arch/s390/kernel/kprobes.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  *  Kernel Probes (KProbes)
   4  *
   5  * Copyright IBM Corp. 2002, 2006
   6  *
   7  * s390 port, used ppc64 as template. Mike Grundy <grundym@us.ibm.com>
   8  */
   9
  10 #include <linux/moduleloader.h>
  11 #include <linux/kprobes.h>
  12 #include <linux/ptrace.h>
  13 #include <linux/preempt.h>
  14 #include <linux/stop_machine.h>
  15 #include <linux/kdebug.h>
  16 #include <linux/uaccess.h>
  17 #include <linux/extable.h>
  18 #include <linux/module.h>
  19 #include <linux/slab.h>
  20 #include <linux/hardirq.h>
  21 #include <linux/ftrace.h>
  22 #include <asm/set_memory.h>
  23 #include <asm/sections.h>
  24 #include <asm/dis.h>
  25 #include "entry.h"
  26
  27 DEFINE_PER_CPU(struct kprobe *, current_kprobe);
  28 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
  29
  30 struct kretprobe_blackpoint kretprobe_blacklist[] = { };
  31
  32 DEFINE_INSN_CACHE_OPS(s390_insn);
  33
  34 static int insn_page_in_use;
  35
  36 void *alloc_insn_page(void)
  37 {
  38         void *page;
  39
  40         page = module_alloc(PAGE_SIZE);
  41         if (!page)
  42                 return NULL;
  43         __set_memory((unsigned long) page, 1, SET_MEMORY_RO | SET_MEMORY_X);
  44         return page;
  45 }
  46
  47 void free_insn_page(void *page)
  48 {
  49         module_memfree(page);
  50 }
  51
  52 static void *alloc_s390_insn_page(void)
  53 {
  54         if (xchg(&insn_page_in_use, 1) == 1)
  55                 return NULL;
  56         return &kprobes_insn_page;
  57 }
  58
  59 static void free_s390_insn_page(void *page)
  60 {
  61         xchg(&insn_page_in_use, 0);
  62 }
  63
  64 struct kprobe_insn_cache kprobe_s390_insn_slots = {
  65         .mutex = __MUTEX_INITIALIZER(kprobe_s390_insn_slots.mutex),
  66         .alloc = alloc_s390_insn_page,
  67         .free = free_s390_insn_page,
  68         .pages = LIST_HEAD_INIT(kprobe_s390_insn_slots.pages),
  69         .insn_size = MAX_INSN_SIZE,
  70 };
  71
  72 static void copy_instruction(struct kprobe *p)
  73 {
  74         kprobe_opcode_t insn[MAX_INSN_SIZE];
  75         s64 disp, new_disp;
  76         u64 addr, new_addr;
  77         unsigned int len;
  78
  79         len = insn_length(*p->addr >> 8);
  80         memcpy(&insn, p->addr, len);
  81         p->opcode = insn[0];
  82         if (probe_is_insn_relative_long(&insn[0])) {
  83                 /*
  84                  * For pc-relative instructions in RIL-b or RIL-c format patch
  85                  * the RI2 displacement field. We have already made sure that
  86                  * the insn slot for the patched instruction is within the same
  87                  * 2GB area as the original instruction (either kernel image or
  88                  * module area). Therefore the new displacement will always fit.
  89                  */
  90                 disp = *(s32 *)&insn[1];
  91                 addr = (u64)(unsigned long)p->addr;
  92                 new_addr = (u64)(unsigned long)p->ainsn.insn;
  93                 new_disp = ((addr + (disp * 2)) - new_addr) / 2;
  94                 *(s32 *)&insn[1] = new_disp;
  95         }
  96         s390_kernel_write(p->ainsn.insn, &insn, len);
  97 }
  98 NOKPROBE_SYMBOL(copy_instruction);
  99
 100 static inline int is_kernel_addr(void *addr)
 101 {
 102         return addr < (void *)_end;
 103 }
 104
 105 static int s390_get_insn_slot(struct kprobe *p)
 106 {
 107         /*
 108          * Get an insn slot that is within the same 2GB area like the original
 109          * instruction. That way instructions with a 32bit signed displacement
 110          * field can be patched and executed within the insn slot.
 111          */
 112         p->ainsn.insn = NULL;
 113         if (is_kernel_addr(p->addr))
 114                 p->ainsn.insn = get_s390_insn_slot();
 115         else if (is_module_addr(p->addr))
 116                 p->ainsn.insn = get_insn_slot();
 117         return p->ainsn.insn ? 0 : -ENOMEM;
 118 }
 119 NOKPROBE_SYMBOL(s390_get_insn_slot);
 120
 121 static void s390_free_insn_slot(struct kprobe *p)
 122 {
 123         if (!p->ainsn.insn)
 124                 return;
 125         if (is_kernel_addr(p->addr))
 126                 free_s390_insn_slot(p->ainsn.insn, 0);
 127         else
 128                 free_insn_slot(p->ainsn.insn, 0);
 129         p->ainsn.insn = NULL;
 130 }
 131 NOKPROBE_SYMBOL(s390_free_insn_slot);
 132
 133 int arch_prepare_kprobe(struct kprobe *p)
 134 {
 135         if ((unsigned long) p->addr & 0x01)
 136                 return -EINVAL;
 137         /* Make sure the probe isn't going on a difficult instruction */
 138         if (probe_is_prohibited_opcode(p->addr))
 139                 return -EINVAL;
 140         if (s390_get_insn_slot(p))
 141                 return -ENOMEM;
 142         copy_instruction(p);
 143         return 0;
 144 }
 145 NOKPROBE_SYMBOL(arch_prepare_kprobe);
 146
 147 struct swap_insn_args {
 148         struct kprobe *p;
 149         unsigned int arm_kprobe : 1;
 150 };
 151
 152 static int swap_instruction(void *data)
 153 {
 154         struct swap_insn_args *args = data;
 155         struct kprobe *p = args->p;
 156         u16 opc;
 157
 158         opc = args->arm_kprobe ? BREAKPOINT_INSTRUCTION : p->opcode;
 159         s390_kernel_write(p->addr, &opc, sizeof(opc));
 160         return 0;
 161 }
 162 NOKPROBE_SYMBOL(swap_instruction);
 163
 164 void arch_arm_kprobe(struct kprobe *p)
 165 {
 166         struct swap_insn_args args = {.p = p, .arm_kprobe = 1};
 167
 168         stop_machine_cpuslocked(swap_instruction, &args, NULL);
 169 }
 170 NOKPROBE_SYMBOL(arch_arm_kprobe);
 171
 172 void arch_disarm_kprobe(struct kprobe *p)
 173 {
 174         struct swap_insn_args args = {.p = p, .arm_kprobe = 0};
 175
 176         stop_machine_cpuslocked(swap_instruction, &args, NULL);
 177 }
 178 NOKPROBE_SYMBOL(arch_disarm_kprobe);
 179
 180 void arch_remove_kprobe(struct kprobe *p)
 181 {
 182         s390_free_insn_slot(p);
 183 }
 184 NOKPROBE_SYMBOL(arch_remove_kprobe);
 185
 186 static void enable_singlestep(struct kprobe_ctlblk *kcb,
 187                               struct pt_regs *regs,
 188                               unsigned long ip)
 189 {
 190         struct per_regs per_kprobe;
 191
 192         /* Set up the PER control registers %cr9-%cr11 */
 193         per_kprobe.control = PER_EVENT_IFETCH;
 194         per_kprobe.start = ip;
 195         per_kprobe.end = ip;
 196
 197         /* Save control regs and psw mask */
 198         __ctl_store(kcb->kprobe_saved_ctl, 9, 11);
 199         kcb->kprobe_saved_imask = regs->psw.mask &
 200                 (PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT);
 201
 202         /* Set PER control regs, turns on single step for the given address */
 203         __ctl_load(per_kprobe, 9, 11);
 204         regs->psw.mask |= PSW_MASK_PER;
 205         regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);
 206         regs->psw.addr = ip;
 207 }
 208 NOKPROBE_SYMBOL(enable_singlestep);
 209
 210 static void disable_singlestep(struct kprobe_ctlblk *kcb,
 211                                struct pt_regs *regs,
 212                                unsigned long ip)
 213 {
 214         /* Restore control regs and psw mask, set new psw address */
 215         __ctl_load(kcb->kprobe_saved_ctl, 9, 11);
 216         regs->psw.mask &= ~PSW_MASK_PER;
 217         regs->psw.mask |= kcb->kprobe_saved_imask;
 218         regs->psw.addr = ip;
 219 }
 220 NOKPROBE_SYMBOL(disable_singlestep);
 221
 222 /*
 223  * Activate a kprobe by storing its pointer to current_kprobe. The
 224  * previous kprobe is stored in kcb->prev_kprobe. A stack of up to
 225  * two kprobes can be active, see KPROBE_REENTER.
 226  */
 227 static void push_kprobe(struct kprobe_ctlblk *kcb, struct kprobe *p)
 228 {
 229         kcb->prev_kprobe.kp = __this_cpu_read(current_kprobe);
 230         kcb->prev_kprobe.status = kcb->kprobe_status;
 231         __this_cpu_write(current_kprobe, p);
 232 }
 233 NOKPROBE_SYMBOL(push_kprobe);
 234
 235 /*
 236  * Deactivate a kprobe by backing up to the previous state. If the
 237  * current state is KPROBE_REENTER prev_kprobe.kp will be non-NULL,
 238  * for any other state prev_kprobe.kp will be NULL.
 239  */
 240 static void pop_kprobe(struct kprobe_ctlblk *kcb)
 241 {
 242         __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
 243         kcb->kprobe_status = kcb->prev_kprobe.status;
 244 }
 245 NOKPROBE_SYMBOL(pop_kprobe);
 246
 247 void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
 248 {
 249         ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];
 250         ri->fp = NULL;
 251
 252         /* Replace the return addr with trampoline addr */
 253         regs->gprs[14] = (unsigned long) &kretprobe_trampoline;
 254 }
 255 NOKPROBE_SYMBOL(arch_prepare_kretprobe);
 256
 257 static void kprobe_reenter_check(struct kprobe_ctlblk *kcb, struct kprobe *p)
 258 {
 259         switch (kcb->kprobe_status) {
 260         case KPROBE_HIT_SSDONE:
 261         case KPROBE_HIT_ACTIVE:
 262                 kprobes_inc_nmissed_count(p);
 263                 break;
 264         case KPROBE_HIT_SS:
 265         case KPROBE_REENTER:
 266         default:
 267                 /*
 268                  * A kprobe on the code path to single step an instruction
 269                  * is a BUG. The code path resides in the .kprobes.text
 270                  * section and is executed with interrupts disabled.
 271                  */
 272                 pr_err("Invalid kprobe detected.\n");
 273                 dump_kprobe(p);
 274                 BUG();
 275         }
 276 }
 277 NOKPROBE_SYMBOL(kprobe_reenter_check);
 278
 279 static int kprobe_handler(struct pt_regs *regs)
 280 {
 281         struct kprobe_ctlblk *kcb;
 282         struct kprobe *p;
 283
 284         /*
 285          * We want to disable preemption for the entire duration of kprobe
 286          * processing. That includes the calls to the pre/post handlers
 287          * and single stepping the kprobe instruction.
 288          */
 289         preempt_disable();
 290         kcb = get_kprobe_ctlblk();
 291         p = get_kprobe((void *)(regs->psw.addr - 2));
 292
 293         if (p) {
 294                 if (kprobe_running()) {
 295                         /*
 296                          * We have hit a kprobe while another is still
 297                          * active. This can happen in the pre and post
 298                          * handler. Single step the instruction of the
 299                          * new probe but do not call any handler function
 300                          * of this secondary kprobe.
 301                          * push_kprobe and pop_kprobe saves and restores
 302                          * the currently active kprobe.
 303                          */
 304                         kprobe_reenter_check(kcb, p);
 305                         push_kprobe(kcb, p);
 306                         kcb->kprobe_status = KPROBE_REENTER;
 307                 } else {
 308                         /*
 309                          * If we have no pre-handler or it returned 0, we
 310                          * continue with single stepping. If we have a
 311                          * pre-handler and it returned non-zero, it prepped
 312                          * for changing execution path, so get out doing
 313                          * nothing more here.
 314                          */
 315                         push_kprobe(kcb, p);
 316                         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 317                         if (p->pre_handler && p->pre_handler(p, regs)) {
 318                                 pop_kprobe(kcb);
 319                                 preempt_enable_no_resched();
 320                                 return 1;
 321                         }
 322                         kcb->kprobe_status = KPROBE_HIT_SS;
 323                 }
 324                 enable_singlestep(kcb, regs, (unsigned long) p->ainsn.insn);
 325                 return 1;
 326         } /* else:
 327            * No kprobe at this address and no active kprobe. The trap has
 328            * not been caused by a kprobe breakpoint. The race of breakpoint
 329            * vs. kprobe remove does not exist because on s390 as we use
 330            * stop_machine to arm/disarm the breakpoints.
 331            */
 332         preempt_enable_no_resched();
 333         return 0;
 334 }
 335 NOKPROBE_SYMBOL(kprobe_handler);
 336
 337 /*
 338  * Function return probe trampoline:
 339  *      - init_kprobes() establishes a probepoint here
 340  *      - When the probed function returns, this probe
 341  *              causes the handlers to fire
 342  */
 343 static void __used kretprobe_trampoline_holder(void)
 344 {
 345         asm volatile(".global kretprobe_trampoline\n"
 346                      "kretprobe_trampoline: bcr 0,0\n");
 347 }
 348
 349 /*
 350  * Called when the probe at kretprobe trampoline is hit
 351  */
 352 static int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
 353 {
 354         regs->psw.addr = __kretprobe_trampoline_handler(regs, &kretprobe_trampoline, NULL);
 355         /*
 356          * By returning a non-zero value, we are telling
 357          * kprobe_handler() that we don't want the post_handler
 358          * to run (and have re-enabled preemption)
 359          */
 360         return 1;
 361 }
 362 NOKPROBE_SYMBOL(trampoline_probe_handler);
 363
 364 /*
 365  * Called after single-stepping.  p->addr is the address of the
 366  * instruction whose first byte has been replaced by the "breakpoint"
 367  * instruction.  To avoid the SMP problems that can occur when we
 368  * temporarily put back the original opcode to single-step, we
 369  * single-stepped a copy of the instruction.  The address of this
 370  * copy is p->ainsn.insn.
 371  */
 372 static void resume_execution(struct kprobe *p, struct pt_regs *regs)
 373 {
 374         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 375         unsigned long ip = regs->psw.addr;
 376         int fixup = probe_get_fixup_type(p->ainsn.insn);
 377
 378         if (fixup & FIXUP_PSW_NORMAL)
 379                 ip += (unsigned long) p->addr - (unsigned long) p->ainsn.insn;
 380
 381         if (fixup & FIXUP_BRANCH_NOT_TAKEN) {
 382                 int ilen = insn_length(p->ainsn.insn[0] >> 8);
 383                 if (ip - (unsigned long) p->ainsn.insn == ilen)
 384                         ip = (unsigned long) p->addr + ilen;
 385         }
 386
 387         if (fixup & FIXUP_RETURN_REGISTER) {
 388                 int reg = (p->ainsn.insn[0] & 0xf0) >> 4;
 389                 regs->gprs[reg] += (unsigned long) p->addr -
 390                                    (unsigned long) p->ainsn.insn;
 391         }
 392
 393         disable_singlestep(kcb, regs, ip);
 394 }
 395 NOKPROBE_SYMBOL(resume_execution);
 396
 397 static int post_kprobe_handler(struct pt_regs *regs)
 398 {
 399         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 400         struct kprobe *p = kprobe_running();
 401
 402         if (!p)
 403                 return 0;
 404
 405         if (kcb->kprobe_status != KPROBE_REENTER && p->post_handler) {
 406                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
 407                 p->post_handler(p, regs, 0);
 408         }
 409
 410         resume_execution(p, regs);
 411         pop_kprobe(kcb);
 412         preempt_enable_no_resched();
 413
 414         /*
 415          * if somebody else is singlestepping across a probe point, psw mask
 416          * will have PER set, in which case, continue the remaining processing
 417          * of do_single_step, as if this is not a probe hit.
 418          */
 419         if (regs->psw.mask & PSW_MASK_PER)
 420                 return 0;
 421
 422         return 1;
 423 }
 424 NOKPROBE_SYMBOL(post_kprobe_handler);
 425
 426 static int kprobe_trap_handler(struct pt_regs *regs, int trapnr)
 427 {
 428         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 429         struct kprobe *p = kprobe_running();
 430         const struct exception_table_entry *entry;
 431
 432         switch(kcb->kprobe_status) {
 433         case KPROBE_HIT_SS:
 434         case KPROBE_REENTER:
 435                 /*
 436                  * We are here because the instruction being single
 437                  * stepped caused a page fault. We reset the current
 438                  * kprobe and the nip points back to the probe address
 439                  * and allow the page fault handler to continue as a
 440                  * normal page fault.
 441                  */
 442                 disable_singlestep(kcb, regs, (unsigned long) p->addr);
 443                 pop_kprobe(kcb);
 444                 preempt_enable_no_resched();
 445                 break;
 446         case KPROBE_HIT_ACTIVE:
 447         case KPROBE_HIT_SSDONE:
 448                 /*
 449                  * We increment the nmissed count for accounting,
 450                  * we can also use npre/npostfault count for accounting
 451                  * these specific fault cases.
 452                  */
 453                 kprobes_inc_nmissed_count(p);
 454
 455                 /*
 456                  * We come here because instructions in the pre/post
 457                  * handler caused the page_fault, this could happen
 458                  * if handler tries to access user space by
 459                  * copy_from_user(), get_user() etc. Let the
 460                  * user-specified handler try to fix it first.
 461                  */
 462                 if (p->fault_handler && p->fault_handler(p, regs, trapnr))
 463                         return 1;
 464
 465                 /*
 466                  * In case the user-specified fault handler returned
 467                  * zero, try to fix up.
 468                  */
 469                 entry = s390_search_extables(regs->psw.addr);
 470                 if (entry && ex_handle(entry, regs))
 471                         return 1;
 472
 473                 /*
 474                  * fixup_exception() could not handle it,
 475                  * Let do_page_fault() fix it.
 476                  */
 477                 break;
 478         default:
 479                 break;
 480         }
 481         return 0;
 482 }
 483 NOKPROBE_SYMBOL(kprobe_trap_handler);
 484
 485 int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 486 {
 487         int ret;
 488
 489         if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
 490                 local_irq_disable();
 491         ret = kprobe_trap_handler(regs, trapnr);
 492         if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
 493                 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
 494         return ret;
 495 }
 496 NOKPROBE_SYMBOL(kprobe_fault_handler);
 497
 498 /*
 499  * Wrapper routine to for handling exceptions.
 500  */
 501 int kprobe_exceptions_notify(struct notifier_block *self,
 502                              unsigned long val, void *data)
 503 {
 504         struct die_args *args = (struct die_args *) data;
 505         struct pt_regs *regs = args->regs;
 506         int ret = NOTIFY_DONE;
 507
 508         if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
 509                 local_irq_disable();
 510
 511         switch (val) {
 512         case DIE_BPT:
 513                 if (kprobe_handler(regs))
 514                         ret = NOTIFY_STOP;
 515                 break;
 516         case DIE_SSTEP:
 517                 if (post_kprobe_handler(regs))
 518                         ret = NOTIFY_STOP;
 519                 break;
 520         case DIE_TRAP:
 521                 if (!preemptible() && kprobe_running() &&
 522                     kprobe_trap_handler(regs, args->trapnr))
 523                         ret = NOTIFY_STOP;
 524                 break;
 525         default:
 526                 break;
 527         }
 528
 529         if (regs->psw.mask & (PSW_MASK_IO | PSW_MASK_EXT))
 530                 local_irq_restore(regs->psw.mask & ~PSW_MASK_PER);
 531
 532         return ret;
 533 }
 534 NOKPROBE_SYMBOL(kprobe_exceptions_notify);
 535
 536 static struct kprobe trampoline = {
 537         .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
 538         .pre_handler = trampoline_probe_handler
 539 };
 540
 541 int __init arch_init_kprobes(void)
 542 {
 543         return register_kprobe(&trampoline);
 544 }
 545
 546 int arch_trampoline_kprobe(struct kprobe *p)
 547 {
 548         return p->addr == (kprobe_opcode_t *) &kretprobe_trampoline;
 549 }
 550 NOKPROBE_SYMBOL(arch_trampoline_kprobe);