arch/x86/kernel/signal.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *  Copyright (C) 1991, 1992  Linus Torvalds
   4  *  Copyright (C) 2000, 2001, 2002 Andi Kleen SuSE Labs
   5  *
   6  *  1997-11-28  Modified for POSIX.1b signals by Richard Henderson
   7  *  2000-06-20  Pentium III FXSR, SSE support by Gareth Hughes
   8  *  2000-2002   x86-64 support by Andi Kleen
   9  */
  10
  11 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  12
  13 #include <linux/sched.h>
  14 #include <linux/sched/task_stack.h>
  15 #include <linux/mm.h>
  16 #include <linux/smp.h>
  17 #include <linux/kernel.h>
  18 #include <linux/errno.h>
  19 #include <linux/wait.h>
  20 #include <linux/tracehook.h>
  21 #include <linux/unistd.h>
  22 #include <linux/stddef.h>
  23 #include <linux/personality.h>
  24 #include <linux/uaccess.h>
  25 #include <linux/user-return-notifier.h>
  26 #include <linux/uprobes.h>
  27 #include <linux/context_tracking.h>
  28
  29 #include <asm/processor.h>
  30 #include <asm/ucontext.h>
  31 #include <asm/fpu/internal.h>
  32 #include <asm/fpu/signal.h>
  33 #include <asm/vdso.h>
  34 #include <asm/mce.h>
  35 #include <asm/sighandling.h>
  36 #include <asm/vm86.h>
  37
  38 #ifdef CONFIG_X86_64
  39 #include <asm/proto.h>
  40 #include <asm/ia32_unistd.h>
  41 #endif /* CONFIG_X86_64 */
  42
  43 #include <asm/syscall.h>
  44 #include <asm/syscalls.h>
  45
  46 #include <asm/sigframe.h>
  47 #include <asm/signal.h>
  48
  49 #define COPY(x)                 do {                    \
  50         get_user_ex(regs->x, &sc->x);                   \
  51 } while (0)
  52
  53 #define GET_SEG(seg)            ({                      \
  54         unsigned short tmp;                             \
  55         get_user_ex(tmp, &sc->seg);                     \
  56         tmp;                                            \
  57 })
  58
  59 #define COPY_SEG(seg)           do {                    \
  60         regs->seg = GET_SEG(seg);                       \
  61 } while (0)
  62
  63 #define COPY_SEG_CPL3(seg)      do {                    \
  64         regs->seg = GET_SEG(seg) | 3;                   \
  65 } while (0)
  66
  67 #ifdef CONFIG_X86_64
  68 /*
  69  * If regs->ss will cause an IRET fault, change it.  Otherwise leave it
  70  * alone.  Using this generally makes no sense unless
  71  * user_64bit_mode(regs) would return true.
  72  */
  73 static void force_valid_ss(struct pt_regs *regs)
  74 {
  75         u32 ar;
  76         asm volatile ("lar %[old_ss], %[ar]\n\t"
  77                       "jz 1f\n\t"               /* If invalid: */
  78                       "xorl %[ar], %[ar]\n\t"   /* set ar = 0 */
  79                       "1:"
  80                       : [ar] "=r" (ar)
  81                       : [old_ss] "rm" ((u16)regs->ss));
  82
  83         /*
  84          * For a valid 64-bit user context, we need DPL 3, type
  85          * read-write data or read-write exp-down data, and S and P
  86          * set.  We can't use VERW because VERW doesn't check the
  87          * P bit.
  88          */
  89         ar &= AR_DPL_MASK | AR_S | AR_P | AR_TYPE_MASK;
  90         if (ar != (AR_DPL3 | AR_S | AR_P | AR_TYPE_RWDATA) &&
  91             ar != (AR_DPL3 | AR_S | AR_P | AR_TYPE_RWDATA_EXPDOWN))
  92                 regs->ss = __USER_DS;
  93 }
  94 #endif
  95
  96 static int restore_sigcontext(struct pt_regs *regs,
  97                               struct sigcontext __user *sc,
  98                               unsigned long uc_flags)
  99 {
 100         unsigned long buf_val;
 101         void __user *buf;
 102         unsigned int tmpflags;
 103         unsigned int err = 0;
 104
 105         /* Always make any pending restarted system calls return -EINTR */
 106         current->restart_block.fn = do_no_restart_syscall;
 107
 108         get_user_try {
 109
 110 #ifdef CONFIG_X86_32
 111                 set_user_gs(regs, GET_SEG(gs));
 112                 COPY_SEG(fs);
 113                 COPY_SEG(es);
 114                 COPY_SEG(ds);
 115 #endif /* CONFIG_X86_32 */
 116
 117                 COPY(di); COPY(si); COPY(bp); COPY(sp); COPY(bx);
 118                 COPY(dx); COPY(cx); COPY(ip); COPY(ax);
 119
 120 #ifdef CONFIG_X86_64
 121                 COPY(r8);
 122                 COPY(r9);
 123                 COPY(r10);
 124                 COPY(r11);
 125                 COPY(r12);
 126                 COPY(r13);
 127                 COPY(r14);
 128                 COPY(r15);
 129 #endif /* CONFIG_X86_64 */
 130
 131                 COPY_SEG_CPL3(cs);
 132                 COPY_SEG_CPL3(ss);
 133
 134 #ifdef CONFIG_X86_64
 135                 /*
 136                  * Fix up SS if needed for the benefit of old DOSEMU and
 137                  * CRIU.
 138                  */
 139                 if (unlikely(!(uc_flags & UC_STRICT_RESTORE_SS) &&
 140                              user_64bit_mode(regs)))
 141                         force_valid_ss(regs);
 142 #endif
 143
 144                 get_user_ex(tmpflags, &sc->flags);
 145                 regs->flags = (regs->flags & ~FIX_EFLAGS) | (tmpflags & FIX_EFLAGS);
 146                 regs->orig_ax = -1;             /* disable syscall checks */
 147
 148                 get_user_ex(buf_val, &sc->fpstate);
 149                 buf = (void __user *)buf_val;
 150         } get_user_catch(err);
 151
 152         err |= fpu__restore_sig(buf, IS_ENABLED(CONFIG_X86_32));
 153
 154         force_iret();
 155
 156         return err;
 157 }
 158
 159 int setup_sigcontext(struct sigcontext __user *sc, void __user *fpstate,
 160                      struct pt_regs *regs, unsigned long mask)
 161 {
 162         int err = 0;
 163
 164         put_user_try {
 165
 166 #ifdef CONFIG_X86_32
 167                 put_user_ex(get_user_gs(regs), (unsigned int __user *)&sc->gs);
 168                 put_user_ex(regs->fs, (unsigned int __user *)&sc->fs);
 169                 put_user_ex(regs->es, (unsigned int __user *)&sc->es);
 170                 put_user_ex(regs->ds, (unsigned int __user *)&sc->ds);
 171 #endif /* CONFIG_X86_32 */
 172
 173                 put_user_ex(regs->di, &sc->di);
 174                 put_user_ex(regs->si, &sc->si);
 175                 put_user_ex(regs->bp, &sc->bp);
 176                 put_user_ex(regs->sp, &sc->sp);
 177                 put_user_ex(regs->bx, &sc->bx);
 178                 put_user_ex(regs->dx, &sc->dx);
 179                 put_user_ex(regs->cx, &sc->cx);
 180                 put_user_ex(regs->ax, &sc->ax);
 181 #ifdef CONFIG_X86_64
 182                 put_user_ex(regs->r8, &sc->r8);
 183                 put_user_ex(regs->r9, &sc->r9);
 184                 put_user_ex(regs->r10, &sc->r10);
 185                 put_user_ex(regs->r11, &sc->r11);
 186                 put_user_ex(regs->r12, &sc->r12);
 187                 put_user_ex(regs->r13, &sc->r13);
 188                 put_user_ex(regs->r14, &sc->r14);
 189                 put_user_ex(regs->r15, &sc->r15);
 190 #endif /* CONFIG_X86_64 */
 191
 192                 put_user_ex(current->thread.trap_nr, &sc->trapno);
 193                 put_user_ex(current->thread.error_code, &sc->err);
 194                 put_user_ex(regs->ip, &sc->ip);
 195 #ifdef CONFIG_X86_32
 196                 put_user_ex(regs->cs, (unsigned int __user *)&sc->cs);
 197                 put_user_ex(regs->flags, &sc->flags);
 198                 put_user_ex(regs->sp, &sc->sp_at_signal);
 199                 put_user_ex(regs->ss, (unsigned int __user *)&sc->ss);
 200 #else /* !CONFIG_X86_32 */
 201                 put_user_ex(regs->flags, &sc->flags);
 202                 put_user_ex(regs->cs, &sc->cs);
 203                 put_user_ex(0, &sc->gs);
 204                 put_user_ex(0, &sc->fs);
 205                 put_user_ex(regs->ss, &sc->ss);
 206 #endif /* CONFIG_X86_32 */
 207
 208                 put_user_ex(fpstate, &sc->fpstate);
 209
 210                 /* non-iBCS2 extensions.. */
 211                 put_user_ex(mask, &sc->oldmask);
 212                 put_user_ex(current->thread.cr2, &sc->cr2);
 213         } put_user_catch(err);
 214
 215         return err;
 216 }
 217
 218 /*
 219  * Set up a signal frame.
 220  */
 221
 222 /*
 223  * Determine which stack to use..
 224  */
 225 static unsigned long align_sigframe(unsigned long sp)
 226 {
 227 #ifdef CONFIG_X86_32
 228         /*
 229          * Align the stack pointer according to the i386 ABI,
 230          * i.e. so that on function entry ((sp + 4) & 15) == 0.
 231          */
 232         sp = ((sp + 4) & -16ul) - 4;
 233 #else /* !CONFIG_X86_32 */
 234         sp = round_down(sp, 16) - 8;
 235 #endif
 236         return sp;
 237 }
 238
 239 static void __user *
 240 get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size,
 241              void __user **fpstate)
 242 {
 243         /* Default to using normal stack */
 244         unsigned long math_size = 0;
 245         unsigned long sp = regs->sp;
 246         unsigned long buf_fx = 0;
 247         int onsigstack = on_sig_stack(sp);
 248         struct fpu *fpu = &current->thread.fpu;
 249
 250         /* redzone */
 251         if (IS_ENABLED(CONFIG_X86_64))
 252                 sp -= 128;
 253
 254         /* This is the X/Open sanctioned signal stack switching.  */
 255         if (ka->sa.sa_flags & SA_ONSTACK) {
 256                 if (sas_ss_flags(sp) == 0)
 257                         sp = current->sas_ss_sp + current->sas_ss_size;
 258         } else if (IS_ENABLED(CONFIG_X86_32) &&
 259                    !onsigstack &&
 260                    regs->ss != __USER_DS &&
 261                    !(ka->sa.sa_flags & SA_RESTORER) &&
 262                    ka->sa.sa_restorer) {
 263                 /* This is the legacy signal stack switching. */
 264                 sp = (unsigned long) ka->sa.sa_restorer;
 265         }
 266
 267         if (fpu->initialized) {
 268                 sp = fpu__alloc_mathframe(sp, IS_ENABLED(CONFIG_X86_32),
 269                                           &buf_fx, &math_size);
 270                 *fpstate = (void __user *)sp;
 271         }
 272
 273         sp = align_sigframe(sp - frame_size);
 274
 275         /*
 276          * If we are on the alternate signal stack and would overflow it, don't.
 277          * Return an always-bogus address instead so we will die with SIGSEGV.
 278          */
 279         if (onsigstack && !likely(on_sig_stack(sp)))
 280                 return (void __user *)-1L;
 281
 282         /* save i387 and extended state */
 283         if (fpu->initialized &&
 284             copy_fpstate_to_sigframe(*fpstate, (void __user *)buf_fx, math_size) < 0)
 285                 return (void __user *)-1L;
 286
 287         return (void __user *)sp;
 288 }
 289
 290 #ifdef CONFIG_X86_32
 291 static const struct {
 292         u16 poplmovl;
 293         u32 val;
 294         u16 int80;
 295 } __attribute__((packed)) retcode = {
 296         0xb858,         /* popl %eax; movl $..., %eax */
 297         __NR_sigreturn,
 298         0x80cd,         /* int $0x80 */
 299 };
 300
 301 static const struct {
 302         u8  movl;
 303         u32 val;
 304         u16 int80;
 305         u8  pad;
 306 } __attribute__((packed)) rt_retcode = {
 307         0xb8,           /* movl $..., %eax */
 308         __NR_rt_sigreturn,
 309         0x80cd,         /* int $0x80 */
 310         0
 311 };
 312
 313 static int
 314 __setup_frame(int sig, struct ksignal *ksig, sigset_t *set,
 315               struct pt_regs *regs)
 316 {
 317         struct sigframe __user *frame;
 318         void __user *restorer;
 319         int err = 0;
 320         void __user *fpstate = NULL;
 321
 322         frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fpstate);
 323
 324         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
 325                 return -EFAULT;
 326
 327         if (__put_user(sig, &frame->sig))
 328                 return -EFAULT;
 329
 330         if (setup_sigcontext(&frame->sc, fpstate, regs, set->sig[0]))
 331                 return -EFAULT;
 332
 333         if (_NSIG_WORDS > 1) {
 334                 if (__copy_to_user(&frame->extramask, &set->sig[1],
 335                                    sizeof(frame->extramask)))
 336                         return -EFAULT;
 337         }
 338
 339         if (current->mm->context.vdso)
 340                 restorer = current->mm->context.vdso +
 341                         vdso_image_32.sym___kernel_sigreturn;
 342         else
 343                 restorer = &frame->retcode;
 344         if (ksig->ka.sa.sa_flags & SA_RESTORER)
 345                 restorer = ksig->ka.sa.sa_restorer;
 346
 347         /* Set up to return from userspace.  */
 348         err |= __put_user(restorer, &frame->pretcode);
 349
 350         /*
 351          * This is popl %eax ; movl $__NR_sigreturn, %eax ; int $0x80
 352          *
 353          * WE DO NOT USE IT ANY MORE! It's only left here for historical
 354          * reasons and because gdb uses it as a signature to notice
 355          * signal handler stack frames.
 356          */
 357         err |= __put_user(*((u64 *)&retcode), (u64 *)frame->retcode);
 358
 359         if (err)
 360                 return -EFAULT;
 361
 362         /* Set up registers for signal handler */
 363         regs->sp = (unsigned long)frame;
 364         regs->ip = (unsigned long)ksig->ka.sa.sa_handler;
 365         regs->ax = (unsigned long)sig;
 366         regs->dx = 0;
 367         regs->cx = 0;
 368
 369         regs->ds = __USER_DS;
 370         regs->es = __USER_DS;
 371         regs->ss = __USER_DS;
 372         regs->cs = __USER_CS;
 373
 374         return 0;
 375 }
 376
 377 static int __setup_rt_frame(int sig, struct ksignal *ksig,
 378                             sigset_t *set, struct pt_regs *regs)
 379 {
 380         struct rt_sigframe __user *frame;
 381         void __user *restorer;
 382         int err = 0;
 383         void __user *fpstate = NULL;
 384
 385         frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fpstate);
 386
 387         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
 388                 return -EFAULT;
 389
 390         put_user_try {
 391                 put_user_ex(sig, &frame->sig);
 392                 put_user_ex(&frame->info, &frame->pinfo);
 393                 put_user_ex(&frame->uc, &frame->puc);
 394
 395                 /* Create the ucontext.  */
 396                 if (boot_cpu_has(X86_FEATURE_XSAVE))
 397                         put_user_ex(UC_FP_XSTATE, &frame->uc.uc_flags);
 398                 else
 399                         put_user_ex(0, &frame->uc.uc_flags);
 400                 put_user_ex(0, &frame->uc.uc_link);
 401                 save_altstack_ex(&frame->uc.uc_stack, regs->sp);
 402
 403                 /* Set up to return from userspace.  */
 404                 restorer = current->mm->context.vdso +
 405                         vdso_image_32.sym___kernel_rt_sigreturn;
 406                 if (ksig->ka.sa.sa_flags & SA_RESTORER)
 407                         restorer = ksig->ka.sa.sa_restorer;
 408                 put_user_ex(restorer, &frame->pretcode);
 409
 410                 /*
 411                  * This is movl $__NR_rt_sigreturn, %ax ; int $0x80
 412                  *
 413                  * WE DO NOT USE IT ANY MORE! It's only left here for historical
 414                  * reasons and because gdb uses it as a signature to notice
 415                  * signal handler stack frames.
 416                  */
 417                 put_user_ex(*((u64 *)&rt_retcode), (u64 *)frame->retcode);
 418         } put_user_catch(err);
 419
 420         err |= copy_siginfo_to_user(&frame->info, &ksig->info);
 421         err |= setup_sigcontext(&frame->uc.uc_mcontext, fpstate,
 422                                 regs, set->sig[0]);
 423         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 424
 425         if (err)
 426                 return -EFAULT;
 427
 428         /* Set up registers for signal handler */
 429         regs->sp = (unsigned long)frame;
 430         regs->ip = (unsigned long)ksig->ka.sa.sa_handler;
 431         regs->ax = (unsigned long)sig;
 432         regs->dx = (unsigned long)&frame->info;
 433         regs->cx = (unsigned long)&frame->uc;
 434
 435         regs->ds = __USER_DS;
 436         regs->es = __USER_DS;
 437         regs->ss = __USER_DS;
 438         regs->cs = __USER_CS;
 439
 440         return 0;
 441 }
 442 #else /* !CONFIG_X86_32 */
 443 static unsigned long frame_uc_flags(struct pt_regs *regs)
 444 {
 445         unsigned long flags;
 446
 447         if (boot_cpu_has(X86_FEATURE_XSAVE))
 448                 flags = UC_FP_XSTATE | UC_SIGCONTEXT_SS;
 449         else
 450                 flags = UC_SIGCONTEXT_SS;
 451
 452         if (likely(user_64bit_mode(regs)))
 453                 flags |= UC_STRICT_RESTORE_SS;
 454
 455         return flags;
 456 }
 457
 458 static int __setup_rt_frame(int sig, struct ksignal *ksig,
 459                             sigset_t *set, struct pt_regs *regs)
 460 {
 461         struct rt_sigframe __user *frame;
 462         void __user *fp = NULL;
 463         int err = 0;
 464
 465         frame = get_sigframe(&ksig->ka, regs, sizeof(struct rt_sigframe), &fp);
 466
 467         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
 468                 return -EFAULT;
 469
 470         if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
 471                 if (copy_siginfo_to_user(&frame->info, &ksig->info))
 472                         return -EFAULT;
 473         }
 474
 475         put_user_try {
 476                 /* Create the ucontext.  */
 477                 put_user_ex(frame_uc_flags(regs), &frame->uc.uc_flags);
 478                 put_user_ex(0, &frame->uc.uc_link);
 479                 save_altstack_ex(&frame->uc.uc_stack, regs->sp);
 480
 481                 /* Set up to return from userspace.  If provided, use a stub
 482                    already in userspace.  */
 483                 /* x86-64 should always use SA_RESTORER. */
 484                 if (ksig->ka.sa.sa_flags & SA_RESTORER) {
 485                         put_user_ex(ksig->ka.sa.sa_restorer, &frame->pretcode);
 486                 } else {
 487                         /* could use a vstub here */
 488                         err |= -EFAULT;
 489                 }
 490         } put_user_catch(err);
 491
 492         err |= setup_sigcontext(&frame->uc.uc_mcontext, fp, regs, set->sig[0]);
 493         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 494
 495         if (err)
 496                 return -EFAULT;
 497
 498         /* Set up registers for signal handler */
 499         regs->di = sig;
 500         /* In case the signal handler was declared without prototypes */
 501         regs->ax = 0;
 502
 503         /* This also works for non SA_SIGINFO handlers because they expect the
 504            next argument after the signal number on the stack. */
 505         regs->si = (unsigned long)&frame->info;
 506         regs->dx = (unsigned long)&frame->uc;
 507         regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
 508
 509         regs->sp = (unsigned long)frame;
 510
 511         /*
 512          * Set up the CS and SS registers to run signal handlers in
 513          * 64-bit mode, even if the handler happens to be interrupting
 514          * 32-bit or 16-bit code.
 515          *
 516          * SS is subtle.  In 64-bit mode, we don't need any particular
 517          * SS descriptor, but we do need SS to be valid.  It's possible
 518          * that the old SS is entirely bogus -- this can happen if the
 519          * signal we're trying to deliver is #GP or #SS caused by a bad
 520          * SS value.  We also have a compatbility issue here: DOSEMU
 521          * relies on the contents of the SS register indicating the
 522          * SS value at the time of the signal, even though that code in
 523          * DOSEMU predates sigreturn's ability to restore SS.  (DOSEMU
 524          * avoids relying on sigreturn to restore SS; instead it uses
 525          * a trampoline.)  So we do our best: if the old SS was valid,
 526          * we keep it.  Otherwise we replace it.
 527          */
 528         regs->cs = __USER_CS;
 529
 530         if (unlikely(regs->ss != __USER_DS))
 531                 force_valid_ss(regs);
 532
 533         return 0;
 534 }
 535 #endif /* CONFIG_X86_32 */
 536
 537 static int x32_setup_rt_frame(struct ksignal *ksig,
 538                               compat_sigset_t *set,
 539                               struct pt_regs *regs)
 540 {
 541 #ifdef CONFIG_X86_X32_ABI
 542         struct rt_sigframe_x32 __user *frame;
 543         void __user *restorer;
 544         int err = 0;
 545         void __user *fpstate = NULL;
 546
 547         frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fpstate);
 548
 549         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
 550                 return -EFAULT;
 551
 552         if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
 553                 if (__copy_siginfo_to_user32(&frame->info, &ksig->info, true))
 554                         return -EFAULT;
 555         }
 556
 557         put_user_try {
 558                 /* Create the ucontext.  */
 559                 put_user_ex(frame_uc_flags(regs), &frame->uc.uc_flags);
 560                 put_user_ex(0, &frame->uc.uc_link);
 561                 compat_save_altstack_ex(&frame->uc.uc_stack, regs->sp);
 562                 put_user_ex(0, &frame->uc.uc__pad0);
 563
 564                 if (ksig->ka.sa.sa_flags & SA_RESTORER) {
 565                         restorer = ksig->ka.sa.sa_restorer;
 566                 } else {
 567                         /* could use a vstub here */
 568                         restorer = NULL;
 569                         err |= -EFAULT;
 570                 }
 571                 put_user_ex(restorer, &frame->pretcode);
 572         } put_user_catch(err);
 573
 574         err |= setup_sigcontext(&frame->uc.uc_mcontext, fpstate,
 575                                 regs, set->sig[0]);
 576         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 577
 578         if (err)
 579                 return -EFAULT;
 580
 581         /* Set up registers for signal handler */
 582         regs->sp = (unsigned long) frame;
 583         regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
 584
 585         /* We use the x32 calling convention here... */
 586         regs->di = ksig->sig;
 587         regs->si = (unsigned long) &frame->info;
 588         regs->dx = (unsigned long) &frame->uc;
 589
 590         loadsegment(ds, __USER_DS);
 591         loadsegment(es, __USER_DS);
 592
 593         regs->cs = __USER_CS;
 594         regs->ss = __USER_DS;
 595 #endif  /* CONFIG_X86_X32_ABI */
 596
 597         return 0;
 598 }
 599
 600 /*
 601  * Do a signal return; undo the signal stack.
 602  */
 603 #ifdef CONFIG_X86_32
 604 asmlinkage unsigned long sys_sigreturn(void)
 605 {
 606         struct pt_regs *regs = current_pt_regs();
 607         struct sigframe __user *frame;
 608         sigset_t set;
 609
 610         frame = (struct sigframe __user *)(regs->sp - 8);
 611
 612         if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
 613                 goto badframe;
 614         if (__get_user(set.sig[0], &frame->sc.oldmask) || (_NSIG_WORDS > 1
 615                 && __copy_from_user(&set.sig[1], &frame->extramask,
 616                                     sizeof(frame->extramask))))
 617                 goto badframe;
 618
 619         set_current_blocked(&set);
 620
 621         /*
 622          * x86_32 has no uc_flags bits relevant to restore_sigcontext.
 623          * Save a few cycles by skipping the __get_user.
 624          */
 625         if (restore_sigcontext(regs, &frame->sc, 0))
 626                 goto badframe;
 627         return regs->ax;
 628
 629 badframe:
 630         signal_fault(regs, frame, "sigreturn");
 631
 632         return 0;
 633 }
 634 #endif /* CONFIG_X86_32 */
 635
 636 asmlinkage long sys_rt_sigreturn(void)
 637 {
 638         struct pt_regs *regs = current_pt_regs();
 639         struct rt_sigframe __user *frame;
 640         sigset_t set;
 641         unsigned long uc_flags;
 642
 643         frame = (struct rt_sigframe __user *)(regs->sp - sizeof(long));
 644         if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
 645                 goto badframe;
 646         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
 647                 goto badframe;
 648         if (__get_user(uc_flags, &frame->uc.uc_flags))
 649                 goto badframe;
 650
 651         set_current_blocked(&set);
 652
 653         if (restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags))
 654                 goto badframe;
 655
 656         if (restore_altstack(&frame->uc.uc_stack))
 657                 goto badframe;
 658
 659         return regs->ax;
 660
 661 badframe:
 662         signal_fault(regs, frame, "rt_sigreturn");
 663         return 0;
 664 }
 665
 666 static inline int is_ia32_compat_frame(struct ksignal *ksig)
 667 {
 668         return IS_ENABLED(CONFIG_IA32_EMULATION) &&
 669                 ksig->ka.sa.sa_flags & SA_IA32_ABI;
 670 }
 671
 672 static inline int is_ia32_frame(struct ksignal *ksig)
 673 {
 674         return IS_ENABLED(CONFIG_X86_32) || is_ia32_compat_frame(ksig);
 675 }
 676
 677 static inline int is_x32_frame(struct ksignal *ksig)
 678 {
 679         return IS_ENABLED(CONFIG_X86_X32_ABI) &&
 680                 ksig->ka.sa.sa_flags & SA_X32_ABI;
 681 }
 682
 683 static int
 684 setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs)
 685 {
 686         int usig = ksig->sig;
 687         sigset_t *set = sigmask_to_save();
 688         compat_sigset_t *cset = (compat_sigset_t *) set;
 689
 690         /* Set up the stack frame */
 691         if (is_ia32_frame(ksig)) {
 692                 if (ksig->ka.sa.sa_flags & SA_SIGINFO)
 693                         return ia32_setup_rt_frame(usig, ksig, cset, regs);
 694                 else
 695                         return ia32_setup_frame(usig, ksig, cset, regs);
 696         } else if (is_x32_frame(ksig)) {
 697                 return x32_setup_rt_frame(ksig, cset, regs);
 698         } else {
 699                 return __setup_rt_frame(ksig->sig, ksig, set, regs);
 700         }
 701 }
 702
 703 static void
 704 handle_signal(struct ksignal *ksig, struct pt_regs *regs)
 705 {
 706         bool stepping, failed;
 707         struct fpu *fpu = &current->thread.fpu;
 708
 709         if (v8086_mode(regs))
 710                 save_v86_state((struct kernel_vm86_regs *) regs, VM86_SIGNAL);
 711
 712         /* Are we from a system call? */
 713         if (syscall_get_nr(current, regs) >= 0) {
 714                 /* If so, check system call restarting.. */
 715                 switch (syscall_get_error(current, regs)) {
 716                 case -ERESTART_RESTARTBLOCK:
 717                 case -ERESTARTNOHAND:
 718                         regs->ax = -EINTR;
 719                         break;
 720
 721                 case -ERESTARTSYS:
 722                         if (!(ksig->ka.sa.sa_flags & SA_RESTART)) {
 723                                 regs->ax = -EINTR;
 724                                 break;
 725                         }
 726                 /* fallthrough */
 727                 case -ERESTARTNOINTR:
 728                         regs->ax = regs->orig_ax;
 729                         regs->ip -= 2;
 730                         break;
 731                 }
 732         }
 733
 734         /*
 735          * If TF is set due to a debugger (TIF_FORCED_TF), clear TF now
 736          * so that register information in the sigcontext is correct and
 737          * then notify the tracer before entering the signal handler.
 738          */
 739         stepping = test_thread_flag(TIF_SINGLESTEP);
 740         if (stepping)
 741                 user_disable_single_step(current);
 742
 743         failed = (setup_rt_frame(ksig, regs) < 0);
 744         if (!failed) {
 745                 /*
 746                  * Clear the direction flag as per the ABI for function entry.
 747                  *
 748                  * Clear RF when entering the signal handler, because
 749                  * it might disable possible debug exception from the
 750                  * signal handler.
 751                  *
 752                  * Clear TF for the case when it wasn't set by debugger to
 753                  * avoid the recursive send_sigtrap() in SIGTRAP handler.
 754                  */
 755                 regs->flags &= ~(X86_EFLAGS_DF|X86_EFLAGS_RF|X86_EFLAGS_TF);
 756                 /*
 757                  * Ensure the signal handler starts with the new fpu state.
 758                  */
 759                 if (fpu->initialized)
 760                         fpu__clear(fpu);
 761         }
 762         signal_setup_done(failed, ksig, stepping);
 763 }
 764
 765 static inline unsigned long get_nr_restart_syscall(const struct pt_regs *regs)
 766 {
 767         /*
 768          * This function is fundamentally broken as currently
 769          * implemented.
 770          *
 771          * The idea is that we want to trigger a call to the
 772          * restart_block() syscall and that we want in_ia32_syscall(),
 773          * in_x32_syscall(), etc. to match whatever they were in the
 774          * syscall being restarted.  We assume that the syscall
 775          * instruction at (regs->ip - 2) matches whatever syscall
 776          * instruction we used to enter in the first place.
 777          *
 778          * The problem is that we can get here when ptrace pokes
 779          * syscall-like values into regs even if we're not in a syscall
 780          * at all.
 781          *
 782          * For now, we maintain historical behavior and guess based on
 783          * stored state.  We could do better by saving the actual
 784          * syscall arch in restart_block or (with caveats on x32) by
 785          * checking if regs->ip points to 'int $0x80'.  The current
 786          * behavior is incorrect if a tracer has a different bitness
 787          * than the tracee.
 788          */
 789 #ifdef CONFIG_IA32_EMULATION
 790         if (current_thread_info()->status & (TS_COMPAT|TS_I386_REGS_POKED))
 791                 return __NR_ia32_restart_syscall;
 792 #endif
 793 #ifdef CONFIG_X86_X32_ABI
 794         return __NR_restart_syscall | (regs->orig_ax & __X32_SYSCALL_BIT);
 795 #else
 796         return __NR_restart_syscall;
 797 #endif
 798 }
 799
 800 /*
 801  * Note that 'init' is a special process: it doesn't get signals it doesn't
 802  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 803  * mistake.
 804  */
 805 void do_signal(struct pt_regs *regs)
 806 {
 807         struct ksignal ksig;
 808
 809         if (get_signal(&ksig)) {
 810                 /* Whee! Actually deliver the signal.  */
 811                 handle_signal(&ksig, regs);
 812                 return;
 813         }
 814
 815         /* Did we come from a system call? */
 816         if (syscall_get_nr(current, regs) >= 0) {
 817                 /* Restart the system call - no handlers present */
 818                 switch (syscall_get_error(current, regs)) {
 819                 case -ERESTARTNOHAND:
 820                 case -ERESTARTSYS:
 821                 case -ERESTARTNOINTR:
 822                         regs->ax = regs->orig_ax;
 823                         regs->ip -= 2;
 824                         break;
 825
 826                 case -ERESTART_RESTARTBLOCK:
 827                         regs->ax = get_nr_restart_syscall(regs);
 828                         regs->ip -= 2;
 829                         break;
 830                 }
 831         }
 832
 833         /*
 834          * If there's no signal to deliver, we just put the saved sigmask
 835          * back.
 836          */
 837         restore_saved_sigmask();
 838 }
 839
 840 void signal_fault(struct pt_regs *regs, void __user *frame, char *where)
 841 {
 842         struct task_struct *me = current;
 843
 844         if (show_unhandled_signals && printk_ratelimit()) {
 845                 printk("%s"
 846                        "%s[%d] bad frame in %s frame:%p ip:%lx sp:%lx orax:%lx",
 847                        task_pid_nr(current) > 1 ? KERN_INFO : KERN_EMERG,
 848                        me->comm, me->pid, where, frame,
 849                        regs->ip, regs->sp, regs->orig_ax);
 850                 print_vma_addr(KERN_CONT " in ", regs->ip);
 851                 pr_cont("\n");
 852         }
 853
 854         force_sig(SIGSEGV, me);
 855 }
 856
 857 #ifdef CONFIG_X86_X32_ABI
 858 asmlinkage long sys32_x32_rt_sigreturn(void)
 859 {
 860         struct pt_regs *regs = current_pt_regs();
 861         struct rt_sigframe_x32 __user *frame;
 862         sigset_t set;
 863         unsigned long uc_flags;
 864
 865         frame = (struct rt_sigframe_x32 __user *)(regs->sp - 8);
 866
 867         if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
 868                 goto badframe;
 869         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
 870                 goto badframe;
 871         if (__get_user(uc_flags, &frame->uc.uc_flags))
 872                 goto badframe;
 873
 874         set_current_blocked(&set);
 875
 876         if (restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags))
 877                 goto badframe;
 878
 879         if (compat_restore_altstack(&frame->uc.uc_stack))
 880                 goto badframe;
 881
 882         return regs->ax;
 883
 884 badframe:
 885         signal_fault(regs, frame, "x32 rt_sigreturn");
 886         return 0;
 887 }
 888 #endif