arch/csky/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
  12 #include "decode-insn.h"
  13
  14 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
  15 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
  16
  17 static void __kprobes
  18 post_kprobe_handler(struct kprobe_ctlblk *, struct pt_regs *);
  19
  20 struct csky_insn_patch {
  21         kprobe_opcode_t *addr;
  22         u32             opcode;
  23         atomic_t        cpu_count;
  24 };
  25
  26 static int __kprobes patch_text_cb(void *priv)
  27 {
  28         struct csky_insn_patch *param = priv;
  29         unsigned int addr = (unsigned int)param->addr;
  30
  31         if (atomic_inc_return(&param->cpu_count) == 1) {
  32                 *(u16 *) addr = cpu_to_le16(param->opcode);
  33                 dcache_wb_range(addr, addr + 2);
  34                 atomic_inc(&param->cpu_count);
  35         } else {
  36                 while (atomic_read(&param->cpu_count) <= num_online_cpus())
  37                         cpu_relax();
  38         }
  39
  40         icache_inv_range(addr, addr + 2);
  41
  42         return 0;
  43 }
  44
  45 static int __kprobes patch_text(kprobe_opcode_t *addr, u32 opcode)
  46 {
  47         struct csky_insn_patch param = { addr, opcode, ATOMIC_INIT(0) };
  48
  49         return stop_machine_cpuslocked(patch_text_cb, &param, cpu_online_mask);
  50 }
  51
  52 static void __kprobes arch_prepare_ss_slot(struct kprobe *p)
  53 {
  54         unsigned long offset = is_insn32(p->opcode) ? 4 : 2;
  55
  56         p->ainsn.api.restore = (unsigned long)p->addr + offset;
  57
  58         patch_text(p->ainsn.api.insn, p->opcode);
  59 }
  60
  61 static void __kprobes arch_prepare_simulate(struct kprobe *p)
  62 {
  63         p->ainsn.api.restore = 0;
  64 }
  65
  66 static void __kprobes arch_simulate_insn(struct kprobe *p, struct pt_regs *regs)
  67 {
  68         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
  69
  70         if (p->ainsn.api.handler)
  71                 p->ainsn.api.handler((u32)p->opcode, (long)p->addr, regs);
  72
  73         post_kprobe_handler(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 & 0x1) {
  81                 pr_warn("Address not aligned.\n");
  82                 return -EINVAL;
  83         }
  84
  85         /* copy instruction */
  86         p->opcode = le32_to_cpu(*p->addr);
  87
  88         /* decode instruction */
  89         switch (csky_probe_decode_insn(p->addr, &p->ainsn.api)) {
  90         case INSN_REJECTED:     /* insn not supported */
  91                 return -EINVAL;
  92
  93         case INSN_GOOD_NO_SLOT: /* insn need simulation */
  94                 p->ainsn.api.insn = NULL;
  95                 break;
  96
  97         case INSN_GOOD: /* instruction uses slot */
  98                 p->ainsn.api.insn = get_insn_slot();
  99                 if (!p->ainsn.api.insn)
 100                         return -ENOMEM;
 101                 break;
 102         }
 103
 104         /* prepare the instruction */
 105         if (p->ainsn.api.insn)
 106                 arch_prepare_ss_slot(p);
 107         else
 108                 arch_prepare_simulate(p);
 109
 110         return 0;
 111 }
 112
 113 /* install breakpoint in text */
 114 void __kprobes arch_arm_kprobe(struct kprobe *p)
 115 {
 116         patch_text(p->addr, USR_BKPT);
 117 }
 118
 119 /* remove breakpoint from text */
 120 void __kprobes arch_disarm_kprobe(struct kprobe *p)
 121 {
 122         patch_text(p->addr, p->opcode);
 123 }
 124
 125 void __kprobes arch_remove_kprobe(struct kprobe *p)
 126 {
 127 }
 128
 129 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
 130 {
 131         kcb->prev_kprobe.kp = kprobe_running();
 132         kcb->prev_kprobe.status = kcb->kprobe_status;
 133 }
 134
 135 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
 136 {
 137         __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
 138         kcb->kprobe_status = kcb->prev_kprobe.status;
 139 }
 140
 141 static void __kprobes set_current_kprobe(struct kprobe *p)
 142 {
 143         __this_cpu_write(current_kprobe, p);
 144 }
 145
 146 /*
 147  * Interrupts need to be disabled before single-step mode is set, and not
 148  * reenabled until after single-step mode ends.
 149  * Without disabling interrupt on local CPU, there is a chance of
 150  * interrupt occurrence in the period of exception return and  start of
 151  * out-of-line single-step, that result in wrongly single stepping
 152  * into the interrupt handler.
 153  */
 154 static void __kprobes kprobes_save_local_irqflag(struct kprobe_ctlblk *kcb,
 155                                                 struct pt_regs *regs)
 156 {
 157         kcb->saved_sr = regs->sr;
 158         regs->sr &= ~BIT(6);
 159 }
 160
 161 static void __kprobes kprobes_restore_local_irqflag(struct kprobe_ctlblk *kcb,
 162                                                 struct pt_regs *regs)
 163 {
 164         regs->sr = kcb->saved_sr;
 165 }
 166
 167 static void __kprobes
 168 set_ss_context(struct kprobe_ctlblk *kcb, unsigned long addr, struct kprobe *p)
 169 {
 170         unsigned long offset = is_insn32(p->opcode) ? 4 : 2;
 171
 172         kcb->ss_ctx.ss_pending = true;
 173         kcb->ss_ctx.match_addr = addr + offset;
 174 }
 175
 176 static void __kprobes clear_ss_context(struct kprobe_ctlblk *kcb)
 177 {
 178         kcb->ss_ctx.ss_pending = false;
 179         kcb->ss_ctx.match_addr = 0;
 180 }
 181
 182 #define TRACE_MODE_SI           BIT(14)
 183 #define TRACE_MODE_MASK         ~(0x3 << 14)
 184 #define TRACE_MODE_RUN          0
 185
 186 static void __kprobes setup_singlestep(struct kprobe *p,
 187                                        struct pt_regs *regs,
 188                                        struct kprobe_ctlblk *kcb, int reenter)
 189 {
 190         unsigned long slot;
 191
 192         if (reenter) {
 193                 save_previous_kprobe(kcb);
 194                 set_current_kprobe(p);
 195                 kcb->kprobe_status = KPROBE_REENTER;
 196         } else {
 197                 kcb->kprobe_status = KPROBE_HIT_SS;
 198         }
 199
 200         if (p->ainsn.api.insn) {
 201                 /* prepare for single stepping */
 202                 slot = (unsigned long)p->ainsn.api.insn;
 203
 204                 set_ss_context(kcb, slot, p);   /* mark pending ss */
 205
 206                 /* IRQs and single stepping do not mix well. */
 207                 kprobes_save_local_irqflag(kcb, regs);
 208                 regs->sr = (regs->sr & TRACE_MODE_MASK) | TRACE_MODE_SI;
 209                 instruction_pointer_set(regs, slot);
 210         } else {
 211                 /* insn simulation */
 212                 arch_simulate_insn(p, regs);
 213         }
 214 }
 215
 216 static int __kprobes reenter_kprobe(struct kprobe *p,
 217                                     struct pt_regs *regs,
 218                                     struct kprobe_ctlblk *kcb)
 219 {
 220         switch (kcb->kprobe_status) {
 221         case KPROBE_HIT_SSDONE:
 222         case KPROBE_HIT_ACTIVE:
 223                 kprobes_inc_nmissed_count(p);
 224                 setup_singlestep(p, regs, kcb, 1);
 225                 break;
 226         case KPROBE_HIT_SS:
 227         case KPROBE_REENTER:
 228                 pr_warn("Unrecoverable kprobe detected.\n");
 229                 dump_kprobe(p);
 230                 BUG();
 231                 break;
 232         default:
 233                 WARN_ON(1);
 234                 return 0;
 235         }
 236
 237         return 1;
 238 }
 239
 240 static void __kprobes
 241 post_kprobe_handler(struct kprobe_ctlblk *kcb, struct pt_regs *regs)
 242 {
 243         struct kprobe *cur = kprobe_running();
 244
 245         if (!cur)
 246                 return;
 247
 248         /* return addr restore if non-branching insn */
 249         if (cur->ainsn.api.restore != 0)
 250                 regs->pc = cur->ainsn.api.restore;
 251
 252         /* restore back original saved kprobe variables and continue */
 253         if (kcb->kprobe_status == KPROBE_REENTER) {
 254                 restore_previous_kprobe(kcb);
 255                 return;
 256         }
 257
 258         /* call post handler */
 259         kcb->kprobe_status = KPROBE_HIT_SSDONE;
 260         if (cur->post_handler)  {
 261                 /* post_handler can hit breakpoint and single step
 262                  * again, so we enable D-flag for recursive exception.
 263                  */
 264                 cur->post_handler(cur, regs, 0);
 265         }
 266
 267         reset_current_kprobe();
 268 }
 269
 270 int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int trapnr)
 271 {
 272         struct kprobe *cur = kprobe_running();
 273         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 274
 275         switch (kcb->kprobe_status) {
 276         case KPROBE_HIT_SS:
 277         case KPROBE_REENTER:
 278                 /*
 279                  * We are here because the instruction being single
 280                  * stepped caused a page fault. We reset the current
 281                  * kprobe and the ip points back to the probe address
 282                  * and allow the page fault handler to continue as a
 283                  * normal page fault.
 284                  */
 285                 regs->pc = (unsigned long) cur->addr;
 286                 if (!instruction_pointer(regs))
 287                         BUG();
 288
 289                 if (kcb->kprobe_status == KPROBE_REENTER)
 290                         restore_previous_kprobe(kcb);
 291                 else
 292                         reset_current_kprobe();
 293
 294                 break;
 295         case KPROBE_HIT_ACTIVE:
 296         case KPROBE_HIT_SSDONE:
 297                 /*
 298                  * We increment the nmissed count for accounting,
 299                  * we can also use npre/npostfault count for accounting
 300                  * these specific fault cases.
 301                  */
 302                 kprobes_inc_nmissed_count(cur);
 303
 304                 /*
 305                  * We come here because instructions in the pre/post
 306                  * handler caused the page_fault, this could happen
 307                  * if handler tries to access user space by
 308                  * copy_from_user(), get_user() etc. Let the
 309                  * user-specified handler try to fix it first.
 310                  */
 311                 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
 312                         return 1;
 313
 314                 /*
 315                  * In case the user-specified fault handler returned
 316                  * zero, try to fix up.
 317                  */
 318                 if (fixup_exception(regs))
 319                         return 1;
 320         }
 321         return 0;
 322 }
 323
 324 int __kprobes
 325 kprobe_breakpoint_handler(struct pt_regs *regs)
 326 {
 327         struct kprobe *p, *cur_kprobe;
 328         struct kprobe_ctlblk *kcb;
 329         unsigned long addr = instruction_pointer(regs);
 330
 331         kcb = get_kprobe_ctlblk();
 332         cur_kprobe = kprobe_running();
 333
 334         p = get_kprobe((kprobe_opcode_t *) addr);
 335
 336         if (p) {
 337                 if (cur_kprobe) {
 338                         if (reenter_kprobe(p, regs, kcb))
 339                                 return 1;
 340                 } else {
 341                         /* Probe hit */
 342                         set_current_kprobe(p);
 343                         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 344
 345                         /*
 346                          * If we have no pre-handler or it returned 0, we
 347                          * continue with normal processing.  If we have a
 348                          * pre-handler and it returned non-zero, it will
 349                          * modify the execution path and no need to single
 350                          * stepping. Let's just reset current kprobe and exit.
 351                          *
 352                          * pre_handler can hit a breakpoint and can step thru
 353                          * before return.
 354                          */
 355                         if (!p->pre_handler || !p->pre_handler(p, regs))
 356                                 setup_singlestep(p, regs, kcb, 0);
 357                         else
 358                                 reset_current_kprobe();
 359                 }
 360                 return 1;
 361         }
 362
 363         /*
 364          * The breakpoint instruction was removed right
 365          * after we hit it.  Another cpu has removed
 366          * either a probepoint or a debugger breakpoint
 367          * at this address.  In either case, no further
 368          * handling of this interrupt is appropriate.
 369          * Return back to original instruction, and continue.
 370          */
 371         return 0;
 372 }
 373
 374 int __kprobes
 375 kprobe_single_step_handler(struct pt_regs *regs)
 376 {
 377         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 378
 379         if ((kcb->ss_ctx.ss_pending)
 380             && (kcb->ss_ctx.match_addr == instruction_pointer(regs))) {
 381                 clear_ss_context(kcb);  /* clear pending ss */
 382
 383                 kprobes_restore_local_irqflag(kcb, regs);
 384                 regs->sr = (regs->sr & TRACE_MODE_MASK) | TRACE_MODE_RUN;
 385
 386                 post_kprobe_handler(kcb, regs);
 387                 return 1;
 388         }
 389         return 0;
 390 }
 391
 392 /*
 393  * Provide a blacklist of symbols identifying ranges which cannot be kprobed.
 394  * This blacklist is exposed to userspace via debugfs (kprobes/blacklist).
 395  */
 396 int __init arch_populate_kprobe_blacklist(void)
 397 {
 398         int ret;
 399
 400         ret = kprobe_add_area_blacklist((unsigned long)__irqentry_text_start,
 401                                         (unsigned long)__irqentry_text_end);
 402         return ret;
 403 }
 404
 405 void __kprobes __used *trampoline_probe_handler(struct pt_regs *regs)
 406 {
 407         return (void *)kretprobe_trampoline_handler(regs, &kretprobe_trampoline, NULL);
 408 }
 409
 410 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 411                                       struct pt_regs *regs)
 412 {
 413         ri->ret_addr = (kprobe_opcode_t *)regs->lr;
 414         ri->fp = NULL;
 415         regs->lr = (unsigned 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         return 0;
 426 }