signal.c

   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/irq-entry-common.h>
  13#include <linux/kernel.h>
  14#include <linux/signal.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/ratelimit.h>
  21#include <linux/rseq.h>
  22#include <linux/syscalls.h>
  23#include <linux/pkeys.h>
  24
  25#include <asm/daifflags.h>
  26#include <asm/debug-monitors.h>
  27#include <asm/elf.h>
  28#include <asm/exception.h>
  29#include <asm/cacheflush.h>
  30#include <asm/gcs.h>
  31#include <asm/ucontext.h>
  32#include <asm/unistd.h>
  33#include <asm/fpsimd.h>
  34#include <asm/ptrace.h>
  35#include <asm/syscall.h>
  36#include <asm/signal32.h>
  37#include <asm/traps.h>
  38#include <asm/vdso.h>
  39
  40#define GCS_SIGNAL_CAP(addr) (((unsigned long)addr) & GCS_CAP_ADDR_MASK)
  41
  42/*
  43 * Do a signal return; undo the signal stack. These are aligned to 128-bit.
  44 */
  45struct rt_sigframe {
  46	struct siginfo info;
  47	struct ucontext uc;
  48};
  49
  50struct rt_sigframe_user_layout {
  51	struct rt_sigframe __user *sigframe;
  52	struct frame_record __user *next_frame;
  53
  54	unsigned long size;	/* size of allocated sigframe data */
  55	unsigned long limit;	/* largest allowed size */
  56
  57	unsigned long fpsimd_offset;
  58	unsigned long esr_offset;
  59	unsigned long gcs_offset;
  60	unsigned long sve_offset;
  61	unsigned long tpidr2_offset;
  62	unsigned long za_offset;
  63	unsigned long zt_offset;
  64	unsigned long fpmr_offset;
  65	unsigned long poe_offset;
  66	unsigned long extra_offset;
  67	unsigned long end_offset;
  68};
  69
  70/*
  71 * Holds any EL0-controlled state that influences unprivileged memory accesses.
  72 * This includes both accesses done in userspace and uaccess done in the kernel.
  73 *
  74 * This state needs to be carefully managed to ensure that it doesn't cause
  75 * uaccess to fail when setting up the signal frame, and the signal handler
  76 * itself also expects a well-defined state when entered.
  77 */
  78struct user_access_state {
  79	u64 por_el0;
  80};
  81
  82#define TERMINATOR_SIZE round_up(sizeof(struct _aarch64_ctx), 16)
  83#define EXTRA_CONTEXT_SIZE round_up(sizeof(struct extra_context), 16)
  84
  85/*
  86 * Save the user access state into ua_state and reset it to disable any
  87 * restrictions.
  88 */
  89static void save_reset_user_access_state(struct user_access_state *ua_state)
  90{
  91	if (system_supports_poe()) {
  92		u64 por_enable_all = 0;
  93
  94		for (int pkey = 0; pkey < arch_max_pkey(); pkey++)
  95			por_enable_all |= POR_ELx_PERM_PREP(pkey, POE_RWX);
  96
  97		ua_state->por_el0 = read_sysreg_s(SYS_POR_EL0);
  98		write_sysreg_s(por_enable_all, SYS_POR_EL0);
  99		/*
 100		 * No ISB required as we can tolerate spurious Overlay faults -
 101		 * the fault handler will check again based on the new value
 102		 * of POR_EL0.
 103		 */
 104	}
 105}
 106
 107/*
 108 * Set the user access state for invoking the signal handler.
 109 *
 110 * No uaccess should be done after that function is called.
 111 */
 112static void set_handler_user_access_state(void)
 113{
 114	if (system_supports_poe())
 115		write_sysreg_s(POR_EL0_INIT, SYS_POR_EL0);
 116}
 117
 118/*
 119 * Restore the user access state to the values saved in ua_state.
 120 *
 121 * No uaccess should be done after that function is called.
 122 */
 123static void restore_user_access_state(const struct user_access_state *ua_state)
 124{
 125	if (system_supports_poe())
 126		write_sysreg_s(ua_state->por_el0, SYS_POR_EL0);
 127}
 128
 129static void init_user_layout(struct rt_sigframe_user_layout *user)
 130{
 131	const size_t reserved_size =
 132		sizeof(user->sigframe->uc.uc_mcontext.__reserved);
 133
 134	memset(user, 0, sizeof(*user));
 135	user->size = offsetof(struct rt_sigframe, uc.uc_mcontext.__reserved);
 136
 137	user->limit = user->size + reserved_size;
 138
 139	user->limit -= TERMINATOR_SIZE;
 140	user->limit -= EXTRA_CONTEXT_SIZE;
 141	/* Reserve space for extension and terminator ^ */
 142}
 143
 144static size_t sigframe_size(struct rt_sigframe_user_layout const *user)
 145{
 146	return round_up(max(user->size, sizeof(struct rt_sigframe)), 16);
 147}
 148
 149/*
 150 * Sanity limit on the approximate maximum size of signal frame we'll
 151 * try to generate.  Stack alignment padding and the frame record are
 152 * not taken into account.  This limit is not a guarantee and is
 153 * NOT ABI.
 154 */
 155#define SIGFRAME_MAXSZ SZ_256K
 156
 157static int __sigframe_alloc(struct rt_sigframe_user_layout *user,
 158			    unsigned long *offset, size_t size, bool extend)
 159{
 160	size_t padded_size = round_up(size, 16);
 161
 162	if (padded_size > user->limit - user->size &&
 163	    !user->extra_offset &&
 164	    extend) {
 165		int ret;
 166
 167		user->limit += EXTRA_CONTEXT_SIZE;
 168		ret = __sigframe_alloc(user, &user->extra_offset,
 169				       sizeof(struct extra_context), false);
 170		if (ret) {
 171			user->limit -= EXTRA_CONTEXT_SIZE;
 172			return ret;
 173		}
 174
 175		/* Reserve space for the __reserved[] terminator */
 176		user->size += TERMINATOR_SIZE;
 177
 178		/*
 179		 * Allow expansion up to SIGFRAME_MAXSZ, ensuring space for
 180		 * the terminator:
 181		 */
 182		user->limit = SIGFRAME_MAXSZ - TERMINATOR_SIZE;
 183	}
 184
 185	/* Still not enough space?  Bad luck! */
 186	if (padded_size > user->limit - user->size)
 187		return -ENOMEM;
 188
 189	*offset = user->size;
 190	user->size += padded_size;
 191
 192	return 0;
 193}
 194
 195/*
 196 * Allocate space for an optional record of <size> bytes in the user
 197 * signal frame.  The offset from the signal frame base address to the
 198 * allocated block is assigned to *offset.
 199 */
 200static int sigframe_alloc(struct rt_sigframe_user_layout *user,
 201			  unsigned long *offset, size_t size)
 202{
 203	return __sigframe_alloc(user, offset, size, true);
 204}
 205
 206/* Allocate the null terminator record and prevent further allocations */
 207static int sigframe_alloc_end(struct rt_sigframe_user_layout *user)
 208{
 209	int ret;
 210
 211	/* Un-reserve the space reserved for the terminator: */
 212	user->limit += TERMINATOR_SIZE;
 213
 214	ret = sigframe_alloc(user, &user->end_offset,
 215			     sizeof(struct _aarch64_ctx));
 216	if (ret)
 217		return ret;
 218
 219	/* Prevent further allocation: */
 220	user->limit = user->size;
 221	return 0;
 222}
 223
 224static void __user *apply_user_offset(
 225	struct rt_sigframe_user_layout const *user, unsigned long offset)
 226{
 227	char __user *base = (char __user *)user->sigframe;
 228
 229	return base + offset;
 230}
 231
 232struct user_ctxs {
 233	struct fpsimd_context __user *fpsimd;
 234	u32 fpsimd_size;
 235	struct sve_context __user *sve;
 236	u32 sve_size;
 237	struct tpidr2_context __user *tpidr2;
 238	u32 tpidr2_size;
 239	struct za_context __user *za;
 240	u32 za_size;
 241	struct zt_context __user *zt;
 242	u32 zt_size;
 243	struct fpmr_context __user *fpmr;
 244	u32 fpmr_size;
 245	struct poe_context __user *poe;
 246	u32 poe_size;
 247	struct gcs_context __user *gcs;
 248	u32 gcs_size;
 249};
 250
 251static int preserve_fpsimd_context(struct fpsimd_context __user *ctx)
 252{
 253	struct user_fpsimd_state const *fpsimd =
 254		&current->thread.uw.fpsimd_state;
 255	int err;
 256
 257	fpsimd_sync_from_effective_state(current);
 258
 259	/* copy the FP and status/control registers */
 260	err = __copy_to_user(ctx->vregs, fpsimd->vregs, sizeof(fpsimd->vregs));
 261	__put_user_error(fpsimd->fpsr, &ctx->fpsr, err);
 262	__put_user_error(fpsimd->fpcr, &ctx->fpcr, err);
 263
 264	/* copy the magic/size information */
 265	__put_user_error(FPSIMD_MAGIC, &ctx->head.magic, err);
 266	__put_user_error(sizeof(struct fpsimd_context), &ctx->head.size, err);
 267
 268	return err ? -EFAULT : 0;
 269}
 270
 271static int read_fpsimd_context(struct user_fpsimd_state *fpsimd,
 272			       struct user_ctxs *user)
 273{
 274	int err;
 275
 276	/* check the size information */
 277	if (user->fpsimd_size != sizeof(struct fpsimd_context))
 278		return -EINVAL;
 279
 280	/* copy the FP and status/control registers */
 281	err = __copy_from_user(fpsimd->vregs, &(user->fpsimd->vregs),
 282			       sizeof(fpsimd->vregs));
 283	__get_user_error(fpsimd->fpsr, &(user->fpsimd->fpsr), err);
 284	__get_user_error(fpsimd->fpcr, &(user->fpsimd->fpcr), err);
 285
 286	return err ? -EFAULT : 0;
 287}
 288
 289static int restore_fpsimd_context(struct user_ctxs *user)
 290{
 291	struct user_fpsimd_state fpsimd;
 292	int err;
 293
 294	err = read_fpsimd_context(&fpsimd, user);
 295	if (err)
 296		return err;
 297
 298	clear_thread_flag(TIF_SVE);
 299	current->thread.svcr &= ~SVCR_SM_MASK;
 300	current->thread.fp_type = FP_STATE_FPSIMD;
 301
 302	/* load the hardware registers from the fpsimd_state structure */
 303	fpsimd_update_current_state(&fpsimd);
 304	return 0;
 305}
 306
 307static int preserve_fpmr_context(struct fpmr_context __user *ctx)
 308{
 309	int err = 0;
 310
 311	__put_user_error(FPMR_MAGIC, &ctx->head.magic, err);
 312	__put_user_error(sizeof(*ctx), &ctx->head.size, err);
 313	__put_user_error(current->thread.uw.fpmr, &ctx->fpmr, err);
 314
 315	return err;
 316}
 317
 318static int restore_fpmr_context(struct user_ctxs *user)
 319{
 320	u64 fpmr;
 321	int err = 0;
 322
 323	if (user->fpmr_size != sizeof(*user->fpmr))
 324		return -EINVAL;
 325
 326	__get_user_error(fpmr, &user->fpmr->fpmr, err);
 327	if (!err)
 328		current->thread.uw.fpmr = fpmr;
 329
 330	return err;
 331}
 332
 333static int preserve_poe_context(struct poe_context __user *ctx,
 334				const struct user_access_state *ua_state)
 335{
 336	int err = 0;
 337
 338	__put_user_error(POE_MAGIC, &ctx->head.magic, err);
 339	__put_user_error(sizeof(*ctx), &ctx->head.size, err);
 340	__put_user_error(ua_state->por_el0, &ctx->por_el0, err);
 341
 342	return err;
 343}
 344
 345static int restore_poe_context(struct user_ctxs *user,
 346			       struct user_access_state *ua_state)
 347{
 348	u64 por_el0;
 349	int err = 0;
 350
 351	if (user->poe_size != sizeof(*user->poe))
 352		return -EINVAL;
 353
 354	__get_user_error(por_el0, &(user->poe->por_el0), err);
 355	if (!err)
 356		ua_state->por_el0 = por_el0;
 357
 358	return err;
 359}
 360
 361#ifdef CONFIG_ARM64_SVE
 362
 363static int preserve_sve_context(struct sve_context __user *ctx)
 364{
 365	int err = 0;
 366	u16 reserved[ARRAY_SIZE(ctx->__reserved)];
 367	u16 flags = 0;
 368	unsigned int vl = task_get_sve_vl(current);
 369	unsigned int vq = 0;
 370
 371	if (thread_sm_enabled(&current->thread)) {
 372		vl = task_get_sme_vl(current);
 373		vq = sve_vq_from_vl(vl);
 374		flags |= SVE_SIG_FLAG_SM;
 375	} else if (current->thread.fp_type == FP_STATE_SVE) {
 376		vq = sve_vq_from_vl(vl);
 377	}
 378
 379	memset(reserved, 0, sizeof(reserved));
 380
 381	__put_user_error(SVE_MAGIC, &ctx->head.magic, err);
 382	__put_user_error(round_up(SVE_SIG_CONTEXT_SIZE(vq), 16),
 383			 &ctx->head.size, err);
 384	__put_user_error(vl, &ctx->vl, err);
 385	__put_user_error(flags, &ctx->flags, err);
 386	BUILD_BUG_ON(sizeof(ctx->__reserved) != sizeof(reserved));
 387	err |= __copy_to_user(&ctx->__reserved, reserved, sizeof(reserved));
 388
 389	if (vq) {
 390		err |= __copy_to_user((char __user *)ctx + SVE_SIG_REGS_OFFSET,
 391				      current->thread.sve_state,
 392				      SVE_SIG_REGS_SIZE(vq));
 393	}
 394
 395	return err ? -EFAULT : 0;
 396}
 397
 398static int restore_sve_fpsimd_context(struct user_ctxs *user)
 399{
 400	int err = 0;
 401	unsigned int vl, vq;
 402	struct user_fpsimd_state fpsimd;
 403	u16 user_vl, flags;
 404	bool sm;
 405
 406	if (user->sve_size < sizeof(*user->sve))
 407		return -EINVAL;
 408
 409	__get_user_error(user_vl, &(user->sve->vl), err);
 410	__get_user_error(flags, &(user->sve->flags), err);
 411	if (err)
 412		return err;
 413
 414	sm = flags & SVE_SIG_FLAG_SM;
 415	if (sm) {
 416		if (!system_supports_sme())
 417			return -EINVAL;
 418
 419		vl = task_get_sme_vl(current);
 420	} else {
 421		/*
 422		 * A SME only system use SVE for streaming mode so can
 423		 * have a SVE formatted context with a zero VL and no
 424		 * payload data.
 425		 */
 426		if (!system_supports_sve() && !system_supports_sme())
 427			return -EINVAL;
 428
 429		vl = task_get_sve_vl(current);
 430	}
 431
 432	if (user_vl != vl)
 433		return -EINVAL;
 434
 435	/*
 436	 * Non-streaming SVE state may be preserved without an SVE payload, in
 437	 * which case the SVE context only has a header with VL==0, and all
 438	 * state can be restored from the FPSIMD context.
 439	 *
 440	 * Streaming SVE state is always preserved with an SVE payload. For
 441	 * consistency and robustness, reject restoring streaming SVE state
 442	 * without an SVE payload.
 443	 */
 444	if (!sm && user->sve_size == sizeof(*user->sve))
 445		return restore_fpsimd_context(user);
 446
 447	vq = sve_vq_from_vl(vl);
 448
 449	if (user->sve_size < SVE_SIG_CONTEXT_SIZE(vq))
 450		return -EINVAL;
 451
 452	if (sm) {
 453		sme_alloc(current, false);
 454		if (!current->thread.sme_state)
 455			return -ENOMEM;
 456	}
 457
 458	sve_alloc(current, true);
 459	if (!current->thread.sve_state) {
 460		clear_thread_flag(TIF_SVE);
 461		return -ENOMEM;
 462	}
 463
 464	if (sm) {
 465		current->thread.svcr |= SVCR_SM_MASK;
 466		set_thread_flag(TIF_SME);
 467	} else {
 468		current->thread.svcr &= ~SVCR_SM_MASK;
 469		set_thread_flag(TIF_SVE);
 470	}
 471
 472	current->thread.fp_type = FP_STATE_SVE;
 473
 474	err = __copy_from_user(current->thread.sve_state,
 475			       (char __user const *)user->sve +
 476					SVE_SIG_REGS_OFFSET,
 477			       SVE_SIG_REGS_SIZE(vq));
 478	if (err)
 479		return -EFAULT;
 480
 481	err = read_fpsimd_context(&fpsimd, user);
 482	if (err)
 483		return err;
 484
 485	/* Merge the FPSIMD registers into the SVE state */
 486	fpsimd_update_current_state(&fpsimd);
 487
 488	return 0;
 489}
 490
 491#else /* ! CONFIG_ARM64_SVE */
 492
 493static int restore_sve_fpsimd_context(struct user_ctxs *user)
 494{
 495	WARN_ON_ONCE(1);
 496	return -EINVAL;
 497}
 498
 499/* Turn any non-optimised out attempts to use this into a link error: */
 500extern int preserve_sve_context(void __user *ctx);
 501
 502#endif /* ! CONFIG_ARM64_SVE */
 503
 504#ifdef CONFIG_ARM64_SME
 505
 506static int preserve_tpidr2_context(struct tpidr2_context __user *ctx)
 507{
 508	u64 tpidr2_el0 = read_sysreg_s(SYS_TPIDR2_EL0);
 509	int err = 0;
 510
 511	__put_user_error(TPIDR2_MAGIC, &ctx->head.magic, err);
 512	__put_user_error(sizeof(*ctx), &ctx->head.size, err);
 513	__put_user_error(tpidr2_el0, &ctx->tpidr2, err);
 514
 515	return err;
 516}
 517
 518static int restore_tpidr2_context(struct user_ctxs *user)
 519{
 520	u64 tpidr2_el0;
 521	int err = 0;
 522
 523	if (user->tpidr2_size != sizeof(*user->tpidr2))
 524		return -EINVAL;
 525
 526	__get_user_error(tpidr2_el0, &user->tpidr2->tpidr2, err);
 527	if (!err)
 528		write_sysreg_s(tpidr2_el0, SYS_TPIDR2_EL0);
 529
 530	return err;
 531}
 532
 533static int preserve_za_context(struct za_context __user *ctx)
 534{
 535	int err = 0;
 536	u16 reserved[ARRAY_SIZE(ctx->__reserved)];
 537	unsigned int vl = task_get_sme_vl(current);
 538	unsigned int vq;
 539
 540	if (thread_za_enabled(&current->thread))
 541		vq = sve_vq_from_vl(vl);
 542	else
 543		vq = 0;
 544
 545	memset(reserved, 0, sizeof(reserved));
 546
 547	__put_user_error(ZA_MAGIC, &ctx->head.magic, err);
 548	__put_user_error(round_up(ZA_SIG_CONTEXT_SIZE(vq), 16),
 549			 &ctx->head.size, err);
 550	__put_user_error(vl, &ctx->vl, err);
 551	BUILD_BUG_ON(sizeof(ctx->__reserved) != sizeof(reserved));
 552	err |= __copy_to_user(&ctx->__reserved, reserved, sizeof(reserved));
 553
 554	if (vq) {
 555		err |= __copy_to_user((char __user *)ctx + ZA_SIG_REGS_OFFSET,
 556				      current->thread.sme_state,
 557				      ZA_SIG_REGS_SIZE(vq));
 558	}
 559
 560	return err ? -EFAULT : 0;
 561}
 562
 563static int restore_za_context(struct user_ctxs *user)
 564{
 565	int err = 0;
 566	unsigned int vq;
 567	u16 user_vl;
 568
 569	if (user->za_size < sizeof(*user->za))
 570		return -EINVAL;
 571
 572	__get_user_error(user_vl, &(user->za->vl), err);
 573	if (err)
 574		return err;
 575
 576	if (user_vl != task_get_sme_vl(current))
 577		return -EINVAL;
 578
 579	if (user->za_size == sizeof(*user->za)) {
 580		current->thread.svcr &= ~SVCR_ZA_MASK;
 581		return 0;
 582	}
 583
 584	vq = sve_vq_from_vl(user_vl);
 585
 586	if (user->za_size < ZA_SIG_CONTEXT_SIZE(vq))
 587		return -EINVAL;
 588
 589	sve_alloc(current, false);
 590	if (!current->thread.sve_state)
 591		return -ENOMEM;
 592
 593	sme_alloc(current, true);
 594	if (!current->thread.sme_state) {
 595		current->thread.svcr &= ~SVCR_ZA_MASK;
 596		clear_thread_flag(TIF_SME);
 597		return -ENOMEM;
 598	}
 599
 600	err = __copy_from_user(current->thread.sme_state,
 601			       (char __user const *)user->za +
 602					ZA_SIG_REGS_OFFSET,
 603			       ZA_SIG_REGS_SIZE(vq));
 604	if (err)
 605		return -EFAULT;
 606
 607	set_thread_flag(TIF_SME);
 608	current->thread.svcr |= SVCR_ZA_MASK;
 609
 610	return 0;
 611}
 612
 613static int preserve_zt_context(struct zt_context __user *ctx)
 614{
 615	int err = 0;
 616	u16 reserved[ARRAY_SIZE(ctx->__reserved)];
 617
 618	if (WARN_ON(!thread_za_enabled(&current->thread)))
 619		return -EINVAL;
 620
 621	memset(reserved, 0, sizeof(reserved));
 622
 623	__put_user_error(ZT_MAGIC, &ctx->head.magic, err);
 624	__put_user_error(round_up(ZT_SIG_CONTEXT_SIZE(1), 16),
 625			 &ctx->head.size, err);
 626	__put_user_error(1, &ctx->nregs, err);
 627	BUILD_BUG_ON(sizeof(ctx->__reserved) != sizeof(reserved));
 628	err |= __copy_to_user(&ctx->__reserved, reserved, sizeof(reserved));
 629
 630	err |= __copy_to_user((char __user *)ctx + ZT_SIG_REGS_OFFSET,
 631			      thread_zt_state(&current->thread),
 632			      ZT_SIG_REGS_SIZE(1));
 633
 634	return err ? -EFAULT : 0;
 635}
 636
 637static int restore_zt_context(struct user_ctxs *user)
 638{
 639	int err;
 640	u16 nregs;
 641
 642	/* ZA must be restored first for this check to be valid */
 643	if (!thread_za_enabled(&current->thread))
 644		return -EINVAL;
 645
 646	if (user->zt_size != ZT_SIG_CONTEXT_SIZE(1))
 647		return -EINVAL;
 648
 649	if (__copy_from_user(&nregs, &(user->zt->nregs), sizeof(nregs)))
 650		return -EFAULT;
 651
 652	if (nregs != 1)
 653		return -EINVAL;
 654
 655	err = __copy_from_user(thread_zt_state(&current->thread),
 656			       (char __user const *)user->zt +
 657					ZT_SIG_REGS_OFFSET,
 658			       ZT_SIG_REGS_SIZE(1));
 659	if (err)
 660		return -EFAULT;
 661
 662	return 0;
 663}
 664
 665#else /* ! CONFIG_ARM64_SME */
 666
 667/* Turn any non-optimised out attempts to use these into a link error: */
 668extern int preserve_tpidr2_context(void __user *ctx);
 669extern int restore_tpidr2_context(struct user_ctxs *user);
 670extern int preserve_za_context(void __user *ctx);
 671extern int restore_za_context(struct user_ctxs *user);
 672extern int preserve_zt_context(void __user *ctx);
 673extern int restore_zt_context(struct user_ctxs *user);
 674
 675#endif /* ! CONFIG_ARM64_SME */
 676
 677#ifdef CONFIG_ARM64_GCS
 678
 679static int preserve_gcs_context(struct gcs_context __user *ctx)
 680{
 681	int err = 0;
 682	u64 gcspr = read_sysreg_s(SYS_GCSPR_EL0);
 683
 684	/*
 685	 * If GCS is enabled we will add a cap token to the frame,
 686	 * include it in the GCSPR_EL0 we report to support stack
 687	 * switching via sigreturn if GCS is enabled.  We do not allow
 688	 * enabling via sigreturn so the token is only relevant for
 689	 * threads with GCS enabled.
 690	 */
 691	if (task_gcs_el0_enabled(current))
 692		gcspr -= 8;
 693
 694	__put_user_error(GCS_MAGIC, &ctx->head.magic, err);
 695	__put_user_error(sizeof(*ctx), &ctx->head.size, err);
 696	__put_user_error(gcspr, &ctx->gcspr, err);
 697	__put_user_error(0, &ctx->reserved, err);
 698	__put_user_error(current->thread.gcs_el0_mode,
 699			 &ctx->features_enabled, err);
 700
 701	return err;
 702}
 703
 704static int restore_gcs_context(struct user_ctxs *user)
 705{
 706	u64 gcspr, enabled;
 707	int err = 0;
 708
 709	if (user->gcs_size != sizeof(*user->gcs))
 710		return -EINVAL;
 711
 712	__get_user_error(gcspr, &user->gcs->gcspr, err);
 713	__get_user_error(enabled, &user->gcs->features_enabled, err);
 714	if (err)
 715		return err;
 716
 717	/* Don't allow unknown modes */
 718	if (enabled & ~PR_SHADOW_STACK_SUPPORTED_STATUS_MASK)
 719		return -EINVAL;
 720
 721	err = gcs_check_locked(current, enabled);
 722	if (err != 0)
 723		return err;
 724
 725	/* Don't allow enabling */
 726	if (!task_gcs_el0_enabled(current) &&
 727	    (enabled & PR_SHADOW_STACK_ENABLE))
 728		return -EINVAL;
 729
 730	/* If we are disabling disable everything */
 731	if (!(enabled & PR_SHADOW_STACK_ENABLE))
 732		enabled = 0;
 733
 734	current->thread.gcs_el0_mode = enabled;
 735
 736	/*
 737	 * We let userspace set GCSPR_EL0 to anything here, we will
 738	 * validate later in gcs_restore_signal().
 739	 */
 740	write_sysreg_s(gcspr, SYS_GCSPR_EL0);
 741
 742	return 0;
 743}
 744
 745#else /* ! CONFIG_ARM64_GCS */
 746
 747/* Turn any non-optimised out attempts to use these into a link error: */
 748extern int preserve_gcs_context(void __user *ctx);
 749extern int restore_gcs_context(struct user_ctxs *user);
 750
 751#endif /* ! CONFIG_ARM64_GCS */
 752
 753static int parse_user_sigframe(struct user_ctxs *user,
 754			       struct rt_sigframe __user *sf)
 755{
 756	struct sigcontext __user *const sc = &sf->uc.uc_mcontext;
 757	struct _aarch64_ctx __user *head;
 758	char __user *base = (char __user *)&sc->__reserved;
 759	size_t offset = 0;
 760	size_t limit = sizeof(sc->__reserved);
 761	bool have_extra_context = false;
 762	char const __user *const sfp = (char const __user *)sf;
 763
 764	user->fpsimd = NULL;
 765	user->sve = NULL;
 766	user->tpidr2 = NULL;
 767	user->za = NULL;
 768	user->zt = NULL;
 769	user->fpmr = NULL;
 770	user->poe = NULL;
 771	user->gcs = NULL;
 772
 773	if (!IS_ALIGNED((unsigned long)base, 16))
 774		goto invalid;
 775
 776	while (1) {
 777		int err = 0;
 778		u32 magic, size;
 779		char const __user *userp;
 780		struct extra_context const __user *extra;
 781		u64 extra_datap;
 782		u32 extra_size;
 783		struct _aarch64_ctx const __user *end;
 784		u32 end_magic, end_size;
 785
 786		if (limit - offset < sizeof(*head))
 787			goto invalid;
 788
 789		if (!IS_ALIGNED(offset, 16))
 790			goto invalid;
 791
 792		head = (struct _aarch64_ctx __user *)(base + offset);
 793		__get_user_error(magic, &head->magic, err);
 794		__get_user_error(size, &head->size, err);
 795		if (err)
 796			return err;
 797
 798		if (limit - offset < size)
 799			goto invalid;
 800
 801		switch (magic) {
 802		case 0:
 803			if (size)
 804				goto invalid;
 805
 806			goto done;
 807
 808		case FPSIMD_MAGIC:
 809			if (!system_supports_fpsimd())
 810				goto invalid;
 811			if (user->fpsimd)
 812				goto invalid;
 813
 814			user->fpsimd = (struct fpsimd_context __user *)head;
 815			user->fpsimd_size = size;
 816			break;
 817
 818		case ESR_MAGIC:
 819			/* ignore */
 820			break;
 821
 822		case POE_MAGIC:
 823			if (!system_supports_poe())
 824				goto invalid;
 825
 826			if (user->poe)
 827				goto invalid;
 828
 829			user->poe = (struct poe_context __user *)head;
 830			user->poe_size = size;
 831			break;
 832
 833		case SVE_MAGIC:
 834			if (!system_supports_sve() && !system_supports_sme())
 835				goto invalid;
 836
 837			if (user->sve)
 838				goto invalid;
 839
 840			user->sve = (struct sve_context __user *)head;
 841			user->sve_size = size;
 842			break;
 843
 844		case TPIDR2_MAGIC:
 845			if (!system_supports_tpidr2())
 846				goto invalid;
 847
 848			if (user->tpidr2)
 849				goto invalid;
 850
 851			user->tpidr2 = (struct tpidr2_context __user *)head;
 852			user->tpidr2_size = size;
 853			break;
 854
 855		case ZA_MAGIC:
 856			if (!system_supports_sme())
 857				goto invalid;
 858
 859			if (user->za)
 860				goto invalid;
 861
 862			user->za = (struct za_context __user *)head;
 863			user->za_size = size;
 864			break;
 865
 866		case ZT_MAGIC:
 867			if (!system_supports_sme2())
 868				goto invalid;
 869
 870			if (user->zt)
 871				goto invalid;
 872
 873			user->zt = (struct zt_context __user *)head;
 874			user->zt_size = size;
 875			break;
 876
 877		case FPMR_MAGIC:
 878			if (!system_supports_fpmr())
 879				goto invalid;
 880
 881			if (user->fpmr)
 882				goto invalid;
 883
 884			user->fpmr = (struct fpmr_context __user *)head;
 885			user->fpmr_size = size;
 886			break;
 887
 888		case GCS_MAGIC:
 889			if (!system_supports_gcs())
 890				goto invalid;
 891
 892			if (user->gcs)
 893				goto invalid;
 894
 895			user->gcs = (struct gcs_context __user *)head;
 896			user->gcs_size = size;
 897			break;
 898
 899		case EXTRA_MAGIC:
 900			if (have_extra_context)
 901				goto invalid;
 902
 903			if (size < sizeof(*extra))
 904				goto invalid;
 905
 906			userp = (char const __user *)head;
 907
 908			extra = (struct extra_context const __user *)userp;
 909			userp += size;
 910
 911			__get_user_error(extra_datap, &extra->datap, err);
 912			__get_user_error(extra_size, &extra->size, err);
 913			if (err)
 914				return err;
 915
 916			/* Check for the dummy terminator in __reserved[]: */
 917
 918			if (limit - offset - size < TERMINATOR_SIZE)
 919				goto invalid;
 920
 921			end = (struct _aarch64_ctx const __user *)userp;
 922			userp += TERMINATOR_SIZE;
 923
 924			__get_user_error(end_magic, &end->magic, err);
 925			__get_user_error(end_size, &end->size, err);
 926			if (err)
 927				return err;
 928
 929			if (end_magic || end_size)
 930				goto invalid;
 931
 932			/* Prevent looping/repeated parsing of extra_context */
 933			have_extra_context = true;
 934
 935			base = (__force void __user *)extra_datap;
 936			if (!IS_ALIGNED((unsigned long)base, 16))
 937				goto invalid;
 938
 939			if (!IS_ALIGNED(extra_size, 16))
 940				goto invalid;
 941
 942			if (base != userp)
 943				goto invalid;
 944
 945			/* Reject "unreasonably large" frames: */
 946			if (extra_size > sfp + SIGFRAME_MAXSZ - userp)
 947				goto invalid;
 948
 949			/*
 950			 * Ignore trailing terminator in __reserved[]
 951			 * and start parsing extra data:
 952			 */
 953			offset = 0;
 954			limit = extra_size;
 955
 956			if (!access_ok(base, limit))
 957				goto invalid;
 958
 959			continue;
 960
 961		default:
 962			goto invalid;
 963		}
 964
 965		if (size < sizeof(*head))
 966			goto invalid;
 967
 968		if (limit - offset < size)
 969			goto invalid;
 970
 971		offset += size;
 972	}
 973
 974done:
 975	return 0;
 976
 977invalid:
 978	return -EINVAL;
 979}
 980
 981static int restore_sigframe(struct pt_regs *regs,
 982			    struct rt_sigframe __user *sf,
 983			    struct user_access_state *ua_state)
 984{
 985	sigset_t set;
 986	int i, err;
 987	struct user_ctxs user;
 988
 989	err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
 990	if (err == 0)
 991		set_current_blocked(&set);
 992
 993	for (i = 0; i < 31; i++)
 994		__get_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i],
 995				 err);
 996	__get_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err);
 997	__get_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err);
 998	__get_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err);
 999
1000	/*
1001	 * Avoid sys_rt_sigreturn() restarting.
1002	 */
1003	forget_syscall(regs);
1004
1005	fpsimd_save_and_flush_current_state();
1006
1007	err |= !valid_user_regs(&regs->user_regs, current);
1008	if (err == 0)
1009		err = parse_user_sigframe(&user, sf);
1010
1011	if (err == 0 && system_supports_fpsimd()) {
1012		if (!user.fpsimd)
1013			return -EINVAL;
1014
1015		if (user.sve)
1016			err = restore_sve_fpsimd_context(&user);
1017		else
1018			err = restore_fpsimd_context(&user);
1019	}
1020
1021	if (err == 0 && system_supports_gcs() && user.gcs)
1022		err = restore_gcs_context(&user);
1023
1024	if (err == 0 && system_supports_tpidr2() && user.tpidr2)
1025		err = restore_tpidr2_context(&user);
1026
1027	if (err == 0 && system_supports_fpmr() && user.fpmr)
1028		err = restore_fpmr_context(&user);
1029
1030	if (err == 0 && system_supports_sme() && user.za)
1031		err = restore_za_context(&user);
1032
1033	if (err == 0 && system_supports_sme2() && user.zt)
1034		err = restore_zt_context(&user);
1035
1036	if (err == 0 && system_supports_poe() && user.poe)
1037		err = restore_poe_context(&user, ua_state);
1038
1039	return err;
1040}
1041
1042#ifdef CONFIG_ARM64_GCS
1043static int gcs_restore_signal(void)
1044{
1045	u64 gcspr_el0, cap;
1046	int ret;
1047
1048	if (!system_supports_gcs())
1049		return 0;
1050
1051	if (!(current->thread.gcs_el0_mode & PR_SHADOW_STACK_ENABLE))
1052		return 0;
1053
1054	gcspr_el0 = read_sysreg_s(SYS_GCSPR_EL0);
1055
1056	/*
1057	 * Ensure that any changes to the GCS done via GCS operations
1058	 * are visible to the normal reads we do to validate the
1059	 * token.
1060	 */
1061	gcsb_dsync();
1062
1063	/*
1064	 * GCSPR_EL0 should be pointing at a capped GCS, read the cap.
1065	 * We don't enforce that this is in a GCS page, if it is not
1066	 * then faults will be generated on GCS operations - the main
1067	 * concern is to protect GCS pages.
1068	 */
1069	ret = copy_from_user(&cap, (unsigned long __user *)gcspr_el0,
1070			     sizeof(cap));
1071	if (ret)
1072		return -EFAULT;
1073
1074	/*
1075	 * Check that the cap is the actual GCS before replacing it.
1076	 */
1077	if (cap != GCS_SIGNAL_CAP(gcspr_el0))
1078		return -EINVAL;
1079
1080	/* Invalidate the token to prevent reuse */
1081	put_user_gcs(0, (unsigned long __user *)gcspr_el0, &ret);
1082	if (ret != 0)
1083		return -EFAULT;
1084
1085	write_sysreg_s(gcspr_el0 + 8, SYS_GCSPR_EL0);
1086
1087	return 0;
1088}
1089
1090#else
1091static int gcs_restore_signal(void) { return 0; }
1092#endif
1093
1094SYSCALL_DEFINE0(rt_sigreturn)
1095{
1096	struct pt_regs *regs = current_pt_regs();
1097	struct rt_sigframe __user *frame;
1098	struct user_access_state ua_state;
1099
1100	/* Always make any pending restarted system calls return -EINTR */
1101	current->restart_block.fn = do_no_restart_syscall;
1102
1103	/*
1104	 * Since we stacked the signal on a 128-bit boundary, then 'sp' should
1105	 * be word aligned here.
1106	 */
1107	if (regs->sp & 15)
1108		goto badframe;
1109
1110	frame = (struct rt_sigframe __user *)regs->sp;
1111
1112	if (!access_ok(frame, sizeof (*frame)))
1113		goto badframe;
1114
1115	if (restore_sigframe(regs, frame, &ua_state))
1116		goto badframe;
1117
1118	if (gcs_restore_signal())
1119		goto badframe;
1120
1121	if (restore_altstack(&frame->uc.uc_stack))
1122		goto badframe;
1123
1124	restore_user_access_state(&ua_state);
1125
1126	return regs->regs[0];
1127
1128badframe:
1129	arm64_notify_segfault(regs->sp);
1130	return 0;
1131}
1132
1133/*
1134 * Determine the layout of optional records in the signal frame
1135 *
1136 * add_all: if true, lays out the biggest possible signal frame for
1137 *	this task; otherwise, generates a layout for the current state
1138 *	of the task.
1139 */
1140static int setup_sigframe_layout(struct rt_sigframe_user_layout *user,
1141				 bool add_all)
1142{
1143	int err;
1144
1145	if (system_supports_fpsimd()) {
1146		err = sigframe_alloc(user, &user->fpsimd_offset,
1147				     sizeof(struct fpsimd_context));
1148		if (err)
1149			return err;
1150	}
1151
1152	/* fault information, if valid */
1153	if (add_all || current->thread.fault_code) {
1154		err = sigframe_alloc(user, &user->esr_offset,
1155				     sizeof(struct esr_context));
1156		if (err)
1157			return err;
1158	}
1159
1160#ifdef CONFIG_ARM64_GCS
1161	if (system_supports_gcs() && (add_all || current->thread.gcspr_el0)) {
1162		err = sigframe_alloc(user, &user->gcs_offset,
1163				     sizeof(struct gcs_context));
1164		if (err)
1165			return err;
1166	}
1167#endif
1168
1169	if (system_supports_sve() || system_supports_sme()) {
1170		unsigned int vq = 0;
1171
1172		if (add_all || current->thread.fp_type == FP_STATE_SVE ||
1173		    thread_sm_enabled(&current->thread)) {
1174			int vl = max(sve_max_vl(), sme_max_vl());
1175
1176			if (!add_all)
1177				vl = thread_get_cur_vl(&current->thread);
1178
1179			vq = sve_vq_from_vl(vl);
1180		}
1181
1182		err = sigframe_alloc(user, &user->sve_offset,
1183				     SVE_SIG_CONTEXT_SIZE(vq));
1184		if (err)
1185			return err;
1186	}
1187
1188	if (system_supports_tpidr2()) {
1189		err = sigframe_alloc(user, &user->tpidr2_offset,
1190				     sizeof(struct tpidr2_context));
1191		if (err)
1192			return err;
1193	}
1194
1195	if (system_supports_sme()) {
1196		unsigned int vl;
1197		unsigned int vq = 0;
1198
1199		if (add_all)
1200			vl = sme_max_vl();
1201		else
1202			vl = task_get_sme_vl(current);
1203
1204		if (thread_za_enabled(&current->thread))
1205			vq = sve_vq_from_vl(vl);
1206
1207		err = sigframe_alloc(user, &user->za_offset,
1208				     ZA_SIG_CONTEXT_SIZE(vq));
1209		if (err)
1210			return err;
1211	}
1212
1213	if (system_supports_sme2()) {
1214		if (add_all || thread_za_enabled(&current->thread)) {
1215			err = sigframe_alloc(user, &user->zt_offset,
1216					     ZT_SIG_CONTEXT_SIZE(1));
1217			if (err)
1218				return err;
1219		}
1220	}
1221
1222	if (system_supports_fpmr()) {
1223		err = sigframe_alloc(user, &user->fpmr_offset,
1224				     sizeof(struct fpmr_context));
1225		if (err)
1226			return err;
1227	}
1228
1229	if (system_supports_poe()) {
1230		err = sigframe_alloc(user, &user->poe_offset,
1231				     sizeof(struct poe_context));
1232		if (err)
1233			return err;
1234	}
1235
1236	return sigframe_alloc_end(user);
1237}
1238
1239static int setup_sigframe(struct rt_sigframe_user_layout *user,
1240			  struct pt_regs *regs, sigset_t *set,
1241			  const struct user_access_state *ua_state)
1242{
1243	int i, err = 0;
1244	struct rt_sigframe __user *sf = user->sigframe;
1245
1246	/* set up the stack frame for unwinding */
1247	__put_user_error(regs->regs[29], &user->next_frame->fp, err);
1248	__put_user_error(regs->regs[30], &user->next_frame->lr, err);
1249
1250	for (i = 0; i < 31; i++)
1251		__put_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i],
1252				 err);
1253	__put_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err);
1254	__put_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err);
1255	__put_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err);
1256
1257	__put_user_error(current->thread.fault_address, &sf->uc.uc_mcontext.fault_address, err);
1258
1259	err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(*set));
1260
1261	if (err == 0 && system_supports_fpsimd()) {
1262		struct fpsimd_context __user *fpsimd_ctx =
1263			apply_user_offset(user, user->fpsimd_offset);
1264		err |= preserve_fpsimd_context(fpsimd_ctx);
1265	}
1266
1267	/* fault information, if valid */
1268	if (err == 0 && user->esr_offset) {
1269		struct esr_context __user *esr_ctx =
1270			apply_user_offset(user, user->esr_offset);
1271
1272		__put_user_error(ESR_MAGIC, &esr_ctx->head.magic, err);
1273		__put_user_error(sizeof(*esr_ctx), &esr_ctx->head.size, err);
1274		__put_user_error(current->thread.fault_code, &esr_ctx->esr, err);
1275	}
1276
1277	if (system_supports_gcs() && err == 0 && user->gcs_offset) {
1278		struct gcs_context __user *gcs_ctx =
1279			apply_user_offset(user, user->gcs_offset);
1280		err |= preserve_gcs_context(gcs_ctx);
1281	}
1282
1283	/* Scalable Vector Extension state (including streaming), if present */
1284	if ((system_supports_sve() || system_supports_sme()) &&
1285	    err == 0 && user->sve_offset) {
1286		struct sve_context __user *sve_ctx =
1287			apply_user_offset(user, user->sve_offset);
1288		err |= preserve_sve_context(sve_ctx);
1289	}
1290
1291	/* TPIDR2 if supported */
1292	if (system_supports_tpidr2() && err == 0) {
1293		struct tpidr2_context __user *tpidr2_ctx =
1294			apply_user_offset(user, user->tpidr2_offset);
1295		err |= preserve_tpidr2_context(tpidr2_ctx);
1296	}
1297
1298	/* FPMR if supported */
1299	if (system_supports_fpmr() && err == 0) {
1300		struct fpmr_context __user *fpmr_ctx =
1301			apply_user_offset(user, user->fpmr_offset);
1302		err |= preserve_fpmr_context(fpmr_ctx);
1303	}
1304
1305	if (system_supports_poe() && err == 0) {
1306		struct poe_context __user *poe_ctx =
1307			apply_user_offset(user, user->poe_offset);
1308
1309		err |= preserve_poe_context(poe_ctx, ua_state);
1310	}
1311
1312	/* ZA state if present */
1313	if (system_supports_sme() && err == 0 && user->za_offset) {
1314		struct za_context __user *za_ctx =
1315			apply_user_offset(user, user->za_offset);
1316		err |= preserve_za_context(za_ctx);
1317	}
1318
1319	/* ZT state if present */
1320	if (system_supports_sme2() && err == 0 && user->zt_offset) {
1321		struct zt_context __user *zt_ctx =
1322			apply_user_offset(user, user->zt_offset);
1323		err |= preserve_zt_context(zt_ctx);
1324	}
1325
1326	if (err == 0 && user->extra_offset) {
1327		char __user *sfp = (char __user *)user->sigframe;
1328		char __user *userp =
1329			apply_user_offset(user, user->extra_offset);
1330
1331		struct extra_context __user *extra;
1332		struct _aarch64_ctx __user *end;
1333		u64 extra_datap;
1334		u32 extra_size;
1335
1336		extra = (struct extra_context __user *)userp;
1337		userp += EXTRA_CONTEXT_SIZE;
1338
1339		end = (struct _aarch64_ctx __user *)userp;
1340		userp += TERMINATOR_SIZE;
1341
1342		/*
1343		 * extra_datap is just written to the signal frame.
1344		 * The value gets cast back to a void __user *
1345		 * during sigreturn.
1346		 */
1347		extra_datap = (__force u64)userp;
1348		extra_size = sfp + round_up(user->size, 16) - userp;
1349
1350		__put_user_error(EXTRA_MAGIC, &extra->head.magic, err);
1351		__put_user_error(EXTRA_CONTEXT_SIZE, &extra->head.size, err);
1352		__put_user_error(extra_datap, &extra->datap, err);
1353		__put_user_error(extra_size, &extra->size, err);
1354
1355		/* Add the terminator */
1356		__put_user_error(0, &end->magic, err);
1357		__put_user_error(0, &end->size, err);
1358	}
1359
1360	/* set the "end" magic */
1361	if (err == 0) {
1362		struct _aarch64_ctx __user *end =
1363			apply_user_offset(user, user->end_offset);
1364
1365		__put_user_error(0, &end->magic, err);
1366		__put_user_error(0, &end->size, err);
1367	}
1368
1369	return err;
1370}
1371
1372static int get_sigframe(struct rt_sigframe_user_layout *user,
1373			 struct ksignal *ksig, struct pt_regs *regs)
1374{
1375	unsigned long sp, sp_top;
1376	int err;
1377
1378	init_user_layout(user);
1379	err = setup_sigframe_layout(user, false);
1380	if (err)
1381		return err;
1382
1383	sp = sp_top = sigsp(regs->sp, ksig);
1384
1385	sp = round_down(sp - sizeof(struct frame_record), 16);
1386	user->next_frame = (struct frame_record __user *)sp;
1387
1388	sp = round_down(sp, 16) - sigframe_size(user);
1389	user->sigframe = (struct rt_sigframe __user *)sp;
1390
1391	/*
1392	 * Check that we can actually write to the signal frame.
1393	 */
1394	if (!access_ok(user->sigframe, sp_top - sp))
1395		return -EFAULT;
1396
1397	return 0;
1398}
1399
1400#ifdef CONFIG_ARM64_GCS
1401
1402static int gcs_signal_entry(__sigrestore_t sigtramp, struct ksignal *ksig)
1403{
1404	u64 gcspr_el0;
1405	int ret = 0;
1406
1407	if (!system_supports_gcs())
1408		return 0;
1409
1410	if (!task_gcs_el0_enabled(current))
1411		return 0;
1412
1413	/*
1414	 * We are entering a signal handler, current register state is
1415	 * active.
1416	 */
1417	gcspr_el0 = read_sysreg_s(SYS_GCSPR_EL0);
1418
1419	/*
1420	 * Push a cap and the GCS entry for the trampoline onto the GCS.
1421	 */
1422	put_user_gcs((unsigned long)sigtramp,
1423		     (unsigned long __user *)(gcspr_el0 - 16), &ret);
1424	put_user_gcs(GCS_SIGNAL_CAP(gcspr_el0 - 8),
1425		     (unsigned long __user *)(gcspr_el0 - 8), &ret);
1426	if (ret != 0)
1427		return ret;
1428
1429	gcspr_el0 -= 16;
1430	write_sysreg_s(gcspr_el0, SYS_GCSPR_EL0);
1431
1432	return 0;
1433}
1434#else
1435
1436static int gcs_signal_entry(__sigrestore_t sigtramp, struct ksignal *ksig)
1437{
1438	return 0;
1439}
1440
1441#endif
1442
1443static int setup_return(struct pt_regs *regs, struct ksignal *ksig,
1444			 struct rt_sigframe_user_layout *user, int usig)
1445{
1446	__sigrestore_t sigtramp;
1447	int err;
1448
1449	if (ksig->ka.sa.sa_flags & SA_RESTORER)
1450		sigtramp = ksig->ka.sa.sa_restorer;
1451	else
1452		sigtramp = VDSO_SYMBOL(current->mm->context.vdso, sigtramp);
1453
1454	err = gcs_signal_entry(sigtramp, ksig);
1455	if (err)
1456		return err;
1457
1458	/*
1459	 * We must not fail from this point onwards. We are going to update
1460	 * registers, including SP, in order to invoke the signal handler. If
1461	 * we failed and attempted to deliver a nested SIGSEGV to a handler
1462	 * after that point, the subsequent sigreturn would end up restoring
1463	 * the (partial) state for the original signal handler.
1464	 */
1465
1466	regs->regs[0] = usig;
1467	if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
1468		regs->regs[1] = (unsigned long)&user->sigframe->info;
1469		regs->regs[2] = (unsigned long)&user->sigframe->uc;
1470	}
1471	regs->sp = (unsigned long)user->sigframe;
1472	regs->regs[29] = (unsigned long)&user->next_frame->fp;
1473	regs->regs[30] = (unsigned long)sigtramp;
1474	regs->pc = (unsigned long)ksig->ka.sa.sa_handler;
1475
1476	/*
1477	 * Signal delivery is a (wacky) indirect function call in
1478	 * userspace, so simulate the same setting of BTYPE as a BLR
1479	 * <register containing the signal handler entry point>.
1480	 * Signal delivery to a location in a PROT_BTI guarded page
1481	 * that is not a function entry point will now trigger a
1482	 * SIGILL in userspace.
1483	 *
1484	 * If the signal handler entry point is not in a PROT_BTI
1485	 * guarded page, this is harmless.
1486	 */
1487	if (system_supports_bti()) {
1488		regs->pstate &= ~PSR_BTYPE_MASK;
1489		regs->pstate |= PSR_BTYPE_C;
1490	}
1491
1492	/* TCO (Tag Check Override) always cleared for signal handlers */
1493	regs->pstate &= ~PSR_TCO_BIT;
1494
1495	/* Signal handlers are invoked with ZA and streaming mode disabled */
1496	if (system_supports_sme()) {
1497		task_smstop_sm(current);
1498		current->thread.svcr &= ~SVCR_ZA_MASK;
1499		write_sysreg_s(0, SYS_TPIDR2_EL0);
1500	}
1501
1502	return 0;
1503}
1504
1505static int setup_rt_frame(int usig, struct ksignal *ksig, sigset_t *set,
1506			  struct pt_regs *regs)
1507{
1508	struct rt_sigframe_user_layout user;
1509	struct rt_sigframe __user *frame;
1510	struct user_access_state ua_state;
1511	int err = 0;
1512
1513	fpsimd_save_and_flush_current_state();
1514
1515	if (get_sigframe(&user, ksig, regs))
1516		return 1;
1517
1518	save_reset_user_access_state(&ua_state);
1519	frame = user.sigframe;
1520
1521	__put_user_error(0, &frame->uc.uc_flags, err);
1522	__put_user_error(NULL, &frame->uc.uc_link, err);
1523
1524	err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
1525	err |= setup_sigframe(&user, regs, set, &ua_state);
1526	if (ksig->ka.sa.sa_flags & SA_SIGINFO)
1527		err |= copy_siginfo_to_user(&frame->info, &ksig->info);
1528
1529	if (err == 0)
1530		err = setup_return(regs, ksig, &user, usig);
1531
1532	/*
1533	 * We must not fail if setup_return() succeeded - see comment at the
1534	 * beginning of setup_return().
1535	 */
1536
1537	if (err == 0)
1538		set_handler_user_access_state();
1539	else
1540		restore_user_access_state(&ua_state);
1541
1542	return err;
1543}
1544
1545static void setup_restart_syscall(struct pt_regs *regs)
1546{
1547	if (is_compat_task())
1548		compat_setup_restart_syscall(regs);
1549	else
1550		regs->regs[8] = __NR_restart_syscall;
1551}
1552
1553/*
1554 * OK, we're invoking a handler
1555 */
1556static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
1557{
1558	sigset_t *oldset = sigmask_to_save();
1559	int usig = ksig->sig;
1560	int ret;
1561
1562	rseq_signal_deliver(ksig, regs);
1563
1564	/*
1565	 * Set up the stack frame
1566	 */
1567	if (is_compat_task()) {
1568		if (ksig->ka.sa.sa_flags & SA_SIGINFO)
1569			ret = compat_setup_rt_frame(usig, ksig, oldset, regs);
1570		else
1571			ret = compat_setup_frame(usig, ksig, oldset, regs);
1572	} else {
1573		ret = setup_rt_frame(usig, ksig, oldset, regs);
1574	}
1575
1576	/*
1577	 * Check that the resulting registers are actually sane.
1578	 */
1579	ret |= !valid_user_regs(&regs->user_regs, current);
1580
1581	/* Step into the signal handler if we are stepping */
1582	signal_setup_done(ret, ksig, test_thread_flag(TIF_SINGLESTEP));
1583}
1584
1585/*
1586 * Note that 'init' is a special process: it doesn't get signals it doesn't
1587 * want to handle. Thus you cannot kill init even with a SIGKILL even by
1588 * mistake.
1589 *
1590 * Note that we go through the signals twice: once to check the signals that
1591 * the kernel can handle, and then we build all the user-level signal handling
1592 * stack-frames in one go after that.
1593 */
1594void arch_do_signal_or_restart(struct pt_regs *regs)
1595{
1596	unsigned long continue_addr = 0, restart_addr = 0;
1597	int retval = 0;
1598	struct ksignal ksig;
1599	bool syscall = in_syscall(regs);
1600
1601	/*
1602	 * If we were from a system call, check for system call restarting...
1603	 */
1604	if (syscall) {
1605		continue_addr = regs->pc;
1606		restart_addr = continue_addr - (compat_thumb_mode(regs) ? 2 : 4);
1607		retval = regs->regs[0];
1608
1609		/*
1610		 * Avoid additional syscall restarting via ret_to_user.
1611		 */
1612		forget_syscall(regs);
1613
1614		/*
1615		 * Prepare for system call restart. We do this here so that a
1616		 * debugger will see the already changed PC.
1617		 */
1618		switch (retval) {
1619		case -ERESTARTNOHAND:
1620		case -ERESTARTSYS:
1621		case -ERESTARTNOINTR:
1622		case -ERESTART_RESTARTBLOCK:
1623			regs->regs[0] = regs->orig_x0;
1624			regs->pc = restart_addr;
1625			break;
1626		}
1627	}
1628
1629	/*
1630	 * Get the signal to deliver. When running under ptrace, at this point
1631	 * the debugger may change all of our registers.
1632	 */
1633	if (get_signal(&ksig)) {
1634		/*
1635		 * Depending on the signal settings, we may need to revert the
1636		 * decision to restart the system call, but skip this if a
1637		 * debugger has chosen to restart at a different PC.
1638		 */
1639		if (regs->pc == restart_addr &&
1640		    (retval == -ERESTARTNOHAND ||
1641		     retval == -ERESTART_RESTARTBLOCK ||
1642		     (retval == -ERESTARTSYS &&
1643		      !(ksig.ka.sa.sa_flags & SA_RESTART)))) {
1644			syscall_set_return_value(current, regs, -EINTR, 0);
1645			regs->pc = continue_addr;
1646		}
1647
1648		handle_signal(&ksig, regs);
1649		return;
1650	}
1651
1652	/*
1653	 * Handle restarting a different system call. As above, if a debugger
1654	 * has chosen to restart at a different PC, ignore the restart.
1655	 */
1656	if (syscall && regs->pc == restart_addr) {
1657		if (retval == -ERESTART_RESTARTBLOCK)
1658			setup_restart_syscall(regs);
1659		user_rewind_single_step(current);
1660	}
1661
1662	restore_saved_sigmask();
1663}
1664
1665unsigned long __ro_after_init signal_minsigstksz;
1666
1667/*
1668 * Determine the stack space required for guaranteed signal devliery.
1669 * This function is used to populate AT_MINSIGSTKSZ at process startup.
1670 * cpufeatures setup is assumed to be complete.
1671 */
1672void __init minsigstksz_setup(void)
1673{
1674	struct rt_sigframe_user_layout user;
1675
1676	init_user_layout(&user);
1677
1678	/*
1679	 * If this fails, SIGFRAME_MAXSZ needs to be enlarged.  It won't
1680	 * be big enough, but it's our best guess:
1681	 */
1682	if (WARN_ON(setup_sigframe_layout(&user, true)))
1683		return;
1684
1685	signal_minsigstksz = sigframe_size(&user) +
1686		round_up(sizeof(struct frame_record), 16) +
1687		16; /* max alignment padding */
1688}
1689
1690/*
1691 * Compile-time assertions for siginfo_t offsets. Check NSIG* as well, as
1692 * changes likely come with new fields that should be added below.
1693 */
1694static_assert(NSIGILL	== 11);
1695static_assert(NSIGFPE	== 15);
1696static_assert(NSIGSEGV	== 10);
1697static_assert(NSIGBUS	== 5);
1698static_assert(NSIGTRAP	== 6);
1699static_assert(NSIGCHLD	== 6);
1700static_assert(NSIGSYS	== 2);
1701static_assert(sizeof(siginfo_t) == 128);
1702static_assert(__alignof__(siginfo_t) == 8);
1703static_assert(offsetof(siginfo_t, si_signo)	== 0x00);
1704static_assert(offsetof(siginfo_t, si_errno)	== 0x04);
1705static_assert(offsetof(siginfo_t, si_code)	== 0x08);
1706static_assert(offsetof(siginfo_t, si_pid)	== 0x10);
1707static_assert(offsetof(siginfo_t, si_uid)	== 0x14);
1708static_assert(offsetof(siginfo_t, si_tid)	== 0x10);
1709static_assert(offsetof(siginfo_t, si_overrun)	== 0x14);
1710static_assert(offsetof(siginfo_t, si_status)	== 0x18);
1711static_assert(offsetof(siginfo_t, si_utime)	== 0x20);
1712static_assert(offsetof(siginfo_t, si_stime)	== 0x28);
1713static_assert(offsetof(siginfo_t, si_value)	== 0x18);
1714static_assert(offsetof(siginfo_t, si_int)	== 0x18);
1715static_assert(offsetof(siginfo_t, si_ptr)	== 0x18);
1716static_assert(offsetof(siginfo_t, si_addr)	== 0x10);
1717static_assert(offsetof(siginfo_t, si_addr_lsb)	== 0x18);
1718static_assert(offsetof(siginfo_t, si_lower)	== 0x20);
1719static_assert(offsetof(siginfo_t, si_upper)	== 0x28);
1720static_assert(offsetof(siginfo_t, si_pkey)	== 0x20);
1721static_assert(offsetof(siginfo_t, si_perf_data)	== 0x18);
1722static_assert(offsetof(siginfo_t, si_perf_type)	== 0x20);
1723static_assert(offsetof(siginfo_t, si_perf_flags) == 0x24);
1724static_assert(offsetof(siginfo_t, si_band)	== 0x10);
1725static_assert(offsetof(siginfo_t, si_fd)	== 0x18);
1726static_assert(offsetof(siginfo_t, si_call_addr)	== 0x10);
1727static_assert(offsetof(siginfo_t, si_syscall)	== 0x18);
1728static_assert(offsetof(siginfo_t, si_arch)	== 0x1c);