
 386 void __kprobes __used *trampoline_probe_handler(struct pt_regs *regs)
 387 {
 388         return (void *)kretprobe_trampoline_handler(regs, &kretprobe_trampoline, NULL);
 389 }
 390
 391 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 392                                       struct pt_regs *regs)
 393 {
 394         ri->ret_addr = (kprobe_opcode_t *)regs->ra;
 395         ri->fp = NULL;
 396         regs->ra = (unsigned long) &kretprobe_trampoline;
 397 }
 398
 399 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
 400 {
 401         return 0;
 402 }
 403
 404 int __init arch_init_kprobes(void)
 405 {
 406         return 0;
 407 }