arch/riscv/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 #include <asm/bug.h>
  14 #include <asm/patch.h>
  15
  16 #include "decode-insn.h"
  17
  18 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
  19 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
  20
  21 static void __kprobes
  22 post_kprobe_handler(struct kprobe *, struct kprobe_ctlblk *, struct pt_regs *);
  23
  24 static void __kprobes arch_prepare_ss_slot(struct kprobe *p)
  25 {
  26         unsigned long offset = GET_INSN_LENGTH(p->opcode);
  27
  28         p->ainsn.api.restore = (unsigned long)p->addr + offset;
  29
  30         patch_text(p->ainsn.api.insn, p->opcode);
  31         patch_text((void *)((unsigned long)(p->ainsn.api.insn) + offset),
  32                    __BUG_INSN_32);
  33 }
  34
  35 static void __kprobes arch_prepare_simulate(struct kprobe *p)
  36 {
  37         p->ainsn.api.restore = 0;
  38 }
  39
  40 static void __kprobes arch_simulate_insn(struct kprobe *p, struct pt_regs *regs)
  41 {
  42         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
  43
  44         if (p->ainsn.api.handler)
  45                 p->ainsn.api.handler((u32)p->opcode,
  46                                         (unsigned long)p->addr, regs);
  47
  48         post_kprobe_handler(p, kcb, regs);
  49 }
  50
  51 int __kprobes arch_prepare_kprobe(struct kprobe *p)
  52 {
  53         unsigned long probe_addr = (unsigned long)p->addr;
  54
  55         if (probe_addr & 0x1)
  56                 return -EILSEQ;
  57
  58         /* copy instruction */
  59         p->opcode = *p->addr;
  60
  61         /* decode instruction */
  62         switch (riscv_probe_decode_insn(p->addr, &p->ainsn.api)) {
  63         case INSN_REJECTED:     /* insn not supported */
  64                 return -EINVAL;
  65
  66         case INSN_GOOD_NO_SLOT: /* insn need simulation */
  67                 p->ainsn.api.insn = NULL;
  68                 break;
  69
  70         case INSN_GOOD: /* instruction uses slot */
  71                 p->ainsn.api.insn = get_insn_slot();
  72                 if (!p->ainsn.api.insn)
  73                         return -ENOMEM;
  74                 break;
  75         }
  76
  77         /* prepare the instruction */
  78         if (p->ainsn.api.insn)
  79                 arch_prepare_ss_slot(p);
  80         else
  81                 arch_prepare_simulate(p);
  82
  83         return 0;
  84 }
  85
  86 #ifdef CONFIG_MMU
  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 #endif
  95
  96 /* install breakpoint in text */
  97 void __kprobes arch_arm_kprobe(struct kprobe *p)
  98 {
  99         if ((p->opcode & __INSN_LENGTH_MASK) == __INSN_LENGTH_32)
 100                 patch_text(p->addr, __BUG_INSN_32);
 101         else
 102                 patch_text(p->addr, __BUG_INSN_16);
 103 }
 104
 105 /* remove breakpoint from text */
 106 void __kprobes arch_disarm_kprobe(struct kprobe *p)
 107 {
 108         patch_text(p->addr, p->opcode);
 109 }
 110
 111 void __kprobes arch_remove_kprobe(struct kprobe *p)
 112 {
 113 }
 114
 115 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
 116 {
 117         kcb->prev_kprobe.kp = kprobe_running();
 118         kcb->prev_kprobe.status = kcb->kprobe_status;
 119 }
 120
 121 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
 122 {
 123         __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
 124         kcb->kprobe_status = kcb->prev_kprobe.status;
 125 }
 126
 127 static void __kprobes set_current_kprobe(struct kprobe *p)
 128 {
 129         __this_cpu_write(current_kprobe, p);
 130 }
 131
 132 /*
 133  * Interrupts need to be disabled before single-step mode is set, and not
 134  * reenabled until after single-step mode ends.
 135  * Without disabling interrupt on local CPU, there is a chance of
 136  * interrupt occurrence in the period of exception return and  start of
 137  * out-of-line single-step, that result in wrongly single stepping
 138  * into the interrupt handler.
 139  */
 140 static void __kprobes kprobes_save_local_irqflag(struct kprobe_ctlblk *kcb,
 141                                                 struct pt_regs *regs)
 142 {
 143         kcb->saved_status = regs->status;
 144         regs->status &= ~SR_SPIE;
 145 }
 146
 147 static void __kprobes kprobes_restore_local_irqflag(struct kprobe_ctlblk *kcb,
 148                                                 struct pt_regs *regs)
 149 {
 150         regs->status = kcb->saved_status;
 151 }
 152
 153 static void __kprobes setup_singlestep(struct kprobe *p,
 154                                        struct pt_regs *regs,
 155                                        struct kprobe_ctlblk *kcb, int reenter)
 156 {
 157         unsigned long slot;
 158
 159         if (reenter) {
 160                 save_previous_kprobe(kcb);
 161                 set_current_kprobe(p);
 162                 kcb->kprobe_status = KPROBE_REENTER;
 163         } else {
 164                 kcb->kprobe_status = KPROBE_HIT_SS;
 165         }
 166
 167         if (p->ainsn.api.insn) {
 168                 /* prepare for single stepping */
 169                 slot = (unsigned long)p->ainsn.api.insn;
 170
 171                 /* IRQs and single stepping do not mix well. */
 172                 kprobes_save_local_irqflag(kcb, regs);
 173
 174                 instruction_pointer_set(regs, slot);
 175         } else {
 176                 /* insn simulation */
 177                 arch_simulate_insn(p, regs);
 178         }
 179 }
 180
 181 static int __kprobes reenter_kprobe(struct kprobe *p,
 182                                     struct pt_regs *regs,
 183                                     struct kprobe_ctlblk *kcb)
 184 {
 185         switch (kcb->kprobe_status) {
 186         case KPROBE_HIT_SSDONE:
 187         case KPROBE_HIT_ACTIVE:
 188                 kprobes_inc_nmissed_count(p);
 189                 setup_singlestep(p, regs, kcb, 1);
 190                 break;
 191         case KPROBE_HIT_SS:
 192         case KPROBE_REENTER:
 193                 pr_warn("Failed to recover from reentered kprobes.\n");
 194                 dump_kprobe(p);
 195                 BUG();
 196                 break;
 197         default:
 198                 WARN_ON(1);
 199                 return 0;
 200         }
 201
 202         return 1;
 203 }
 204
 205 static void __kprobes
 206 post_kprobe_handler(struct kprobe *cur, struct kprobe_ctlblk *kcb, struct pt_regs *regs)
 207 {
 208         /* return addr restore if non-branching insn */
 209         if (cur->ainsn.api.restore != 0)
 210                 regs->epc = cur->ainsn.api.restore;
 211
 212         /* restore back original saved kprobe variables and continue */
 213         if (kcb->kprobe_status == KPROBE_REENTER) {
 214                 restore_previous_kprobe(kcb);
 215                 return;
 216         }
 217
 218         /* call post handler */
 219         kcb->kprobe_status = KPROBE_HIT_SSDONE;
 220         if (cur->post_handler)  {
 221                 /* post_handler can hit breakpoint and single step
 222                  * again, so we enable D-flag for recursive exception.
 223                  */
 224                 cur->post_handler(cur, regs, 0);
 225         }
 226
 227         reset_current_kprobe();
 228 }
 229
 230 int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int trapnr)
 231 {
 232         struct kprobe *cur = kprobe_running();
 233         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 234
 235         switch (kcb->kprobe_status) {
 236         case KPROBE_HIT_SS:
 237         case KPROBE_REENTER:
 238                 /*
 239                  * We are here because the instruction being single
 240                  * stepped caused a page fault. We reset the current
 241                  * kprobe and the ip points back to the probe address
 242                  * and allow the page fault handler to continue as a
 243                  * normal page fault.
 244                  */
 245                 regs->epc = (unsigned long) cur->addr;
 246                 BUG_ON(!instruction_pointer(regs));
 247
 248                 if (kcb->kprobe_status == KPROBE_REENTER)
 249                         restore_previous_kprobe(kcb);
 250                 else {
 251                         kprobes_restore_local_irqflag(kcb, regs);
 252                         reset_current_kprobe();
 253                 }
 254
 255                 break;
 256         case KPROBE_HIT_ACTIVE:
 257         case KPROBE_HIT_SSDONE:
 258                 /*
 259                  * In case the user-specified fault handler returned
 260                  * zero, try to fix up.
 261                  */
 262                 if (fixup_exception(regs))
 263                         return 1;
 264         }
 265         return 0;
 266 }
 267
 268 bool __kprobes
 269 kprobe_breakpoint_handler(struct pt_regs *regs)
 270 {
 271         struct kprobe *p, *cur_kprobe;
 272         struct kprobe_ctlblk *kcb;
 273         unsigned long addr = instruction_pointer(regs);
 274
 275         kcb = get_kprobe_ctlblk();
 276         cur_kprobe = kprobe_running();
 277
 278         p = get_kprobe((kprobe_opcode_t *) addr);
 279
 280         if (p) {
 281                 if (cur_kprobe) {
 282                         if (reenter_kprobe(p, regs, kcb))
 283                                 return true;
 284                 } else {
 285                         /* Probe hit */
 286                         set_current_kprobe(p);
 287                         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 288
 289                         /*
 290                          * If we have no pre-handler or it returned 0, we
 291                          * continue with normal processing.  If we have a
 292                          * pre-handler and it returned non-zero, it will
 293                          * modify the execution path and no need to single
 294                          * stepping. Let's just reset current kprobe and exit.
 295                          *
 296                          * pre_handler can hit a breakpoint and can step thru
 297                          * before return.
 298                          */
 299                         if (!p->pre_handler || !p->pre_handler(p, regs))
 300                                 setup_singlestep(p, regs, kcb, 0);
 301                         else
 302                                 reset_current_kprobe();
 303                 }
 304                 return true;
 305         }
 306
 307         /*
 308          * The breakpoint instruction was removed right
 309          * after we hit it.  Another cpu has removed
 310          * either a probepoint or a debugger breakpoint
 311          * at this address.  In either case, no further
 312          * handling of this interrupt is appropriate.
 313          * Return back to original instruction, and continue.
 314          */
 315         return false;
 316 }
 317
 318 bool __kprobes
 319 kprobe_single_step_handler(struct pt_regs *regs)
 320 {
 321         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 322         unsigned long addr = instruction_pointer(regs);
 323         struct kprobe *cur = kprobe_running();
 324
 325         if (cur && (kcb->kprobe_status & (KPROBE_HIT_SS | KPROBE_REENTER)) &&
 326             ((unsigned long)&cur->ainsn.api.insn[0] + GET_INSN_LENGTH(cur->opcode) == addr)) {
 327                 kprobes_restore_local_irqflag(kcb, regs);
 328                 post_kprobe_handler(cur, kcb, regs);
 329                 return true;
 330         }
 331         /* not ours, kprobes should ignore it */
 332         return false;
 333 }
 334
 335 /*
 336  * Provide a blacklist of symbols identifying ranges which cannot be kprobed.
 337  * This blacklist is exposed to userspace via debugfs (kprobes/blacklist).
 338  */
 339 int __init arch_populate_kprobe_blacklist(void)
 340 {
 341         int ret;
 342
 343         ret = kprobe_add_area_blacklist((unsigned long)__irqentry_text_start,
 344                                         (unsigned long)__irqentry_text_end);
 345         return ret;
 346 }
 347
 348 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
 349 {
 350         return 0;
 351 }
 352
 353 int __init arch_init_kprobes(void)
 354 {
 355         return 0;
 356 }