1/* arch/sparc64/kernel/kprobes.c 2 * 3 * Copyright (C) 2004 David S. Miller <davem@davemloft.net> 4 */ 5 6#include <linux/kernel.h> 7#include <linux/kprobes.h> 8#include <linux/module.h> 9#include <linux/kdebug.h> 10#include <linux/slab.h> 11#include <asm/signal.h> 12#include <asm/cacheflush.h> 13#include <asm/uaccess.h> 14 15/* We do not have hardware single-stepping on sparc64. 16 * So we implement software single-stepping with breakpoint 17 * traps. The top-level scheme is similar to that used 18 * in the x86 kprobes implementation. 19 * 20 * In the kprobe->ainsn.insn[] array we store the original 21 * instruction at index zero and a break instruction at 22 * index one. 23 * 24 * When we hit a kprobe we: 25 * - Run the pre-handler 26 * - Remember "regs->tnpc" and interrupt level stored in 27 * "regs->tstate" so we can restore them later 28 * - Disable PIL interrupts 29 * - Set regs->tpc to point to kprobe->ainsn.insn[0] 30 * - Set regs->tnpc to point to kprobe->ainsn.insn[1] 31 * - Mark that we are actively in a kprobe 32 * 33 * At this point we wait for the second breakpoint at 34 * kprobe->ainsn.insn[1] to hit. When it does we: 35 * - Run the post-handler 36 * - Set regs->tpc to "remembered" regs->tnpc stored above, 37 * restore the PIL interrupt level in "regs->tstate" as well 38 * - Make any adjustments necessary to regs->tnpc in order 39 * to handle relative branches correctly. See below. 40 * - Mark that we are no longer actively in a kprobe. 41 */ 42 43DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL; 44DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk); 45 46struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}}; 47 48int __kprobes arch_prepare_kprobe(struct kprobe *p) 49{ 50 if ((unsigned long) p->addr & 0x3UL) 51 return -EILSEQ; 52 53 p->ainsn.insn[0] = *p->addr; 54 flushi(&p->ainsn.insn[0]); 55 56 p->ainsn.insn[1] = BREAKPOINT_INSTRUCTION_2; 57 flushi(&p->ainsn.insn[1]); 58 59 p->opcode = *p->addr; 60 return 0; 61} 62 63void __kprobes arch_arm_kprobe(struct kprobe *p) 64{ 65 *p->addr = BREAKPOINT_INSTRUCTION; 66 flushi(p->addr); 67} 68 69void __kprobes arch_disarm_kprobe(struct kprobe *p) 70{ 71 *p->addr = p->opcode; 72 flushi(p->addr); 73} 74 75static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb) 76{ 77 kcb->prev_kprobe.kp = kprobe_running(); 78 kcb->prev_kprobe.status = kcb->kprobe_status; 79 kcb->prev_kprobe.orig_tnpc = kcb->kprobe_orig_tnpc; 80 kcb->prev_kprobe.orig_tstate_pil = kcb->kprobe_orig_tstate_pil; 81} 82 83static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb) 84{ 85 __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp; 86 kcb->kprobe_status = kcb->prev_kprobe.status; 87 kcb->kprobe_orig_tnpc = kcb->prev_kprobe.orig_tnpc; 88 kcb->kprobe_orig_tstate_pil = kcb->prev_kprobe.orig_tstate_pil; 89} 90 91static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs, 92 struct kprobe_ctlblk *kcb) 93{ 94 __get_cpu_var(current_kprobe) = p; 95 kcb->kprobe_orig_tnpc = regs->tnpc; 96 kcb->kprobe_orig_tstate_pil = (regs->tstate & TSTATE_PIL); 97} 98 99static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs, 100 struct kprobe_ctlblk *kcb) 101{ 102 regs->tstate |= TSTATE_PIL; 103 104 /*single step inline, if it a breakpoint instruction*/ 105 if (p->opcode == BREAKPOINT_INSTRUCTION) { 106 regs->tpc = (unsigned long) p->addr; 107 regs->tnpc = kcb->kprobe_orig_tnpc; 108 } else { 109 regs->tpc = (unsigned long) &p->ainsn.insn[0]; 110 regs->tnpc = (unsigned long) &p->ainsn.insn[1]; 111 } 112} 113 114static int __kprobes kprobe_handler(struct pt_regs *regs) 115{ 116 struct kprobe *p; 117 void *addr = (void *) regs->tpc; 118 int ret = 0; 119 struct kprobe_ctlblk *kcb; 120 121 /* 122 * We don't want to be preempted for the entire 123 * duration of kprobe processing 124 */ 125 preempt_disable(); 126 kcb = get_kprobe_ctlblk(); 127 128 if (kprobe_running()) { 129 p = get_kprobe(addr); 130 if (p) { 131 if (kcb->kprobe_status == KPROBE_HIT_SS) { 132 regs->tstate = ((regs->tstate & ~TSTATE_PIL) | 133 kcb->kprobe_orig_tstate_pil); 134 goto no_kprobe; 135 } 136 /* We have reentered the kprobe_handler(), since 137 * another probe was hit while within the handler. 138 * We here save the original kprobes variables and 139 * just single step on the instruction of the new probe 140 * without calling any user handlers. 141 */ 142 save_previous_kprobe(kcb); 143 set_current_kprobe(p, regs, kcb); 144 kprobes_inc_nmissed_count(p); 145 kcb->kprobe_status = KPROBE_REENTER; 146 prepare_singlestep(p, regs, kcb); 147 return 1; 148 } else { 149 if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) { 150 /* The breakpoint instruction was removed by 151 * another cpu right after we hit, no further 152 * handling of this interrupt is appropriate 153 */ 154 ret = 1; 155 goto no_kprobe; 156 } 157 p = __get_cpu_var(current_kprobe); 158 if (p->break_handler && p->break_handler(p, regs)) 159 goto ss_probe; 160 } 161 goto no_kprobe; 162 } 163 164 p = get_kprobe(addr); 165 if (!p) { 166 if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) { 167 /* 168 * The breakpoint instruction was removed right 169 * after we hit it. Another cpu has removed 170 * either a probepoint or a debugger breakpoint 171 * at this address. In either case, no further 172 * handling of this interrupt is appropriate. 173 */ 174 ret = 1; 175 } 176 /* Not one of ours: let kernel handle it */ 177 goto no_kprobe; 178 } 179 180 set_current_kprobe(p, regs, kcb); 181 kcb->kprobe_status = KPROBE_HIT_ACTIVE; 182 if (p->pre_handler && p->pre_handler(p, regs)) 183 return 1; 184 185ss_probe: 186 prepare_singlestep(p, regs, kcb); 187 kcb->kprobe_status = KPROBE_HIT_SS; 188 return 1; 189 190no_kprobe: 191 preempt_enable_no_resched(); 192 return ret; 193} 194 195/* If INSN is a relative control transfer instruction, 196 * return the corrected branch destination value. 197 * 198 * regs->tpc and regs->tnpc still hold the values of the 199 * program counters at the time of trap due to the execution 200 * of the BREAKPOINT_INSTRUCTION_2 at p->ainsn.insn[1] 201 * 202 */ 203static unsigned long __kprobes relbranch_fixup(u32 insn, struct kprobe *p, 204 struct pt_regs *regs) 205{ 206 unsigned long real_pc = (unsigned long) p->addr; 207 208 /* Branch not taken, no mods necessary. */ 209 if (regs->tnpc == regs->tpc + 0x4UL) 210 return real_pc + 0x8UL; 211 212 /* The three cases are call, branch w/prediction, 213 * and traditional branch. 214 */ 215 if ((insn & 0xc0000000) == 0x40000000 || 216 (insn & 0xc1c00000) == 0x00400000 || 217 (insn & 0xc1c00000) == 0x00800000) { 218 unsigned long ainsn_addr; 219 220 ainsn_addr = (unsigned long) &p->ainsn.insn[0]; 221 222 /* The instruction did all the work for us 223 * already, just apply the offset to the correct 224 * instruction location. 225 */ 226 return (real_pc + (regs->tnpc - ainsn_addr)); 227 } 228 229 /* It is jmpl or some other absolute PC modification instruction, 230 * leave NPC as-is. 231 */ 232 return regs->tnpc; 233} 234 235/* If INSN is an instruction which writes it's PC location 236 * into a destination register, fix that up. 237 */ 238static void __kprobes retpc_fixup(struct pt_regs *regs, u32 insn, 239 unsigned long real_pc) 240{ 241 unsigned long *slot = NULL; 242 243 /* Simplest case is 'call', which always uses %o7 */ 244 if ((insn & 0xc0000000) == 0x40000000) { 245 slot = ®s->u_regs[UREG_I7]; 246 } 247 248 /* 'jmpl' encodes the register inside of the opcode */ 249 if ((insn & 0xc1f80000) == 0x81c00000) { 250 unsigned long rd = ((insn >> 25) & 0x1f); 251 252 if (rd <= 15) { 253 slot = ®s->u_regs[rd]; 254 } else { 255 /* Hard case, it goes onto the stack. */ 256 flushw_all(); 257 258 rd -= 16; 259 slot = (unsigned long *) 260 (regs->u_regs[UREG_FP] + STACK_BIAS); 261 slot += rd; 262 } 263 } 264 if (slot != NULL) 265 *slot = real_pc; 266} 267 268/* 269 * Called after single-stepping. p->addr is the address of the 270 * instruction which has been replaced by the breakpoint 271 * instruction. To avoid the SMP problems that can occur when we 272 * temporarily put back the original opcode to single-step, we 273 * single-stepped a copy of the instruction. The address of this 274 * copy is &p->ainsn.insn[0]. 275 * 276 * This function prepares to return from the post-single-step 277 * breakpoint trap. 278 */ 279static void __kprobes resume_execution(struct kprobe *p, 280 struct pt_regs *regs, struct kprobe_ctlblk *kcb) 281{ 282 u32 insn = p->ainsn.insn[0]; 283 284 regs->tnpc = relbranch_fixup(insn, p, regs); 285 286 /* This assignment must occur after relbranch_fixup() */ 287 regs->tpc = kcb->kprobe_orig_tnpc; 288 289 retpc_fixup(regs, insn, (unsigned long) p->addr); 290 291 regs->tstate = ((regs->tstate & ~TSTATE_PIL) | 292 kcb->kprobe_orig_tstate_pil); 293} 294 295static int __kprobes post_kprobe_handler(struct pt_regs *regs) 296{ 297 struct kprobe *cur = kprobe_running(); 298 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); 299 300 if (!cur) 301 return 0; 302 303 if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) { 304 kcb->kprobe_status = KPROBE_HIT_SSDONE; 305 cur->post_handler(cur, regs, 0); 306 } 307 308 resume_execution(cur, regs, kcb); 309 310 /*Restore back the original saved kprobes variables and continue. */ 311 if (kcb->kprobe_status == KPROBE_REENTER) { 312 restore_previous_kprobe(kcb); 313 goto out; 314 } 315 reset_current_kprobe(); 316out: 317 preempt_enable_no_resched(); 318 319 return 1; 320} 321 322int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr) 323{ 324 struct kprobe *cur = kprobe_running(); 325 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); 326 const struct exception_table_entry *entry; 327 328 switch(kcb->kprobe_status) { 329 case KPROBE_HIT_SS: 330 case KPROBE_REENTER: 331 /* 332 * We are here because the instruction being single 333 * stepped caused a page fault. We reset the current 334 * kprobe and the tpc points back to the probe address 335 * and allow the page fault handler to continue as a 336 * normal page fault. 337 */ 338 regs->tpc = (unsigned long)cur->addr; 339 regs->tnpc = kcb->kprobe_orig_tnpc; 340 regs->tstate = ((regs->tstate & ~TSTATE_PIL) | 341 kcb->kprobe_orig_tstate_pil); 342 if (kcb->kprobe_status == KPROBE_REENTER) 343 restore_previous_kprobe(kcb); 344 else 345 reset_current_kprobe(); 346 preempt_enable_no_resched(); 347 break; 348 case KPROBE_HIT_ACTIVE: 349 case KPROBE_HIT_SSDONE: 350 /* 351 * We increment the nmissed count for accounting, 352 * we can also use npre/npostfault count for accouting 353 * these specific fault cases. 354 */ 355 kprobes_inc_nmissed_count(cur); 356 357 /* 358 * We come here because instructions in the pre/post 359 * handler caused the page_fault, this could happen 360 * if handler tries to access user space by 361 * copy_from_user(), get_user() etc. Let the 362 * user-specified handler try to fix it first. 363 */ 364 if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr)) 365 return 1; 366 367 /* 368 * In case the user-specified fault handler returned 369 * zero, try to fix up. 370 */ 371 372 entry = search_exception_tables(regs->tpc); 373 if (entry) { 374 regs->tpc = entry->fixup; 375 regs->tnpc = regs->tpc + 4; 376 return 1; 377 } 378 379 /* 380 * fixup_exception() could not handle it, 381 * Let do_page_fault() fix it. 382 */ 383 break; 384 default: 385 break; 386 } 387 388 return 0; 389} 390 391/* 392 * Wrapper routine to for handling exceptions. 393 */ 394int __kprobes kprobe_exceptions_notify(struct notifier_block *self, 395 unsigned long val, void *data) 396{ 397 struct die_args *args = (struct die_args *)data; 398 int ret = NOTIFY_DONE; 399 400 if (args->regs && user_mode(args->regs)) 401 return ret; 402 403 switch (val) { 404 case DIE_DEBUG: 405 if (kprobe_handler(args->regs)) 406 ret = NOTIFY_STOP; 407 break; 408 case DIE_DEBUG_2: 409 if (post_kprobe_handler(args->regs)) 410 ret = NOTIFY_STOP; 411 break; 412 default: 413 break; 414 } 415 return ret; 416} 417 418asmlinkage void __kprobes kprobe_trap(unsigned long trap_level, 419 struct pt_regs *regs) 420{ 421 BUG_ON(trap_level != 0x170 && trap_level != 0x171); 422 423 if (user_mode(regs)) { 424 local_irq_enable(); 425 bad_trap(regs, trap_level); 426 return; 427 } 428 429 /* trap_level == 0x170 --> ta 0x70 430 * trap_level == 0x171 --> ta 0x71 431 */ 432 if (notify_die((trap_level == 0x170) ? DIE_DEBUG : DIE_DEBUG_2, 433 (trap_level == 0x170) ? "debug" : "debug_2", 434 regs, 0, trap_level, SIGTRAP) != NOTIFY_STOP) 435 bad_trap(regs, trap_level); 436} 437 438/* Jprobes support. */ 439int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs) 440{ 441 struct jprobe *jp = container_of(p, struct jprobe, kp); 442 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); 443 444 memcpy(&(kcb->jprobe_saved_regs), regs, sizeof(*regs)); 445 446 regs->tpc = (unsigned long) jp->entry; 447 regs->tnpc = ((unsigned long) jp->entry) + 0x4UL; 448 regs->tstate |= TSTATE_PIL; 449 450 return 1; 451} 452 453void __kprobes jprobe_return(void) 454{ 455 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); 456 register unsigned long orig_fp asm("g1"); 457 458 orig_fp = kcb->jprobe_saved_regs.u_regs[UREG_FP]; 459 __asm__ __volatile__("\n" 460"1: cmp %%sp, %0\n\t" 461 "blu,a,pt %%xcc, 1b\n\t" 462 " restore\n\t" 463 ".globl jprobe_return_trap_instruction\n" 464"jprobe_return_trap_instruction:\n\t" 465 "ta 0x70" 466 : /* no outputs */ 467 : "r" (orig_fp)); 468} 469 470extern void jprobe_return_trap_instruction(void); 471 472int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs) 473{ 474 u32 *addr = (u32 *) regs->tpc; 475 struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); 476 477 if (addr == (u32 *) jprobe_return_trap_instruction) { 478 memcpy(regs, &(kcb->jprobe_saved_regs), sizeof(*regs)); 479 preempt_enable_no_resched(); 480 return 1; 481 } 482 return 0; 483} 484 485/* The value stored in the return address register is actually 2 486 * instructions before where the callee will return to. 487 * Sequences usually look something like this 488 * 489 * call some_function <--- return register points here 490 * nop <--- call delay slot 491 * whatever <--- where callee returns to 492 * 493 * To keep trampoline_probe_handler logic simpler, we normalize the 494 * value kept in ri->ret_addr so we don't need to keep adjusting it 495 * back and forth. 496 */ 497void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri, 498 struct pt_regs *regs) 499{ 500 ri->ret_addr = (kprobe_opcode_t *)(regs->u_regs[UREG_RETPC] + 8); 501 502 /* Replace the return addr with trampoline addr */ 503 regs->u_regs[UREG_RETPC] = 504 ((unsigned long)kretprobe_trampoline) - 8; 505} 506 507/* 508 * Called when the probe at kretprobe trampoline is hit 509 */ 510int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs) 511{ 512 struct kretprobe_instance *ri = NULL; 513 struct hlist_head *head, empty_rp; 514 struct hlist_node *node, *tmp; 515 unsigned long flags, orig_ret_address = 0; 516 unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline; 517 518 INIT_HLIST_HEAD(&empty_rp); 519 kretprobe_hash_lock(current, &head, &flags); 520 521 /* 522 * It is possible to have multiple instances associated with a given 523 * task either because an multiple functions in the call path 524 * have a return probe installed on them, and/or more than one return 525 * return probe was registered for a target function. 526 * 527 * We can handle this because: 528 * - instances are always inserted at the head of the list 529 * - when multiple return probes are registered for the same 530 * function, the first instance's ret_addr will point to the 531 * real return address, and all the rest will point to 532 * kretprobe_trampoline 533 */ 534 hlist_for_each_entry_safe(ri, node, tmp, head, hlist) { 535 if (ri->task != current) 536 /* another task is sharing our hash bucket */ 537 continue; 538 539 if (ri->rp && ri->rp->handler) 540 ri->rp->handler(ri, regs); 541 542 orig_ret_address = (unsigned long)ri->ret_addr; 543 recycle_rp_inst(ri, &empty_rp); 544 545 if (orig_ret_address != trampoline_address) 546 /* 547 * This is the real return address. Any other 548 * instances associated with this task are for 549 * other calls deeper on the call stack 550 */ 551 break; 552 } 553 554 kretprobe_assert(ri, orig_ret_address, trampoline_address); 555 regs->tpc = orig_ret_address; 556 regs->tnpc = orig_ret_address + 4; 557 558 reset_current_kprobe(); 559 kretprobe_hash_unlock(current, &flags); 560 preempt_enable_no_resched(); 561 562 hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) { 563 hlist_del(&ri->hlist); 564 kfree(ri); 565 } 566 /* 567 * By returning a non-zero value, we are telling 568 * kprobe_handler() that we don't want the post_handler 569 * to run (and have re-enabled preemption) 570 */ 571 return 1; 572} 573 574void kretprobe_trampoline_holder(void) 575{ 576 asm volatile(".global kretprobe_trampoline\n" 577 "kretprobe_trampoline:\n" 578 "\tnop\n" 579 "\tnop\n"); 580} 581static struct kprobe trampoline_p = { 582 .addr = (kprobe_opcode_t *) &kretprobe_trampoline, 583 .pre_handler = trampoline_probe_handler 584}; 585 586int __init arch_init_kprobes(void) 587{ 588 return register_kprobe(&trampoline_p); 589} 590 591int __kprobes arch_trampoline_kprobe(struct kprobe *p) 592{ 593 if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline) 594 return 1; 595 596 return 0; 597} 598