arch/parisc/kernel/kprobes.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * arch/parisc/kernel/kprobes.c
   4  *
   5  * PA-RISC kprobes implementation
   6  *
   7  * Copyright (c) 2019 Sven Schnelle <svens@stackframe.org>
   8  */
   9
  10 #include <linux/types.h>
  11 #include <linux/kprobes.h>
  12 #include <linux/slab.h>
  13 #include <asm/cacheflush.h>
  14 #include <asm/patch.h>
  15
  16 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
  17 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
  18
  19 int __kprobes arch_prepare_kprobe(struct kprobe *p)
  20 {
  21         if ((unsigned long)p->addr & 3UL)
  22                 return -EINVAL;
  23
  24         p->ainsn.insn = get_insn_slot();
  25         if (!p->ainsn.insn)
  26                 return -ENOMEM;
  27
  28         memcpy(p->ainsn.insn, p->addr,
  29                 MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
  30         p->opcode = *p->addr;
  31         flush_insn_slot(p);
  32         return 0;
  33 }
  34
  35 void __kprobes arch_remove_kprobe(struct kprobe *p)
  36 {
  37         if (!p->ainsn.insn)
  38                 return;
  39
  40         free_insn_slot(p->ainsn.insn, 0);
  41         p->ainsn.insn = NULL;
  42 }
  43
  44 void __kprobes arch_arm_kprobe(struct kprobe *p)
  45 {
  46         patch_text(p->addr, PARISC_KPROBES_BREAK_INSN);
  47 }
  48
  49 void __kprobes arch_disarm_kprobe(struct kprobe *p)
  50 {
  51         patch_text(p->addr, p->opcode);
  52 }
  53
  54 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
  55 {
  56         kcb->prev_kprobe.kp = kprobe_running();
  57         kcb->prev_kprobe.status = kcb->kprobe_status;
  58 }
  59
  60 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
  61 {
  62         __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
  63         kcb->kprobe_status = kcb->prev_kprobe.status;
  64 }
  65
  66 static inline void __kprobes set_current_kprobe(struct kprobe *p)
  67 {
  68         __this_cpu_write(current_kprobe, p);
  69 }
  70
  71 static void __kprobes setup_singlestep(struct kprobe *p,
  72                 struct kprobe_ctlblk *kcb, struct pt_regs *regs)
  73 {
  74         kcb->iaoq[0] = regs->iaoq[0];
  75         kcb->iaoq[1] = regs->iaoq[1];
  76         regs->iaoq[0] = (unsigned long)p->ainsn.insn;
  77         mtctl(0, 0);
  78         regs->gr[0] |= PSW_R;
  79 }
  80
  81 int __kprobes parisc_kprobe_break_handler(struct pt_regs *regs)
  82 {
  83         struct kprobe *p;
  84         struct kprobe_ctlblk *kcb;
  85
  86         preempt_disable();
  87
  88         kcb = get_kprobe_ctlblk();
  89         p = get_kprobe((unsigned long *)regs->iaoq[0]);
  90
  91         if (!p) {
  92                 preempt_enable_no_resched();
  93                 return 0;
  94         }
  95
  96         if (kprobe_running()) {
  97                 /*
  98                  * We have reentered the kprobe_handler, since another kprobe
  99                  * was hit while within the handler, we save the original
 100                  * kprobes and single step on the instruction of the new probe
 101                  * without calling any user handlers to avoid recursive
 102                  * kprobes.
 103                  */
 104                 save_previous_kprobe(kcb);
 105                 set_current_kprobe(p);
 106                 kprobes_inc_nmissed_count(p);
 107                 setup_singlestep(p, kcb, regs);
 108                 kcb->kprobe_status = KPROBE_REENTER;
 109                 return 1;
 110         }
 111
 112         set_current_kprobe(p);
 113         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 114
 115         /* If we have no pre-handler or it returned 0, we continue with
 116          * normal processing. If we have a pre-handler and it returned
 117          * non-zero - which means user handler setup registers to exit
 118          * to another instruction, we must skip the single stepping.
 119          */
 120
 121         if (!p->pre_handler || !p->pre_handler(p, regs)) {
 122                 setup_singlestep(p, kcb, regs);
 123                 kcb->kprobe_status = KPROBE_HIT_SS;
 124         } else {
 125                 reset_current_kprobe();
 126                 preempt_enable_no_resched();
 127         }
 128         return 1;
 129 }
 130
 131 int __kprobes parisc_kprobe_ss_handler(struct pt_regs *regs)
 132 {
 133         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 134         struct kprobe *p = kprobe_running();
 135
 136         if (!p)
 137                 return 0;
 138
 139         if (regs->iaoq[0] != (unsigned long)p->ainsn.insn+4)
 140                 return 0;
 141
 142         /* restore back original saved kprobe variables and continue */
 143         if (kcb->kprobe_status == KPROBE_REENTER) {
 144                 restore_previous_kprobe(kcb);
 145                 return 1;
 146         }
 147
 148         /* for absolute branch instructions we can copy iaoq_b. for relative
 149          * branch instructions we need to calculate the new address based on the
 150          * difference between iaoq_f and iaoq_b. We cannot use iaoq_b without
 151          * modificationt because it's based on our ainsn.insn address.
 152          */
 153
 154         if (p->post_handler)
 155                 p->post_handler(p, regs, 0);
 156
 157         switch (regs->iir >> 26) {
 158         case 0x38: /* BE */
 159         case 0x39: /* BE,L */
 160         case 0x3a: /* BV */
 161         case 0x3b: /* BVE */
 162                 /* for absolute branches, regs->iaoq[1] has already the right
 163                  * address
 164                  */
 165                 regs->iaoq[0] = kcb->iaoq[1];
 166                 break;
 167         default:
 168                 regs->iaoq[1] = kcb->iaoq[0];
 169                 regs->iaoq[1] += (regs->iaoq[1] - regs->iaoq[0]) + 4;
 170                 regs->iaoq[0] = kcb->iaoq[1];
 171                 break;
 172         }
 173         kcb->kprobe_status = KPROBE_HIT_SSDONE;
 174         reset_current_kprobe();
 175         return 1;
 176 }
 177
 178 static inline void kretprobe_trampoline(void)
 179 {
 180         asm volatile("nop");
 181         asm volatile("nop");
 182 }
 183
 184 static int __kprobes trampoline_probe_handler(struct kprobe *p,
 185                                               struct pt_regs *regs);
 186
 187 static struct kprobe trampoline_p = {
 188         .pre_handler = trampoline_probe_handler
 189 };
 190
 191 static int __kprobes trampoline_probe_handler(struct kprobe *p,
 192                                               struct pt_regs *regs)
 193 {
 194         struct kretprobe_instance *ri = NULL;
 195         struct hlist_head *head, empty_rp;
 196         struct hlist_node *tmp;
 197         unsigned long flags, orig_ret_address = 0;
 198         unsigned long trampoline_address = (unsigned long)trampoline_p.addr;
 199         kprobe_opcode_t *correct_ret_addr = NULL;
 200
 201         INIT_HLIST_HEAD(&empty_rp);
 202         kretprobe_hash_lock(current, &head, &flags);
 203
 204         /*
 205          * It is possible to have multiple instances associated with a given
 206          * task either because multiple functions in the call path have
 207          * a return probe installed on them, and/or more than one return
 208          * probe was registered for a target function.
 209          *
 210          * We can handle this because:
 211          *     - instances are always inserted at the head of the list
 212          *     - when multiple return probes are registered for the same
 213          *       function, the first instance's ret_addr will point to the
 214          *       real return address, and all the rest will point to
 215          *       kretprobe_trampoline
 216          */
 217         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
 218                 if (ri->task != current)
 219                         /* another task is sharing our hash bucket */
 220                         continue;
 221
 222                 orig_ret_address = (unsigned long)ri->ret_addr;
 223
 224                 if (orig_ret_address != trampoline_address)
 225                         /*
 226                          * This is the real return address. Any other
 227                          * instances associated with this task are for
 228                          * other calls deeper on the call stack
 229                          */
 230                         break;
 231         }
 232
 233         kretprobe_assert(ri, orig_ret_address, trampoline_address);
 234
 235         correct_ret_addr = ri->ret_addr;
 236         hlist_for_each_entry_safe(ri, tmp, head, hlist) {
 237                 if (ri->task != current)
 238                         /* another task is sharing our hash bucket */
 239                         continue;
 240
 241                 orig_ret_address = (unsigned long)ri->ret_addr;
 242                 if (ri->rp && ri->rp->handler) {
 243                         __this_cpu_write(current_kprobe, &ri->rp->kp);
 244                         get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
 245                         ri->ret_addr = correct_ret_addr;
 246                         ri->rp->handler(ri, regs);
 247                         __this_cpu_write(current_kprobe, NULL);
 248                 }
 249
 250                 recycle_rp_inst(ri, &empty_rp);
 251
 252                 if (orig_ret_address != trampoline_address)
 253                         /*
 254                          * This is the real return address. Any other
 255                          * instances associated with this task are for
 256                          * other calls deeper on the call stack
 257                          */
 258                         break;
 259         }
 260
 261         kretprobe_hash_unlock(current, &flags);
 262
 263         hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
 264                 hlist_del(&ri->hlist);
 265                 kfree(ri);
 266         }
 267         instruction_pointer_set(regs, orig_ret_address);
 268         return 1;
 269 }
 270
 271 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 272                                       struct pt_regs *regs)
 273 {
 274         ri->ret_addr = (kprobe_opcode_t *)regs->gr[2];
 275
 276         /* Replace the return addr with trampoline addr. */
 277         regs->gr[2] = (unsigned long)trampoline_p.addr;
 278 }
 279
 280 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
 281 {
 282         return p->addr == trampoline_p.addr;
 283 }
 284
 285 int __init arch_init_kprobes(void)
 286 {
 287         trampoline_p.addr = (kprobe_opcode_t *)
 288                 dereference_function_descriptor(kretprobe_trampoline);
 289         return register_kprobe(&trampoline_p);
 290 }