arch/csky/kernel/probes/kprobes.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2
   3 #define pr_fmt(fmt) "kprobes: " fmt
   4
   5 #include <linux/kprobes.h>
   6 #include <linux/extable.h>
   7 #include <linux/slab.h>
   8 #include <linux/stop_machine.h>
   9 #include <asm/ptrace.h>
  10 #include <linux/uaccess.h>
  11 #include <asm/sections.h>
  12 #include <asm/cacheflush.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 struct csky_insn_patch {
  23         kprobe_opcode_t *addr;
  24         u32             opcode;
  25         atomic_t        cpu_count;
  26 };
  27
  28 static int __kprobes patch_text_cb(void *priv)
  29 {
  30         struct csky_insn_patch *param = priv;
  31         unsigned int addr = (unsigned int)param->addr;
  32
  33         if (atomic_inc_return(&param->cpu_count) == num_online_cpus()) {
  34                 *(u16 *) addr = cpu_to_le16(param->opcode);
  35                 dcache_wb_range(addr, addr + 2);
  36                 atomic_inc(&param->cpu_count);
  37         } else {
  38                 while (atomic_read(&param->cpu_count) <= num_online_cpus())
  39                         cpu_relax();
  40         }
  41
  42         icache_inv_range(addr, addr + 2);
  43
  44         return 0;
  45 }
  46
  47 static int __kprobes patch_text(kprobe_opcode_t *addr, u32 opcode)
  48 {
  49         struct csky_insn_patch param = { addr, opcode, ATOMIC_INIT(0) };
  50
  51         return stop_machine_cpuslocked(patch_text_cb, &param, cpu_online_mask);
  52 }
  53
  54 static void __kprobes arch_prepare_ss_slot(struct kprobe *p)
  55 {
  56         unsigned long offset = is_insn32(p->opcode) ? 4 : 2;
  57
  58         p->ainsn.api.restore = (unsigned long)p->addr + offset;
  59
  60         patch_text(p->ainsn.api.insn, p->opcode);
  61 }
  62
  63 static void __kprobes arch_prepare_simulate(struct kprobe *p)
  64 {
  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         post_kprobe_handler(kcb, regs);
  76 }
  77
  78 int __kprobes arch_prepare_kprobe(struct kprobe *p)
  79 {
  80         unsigned long probe_addr = (unsigned long)p->addr;
  81
  82         if (probe_addr & 0x1)
  83                 return -EILSEQ;
  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         if (p->ainsn.api.insn) {
 128                 free_insn_slot(p->ainsn.api.insn, 0);
 129                 p->ainsn.api.insn = NULL;
 130         }
 131 }
 132
 133 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
 134 {
 135         kcb->prev_kprobe.kp = kprobe_running();
 136         kcb->prev_kprobe.status = kcb->kprobe_status;
 137 }
 138
 139 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
 140 {
 141         __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
 142         kcb->kprobe_status = kcb->prev_kprobe.status;
 143 }
 144
 145 static void __kprobes set_current_kprobe(struct kprobe *p)
 146 {
 147         __this_cpu_write(current_kprobe, p);
 148 }
 149
 150 /*
 151  * Interrupts need to be disabled before single-step mode is set, and not
 152  * reenabled until after single-step mode ends.
 153  * Without disabling interrupt on local CPU, there is a chance of
 154  * interrupt occurrence in the period of exception return and  start of
 155  * out-of-line single-step, that result in wrongly single stepping
 156  * into the interrupt handler.
 157  */
 158 static void __kprobes kprobes_save_local_irqflag(struct kprobe_ctlblk *kcb,
 159                                                 struct pt_regs *regs)
 160 {
 161         kcb->saved_sr = regs->sr;
 162         regs->sr &= ~BIT(6);
 163 }
 164
 165 static void __kprobes kprobes_restore_local_irqflag(struct kprobe_ctlblk *kcb,
 166                                                 struct pt_regs *regs)
 167 {
 168         regs->sr = kcb->saved_sr;
 169 }
 170
 171 static void __kprobes
 172 set_ss_context(struct kprobe_ctlblk *kcb, unsigned long addr, struct kprobe *p)
 173 {
 174         unsigned long offset = is_insn32(p->opcode) ? 4 : 2;
 175
 176         kcb->ss_ctx.ss_pending = true;
 177         kcb->ss_ctx.match_addr = addr + offset;
 178 }
 179
 180 static void __kprobes clear_ss_context(struct kprobe_ctlblk *kcb)
 181 {
 182         kcb->ss_ctx.ss_pending = false;
 183         kcb->ss_ctx.match_addr = 0;
 184 }
 185
 186 #define TRACE_MODE_SI           BIT(14)
 187 #define TRACE_MODE_MASK         ~(0x3 << 14)
 188 #define TRACE_MODE_RUN          0
 189
 190 static void __kprobes setup_singlestep(struct kprobe *p,
 191                                        struct pt_regs *regs,
 192                                        struct kprobe_ctlblk *kcb, int reenter)
 193 {
 194         unsigned long slot;
 195
 196         if (reenter) {
 197                 save_previous_kprobe(kcb);
 198                 set_current_kprobe(p);
 199                 kcb->kprobe_status = KPROBE_REENTER;
 200         } else {
 201                 kcb->kprobe_status = KPROBE_HIT_SS;
 202         }
 203
 204         if (p->ainsn.api.insn) {
 205                 /* prepare for single stepping */
 206                 slot = (unsigned long)p->ainsn.api.insn;
 207
 208                 set_ss_context(kcb, slot, p);   /* mark pending ss */
 209
 210                 /* IRQs and single stepping do not mix well. */
 211                 kprobes_save_local_irqflag(kcb, regs);
 212                 regs->sr = (regs->sr & TRACE_MODE_MASK) | TRACE_MODE_SI;
 213                 instruction_pointer_set(regs, slot);
 214         } else {
 215                 /* insn simulation */
 216                 arch_simulate_insn(p, regs);
 217         }
 218 }
 219
 220 static int __kprobes reenter_kprobe(struct kprobe *p,
 221                                     struct pt_regs *regs,
 222                                     struct kprobe_ctlblk *kcb)
 223 {
 224         switch (kcb->kprobe_status) {
 225         case KPROBE_HIT_SSDONE:
 226         case KPROBE_HIT_ACTIVE:
 227                 kprobes_inc_nmissed_count(p);
 228                 setup_singlestep(p, regs, kcb, 1);
 229                 break;
 230         case KPROBE_HIT_SS:
 231         case KPROBE_REENTER:
 232                 pr_warn("Failed to recover from reentered kprobes.\n");
 233                 dump_kprobe(p);
 234                 BUG();
 235                 break;
 236         default:
 237                 WARN_ON(1);
 238                 return 0;
 239         }
 240
 241         return 1;
 242 }
 243
 244 static void __kprobes
 245 post_kprobe_handler(struct kprobe_ctlblk *kcb, struct pt_regs *regs)
 246 {
 247         struct kprobe *cur = kprobe_running();
 248
 249         if (!cur)
 250                 return;
 251
 252         /* return addr restore if non-branching insn */
 253         if (cur->ainsn.api.restore != 0)
 254                 regs->pc = cur->ainsn.api.restore;
 255
 256         /* restore back original saved kprobe variables and continue */
 257         if (kcb->kprobe_status == KPROBE_REENTER) {
 258                 restore_previous_kprobe(kcb);
 259                 return;
 260         }
 261
 262         /* call post handler */
 263         kcb->kprobe_status = KPROBE_HIT_SSDONE;
 264         if (cur->post_handler)  {
 265                 /* post_handler can hit breakpoint and single step
 266                  * again, so we enable D-flag for recursive exception.
 267                  */
 268                 cur->post_handler(cur, regs, 0);
 269         }
 270
 271         reset_current_kprobe();
 272 }
 273
 274 int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int trapnr)
 275 {
 276         struct kprobe *cur = kprobe_running();
 277         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 278
 279         switch (kcb->kprobe_status) {
 280         case KPROBE_HIT_SS:
 281         case KPROBE_REENTER:
 282                 /*
 283                  * We are here because the instruction being single
 284                  * stepped caused a page fault. We reset the current
 285                  * kprobe and the ip points back to the probe address
 286                  * and allow the page fault handler to continue as a
 287                  * normal page fault.
 288                  */
 289                 regs->pc = (unsigned long) cur->addr;
 290                 BUG_ON(!instruction_pointer(regs));
 291
 292                 if (kcb->kprobe_status == KPROBE_REENTER)
 293                         restore_previous_kprobe(kcb);
 294                 else
 295                         reset_current_kprobe();
 296
 297                 break;
 298         case KPROBE_HIT_ACTIVE:
 299         case KPROBE_HIT_SSDONE:
 300                 /*
 301                  * In case the user-specified fault handler returned
 302                  * zero, try to fix up.
 303                  */
 304                 if (fixup_exception(regs))
 305                         return 1;
 306         }
 307         return 0;
 308 }
 309
 310 int __kprobes
 311 kprobe_breakpoint_handler(struct pt_regs *regs)
 312 {
 313         struct kprobe *p, *cur_kprobe;
 314         struct kprobe_ctlblk *kcb;
 315         unsigned long addr = instruction_pointer(regs);
 316
 317         kcb = get_kprobe_ctlblk();
 318         cur_kprobe = kprobe_running();
 319
 320         p = get_kprobe((kprobe_opcode_t *) addr);
 321
 322         if (p) {
 323                 if (cur_kprobe) {
 324                         if (reenter_kprobe(p, regs, kcb))
 325                                 return 1;
 326                 } else {
 327                         /* Probe hit */
 328                         set_current_kprobe(p);
 329                         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 330
 331                         /*
 332                          * If we have no pre-handler or it returned 0, we
 333                          * continue with normal processing.  If we have a
 334                          * pre-handler and it returned non-zero, it will
 335                          * modify the execution path and no need to single
 336                          * stepping. Let's just reset current kprobe and exit.
 337                          *
 338                          * pre_handler can hit a breakpoint and can step thru
 339                          * before return.
 340                          */
 341                         if (!p->pre_handler || !p->pre_handler(p, regs))
 342                                 setup_singlestep(p, regs, kcb, 0);
 343                         else
 344                                 reset_current_kprobe();
 345                 }
 346                 return 1;
 347         }
 348
 349         /*
 350          * The breakpoint instruction was removed right
 351          * after we hit it.  Another cpu has removed
 352          * either a probepoint or a debugger breakpoint
 353          * at this address.  In either case, no further
 354          * handling of this interrupt is appropriate.
 355          * Return back to original instruction, and continue.
 356          */
 357         return 0;
 358 }
 359
 360 int __kprobes
 361 kprobe_single_step_handler(struct pt_regs *regs)
 362 {
 363         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 364
 365         if ((kcb->ss_ctx.ss_pending)
 366             && (kcb->ss_ctx.match_addr == instruction_pointer(regs))) {
 367                 clear_ss_context(kcb);  /* clear pending ss */
 368
 369                 kprobes_restore_local_irqflag(kcb, regs);
 370                 regs->sr = (regs->sr & TRACE_MODE_MASK) | TRACE_MODE_RUN;
 371
 372                 post_kprobe_handler(kcb, regs);
 373                 return 1;
 374         }
 375         return 0;
 376 }
 377
 378 /*
 379  * Provide a blacklist of symbols identifying ranges which cannot be kprobed.
 380  * This blacklist is exposed to userspace via debugfs (kprobes/blacklist).
 381  */
 382 int __init arch_populate_kprobe_blacklist(void)
 383 {
 384         int ret;
 385
 386         ret = kprobe_add_area_blacklist((unsigned long)__irqentry_text_start,
 387                                         (unsigned long)__irqentry_text_end);
 388         return ret;
 389 }
 390
 391 void __kprobes __used *trampoline_probe_handler(struct pt_regs *regs)
 392 {
 393         return (void *)kretprobe_trampoline_handler(regs, NULL);
 394 }
 395
 396 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 397                                       struct pt_regs *regs)
 398 {
 399         ri->ret_addr = (kprobe_opcode_t *)regs->lr;
 400         ri->fp = NULL;
 401         regs->lr = (unsigned long) &__kretprobe_trampoline;
 402 }
 403
 404 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
 405 {
 406         return 0;
 407 }
 408
 409 int __init arch_init_kprobes(void)
 410 {
 411         return 0;
 412 }