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/personality.h> 15 #include <linux/freezer.h> 16 #include <linux/stddef.h> 17 #include <linux/uaccess.h> 18 #include <linux/sizes.h> 19 #include <linux/string.h> 20 #include <linux/tracehook.h> 21 #include <linux/ratelimit.h> 22 #include <linux/syscalls.h> 23 24 #include <asm/daifflags.h> 25 #include <asm/debug-monitors.h> 26 #include <asm/elf.h> 27 #include <asm/cacheflush.h> 28 #include <asm/ucontext.h> 29 #include <asm/unistd.h> 30 #include <asm/fpsimd.h> 31 #include <asm/ptrace.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 = current->thread.sve_vl; 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 preserve_fpsimd_context(). 248 */ 249 err |= __copy_to_user((char __user *)ctx + SVE_SIG_REGS_OFFSET, 250 current->thread.sve_state, 251 SVE_SIG_REGS_SIZE(vq)); 252 } 253 254 return err ? -EFAULT : 0; 255 } 256 257 static int restore_sve_fpsimd_context(struct user_ctxs *user) 258 { 259 int err; 260 unsigned int vq; 261 struct user_fpsimd_state fpsimd; 262 struct sve_context sve; 263 264 if (__copy_from_user(&sve, user->sve, sizeof(sve))) 265 return -EFAULT; 266 267 if (sve.vl != current->thread.sve_vl) 268 return -EINVAL; 269 270 if (sve.head.size <= sizeof(*user->sve)) { 271 clear_thread_flag(TIF_SVE); 272 goto fpsimd_only; 273 } 274 275 vq = sve_vq_from_vl(sve.vl); 276 277 if (sve.head.size < SVE_SIG_CONTEXT_SIZE(vq)) 278 return -EINVAL; 279 280 /* 281 * Careful: we are about __copy_from_user() directly into 282 * thread.sve_state with preemption enabled, so protection is 283 * needed to prevent a racing context switch from writing stale 284 * registers back over the new data. 285 */ 286 287 fpsimd_flush_task_state(current); 288 /* From now, fpsimd_thread_switch() won't touch thread.sve_state */ 289 290 sve_alloc(current); 291 err = __copy_from_user(current->thread.sve_state, 292 (char __user const *)user->sve + 293 SVE_SIG_REGS_OFFSET, 294 SVE_SIG_REGS_SIZE(vq)); 295 if (err) 296 return -EFAULT; 297 298 set_thread_flag(TIF_SVE); 299 300 fpsimd_only: 301 /* copy the FP and status/control registers */ 302 /* restore_sigframe() already checked that user->fpsimd != NULL. */ 303 err = __copy_from_user(fpsimd.vregs, user->fpsimd->vregs, 304 sizeof(fpsimd.vregs)); 305 __get_user_error(fpsimd.fpsr, &user->fpsimd->fpsr, err); 306 __get_user_error(fpsimd.fpcr, &user->fpsimd->fpcr, err); 307 308 /* load the hardware registers from the fpsimd_state structure */ 309 if (!err) 310 fpsimd_update_current_state(&fpsimd); 311 312 return err ? -EFAULT : 0; 313 } 314 315 #else /* ! CONFIG_ARM64_SVE */ 316 317 /* Turn any non-optimised out attempts to use these into a link error: */ 318 extern int preserve_sve_context(void __user *ctx); 319 extern int restore_sve_fpsimd_context(struct user_ctxs *user); 320 321 #endif /* ! CONFIG_ARM64_SVE */ 322 323 324 static int parse_user_sigframe(struct user_ctxs *user, 325 struct rt_sigframe __user *sf) 326 { 327 struct sigcontext __user *const sc = &sf->uc.uc_mcontext; 328 struct _aarch64_ctx __user *head; 329 char __user *base = (char __user *)&sc->__reserved; 330 size_t offset = 0; 331 size_t limit = sizeof(sc->__reserved); 332 bool have_extra_context = false; 333 char const __user *const sfp = (char const __user *)sf; 334 335 user->fpsimd = NULL; 336 user->sve = NULL; 337 338 if (!IS_ALIGNED((unsigned long)base, 16)) 339 goto invalid; 340 341 while (1) { 342 int err = 0; 343 u32 magic, size; 344 char const __user *userp; 345 struct extra_context const __user *extra; 346 u64 extra_datap; 347 u32 extra_size; 348 struct _aarch64_ctx const __user *end; 349 u32 end_magic, end_size; 350 351 if (limit - offset < sizeof(*head)) 352 goto invalid; 353 354 if (!IS_ALIGNED(offset, 16)) 355 goto invalid; 356 357 head = (struct _aarch64_ctx __user *)(base + offset); 358 __get_user_error(magic, &head->magic, err); 359 __get_user_error(size, &head->size, err); 360 if (err) 361 return err; 362 363 if (limit - offset < size) 364 goto invalid; 365 366 switch (magic) { 367 case 0: 368 if (size) 369 goto invalid; 370 371 goto done; 372 373 case FPSIMD_MAGIC: 374 if (!system_supports_fpsimd()) 375 goto invalid; 376 if (user->fpsimd) 377 goto invalid; 378 379 if (size < sizeof(*user->fpsimd)) 380 goto invalid; 381 382 user->fpsimd = (struct fpsimd_context __user *)head; 383 break; 384 385 case ESR_MAGIC: 386 /* ignore */ 387 break; 388 389 case SVE_MAGIC: 390 if (!system_supports_sve()) 391 goto invalid; 392 393 if (user->sve) 394 goto invalid; 395 396 if (size < sizeof(*user->sve)) 397 goto invalid; 398 399 user->sve = (struct sve_context __user *)head; 400 break; 401 402 case EXTRA_MAGIC: 403 if (have_extra_context) 404 goto invalid; 405 406 if (size < sizeof(*extra)) 407 goto invalid; 408 409 userp = (char const __user *)head; 410 411 extra = (struct extra_context const __user *)userp; 412 userp += size; 413 414 __get_user_error(extra_datap, &extra->datap, err); 415 __get_user_error(extra_size, &extra->size, err); 416 if (err) 417 return err; 418 419 /* Check for the dummy terminator in __reserved[]: */ 420 421 if (limit - offset - size < TERMINATOR_SIZE) 422 goto invalid; 423 424 end = (struct _aarch64_ctx const __user *)userp; 425 userp += TERMINATOR_SIZE; 426 427 __get_user_error(end_magic, &end->magic, err); 428 __get_user_error(end_size, &end->size, err); 429 if (err) 430 return err; 431 432 if (end_magic || end_size) 433 goto invalid; 434 435 /* Prevent looping/repeated parsing of extra_context */ 436 have_extra_context = true; 437 438 base = (__force void __user *)extra_datap; 439 if (!IS_ALIGNED((unsigned long)base, 16)) 440 goto invalid; 441 442 if (!IS_ALIGNED(extra_size, 16)) 443 goto invalid; 444 445 if (base != userp) 446 goto invalid; 447 448 /* Reject "unreasonably large" frames: */ 449 if (extra_size > sfp + SIGFRAME_MAXSZ - userp) 450 goto invalid; 451 452 /* 453 * Ignore trailing terminator in __reserved[] 454 * and start parsing extra data: 455 */ 456 offset = 0; 457 limit = extra_size; 458 459 if (!access_ok(base, limit)) 460 goto invalid; 461 462 continue; 463 464 default: 465 goto invalid; 466 } 467 468 if (size < sizeof(*head)) 469 goto invalid; 470 471 if (limit - offset < size) 472 goto invalid; 473 474 offset += size; 475 } 476 477 done: 478 return 0; 479 480 invalid: 481 return -EINVAL; 482 } 483 484 static int restore_sigframe(struct pt_regs *regs, 485 struct rt_sigframe __user *sf) 486 { 487 sigset_t set; 488 int i, err; 489 struct user_ctxs user; 490 491 err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set)); 492 if (err == 0) 493 set_current_blocked(&set); 494 495 for (i = 0; i < 31; i++) 496 __get_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i], 497 err); 498 __get_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err); 499 __get_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err); 500 __get_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err); 501 502 /* 503 * Avoid sys_rt_sigreturn() restarting. 504 */ 505 forget_syscall(regs); 506 507 err |= !valid_user_regs(®s->user_regs, current); 508 if (err == 0) 509 err = parse_user_sigframe(&user, sf); 510 511 if (err == 0 && system_supports_fpsimd()) { 512 if (!user.fpsimd) 513 return -EINVAL; 514 515 if (user.sve) { 516 if (!system_supports_sve()) 517 return -EINVAL; 518 519 err = restore_sve_fpsimd_context(&user); 520 } else { 521 err = restore_fpsimd_context(user.fpsimd); 522 } 523 } 524 525 return err; 526 } 527 528 SYSCALL_DEFINE0(rt_sigreturn) 529 { 530 struct pt_regs *regs = current_pt_regs(); 531 struct rt_sigframe __user *frame; 532 533 /* Always make any pending restarted system calls return -EINTR */ 534 current->restart_block.fn = do_no_restart_syscall; 535 536 /* 537 * Since we stacked the signal on a 128-bit boundary, then 'sp' should 538 * be word aligned here. 539 */ 540 if (regs->sp & 15) 541 goto badframe; 542 543 frame = (struct rt_sigframe __user *)regs->sp; 544 545 if (!access_ok(frame, sizeof (*frame))) 546 goto badframe; 547 548 if (restore_sigframe(regs, frame)) 549 goto badframe; 550 551 if (restore_altstack(&frame->uc.uc_stack)) 552 goto badframe; 553 554 return regs->regs[0]; 555 556 badframe: 557 arm64_notify_segfault(regs->sp); 558 return 0; 559 } 560 561 /* 562 * Determine the layout of optional records in the signal frame 563 * 564 * add_all: if true, lays out the biggest possible signal frame for 565 * this task; otherwise, generates a layout for the current state 566 * of the task. 567 */ 568 static int setup_sigframe_layout(struct rt_sigframe_user_layout *user, 569 bool add_all) 570 { 571 int err; 572 573 err = sigframe_alloc(user, &user->fpsimd_offset, 574 sizeof(struct fpsimd_context)); 575 if (err) 576 return err; 577 578 /* fault information, if valid */ 579 if (add_all || current->thread.fault_code) { 580 err = sigframe_alloc(user, &user->esr_offset, 581 sizeof(struct esr_context)); 582 if (err) 583 return err; 584 } 585 586 if (system_supports_sve()) { 587 unsigned int vq = 0; 588 589 if (add_all || test_thread_flag(TIF_SVE)) { 590 int vl = sve_max_vl; 591 592 if (!add_all) 593 vl = current->thread.sve_vl; 594 595 vq = sve_vq_from_vl(vl); 596 } 597 598 err = sigframe_alloc(user, &user->sve_offset, 599 SVE_SIG_CONTEXT_SIZE(vq)); 600 if (err) 601 return err; 602 } 603 604 return sigframe_alloc_end(user); 605 } 606 607 static int setup_sigframe(struct rt_sigframe_user_layout *user, 608 struct pt_regs *regs, sigset_t *set) 609 { 610 int i, err = 0; 611 struct rt_sigframe __user *sf = user->sigframe; 612 613 /* set up the stack frame for unwinding */ 614 __put_user_error(regs->regs[29], &user->next_frame->fp, err); 615 __put_user_error(regs->regs[30], &user->next_frame->lr, err); 616 617 for (i = 0; i < 31; i++) 618 __put_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i], 619 err); 620 __put_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err); 621 __put_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err); 622 __put_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err); 623 624 __put_user_error(current->thread.fault_address, &sf->uc.uc_mcontext.fault_address, err); 625 626 err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(*set)); 627 628 if (err == 0 && system_supports_fpsimd()) { 629 struct fpsimd_context __user *fpsimd_ctx = 630 apply_user_offset(user, user->fpsimd_offset); 631 err |= preserve_fpsimd_context(fpsimd_ctx); 632 } 633 634 /* fault information, if valid */ 635 if (err == 0 && user->esr_offset) { 636 struct esr_context __user *esr_ctx = 637 apply_user_offset(user, user->esr_offset); 638 639 __put_user_error(ESR_MAGIC, &esr_ctx->head.magic, err); 640 __put_user_error(sizeof(*esr_ctx), &esr_ctx->head.size, err); 641 __put_user_error(current->thread.fault_code, &esr_ctx->esr, err); 642 } 643 644 /* Scalable Vector Extension state, if present */ 645 if (system_supports_sve() && err == 0 && user->sve_offset) { 646 struct sve_context __user *sve_ctx = 647 apply_user_offset(user, user->sve_offset); 648 err |= preserve_sve_context(sve_ctx); 649 } 650 651 if (err == 0 && user->extra_offset) { 652 char __user *sfp = (char __user *)user->sigframe; 653 char __user *userp = 654 apply_user_offset(user, user->extra_offset); 655 656 struct extra_context __user *extra; 657 struct _aarch64_ctx __user *end; 658 u64 extra_datap; 659 u32 extra_size; 660 661 extra = (struct extra_context __user *)userp; 662 userp += EXTRA_CONTEXT_SIZE; 663 664 end = (struct _aarch64_ctx __user *)userp; 665 userp += TERMINATOR_SIZE; 666 667 /* 668 * extra_datap is just written to the signal frame. 669 * The value gets cast back to a void __user * 670 * during sigreturn. 671 */ 672 extra_datap = (__force u64)userp; 673 extra_size = sfp + round_up(user->size, 16) - userp; 674 675 __put_user_error(EXTRA_MAGIC, &extra->head.magic, err); 676 __put_user_error(EXTRA_CONTEXT_SIZE, &extra->head.size, err); 677 __put_user_error(extra_datap, &extra->datap, err); 678 __put_user_error(extra_size, &extra->size, err); 679 680 /* Add the terminator */ 681 __put_user_error(0, &end->magic, err); 682 __put_user_error(0, &end->size, err); 683 } 684 685 /* set the "end" magic */ 686 if (err == 0) { 687 struct _aarch64_ctx __user *end = 688 apply_user_offset(user, user->end_offset); 689 690 __put_user_error(0, &end->magic, err); 691 __put_user_error(0, &end->size, err); 692 } 693 694 return err; 695 } 696 697 static int get_sigframe(struct rt_sigframe_user_layout *user, 698 struct ksignal *ksig, struct pt_regs *regs) 699 { 700 unsigned long sp, sp_top; 701 int err; 702 703 init_user_layout(user); 704 err = setup_sigframe_layout(user, false); 705 if (err) 706 return err; 707 708 sp = sp_top = sigsp(regs->sp, ksig); 709 710 sp = round_down(sp - sizeof(struct frame_record), 16); 711 user->next_frame = (struct frame_record __user *)sp; 712 713 sp = round_down(sp, 16) - sigframe_size(user); 714 user->sigframe = (struct rt_sigframe __user *)sp; 715 716 /* 717 * Check that we can actually write to the signal frame. 718 */ 719 if (!access_ok(user->sigframe, sp_top - sp)) 720 return -EFAULT; 721 722 return 0; 723 } 724 725 static void setup_return(struct pt_regs *regs, struct k_sigaction *ka, 726 struct rt_sigframe_user_layout *user, int usig) 727 { 728 __sigrestore_t sigtramp; 729 730 regs->regs[0] = usig; 731 regs->sp = (unsigned long)user->sigframe; 732 regs->regs[29] = (unsigned long)&user->next_frame->fp; 733 regs->pc = (unsigned long)ka->sa.sa_handler; 734 735 /* 736 * Signal delivery is a (wacky) indirect function call in 737 * userspace, so simulate the same setting of BTYPE as a BLR 738 * <register containing the signal handler entry point>. 739 * Signal delivery to a location in a PROT_BTI guarded page 740 * that is not a function entry point will now trigger a 741 * SIGILL in userspace. 742 * 743 * If the signal handler entry point is not in a PROT_BTI 744 * guarded page, this is harmless. 745 */ 746 if (system_supports_bti()) { 747 regs->pstate &= ~PSR_BTYPE_MASK; 748 regs->pstate |= PSR_BTYPE_C; 749 } 750 751 if (ka->sa.sa_flags & SA_RESTORER) 752 sigtramp = ka->sa.sa_restorer; 753 else 754 sigtramp = VDSO_SYMBOL(current->mm->context.vdso, sigtramp); 755 756 regs->regs[30] = (unsigned long)sigtramp; 757 } 758 759 static int setup_rt_frame(int usig, struct ksignal *ksig, sigset_t *set, 760 struct pt_regs *regs) 761 { 762 struct rt_sigframe_user_layout user; 763 struct rt_sigframe __user *frame; 764 int err = 0; 765 766 fpsimd_signal_preserve_current_state(); 767 768 if (get_sigframe(&user, ksig, regs)) 769 return 1; 770 771 frame = user.sigframe; 772 773 __put_user_error(0, &frame->uc.uc_flags, err); 774 __put_user_error(NULL, &frame->uc.uc_link, err); 775 776 err |= __save_altstack(&frame->uc.uc_stack, regs->sp); 777 err |= setup_sigframe(&user, regs, set); 778 if (err == 0) { 779 setup_return(regs, &ksig->ka, &user, usig); 780 if (ksig->ka.sa.sa_flags & SA_SIGINFO) { 781 err |= copy_siginfo_to_user(&frame->info, &ksig->info); 782 regs->regs[1] = (unsigned long)&frame->info; 783 regs->regs[2] = (unsigned long)&frame->uc; 784 } 785 } 786 787 return err; 788 } 789 790 static void setup_restart_syscall(struct pt_regs *regs) 791 { 792 if (is_compat_task()) 793 compat_setup_restart_syscall(regs); 794 else 795 regs->regs[8] = __NR_restart_syscall; 796 } 797 798 /* 799 * OK, we're invoking a handler 800 */ 801 static void handle_signal(struct ksignal *ksig, struct pt_regs *regs) 802 { 803 struct task_struct *tsk = current; 804 sigset_t *oldset = sigmask_to_save(); 805 int usig = ksig->sig; 806 int ret; 807 808 rseq_signal_deliver(ksig, regs); 809 810 /* 811 * Set up the stack frame 812 */ 813 if (is_compat_task()) { 814 if (ksig->ka.sa.sa_flags & SA_SIGINFO) 815 ret = compat_setup_rt_frame(usig, ksig, oldset, regs); 816 else 817 ret = compat_setup_frame(usig, ksig, oldset, regs); 818 } else { 819 ret = setup_rt_frame(usig, ksig, oldset, regs); 820 } 821 822 /* 823 * Check that the resulting registers are actually sane. 824 */ 825 ret |= !valid_user_regs(®s->user_regs, current); 826 827 /* 828 * Fast forward the stepping logic so we step into the signal 829 * handler. 830 */ 831 if (!ret) 832 user_fastforward_single_step(tsk); 833 834 signal_setup_done(ret, ksig, 0); 835 } 836 837 /* 838 * Note that 'init' is a special process: it doesn't get signals it doesn't 839 * want to handle. Thus you cannot kill init even with a SIGKILL even by 840 * mistake. 841 * 842 * Note that we go through the signals twice: once to check the signals that 843 * the kernel can handle, and then we build all the user-level signal handling 844 * stack-frames in one go after that. 845 */ 846 static void do_signal(struct pt_regs *regs) 847 { 848 unsigned long continue_addr = 0, restart_addr = 0; 849 int retval = 0; 850 struct ksignal ksig; 851 bool syscall = in_syscall(regs); 852 853 /* 854 * If we were from a system call, check for system call restarting... 855 */ 856 if (syscall) { 857 continue_addr = regs->pc; 858 restart_addr = continue_addr - (compat_thumb_mode(regs) ? 2 : 4); 859 retval = regs->regs[0]; 860 861 /* 862 * Avoid additional syscall restarting via ret_to_user. 863 */ 864 forget_syscall(regs); 865 866 /* 867 * Prepare for system call restart. We do this here so that a 868 * debugger will see the already changed PC. 869 */ 870 switch (retval) { 871 case -ERESTARTNOHAND: 872 case -ERESTARTSYS: 873 case -ERESTARTNOINTR: 874 case -ERESTART_RESTARTBLOCK: 875 regs->regs[0] = regs->orig_x0; 876 regs->pc = restart_addr; 877 break; 878 } 879 } 880 881 /* 882 * Get the signal to deliver. When running under ptrace, at this point 883 * the debugger may change all of our registers. 884 */ 885 if (get_signal(&ksig)) { 886 /* 887 * Depending on the signal settings, we may need to revert the 888 * decision to restart the system call, but skip this if a 889 * debugger has chosen to restart at a different PC. 890 */ 891 if (regs->pc == restart_addr && 892 (retval == -ERESTARTNOHAND || 893 retval == -ERESTART_RESTARTBLOCK || 894 (retval == -ERESTARTSYS && 895 !(ksig.ka.sa.sa_flags & SA_RESTART)))) { 896 regs->regs[0] = -EINTR; 897 regs->pc = continue_addr; 898 } 899 900 handle_signal(&ksig, regs); 901 return; 902 } 903 904 /* 905 * Handle restarting a different system call. As above, if a debugger 906 * has chosen to restart at a different PC, ignore the restart. 907 */ 908 if (syscall && regs->pc == restart_addr) { 909 if (retval == -ERESTART_RESTARTBLOCK) 910 setup_restart_syscall(regs); 911 user_rewind_single_step(current); 912 } 913 914 restore_saved_sigmask(); 915 } 916 917 asmlinkage void do_notify_resume(struct pt_regs *regs, 918 unsigned long thread_flags) 919 { 920 /* 921 * The assembly code enters us with IRQs off, but it hasn't 922 * informed the tracing code of that for efficiency reasons. 923 * Update the trace code with the current status. 924 */ 925 trace_hardirqs_off(); 926 927 do { 928 /* Check valid user FS if needed */ 929 addr_limit_user_check(); 930 931 if (thread_flags & _TIF_NEED_RESCHED) { 932 /* Unmask Debug and SError for the next task */ 933 local_daif_restore(DAIF_PROCCTX_NOIRQ); 934 935 schedule(); 936 } else { 937 local_daif_restore(DAIF_PROCCTX); 938 939 if (thread_flags & _TIF_UPROBE) 940 uprobe_notify_resume(regs); 941 942 if (thread_flags & _TIF_SIGPENDING) 943 do_signal(regs); 944 945 if (thread_flags & _TIF_NOTIFY_RESUME) { 946 clear_thread_flag(TIF_NOTIFY_RESUME); 947 tracehook_notify_resume(regs); 948 rseq_handle_notify_resume(NULL, regs); 949 } 950 951 if (thread_flags & _TIF_FOREIGN_FPSTATE) 952 fpsimd_restore_current_state(); 953 } 954 955 local_daif_mask(); 956 thread_flags = READ_ONCE(current_thread_info()->flags); 957 } while (thread_flags & _TIF_WORK_MASK); 958 } 959 960 unsigned long __ro_after_init signal_minsigstksz; 961 962 /* 963 * Determine the stack space required for guaranteed signal devliery. 964 * This function is used to populate AT_MINSIGSTKSZ at process startup. 965 * cpufeatures setup is assumed to be complete. 966 */ 967 void __init minsigstksz_setup(void) 968 { 969 struct rt_sigframe_user_layout user; 970 971 init_user_layout(&user); 972 973 /* 974 * If this fails, SIGFRAME_MAXSZ needs to be enlarged. It won't 975 * be big enough, but it's our best guess: 976 */ 977 if (WARN_ON(setup_sigframe_layout(&user, true))) 978 return; 979 980 signal_minsigstksz = sigframe_size(&user) + 981 round_up(sizeof(struct frame_record), 16) + 982 16; /* max alignment padding */ 983 } 984