1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Based on arch/arm/kernel/signal.c 4 * 5 * Copyright (C) 1995-2009 Russell King 6 * Copyright (C) 2012 ARM Ltd. 7 */ 8 9 #include <linux/cache.h> 10 #include <linux/compat.h> 11 #include <linux/errno.h> 12 #include <linux/kernel.h> 13 #include <linux/signal.h> 14 #include <linux/freezer.h> 15 #include <linux/stddef.h> 16 #include <linux/uaccess.h> 17 #include <linux/sizes.h> 18 #include <linux/string.h> 19 #include <linux/resume_user_mode.h> 20 #include <linux/ratelimit.h> 21 #include <linux/syscalls.h> 22 23 #include <asm/daifflags.h> 24 #include <asm/debug-monitors.h> 25 #include <asm/elf.h> 26 #include <asm/cacheflush.h> 27 #include <asm/ucontext.h> 28 #include <asm/unistd.h> 29 #include <asm/fpsimd.h> 30 #include <asm/ptrace.h> 31 #include <asm/syscall.h> 32 #include <asm/signal32.h> 33 #include <asm/traps.h> 34 #include <asm/vdso.h> 35 36 /* 37 * Do a signal return; undo the signal stack. These are aligned to 128-bit. 38 */ 39 struct rt_sigframe { 40 struct siginfo info; 41 struct ucontext uc; 42 }; 43 44 struct frame_record { 45 u64 fp; 46 u64 lr; 47 }; 48 49 struct rt_sigframe_user_layout { 50 struct rt_sigframe __user *sigframe; 51 struct frame_record __user *next_frame; 52 53 unsigned long size; /* size of allocated sigframe data */ 54 unsigned long limit; /* largest allowed size */ 55 56 unsigned long fpsimd_offset; 57 unsigned long esr_offset; 58 unsigned long sve_offset; 59 unsigned long extra_offset; 60 unsigned long end_offset; 61 }; 62 63 #define BASE_SIGFRAME_SIZE round_up(sizeof(struct rt_sigframe), 16) 64 #define TERMINATOR_SIZE round_up(sizeof(struct _aarch64_ctx), 16) 65 #define EXTRA_CONTEXT_SIZE round_up(sizeof(struct extra_context), 16) 66 67 static void init_user_layout(struct rt_sigframe_user_layout *user) 68 { 69 const size_t reserved_size = 70 sizeof(user->sigframe->uc.uc_mcontext.__reserved); 71 72 memset(user, 0, sizeof(*user)); 73 user->size = offsetof(struct rt_sigframe, uc.uc_mcontext.__reserved); 74 75 user->limit = user->size + reserved_size; 76 77 user->limit -= TERMINATOR_SIZE; 78 user->limit -= EXTRA_CONTEXT_SIZE; 79 /* Reserve space for extension and terminator ^ */ 80 } 81 82 static size_t sigframe_size(struct rt_sigframe_user_layout const *user) 83 { 84 return round_up(max(user->size, sizeof(struct rt_sigframe)), 16); 85 } 86 87 /* 88 * Sanity limit on the approximate maximum size of signal frame we'll 89 * try to generate. Stack alignment padding and the frame record are 90 * not taken into account. This limit is not a guarantee and is 91 * NOT ABI. 92 */ 93 #define SIGFRAME_MAXSZ SZ_64K 94 95 static int __sigframe_alloc(struct rt_sigframe_user_layout *user, 96 unsigned long *offset, size_t size, bool extend) 97 { 98 size_t padded_size = round_up(size, 16); 99 100 if (padded_size > user->limit - user->size && 101 !user->extra_offset && 102 extend) { 103 int ret; 104 105 user->limit += EXTRA_CONTEXT_SIZE; 106 ret = __sigframe_alloc(user, &user->extra_offset, 107 sizeof(struct extra_context), false); 108 if (ret) { 109 user->limit -= EXTRA_CONTEXT_SIZE; 110 return ret; 111 } 112 113 /* Reserve space for the __reserved[] terminator */ 114 user->size += TERMINATOR_SIZE; 115 116 /* 117 * Allow expansion up to SIGFRAME_MAXSZ, ensuring space for 118 * the terminator: 119 */ 120 user->limit = SIGFRAME_MAXSZ - TERMINATOR_SIZE; 121 } 122 123 /* Still not enough space? Bad luck! */ 124 if (padded_size > user->limit - user->size) 125 return -ENOMEM; 126 127 *offset = user->size; 128 user->size += padded_size; 129 130 return 0; 131 } 132 133 /* 134 * Allocate space for an optional record of <size> bytes in the user 135 * signal frame. The offset from the signal frame base address to the 136 * allocated block is assigned to *offset. 137 */ 138 static int sigframe_alloc(struct rt_sigframe_user_layout *user, 139 unsigned long *offset, size_t size) 140 { 141 return __sigframe_alloc(user, offset, size, true); 142 } 143 144 /* Allocate the null terminator record and prevent further allocations */ 145 static int sigframe_alloc_end(struct rt_sigframe_user_layout *user) 146 { 147 int ret; 148 149 /* Un-reserve the space reserved for the terminator: */ 150 user->limit += TERMINATOR_SIZE; 151 152 ret = sigframe_alloc(user, &user->end_offset, 153 sizeof(struct _aarch64_ctx)); 154 if (ret) 155 return ret; 156 157 /* Prevent further allocation: */ 158 user->limit = user->size; 159 return 0; 160 } 161 162 static void __user *apply_user_offset( 163 struct rt_sigframe_user_layout const *user, unsigned long offset) 164 { 165 char __user *base = (char __user *)user->sigframe; 166 167 return base + offset; 168 } 169 170 static int preserve_fpsimd_context(struct fpsimd_context __user *ctx) 171 { 172 struct user_fpsimd_state const *fpsimd = 173 ¤t->thread.uw.fpsimd_state; 174 int err; 175 176 /* copy the FP and status/control registers */ 177 err = __copy_to_user(ctx->vregs, fpsimd->vregs, sizeof(fpsimd->vregs)); 178 __put_user_error(fpsimd->fpsr, &ctx->fpsr, err); 179 __put_user_error(fpsimd->fpcr, &ctx->fpcr, err); 180 181 /* copy the magic/size information */ 182 __put_user_error(FPSIMD_MAGIC, &ctx->head.magic, err); 183 __put_user_error(sizeof(struct fpsimd_context), &ctx->head.size, err); 184 185 return err ? -EFAULT : 0; 186 } 187 188 static int restore_fpsimd_context(struct fpsimd_context __user *ctx) 189 { 190 struct user_fpsimd_state fpsimd; 191 __u32 magic, size; 192 int err = 0; 193 194 /* check the magic/size information */ 195 __get_user_error(magic, &ctx->head.magic, err); 196 __get_user_error(size, &ctx->head.size, err); 197 if (err) 198 return -EFAULT; 199 if (magic != FPSIMD_MAGIC || size != sizeof(struct fpsimd_context)) 200 return -EINVAL; 201 202 /* copy the FP and status/control registers */ 203 err = __copy_from_user(fpsimd.vregs, ctx->vregs, 204 sizeof(fpsimd.vregs)); 205 __get_user_error(fpsimd.fpsr, &ctx->fpsr, err); 206 __get_user_error(fpsimd.fpcr, &ctx->fpcr, err); 207 208 clear_thread_flag(TIF_SVE); 209 210 /* load the hardware registers from the fpsimd_state structure */ 211 if (!err) 212 fpsimd_update_current_state(&fpsimd); 213 214 return err ? -EFAULT : 0; 215 } 216 217 218 struct user_ctxs { 219 struct fpsimd_context __user *fpsimd; 220 struct sve_context __user *sve; 221 }; 222 223 #ifdef CONFIG_ARM64_SVE 224 225 static int preserve_sve_context(struct sve_context __user *ctx) 226 { 227 int err = 0; 228 u16 reserved[ARRAY_SIZE(ctx->__reserved)]; 229 unsigned int vl = task_get_sve_vl(current); 230 unsigned int vq = 0; 231 232 if (test_thread_flag(TIF_SVE)) 233 vq = sve_vq_from_vl(vl); 234 235 memset(reserved, 0, sizeof(reserved)); 236 237 __put_user_error(SVE_MAGIC, &ctx->head.magic, err); 238 __put_user_error(round_up(SVE_SIG_CONTEXT_SIZE(vq), 16), 239 &ctx->head.size, err); 240 __put_user_error(vl, &ctx->vl, err); 241 BUILD_BUG_ON(sizeof(ctx->__reserved) != sizeof(reserved)); 242 err |= __copy_to_user(&ctx->__reserved, reserved, sizeof(reserved)); 243 244 if (vq) { 245 /* 246 * This assumes that the SVE state has already been saved to 247 * the task struct by calling the function 248 * fpsimd_signal_preserve_current_state(). 249 */ 250 err |= __copy_to_user((char __user *)ctx + SVE_SIG_REGS_OFFSET, 251 current->thread.sve_state, 252 SVE_SIG_REGS_SIZE(vq)); 253 } 254 255 return err ? -EFAULT : 0; 256 } 257 258 static int restore_sve_fpsimd_context(struct user_ctxs *user) 259 { 260 int err; 261 unsigned int vq; 262 struct user_fpsimd_state fpsimd; 263 struct sve_context sve; 264 265 if (__copy_from_user(&sve, user->sve, sizeof(sve))) 266 return -EFAULT; 267 268 if (sve.vl != task_get_sve_vl(current)) 269 return -EINVAL; 270 271 if (sve.head.size <= sizeof(*user->sve)) { 272 clear_thread_flag(TIF_SVE); 273 goto fpsimd_only; 274 } 275 276 vq = sve_vq_from_vl(sve.vl); 277 278 if (sve.head.size < SVE_SIG_CONTEXT_SIZE(vq)) 279 return -EINVAL; 280 281 /* 282 * Careful: we are about __copy_from_user() directly into 283 * thread.sve_state with preemption enabled, so protection is 284 * needed to prevent a racing context switch from writing stale 285 * registers back over the new data. 286 */ 287 288 fpsimd_flush_task_state(current); 289 /* From now, fpsimd_thread_switch() won't touch thread.sve_state */ 290 291 sve_alloc(current); 292 if (!current->thread.sve_state) { 293 clear_thread_flag(TIF_SVE); 294 return -ENOMEM; 295 } 296 297 err = __copy_from_user(current->thread.sve_state, 298 (char __user const *)user->sve + 299 SVE_SIG_REGS_OFFSET, 300 SVE_SIG_REGS_SIZE(vq)); 301 if (err) 302 return -EFAULT; 303 304 set_thread_flag(TIF_SVE); 305 306 fpsimd_only: 307 /* copy the FP and status/control registers */ 308 /* restore_sigframe() already checked that user->fpsimd != NULL. */ 309 err = __copy_from_user(fpsimd.vregs, user->fpsimd->vregs, 310 sizeof(fpsimd.vregs)); 311 __get_user_error(fpsimd.fpsr, &user->fpsimd->fpsr, err); 312 __get_user_error(fpsimd.fpcr, &user->fpsimd->fpcr, err); 313 314 /* load the hardware registers from the fpsimd_state structure */ 315 if (!err) 316 fpsimd_update_current_state(&fpsimd); 317 318 return err ? -EFAULT : 0; 319 } 320 321 #else /* ! CONFIG_ARM64_SVE */ 322 323 /* Turn any non-optimised out attempts to use these into a link error: */ 324 extern int preserve_sve_context(void __user *ctx); 325 extern int restore_sve_fpsimd_context(struct user_ctxs *user); 326 327 #endif /* ! CONFIG_ARM64_SVE */ 328 329 330 static int parse_user_sigframe(struct user_ctxs *user, 331 struct rt_sigframe __user *sf) 332 { 333 struct sigcontext __user *const sc = &sf->uc.uc_mcontext; 334 struct _aarch64_ctx __user *head; 335 char __user *base = (char __user *)&sc->__reserved; 336 size_t offset = 0; 337 size_t limit = sizeof(sc->__reserved); 338 bool have_extra_context = false; 339 char const __user *const sfp = (char const __user *)sf; 340 341 user->fpsimd = NULL; 342 user->sve = NULL; 343 344 if (!IS_ALIGNED((unsigned long)base, 16)) 345 goto invalid; 346 347 while (1) { 348 int err = 0; 349 u32 magic, size; 350 char const __user *userp; 351 struct extra_context const __user *extra; 352 u64 extra_datap; 353 u32 extra_size; 354 struct _aarch64_ctx const __user *end; 355 u32 end_magic, end_size; 356 357 if (limit - offset < sizeof(*head)) 358 goto invalid; 359 360 if (!IS_ALIGNED(offset, 16)) 361 goto invalid; 362 363 head = (struct _aarch64_ctx __user *)(base + offset); 364 __get_user_error(magic, &head->magic, err); 365 __get_user_error(size, &head->size, err); 366 if (err) 367 return err; 368 369 if (limit - offset < size) 370 goto invalid; 371 372 switch (magic) { 373 case 0: 374 if (size) 375 goto invalid; 376 377 goto done; 378 379 case FPSIMD_MAGIC: 380 if (!system_supports_fpsimd()) 381 goto invalid; 382 if (user->fpsimd) 383 goto invalid; 384 385 if (size < sizeof(*user->fpsimd)) 386 goto invalid; 387 388 user->fpsimd = (struct fpsimd_context __user *)head; 389 break; 390 391 case ESR_MAGIC: 392 /* ignore */ 393 break; 394 395 case SVE_MAGIC: 396 if (!system_supports_sve()) 397 goto invalid; 398 399 if (user->sve) 400 goto invalid; 401 402 if (size < sizeof(*user->sve)) 403 goto invalid; 404 405 user->sve = (struct sve_context __user *)head; 406 break; 407 408 case EXTRA_MAGIC: 409 if (have_extra_context) 410 goto invalid; 411 412 if (size < sizeof(*extra)) 413 goto invalid; 414 415 userp = (char const __user *)head; 416 417 extra = (struct extra_context const __user *)userp; 418 userp += size; 419 420 __get_user_error(extra_datap, &extra->datap, err); 421 __get_user_error(extra_size, &extra->size, err); 422 if (err) 423 return err; 424 425 /* Check for the dummy terminator in __reserved[]: */ 426 427 if (limit - offset - size < TERMINATOR_SIZE) 428 goto invalid; 429 430 end = (struct _aarch64_ctx const __user *)userp; 431 userp += TERMINATOR_SIZE; 432 433 __get_user_error(end_magic, &end->magic, err); 434 __get_user_error(end_size, &end->size, err); 435 if (err) 436 return err; 437 438 if (end_magic || end_size) 439 goto invalid; 440 441 /* Prevent looping/repeated parsing of extra_context */ 442 have_extra_context = true; 443 444 base = (__force void __user *)extra_datap; 445 if (!IS_ALIGNED((unsigned long)base, 16)) 446 goto invalid; 447 448 if (!IS_ALIGNED(extra_size, 16)) 449 goto invalid; 450 451 if (base != userp) 452 goto invalid; 453 454 /* Reject "unreasonably large" frames: */ 455 if (extra_size > sfp + SIGFRAME_MAXSZ - userp) 456 goto invalid; 457 458 /* 459 * Ignore trailing terminator in __reserved[] 460 * and start parsing extra data: 461 */ 462 offset = 0; 463 limit = extra_size; 464 465 if (!access_ok(base, limit)) 466 goto invalid; 467 468 continue; 469 470 default: 471 goto invalid; 472 } 473 474 if (size < sizeof(*head)) 475 goto invalid; 476 477 if (limit - offset < size) 478 goto invalid; 479 480 offset += size; 481 } 482 483 done: 484 return 0; 485 486 invalid: 487 return -EINVAL; 488 } 489 490 static int restore_sigframe(struct pt_regs *regs, 491 struct rt_sigframe __user *sf) 492 { 493 sigset_t set; 494 int i, err; 495 struct user_ctxs user; 496 497 err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set)); 498 if (err == 0) 499 set_current_blocked(&set); 500 501 for (i = 0; i < 31; i++) 502 __get_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i], 503 err); 504 __get_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err); 505 __get_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err); 506 __get_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err); 507 508 /* 509 * Avoid sys_rt_sigreturn() restarting. 510 */ 511 forget_syscall(regs); 512 513 err |= !valid_user_regs(®s->user_regs, current); 514 if (err == 0) 515 err = parse_user_sigframe(&user, sf); 516 517 if (err == 0 && system_supports_fpsimd()) { 518 if (!user.fpsimd) 519 return -EINVAL; 520 521 if (user.sve) { 522 if (!system_supports_sve()) 523 return -EINVAL; 524 525 err = restore_sve_fpsimd_context(&user); 526 } else { 527 err = restore_fpsimd_context(user.fpsimd); 528 } 529 } 530 531 return err; 532 } 533 534 SYSCALL_DEFINE0(rt_sigreturn) 535 { 536 struct pt_regs *regs = current_pt_regs(); 537 struct rt_sigframe __user *frame; 538 539 /* Always make any pending restarted system calls return -EINTR */ 540 current->restart_block.fn = do_no_restart_syscall; 541 542 /* 543 * Since we stacked the signal on a 128-bit boundary, then 'sp' should 544 * be word aligned here. 545 */ 546 if (regs->sp & 15) 547 goto badframe; 548 549 frame = (struct rt_sigframe __user *)regs->sp; 550 551 if (!access_ok(frame, sizeof (*frame))) 552 goto badframe; 553 554 if (restore_sigframe(regs, frame)) 555 goto badframe; 556 557 if (restore_altstack(&frame->uc.uc_stack)) 558 goto badframe; 559 560 return regs->regs[0]; 561 562 badframe: 563 arm64_notify_segfault(regs->sp); 564 return 0; 565 } 566 567 /* 568 * Determine the layout of optional records in the signal frame 569 * 570 * add_all: if true, lays out the biggest possible signal frame for 571 * this task; otherwise, generates a layout for the current state 572 * of the task. 573 */ 574 static int setup_sigframe_layout(struct rt_sigframe_user_layout *user, 575 bool add_all) 576 { 577 int err; 578 579 if (system_supports_fpsimd()) { 580 err = sigframe_alloc(user, &user->fpsimd_offset, 581 sizeof(struct fpsimd_context)); 582 if (err) 583 return err; 584 } 585 586 /* fault information, if valid */ 587 if (add_all || current->thread.fault_code) { 588 err = sigframe_alloc(user, &user->esr_offset, 589 sizeof(struct esr_context)); 590 if (err) 591 return err; 592 } 593 594 if (system_supports_sve()) { 595 unsigned int vq = 0; 596 597 if (add_all || test_thread_flag(TIF_SVE)) { 598 int vl = sve_max_vl(); 599 600 if (!add_all) 601 vl = task_get_sve_vl(current); 602 603 vq = sve_vq_from_vl(vl); 604 } 605 606 err = sigframe_alloc(user, &user->sve_offset, 607 SVE_SIG_CONTEXT_SIZE(vq)); 608 if (err) 609 return err; 610 } 611 612 return sigframe_alloc_end(user); 613 } 614 615 static int setup_sigframe(struct rt_sigframe_user_layout *user, 616 struct pt_regs *regs, sigset_t *set) 617 { 618 int i, err = 0; 619 struct rt_sigframe __user *sf = user->sigframe; 620 621 /* set up the stack frame for unwinding */ 622 __put_user_error(regs->regs[29], &user->next_frame->fp, err); 623 __put_user_error(regs->regs[30], &user->next_frame->lr, err); 624 625 for (i = 0; i < 31; i++) 626 __put_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i], 627 err); 628 __put_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err); 629 __put_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err); 630 __put_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err); 631 632 __put_user_error(current->thread.fault_address, &sf->uc.uc_mcontext.fault_address, err); 633 634 err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(*set)); 635 636 if (err == 0 && system_supports_fpsimd()) { 637 struct fpsimd_context __user *fpsimd_ctx = 638 apply_user_offset(user, user->fpsimd_offset); 639 err |= preserve_fpsimd_context(fpsimd_ctx); 640 } 641 642 /* fault information, if valid */ 643 if (err == 0 && user->esr_offset) { 644 struct esr_context __user *esr_ctx = 645 apply_user_offset(user, user->esr_offset); 646 647 __put_user_error(ESR_MAGIC, &esr_ctx->head.magic, err); 648 __put_user_error(sizeof(*esr_ctx), &esr_ctx->head.size, err); 649 __put_user_error(current->thread.fault_code, &esr_ctx->esr, err); 650 } 651 652 /* Scalable Vector Extension state, if present */ 653 if (system_supports_sve() && err == 0 && user->sve_offset) { 654 struct sve_context __user *sve_ctx = 655 apply_user_offset(user, user->sve_offset); 656 err |= preserve_sve_context(sve_ctx); 657 } 658 659 if (err == 0 && user->extra_offset) { 660 char __user *sfp = (char __user *)user->sigframe; 661 char __user *userp = 662 apply_user_offset(user, user->extra_offset); 663 664 struct extra_context __user *extra; 665 struct _aarch64_ctx __user *end; 666 u64 extra_datap; 667 u32 extra_size; 668 669 extra = (struct extra_context __user *)userp; 670 userp += EXTRA_CONTEXT_SIZE; 671 672 end = (struct _aarch64_ctx __user *)userp; 673 userp += TERMINATOR_SIZE; 674 675 /* 676 * extra_datap is just written to the signal frame. 677 * The value gets cast back to a void __user * 678 * during sigreturn. 679 */ 680 extra_datap = (__force u64)userp; 681 extra_size = sfp + round_up(user->size, 16) - userp; 682 683 __put_user_error(EXTRA_MAGIC, &extra->head.magic, err); 684 __put_user_error(EXTRA_CONTEXT_SIZE, &extra->head.size, err); 685 __put_user_error(extra_datap, &extra->datap, err); 686 __put_user_error(extra_size, &extra->size, err); 687 688 /* Add the terminator */ 689 __put_user_error(0, &end->magic, err); 690 __put_user_error(0, &end->size, err); 691 } 692 693 /* set the "end" magic */ 694 if (err == 0) { 695 struct _aarch64_ctx __user *end = 696 apply_user_offset(user, user->end_offset); 697 698 __put_user_error(0, &end->magic, err); 699 __put_user_error(0, &end->size, err); 700 } 701 702 return err; 703 } 704 705 static int get_sigframe(struct rt_sigframe_user_layout *user, 706 struct ksignal *ksig, struct pt_regs *regs) 707 { 708 unsigned long sp, sp_top; 709 int err; 710 711 init_user_layout(user); 712 err = setup_sigframe_layout(user, false); 713 if (err) 714 return err; 715 716 sp = sp_top = sigsp(regs->sp, ksig); 717 718 sp = round_down(sp - sizeof(struct frame_record), 16); 719 user->next_frame = (struct frame_record __user *)sp; 720 721 sp = round_down(sp, 16) - sigframe_size(user); 722 user->sigframe = (struct rt_sigframe __user *)sp; 723 724 /* 725 * Check that we can actually write to the signal frame. 726 */ 727 if (!access_ok(user->sigframe, sp_top - sp)) 728 return -EFAULT; 729 730 return 0; 731 } 732 733 static void setup_return(struct pt_regs *regs, struct k_sigaction *ka, 734 struct rt_sigframe_user_layout *user, int usig) 735 { 736 __sigrestore_t sigtramp; 737 738 regs->regs[0] = usig; 739 regs->sp = (unsigned long)user->sigframe; 740 regs->regs[29] = (unsigned long)&user->next_frame->fp; 741 regs->pc = (unsigned long)ka->sa.sa_handler; 742 743 /* 744 * Signal delivery is a (wacky) indirect function call in 745 * userspace, so simulate the same setting of BTYPE as a BLR 746 * <register containing the signal handler entry point>. 747 * Signal delivery to a location in a PROT_BTI guarded page 748 * that is not a function entry point will now trigger a 749 * SIGILL in userspace. 750 * 751 * If the signal handler entry point is not in a PROT_BTI 752 * guarded page, this is harmless. 753 */ 754 if (system_supports_bti()) { 755 regs->pstate &= ~PSR_BTYPE_MASK; 756 regs->pstate |= PSR_BTYPE_C; 757 } 758 759 /* TCO (Tag Check Override) always cleared for signal handlers */ 760 regs->pstate &= ~PSR_TCO_BIT; 761 762 if (ka->sa.sa_flags & SA_RESTORER) 763 sigtramp = ka->sa.sa_restorer; 764 else 765 sigtramp = VDSO_SYMBOL(current->mm->context.vdso, sigtramp); 766 767 regs->regs[30] = (unsigned long)sigtramp; 768 } 769 770 static int setup_rt_frame(int usig, struct ksignal *ksig, sigset_t *set, 771 struct pt_regs *regs) 772 { 773 struct rt_sigframe_user_layout user; 774 struct rt_sigframe __user *frame; 775 int err = 0; 776 777 fpsimd_signal_preserve_current_state(); 778 779 if (get_sigframe(&user, ksig, regs)) 780 return 1; 781 782 frame = user.sigframe; 783 784 __put_user_error(0, &frame->uc.uc_flags, err); 785 __put_user_error(NULL, &frame->uc.uc_link, err); 786 787 err |= __save_altstack(&frame->uc.uc_stack, regs->sp); 788 err |= setup_sigframe(&user, regs, set); 789 if (err == 0) { 790 setup_return(regs, &ksig->ka, &user, usig); 791 if (ksig->ka.sa.sa_flags & SA_SIGINFO) { 792 err |= copy_siginfo_to_user(&frame->info, &ksig->info); 793 regs->regs[1] = (unsigned long)&frame->info; 794 regs->regs[2] = (unsigned long)&frame->uc; 795 } 796 } 797 798 return err; 799 } 800 801 static void setup_restart_syscall(struct pt_regs *regs) 802 { 803 if (is_compat_task()) 804 compat_setup_restart_syscall(regs); 805 else 806 regs->regs[8] = __NR_restart_syscall; 807 } 808 809 /* 810 * OK, we're invoking a handler 811 */ 812 static void handle_signal(struct ksignal *ksig, struct pt_regs *regs) 813 { 814 sigset_t *oldset = sigmask_to_save(); 815 int usig = ksig->sig; 816 int ret; 817 818 rseq_signal_deliver(ksig, regs); 819 820 /* 821 * Set up the stack frame 822 */ 823 if (is_compat_task()) { 824 if (ksig->ka.sa.sa_flags & SA_SIGINFO) 825 ret = compat_setup_rt_frame(usig, ksig, oldset, regs); 826 else 827 ret = compat_setup_frame(usig, ksig, oldset, regs); 828 } else { 829 ret = setup_rt_frame(usig, ksig, oldset, regs); 830 } 831 832 /* 833 * Check that the resulting registers are actually sane. 834 */ 835 ret |= !valid_user_regs(®s->user_regs, current); 836 837 /* Step into the signal handler if we are stepping */ 838 signal_setup_done(ret, ksig, test_thread_flag(TIF_SINGLESTEP)); 839 } 840 841 /* 842 * Note that 'init' is a special process: it doesn't get signals it doesn't 843 * want to handle. Thus you cannot kill init even with a SIGKILL even by 844 * mistake. 845 * 846 * Note that we go through the signals twice: once to check the signals that 847 * the kernel can handle, and then we build all the user-level signal handling 848 * stack-frames in one go after that. 849 */ 850 static void do_signal(struct pt_regs *regs) 851 { 852 unsigned long continue_addr = 0, restart_addr = 0; 853 int retval = 0; 854 struct ksignal ksig; 855 bool syscall = in_syscall(regs); 856 857 /* 858 * If we were from a system call, check for system call restarting... 859 */ 860 if (syscall) { 861 continue_addr = regs->pc; 862 restart_addr = continue_addr - (compat_thumb_mode(regs) ? 2 : 4); 863 retval = regs->regs[0]; 864 865 /* 866 * Avoid additional syscall restarting via ret_to_user. 867 */ 868 forget_syscall(regs); 869 870 /* 871 * Prepare for system call restart. We do this here so that a 872 * debugger will see the already changed PC. 873 */ 874 switch (retval) { 875 case -ERESTARTNOHAND: 876 case -ERESTARTSYS: 877 case -ERESTARTNOINTR: 878 case -ERESTART_RESTARTBLOCK: 879 regs->regs[0] = regs->orig_x0; 880 regs->pc = restart_addr; 881 break; 882 } 883 } 884 885 /* 886 * Get the signal to deliver. When running under ptrace, at this point 887 * the debugger may change all of our registers. 888 */ 889 if (get_signal(&ksig)) { 890 /* 891 * Depending on the signal settings, we may need to revert the 892 * decision to restart the system call, but skip this if a 893 * debugger has chosen to restart at a different PC. 894 */ 895 if (regs->pc == restart_addr && 896 (retval == -ERESTARTNOHAND || 897 retval == -ERESTART_RESTARTBLOCK || 898 (retval == -ERESTARTSYS && 899 !(ksig.ka.sa.sa_flags & SA_RESTART)))) { 900 syscall_set_return_value(current, regs, -EINTR, 0); 901 regs->pc = continue_addr; 902 } 903 904 handle_signal(&ksig, regs); 905 return; 906 } 907 908 /* 909 * Handle restarting a different system call. As above, if a debugger 910 * has chosen to restart at a different PC, ignore the restart. 911 */ 912 if (syscall && regs->pc == restart_addr) { 913 if (retval == -ERESTART_RESTARTBLOCK) 914 setup_restart_syscall(regs); 915 user_rewind_single_step(current); 916 } 917 918 restore_saved_sigmask(); 919 } 920 921 void do_notify_resume(struct pt_regs *regs, unsigned long thread_flags) 922 { 923 do { 924 if (thread_flags & _TIF_NEED_RESCHED) { 925 /* Unmask Debug and SError for the next task */ 926 local_daif_restore(DAIF_PROCCTX_NOIRQ); 927 928 schedule(); 929 } else { 930 local_daif_restore(DAIF_PROCCTX); 931 932 if (thread_flags & _TIF_UPROBE) 933 uprobe_notify_resume(regs); 934 935 if (thread_flags & _TIF_MTE_ASYNC_FAULT) { 936 clear_thread_flag(TIF_MTE_ASYNC_FAULT); 937 send_sig_fault(SIGSEGV, SEGV_MTEAERR, 938 (void __user *)NULL, current); 939 } 940 941 if (thread_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL)) 942 do_signal(regs); 943 944 if (thread_flags & _TIF_NOTIFY_RESUME) 945 resume_user_mode_work(regs); 946 947 if (thread_flags & _TIF_FOREIGN_FPSTATE) 948 fpsimd_restore_current_state(); 949 } 950 951 local_daif_mask(); 952 thread_flags = read_thread_flags(); 953 } while (thread_flags & _TIF_WORK_MASK); 954 } 955 956 unsigned long __ro_after_init signal_minsigstksz; 957 958 /* 959 * Determine the stack space required for guaranteed signal devliery. 960 * This function is used to populate AT_MINSIGSTKSZ at process startup. 961 * cpufeatures setup is assumed to be complete. 962 */ 963 void __init minsigstksz_setup(void) 964 { 965 struct rt_sigframe_user_layout user; 966 967 init_user_layout(&user); 968 969 /* 970 * If this fails, SIGFRAME_MAXSZ needs to be enlarged. It won't 971 * be big enough, but it's our best guess: 972 */ 973 if (WARN_ON(setup_sigframe_layout(&user, true))) 974 return; 975 976 signal_minsigstksz = sigframe_size(&user) + 977 round_up(sizeof(struct frame_record), 16) + 978 16; /* max alignment padding */ 979 } 980 981 /* 982 * Compile-time assertions for siginfo_t offsets. Check NSIG* as well, as 983 * changes likely come with new fields that should be added below. 984 */ 985 static_assert(NSIGILL == 11); 986 static_assert(NSIGFPE == 15); 987 static_assert(NSIGSEGV == 9); 988 static_assert(NSIGBUS == 5); 989 static_assert(NSIGTRAP == 6); 990 static_assert(NSIGCHLD == 6); 991 static_assert(NSIGSYS == 2); 992 static_assert(sizeof(siginfo_t) == 128); 993 static_assert(__alignof__(siginfo_t) == 8); 994 static_assert(offsetof(siginfo_t, si_signo) == 0x00); 995 static_assert(offsetof(siginfo_t, si_errno) == 0x04); 996 static_assert(offsetof(siginfo_t, si_code) == 0x08); 997 static_assert(offsetof(siginfo_t, si_pid) == 0x10); 998 static_assert(offsetof(siginfo_t, si_uid) == 0x14); 999 static_assert(offsetof(siginfo_t, si_tid) == 0x10); 1000 static_assert(offsetof(siginfo_t, si_overrun) == 0x14); 1001 static_assert(offsetof(siginfo_t, si_status) == 0x18); 1002 static_assert(offsetof(siginfo_t, si_utime) == 0x20); 1003 static_assert(offsetof(siginfo_t, si_stime) == 0x28); 1004 static_assert(offsetof(siginfo_t, si_value) == 0x18); 1005 static_assert(offsetof(siginfo_t, si_int) == 0x18); 1006 static_assert(offsetof(siginfo_t, si_ptr) == 0x18); 1007 static_assert(offsetof(siginfo_t, si_addr) == 0x10); 1008 static_assert(offsetof(siginfo_t, si_addr_lsb) == 0x18); 1009 static_assert(offsetof(siginfo_t, si_lower) == 0x20); 1010 static_assert(offsetof(siginfo_t, si_upper) == 0x28); 1011 static_assert(offsetof(siginfo_t, si_pkey) == 0x20); 1012 static_assert(offsetof(siginfo_t, si_perf_data) == 0x18); 1013 static_assert(offsetof(siginfo_t, si_perf_type) == 0x20); 1014 static_assert(offsetof(siginfo_t, si_band) == 0x10); 1015 static_assert(offsetof(siginfo_t, si_fd) == 0x18); 1016 static_assert(offsetof(siginfo_t, si_call_addr) == 0x10); 1017 static_assert(offsetof(siginfo_t, si_syscall) == 0x18); 1018 static_assert(offsetof(siginfo_t, si_arch) == 0x1c); 1019