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 #include <linux/syscalls.h>
  29
  30 #include <asm/processor.h>
  31 #include <asm/ucontext.h>
  32 #include <asm/fpu/internal.h>
  33 #include <asm/fpu/signal.h>
  34 #include <asm/vdso.h>
  35 #include <asm/mce.h>
  36 #include <asm/sighandling.h>
  37 #include <asm/vm86.h>
  38
  39 #ifdef CONFIG_X86_64
  40 #include <asm/proto.h>
  41 #include <asm/ia32_unistd.h>
  42 #endif /* CONFIG_X86_64 */
  43
  44 #include <asm/syscall.h>
  45 #include <asm/syscalls.h>
  46
  47 #include <asm/sigframe.h>
  48 #include <asm/signal.h>
  49
  50 #ifdef CONFIG_X86_64
  51 /*
  52  * If regs->ss will cause an IRET fault, change it.  Otherwise leave it
  53  * alone.  Using this generally makes no sense unless
  54  * user_64bit_mode(regs) would return true.
  55  */
  56 static void force_valid_ss(struct pt_regs *regs)
  57 {
  58         u32 ar;
  59         asm volatile ("lar %[old_ss], %[ar]\n\t"
  60                       "jz 1f\n\t"               /* If invalid: */
  61                       "xorl %[ar], %[ar]\n\t"   /* set ar = 0 */
  62                       "1:"
  63                       : [ar] "=r" (ar)
  64                       : [old_ss] "rm" ((u16)regs->ss));
  65
  66         /*
  67          * For a valid 64-bit user context, we need DPL 3, type
  68          * read-write data or read-write exp-down data, and S and P
  69          * set.  We can't use VERW because VERW doesn't check the
  70          * P bit.
  71          */
  72         ar &= AR_DPL_MASK | AR_S | AR_P | AR_TYPE_MASK;
  73         if (ar != (AR_DPL3 | AR_S | AR_P | AR_TYPE_RWDATA) &&
  74             ar != (AR_DPL3 | AR_S | AR_P | AR_TYPE_RWDATA_EXPDOWN))
  75                 regs->ss = __USER_DS;
  76 }
  77 # define CONTEXT_COPY_SIZE      offsetof(struct sigcontext, reserved1)
  78 #else
  79 # define CONTEXT_COPY_SIZE      sizeof(struct sigcontext)
  80 #endif
  81
  82 static int restore_sigcontext(struct pt_regs *regs,
  83                               struct sigcontext __user *usc,
  84                               unsigned long uc_flags)
  85 {
  86         struct sigcontext sc;
  87
  88         /* Always make any pending restarted system calls return -EINTR */
  89         current->restart_block.fn = do_no_restart_syscall;
  90
  91         if (copy_from_user(&sc, usc, CONTEXT_COPY_SIZE))
  92                 return -EFAULT;
  93
  94 #ifdef CONFIG_X86_32
  95         set_user_gs(regs, sc.gs);
  96         regs->fs = sc.fs;
  97         regs->es = sc.es;
  98         regs->ds = sc.ds;
  99 #endif /* CONFIG_X86_32 */
 100
 101         regs->bx = sc.bx;
 102         regs->cx = sc.cx;
 103         regs->dx = sc.dx;
 104         regs->si = sc.si;
 105         regs->di = sc.di;
 106         regs->bp = sc.bp;
 107         regs->ax = sc.ax;
 108         regs->sp = sc.sp;
 109         regs->ip = sc.ip;
 110
 111 #ifdef CONFIG_X86_64
 112         regs->r8 = sc.r8;
 113         regs->r9 = sc.r9;
 114         regs->r10 = sc.r10;
 115         regs->r11 = sc.r11;
 116         regs->r12 = sc.r12;
 117         regs->r13 = sc.r13;
 118         regs->r14 = sc.r14;
 119         regs->r15 = sc.r15;
 120 #endif /* CONFIG_X86_64 */
 121
 122         /* Get CS/SS and force CPL3 */
 123         regs->cs = sc.cs | 0x03;
 124         regs->ss = sc.ss | 0x03;
 125
 126         regs->flags = (regs->flags & ~FIX_EFLAGS) | (sc.flags & FIX_EFLAGS);
 127         /* disable syscall checks */
 128         regs->orig_ax = -1;
 129
 130 #ifdef CONFIG_X86_64
 131         /*
 132          * Fix up SS if needed for the benefit of old DOSEMU and
 133          * CRIU.
 134          */
 135         if (unlikely(!(uc_flags & UC_STRICT_RESTORE_SS) && user_64bit_mode(regs)))
 136                 force_valid_ss(regs);
 137 #endif
 138
 139         return fpu__restore_sig((void __user *)sc.fpstate,
 140                                IS_ENABLED(CONFIG_X86_32));
 141 }
 142
 143 int setup_sigcontext(struct sigcontext __user *sc, void __user *fpstate,
 144                      struct pt_regs *regs, unsigned long mask)
 145 {
 146         int err = 0;
 147
 148         put_user_try {
 149
 150 #ifdef CONFIG_X86_32
 151                 put_user_ex(get_user_gs(regs), (unsigned int __user *)&sc->gs);
 152                 put_user_ex(regs->fs, (unsigned int __user *)&sc->fs);
 153                 put_user_ex(regs->es, (unsigned int __user *)&sc->es);
 154                 put_user_ex(regs->ds, (unsigned int __user *)&sc->ds);
 155 #endif /* CONFIG_X86_32 */
 156
 157                 put_user_ex(regs->di, &sc->di);
 158                 put_user_ex(regs->si, &sc->si);
 159                 put_user_ex(regs->bp, &sc->bp);
 160                 put_user_ex(regs->sp, &sc->sp);
 161                 put_user_ex(regs->bx, &sc->bx);
 162                 put_user_ex(regs->dx, &sc->dx);
 163                 put_user_ex(regs->cx, &sc->cx);
 164                 put_user_ex(regs->ax, &sc->ax);
 165 #ifdef CONFIG_X86_64
 166                 put_user_ex(regs->r8, &sc->r8);
 167                 put_user_ex(regs->r9, &sc->r9);
 168                 put_user_ex(regs->r10, &sc->r10);
 169                 put_user_ex(regs->r11, &sc->r11);
 170                 put_user_ex(regs->r12, &sc->r12);
 171                 put_user_ex(regs->r13, &sc->r13);
 172                 put_user_ex(regs->r14, &sc->r14);
 173                 put_user_ex(regs->r15, &sc->r15);
 174 #endif /* CONFIG_X86_64 */
 175
 176                 put_user_ex(current->thread.trap_nr, &sc->trapno);
 177                 put_user_ex(current->thread.error_code, &sc->err);
 178                 put_user_ex(regs->ip, &sc->ip);
 179 #ifdef CONFIG_X86_32
 180                 put_user_ex(regs->cs, (unsigned int __user *)&sc->cs);
 181                 put_user_ex(regs->flags, &sc->flags);
 182                 put_user_ex(regs->sp, &sc->sp_at_signal);
 183                 put_user_ex(regs->ss, (unsigned int __user *)&sc->ss);
 184 #else /* !CONFIG_X86_32 */
 185                 put_user_ex(regs->flags, &sc->flags);
 186                 put_user_ex(regs->cs, &sc->cs);
 187                 put_user_ex(0, &sc->gs);
 188                 put_user_ex(0, &sc->fs);
 189                 put_user_ex(regs->ss, &sc->ss);
 190 #endif /* CONFIG_X86_32 */
 191
 192                 put_user_ex(fpstate, (unsigned long __user *)&sc->fpstate);
 193
 194                 /* non-iBCS2 extensions.. */
 195                 put_user_ex(mask, &sc->oldmask);
 196                 put_user_ex(current->thread.cr2, &sc->cr2);
 197         } put_user_catch(err);
 198
 199         return err;
 200 }
 201
 202 /*
 203  * Set up a signal frame.
 204  */
 205
 206 /*
 207  * Determine which stack to use..
 208  */
 209 static unsigned long align_sigframe(unsigned long sp)
 210 {
 211 #ifdef CONFIG_X86_32
 212         /*
 213          * Align the stack pointer according to the i386 ABI,
 214          * i.e. so that on function entry ((sp + 4) & 15) == 0.
 215          */
 216         sp = ((sp + 4) & -16ul) - 4;
 217 #else /* !CONFIG_X86_32 */
 218         sp = round_down(sp, 16) - 8;
 219 #endif
 220         return sp;
 221 }
 222
 223 static void __user *
 224 get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size,
 225              void __user **fpstate)
 226 {
 227         /* Default to using normal stack */
 228         unsigned long math_size = 0;
 229         unsigned long sp = regs->sp;
 230         unsigned long buf_fx = 0;
 231         int onsigstack = on_sig_stack(sp);
 232         int ret;
 233
 234         /* redzone */
 235         if (IS_ENABLED(CONFIG_X86_64))
 236                 sp -= 128;
 237
 238         /* This is the X/Open sanctioned signal stack switching.  */
 239         if (ka->sa.sa_flags & SA_ONSTACK) {
 240                 if (sas_ss_flags(sp) == 0)
 241                         sp = current->sas_ss_sp + current->sas_ss_size;
 242         } else if (IS_ENABLED(CONFIG_X86_32) &&
 243                    !onsigstack &&
 244                    regs->ss != __USER_DS &&
 245                    !(ka->sa.sa_flags & SA_RESTORER) &&
 246                    ka->sa.sa_restorer) {
 247                 /* This is the legacy signal stack switching. */
 248                 sp = (unsigned long) ka->sa.sa_restorer;
 249         }
 250
 251         sp = fpu__alloc_mathframe(sp, IS_ENABLED(CONFIG_X86_32),
 252                                   &buf_fx, &math_size);
 253         *fpstate = (void __user *)sp;
 254
 255         sp = align_sigframe(sp - frame_size);
 256
 257         /*
 258          * If we are on the alternate signal stack and would overflow it, don't.
 259          * Return an always-bogus address instead so we will die with SIGSEGV.
 260          */
 261         if (onsigstack && !likely(on_sig_stack(sp)))
 262                 return (void __user *)-1L;
 263
 264         /* save i387 and extended state */
 265         ret = copy_fpstate_to_sigframe(*fpstate, (void __user *)buf_fx, math_size);
 266         if (ret < 0)
 267                 return (void __user *)-1L;
 268
 269         return (void __user *)sp;
 270 }
 271
 272 #ifdef CONFIG_X86_32
 273 static const struct {
 274         u16 poplmovl;
 275         u32 val;
 276         u16 int80;
 277 } __attribute__((packed)) retcode = {
 278         0xb858,         /* popl %eax; movl $..., %eax */
 279         __NR_sigreturn,
 280         0x80cd,         /* int $0x80 */
 281 };
 282
 283 static const struct {
 284         u8  movl;
 285         u32 val;
 286         u16 int80;
 287         u8  pad;
 288 } __attribute__((packed)) rt_retcode = {
 289         0xb8,           /* movl $..., %eax */
 290         __NR_rt_sigreturn,
 291         0x80cd,         /* int $0x80 */
 292         0
 293 };
 294
 295 static int
 296 __setup_frame(int sig, struct ksignal *ksig, sigset_t *set,
 297               struct pt_regs *regs)
 298 {
 299         struct sigframe __user *frame;
 300         void __user *restorer;
 301         int err = 0;
 302         void __user *fpstate = NULL;
 303
 304         frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fpstate);
 305
 306         if (!access_ok(frame, sizeof(*frame)))
 307                 return -EFAULT;
 308
 309         if (__put_user(sig, &frame->sig))
 310                 return -EFAULT;
 311
 312         if (setup_sigcontext(&frame->sc, fpstate, regs, set->sig[0]))
 313                 return -EFAULT;
 314
 315         if (__put_user(set->sig[1], &frame->extramask[0]))
 316                 return -EFAULT;
 317
 318         if (current->mm->context.vdso)
 319                 restorer = current->mm->context.vdso +
 320                         vdso_image_32.sym___kernel_sigreturn;
 321         else
 322                 restorer = &frame->retcode;
 323         if (ksig->ka.sa.sa_flags & SA_RESTORER)
 324                 restorer = ksig->ka.sa.sa_restorer;
 325
 326         /* Set up to return from userspace.  */
 327         err |= __put_user(restorer, &frame->pretcode);
 328
 329         /*
 330          * This is popl %eax ; movl $__NR_sigreturn, %eax ; int $0x80
 331          *
 332          * WE DO NOT USE IT ANY MORE! It's only left here for historical
 333          * reasons and because gdb uses it as a signature to notice
 334          * signal handler stack frames.
 335          */
 336         err |= __put_user(*((u64 *)&retcode), (u64 *)frame->retcode);
 337
 338         if (err)
 339                 return -EFAULT;
 340
 341         /* Set up registers for signal handler */
 342         regs->sp = (unsigned long)frame;
 343         regs->ip = (unsigned long)ksig->ka.sa.sa_handler;
 344         regs->ax = (unsigned long)sig;
 345         regs->dx = 0;
 346         regs->cx = 0;
 347
 348         regs->ds = __USER_DS;
 349         regs->es = __USER_DS;
 350         regs->ss = __USER_DS;
 351         regs->cs = __USER_CS;
 352
 353         return 0;
 354 }
 355
 356 static int __setup_rt_frame(int sig, struct ksignal *ksig,
 357                             sigset_t *set, struct pt_regs *regs)
 358 {
 359         struct rt_sigframe __user *frame;
 360         void __user *restorer;
 361         int err = 0;
 362         void __user *fpstate = NULL;
 363
 364         frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fpstate);
 365
 366         if (!access_ok(frame, sizeof(*frame)))
 367                 return -EFAULT;
 368
 369         put_user_try {
 370                 put_user_ex(sig, &frame->sig);
 371                 put_user_ex(&frame->info, &frame->pinfo);
 372                 put_user_ex(&frame->uc, &frame->puc);
 373
 374                 /* Create the ucontext.  */
 375                 if (static_cpu_has(X86_FEATURE_XSAVE))
 376                         put_user_ex(UC_FP_XSTATE, &frame->uc.uc_flags);
 377                 else
 378                         put_user_ex(0, &frame->uc.uc_flags);
 379                 put_user_ex(0, &frame->uc.uc_link);
 380                 save_altstack_ex(&frame->uc.uc_stack, regs->sp);
 381
 382                 /* Set up to return from userspace.  */
 383                 restorer = current->mm->context.vdso +
 384                         vdso_image_32.sym___kernel_rt_sigreturn;
 385                 if (ksig->ka.sa.sa_flags & SA_RESTORER)
 386                         restorer = ksig->ka.sa.sa_restorer;
 387                 put_user_ex(restorer, &frame->pretcode);
 388
 389                 /*
 390                  * This is movl $__NR_rt_sigreturn, %ax ; int $0x80
 391                  *
 392                  * WE DO NOT USE IT ANY MORE! It's only left here for historical
 393                  * reasons and because gdb uses it as a signature to notice
 394                  * signal handler stack frames.
 395                  */
 396                 put_user_ex(*((u64 *)&rt_retcode), (u64 *)frame->retcode);
 397         } put_user_catch(err);
 398
 399         err |= copy_siginfo_to_user(&frame->info, &ksig->info);
 400         err |= setup_sigcontext(&frame->uc.uc_mcontext, fpstate,
 401                                 regs, set->sig[0]);
 402         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 403
 404         if (err)
 405                 return -EFAULT;
 406
 407         /* Set up registers for signal handler */
 408         regs->sp = (unsigned long)frame;
 409         regs->ip = (unsigned long)ksig->ka.sa.sa_handler;
 410         regs->ax = (unsigned long)sig;
 411         regs->dx = (unsigned long)&frame->info;
 412         regs->cx = (unsigned long)&frame->uc;
 413
 414         regs->ds = __USER_DS;
 415         regs->es = __USER_DS;
 416         regs->ss = __USER_DS;
 417         regs->cs = __USER_CS;
 418
 419         return 0;
 420 }
 421 #else /* !CONFIG_X86_32 */
 422 static unsigned long frame_uc_flags(struct pt_regs *regs)
 423 {
 424         unsigned long flags;
 425
 426         if (boot_cpu_has(X86_FEATURE_XSAVE))
 427                 flags = UC_FP_XSTATE | UC_SIGCONTEXT_SS;
 428         else
 429                 flags = UC_SIGCONTEXT_SS;
 430
 431         if (likely(user_64bit_mode(regs)))
 432                 flags |= UC_STRICT_RESTORE_SS;
 433
 434         return flags;
 435 }
 436
 437 static int __setup_rt_frame(int sig, struct ksignal *ksig,
 438                             sigset_t *set, struct pt_regs *regs)
 439 {
 440         struct rt_sigframe __user *frame;
 441         void __user *fp = NULL;
 442         unsigned long uc_flags;
 443         int err = 0;
 444
 445         frame = get_sigframe(&ksig->ka, regs, sizeof(struct rt_sigframe), &fp);
 446
 447         if (!access_ok(frame, sizeof(*frame)))
 448                 return -EFAULT;
 449
 450         if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
 451                 if (copy_siginfo_to_user(&frame->info, &ksig->info))
 452                         return -EFAULT;
 453         }
 454
 455         uc_flags = frame_uc_flags(regs);
 456
 457         put_user_try {
 458                 /* Create the ucontext.  */
 459                 put_user_ex(uc_flags, &frame->uc.uc_flags);
 460                 put_user_ex(0, &frame->uc.uc_link);
 461                 save_altstack_ex(&frame->uc.uc_stack, regs->sp);
 462
 463                 /* Set up to return from userspace.  If provided, use a stub
 464                    already in userspace.  */
 465                 /* x86-64 should always use SA_RESTORER. */
 466                 if (ksig->ka.sa.sa_flags & SA_RESTORER) {
 467                         put_user_ex(ksig->ka.sa.sa_restorer, &frame->pretcode);
 468                 } else {
 469                         /* could use a vstub here */
 470                         err |= -EFAULT;
 471                 }
 472         } put_user_catch(err);
 473
 474         err |= setup_sigcontext(&frame->uc.uc_mcontext, fp, regs, set->sig[0]);
 475         err |= __put_user(set->sig[0], &frame->uc.uc_sigmask.sig[0]);
 476
 477         if (err)
 478                 return -EFAULT;
 479
 480         /* Set up registers for signal handler */
 481         regs->di = sig;
 482         /* In case the signal handler was declared without prototypes */
 483         regs->ax = 0;
 484
 485         /* This also works for non SA_SIGINFO handlers because they expect the
 486            next argument after the signal number on the stack. */
 487         regs->si = (unsigned long)&frame->info;
 488         regs->dx = (unsigned long)&frame->uc;
 489         regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
 490
 491         regs->sp = (unsigned long)frame;
 492
 493         /*
 494          * Set up the CS and SS registers to run signal handlers in
 495          * 64-bit mode, even if the handler happens to be interrupting
 496          * 32-bit or 16-bit code.
 497          *
 498          * SS is subtle.  In 64-bit mode, we don't need any particular
 499          * SS descriptor, but we do need SS to be valid.  It's possible
 500          * that the old SS is entirely bogus -- this can happen if the
 501          * signal we're trying to deliver is #GP or #SS caused by a bad
 502          * SS value.  We also have a compatbility issue here: DOSEMU
 503          * relies on the contents of the SS register indicating the
 504          * SS value at the time of the signal, even though that code in
 505          * DOSEMU predates sigreturn's ability to restore SS.  (DOSEMU
 506          * avoids relying on sigreturn to restore SS; instead it uses
 507          * a trampoline.)  So we do our best: if the old SS was valid,
 508          * we keep it.  Otherwise we replace it.
 509          */
 510         regs->cs = __USER_CS;
 511
 512         if (unlikely(regs->ss != __USER_DS))
 513                 force_valid_ss(regs);
 514
 515         return 0;
 516 }
 517 #endif /* CONFIG_X86_32 */
 518
 519 static int x32_setup_rt_frame(struct ksignal *ksig,
 520                               compat_sigset_t *set,
 521                               struct pt_regs *regs)
 522 {
 523 #ifdef CONFIG_X86_X32_ABI
 524         struct rt_sigframe_x32 __user *frame;
 525         unsigned long uc_flags;
 526         void __user *restorer;
 527         int err = 0;
 528         void __user *fpstate = NULL;
 529
 530         frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fpstate);
 531
 532         if (!access_ok(frame, sizeof(*frame)))
 533                 return -EFAULT;
 534
 535         if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
 536                 if (__copy_siginfo_to_user32(&frame->info, &ksig->info, true))
 537                         return -EFAULT;
 538         }
 539
 540         uc_flags = frame_uc_flags(regs);
 541
 542         put_user_try {
 543                 /* Create the ucontext.  */
 544                 put_user_ex(uc_flags, &frame->uc.uc_flags);
 545                 put_user_ex(0, &frame->uc.uc_link);
 546                 compat_save_altstack_ex(&frame->uc.uc_stack, regs->sp);
 547                 put_user_ex(0, &frame->uc.uc__pad0);
 548
 549                 if (ksig->ka.sa.sa_flags & SA_RESTORER) {
 550                         restorer = ksig->ka.sa.sa_restorer;
 551                 } else {
 552                         /* could use a vstub here */
 553                         restorer = NULL;
 554                         err |= -EFAULT;
 555                 }
 556                 put_user_ex(restorer, (unsigned long __user *)&frame->pretcode);
 557         } put_user_catch(err);
 558
 559         err |= setup_sigcontext(&frame->uc.uc_mcontext, fpstate,
 560                                 regs, set->sig[0]);
 561         err |= __put_user(*(__u64 *)set, (__u64 __user *)&frame->uc.uc_sigmask);
 562
 563         if (err)
 564                 return -EFAULT;
 565
 566         /* Set up registers for signal handler */
 567         regs->sp = (unsigned long) frame;
 568         regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
 569
 570         /* We use the x32 calling convention here... */
 571         regs->di = ksig->sig;
 572         regs->si = (unsigned long) &frame->info;
 573         regs->dx = (unsigned long) &frame->uc;
 574
 575         loadsegment(ds, __USER_DS);
 576         loadsegment(es, __USER_DS);
 577
 578         regs->cs = __USER_CS;
 579         regs->ss = __USER_DS;
 580 #endif  /* CONFIG_X86_X32_ABI */
 581
 582         return 0;
 583 }
 584
 585 /*
 586  * Do a signal return; undo the signal stack.
 587  */
 588 #ifdef CONFIG_X86_32
 589 SYSCALL_DEFINE0(sigreturn)
 590 {
 591         struct pt_regs *regs = current_pt_regs();
 592         struct sigframe __user *frame;
 593         sigset_t set;
 594
 595         frame = (struct sigframe __user *)(regs->sp - 8);
 596
 597         if (!access_ok(frame, sizeof(*frame)))
 598                 goto badframe;
 599         if (__get_user(set.sig[0], &frame->sc.oldmask) ||
 600             __get_user(set.sig[1], &frame->extramask[0]))
 601                 goto badframe;
 602
 603         set_current_blocked(&set);
 604
 605         /*
 606          * x86_32 has no uc_flags bits relevant to restore_sigcontext.
 607          * Save a few cycles by skipping the __get_user.
 608          */
 609         if (restore_sigcontext(regs, &frame->sc, 0))
 610                 goto badframe;
 611         return regs->ax;
 612
 613 badframe:
 614         signal_fault(regs, frame, "sigreturn");
 615
 616         return 0;
 617 }
 618 #endif /* CONFIG_X86_32 */
 619
 620 SYSCALL_DEFINE0(rt_sigreturn)
 621 {
 622         struct pt_regs *regs = current_pt_regs();
 623         struct rt_sigframe __user *frame;
 624         sigset_t set;
 625         unsigned long uc_flags;
 626
 627         frame = (struct rt_sigframe __user *)(regs->sp - sizeof(long));
 628         if (!access_ok(frame, sizeof(*frame)))
 629                 goto badframe;
 630         if (__get_user(*(__u64 *)&set, (__u64 __user *)&frame->uc.uc_sigmask))
 631                 goto badframe;
 632         if (__get_user(uc_flags, &frame->uc.uc_flags))
 633                 goto badframe;
 634
 635         set_current_blocked(&set);
 636
 637         if (restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags))
 638                 goto badframe;
 639
 640         if (restore_altstack(&frame->uc.uc_stack))
 641                 goto badframe;
 642
 643         return regs->ax;
 644
 645 badframe:
 646         signal_fault(regs, frame, "rt_sigreturn");
 647         return 0;
 648 }
 649
 650 static inline int is_ia32_compat_frame(struct ksignal *ksig)
 651 {
 652         return IS_ENABLED(CONFIG_IA32_EMULATION) &&
 653                 ksig->ka.sa.sa_flags & SA_IA32_ABI;
 654 }
 655
 656 static inline int is_ia32_frame(struct ksignal *ksig)
 657 {
 658         return IS_ENABLED(CONFIG_X86_32) || is_ia32_compat_frame(ksig);
 659 }
 660
 661 static inline int is_x32_frame(struct ksignal *ksig)
 662 {
 663         return IS_ENABLED(CONFIG_X86_X32_ABI) &&
 664                 ksig->ka.sa.sa_flags & SA_X32_ABI;
 665 }
 666
 667 static int
 668 setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs)
 669 {
 670         int usig = ksig->sig;
 671         sigset_t *set = sigmask_to_save();
 672         compat_sigset_t *cset = (compat_sigset_t *) set;
 673
 674         /* Perform fixup for the pre-signal frame. */
 675         rseq_signal_deliver(ksig, regs);
 676
 677         /* Set up the stack frame */
 678         if (is_ia32_frame(ksig)) {
 679                 if (ksig->ka.sa.sa_flags & SA_SIGINFO)
 680                         return ia32_setup_rt_frame(usig, ksig, cset, regs);
 681                 else
 682                         return ia32_setup_frame(usig, ksig, cset, regs);
 683         } else if (is_x32_frame(ksig)) {
 684                 return x32_setup_rt_frame(ksig, cset, regs);
 685         } else {
 686                 return __setup_rt_frame(ksig->sig, ksig, set, regs);
 687         }
 688 }
 689
 690 static void
 691 handle_signal(struct ksignal *ksig, struct pt_regs *regs)
 692 {
 693         bool stepping, failed;
 694         struct fpu *fpu = &current->thread.fpu;
 695
 696         if (v8086_mode(regs))
 697                 save_v86_state((struct kernel_vm86_regs *) regs, VM86_SIGNAL);
 698
 699         /* Are we from a system call? */
 700         if (syscall_get_nr(current, regs) >= 0) {
 701                 /* If so, check system call restarting.. */
 702                 switch (syscall_get_error(current, regs)) {
 703                 case -ERESTART_RESTARTBLOCK:
 704                 case -ERESTARTNOHAND:
 705                         regs->ax = -EINTR;
 706                         break;
 707
 708                 case -ERESTARTSYS:
 709                         if (!(ksig->ka.sa.sa_flags & SA_RESTART)) {
 710                                 regs->ax = -EINTR;
 711                                 break;
 712                         }
 713                 /* fallthrough */
 714                 case -ERESTARTNOINTR:
 715                         regs->ax = regs->orig_ax;
 716                         regs->ip -= 2;
 717                         break;
 718                 }
 719         }
 720
 721         /*
 722          * If TF is set due to a debugger (TIF_FORCED_TF), clear TF now
 723          * so that register information in the sigcontext is correct and
 724          * then notify the tracer before entering the signal handler.
 725          */
 726         stepping = test_thread_flag(TIF_SINGLESTEP);
 727         if (stepping)
 728                 user_disable_single_step(current);
 729
 730         failed = (setup_rt_frame(ksig, regs) < 0);
 731         if (!failed) {
 732                 /*
 733                  * Clear the direction flag as per the ABI for function entry.
 734                  *
 735                  * Clear RF when entering the signal handler, because
 736                  * it might disable possible debug exception from the
 737                  * signal handler.
 738                  *
 739                  * Clear TF for the case when it wasn't set by debugger to
 740                  * avoid the recursive send_sigtrap() in SIGTRAP handler.
 741                  */
 742                 regs->flags &= ~(X86_EFLAGS_DF|X86_EFLAGS_RF|X86_EFLAGS_TF);
 743                 /*
 744                  * Ensure the signal handler starts with the new fpu state.
 745                  */
 746                 fpu__clear(fpu);
 747         }
 748         signal_setup_done(failed, ksig, stepping);
 749 }
 750
 751 static inline unsigned long get_nr_restart_syscall(const struct pt_regs *regs)
 752 {
 753         /*
 754          * This function is fundamentally broken as currently
 755          * implemented.
 756          *
 757          * The idea is that we want to trigger a call to the
 758          * restart_block() syscall and that we want in_ia32_syscall(),
 759          * in_x32_syscall(), etc. to match whatever they were in the
 760          * syscall being restarted.  We assume that the syscall
 761          * instruction at (regs->ip - 2) matches whatever syscall
 762          * instruction we used to enter in the first place.
 763          *
 764          * The problem is that we can get here when ptrace pokes
 765          * syscall-like values into regs even if we're not in a syscall
 766          * at all.
 767          *
 768          * For now, we maintain historical behavior and guess based on
 769          * stored state.  We could do better by saving the actual
 770          * syscall arch in restart_block or (with caveats on x32) by
 771          * checking if regs->ip points to 'int $0x80'.  The current
 772          * behavior is incorrect if a tracer has a different bitness
 773          * than the tracee.
 774          */
 775 #ifdef CONFIG_IA32_EMULATION
 776         if (current_thread_info()->status & (TS_COMPAT|TS_I386_REGS_POKED))
 777                 return __NR_ia32_restart_syscall;
 778 #endif
 779 #ifdef CONFIG_X86_X32_ABI
 780         return __NR_restart_syscall | (regs->orig_ax & __X32_SYSCALL_BIT);
 781 #else
 782         return __NR_restart_syscall;
 783 #endif
 784 }
 785
 786 /*
 787  * Note that 'init' is a special process: it doesn't get signals it doesn't
 788  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 789  * mistake.
 790  */
 791 void do_signal(struct pt_regs *regs)
 792 {
 793         struct ksignal ksig;
 794
 795         if (get_signal(&ksig)) {
 796                 /* Whee! Actually deliver the signal.  */
 797                 handle_signal(&ksig, regs);
 798                 return;
 799         }
 800
 801         /* Did we come from a system call? */
 802         if (syscall_get_nr(current, regs) >= 0) {
 803                 /* Restart the system call - no handlers present */
 804                 switch (syscall_get_error(current, regs)) {
 805                 case -ERESTARTNOHAND:
 806                 case -ERESTARTSYS:
 807                 case -ERESTARTNOINTR:
 808                         regs->ax = regs->orig_ax;
 809                         regs->ip -= 2;
 810                         break;
 811
 812                 case -ERESTART_RESTARTBLOCK:
 813                         regs->ax = get_nr_restart_syscall(regs);
 814                         regs->ip -= 2;
 815                         break;
 816                 }
 817         }
 818
 819         /*
 820          * If there's no signal to deliver, we just put the saved sigmask
 821          * back.
 822          */
 823         restore_saved_sigmask();
 824 }
 825
 826 void signal_fault(struct pt_regs *regs, void __user *frame, char *where)
 827 {
 828         struct task_struct *me = current;
 829
 830         if (show_unhandled_signals && printk_ratelimit()) {
 831                 printk("%s"
 832                        "%s[%d] bad frame in %s frame:%p ip:%lx sp:%lx orax:%lx",
 833                        task_pid_nr(current) > 1 ? KERN_INFO : KERN_EMERG,
 834                        me->comm, me->pid, where, frame,
 835                        regs->ip, regs->sp, regs->orig_ax);
 836                 print_vma_addr(KERN_CONT " in ", regs->ip);
 837                 pr_cont("\n");
 838         }
 839
 840         force_sig(SIGSEGV);
 841 }
 842
 843 #ifdef CONFIG_X86_X32_ABI
 844 asmlinkage long sys32_x32_rt_sigreturn(void)
 845 {
 846         struct pt_regs *regs = current_pt_regs();
 847         struct rt_sigframe_x32 __user *frame;
 848         sigset_t set;
 849         unsigned long uc_flags;
 850
 851         frame = (struct rt_sigframe_x32 __user *)(regs->sp - 8);
 852
 853         if (!access_ok(frame, sizeof(*frame)))
 854                 goto badframe;
 855         if (__get_user(set.sig[0], (__u64 __user *)&frame->uc.uc_sigmask))
 856                 goto badframe;
 857         if (__get_user(uc_flags, &frame->uc.uc_flags))
 858                 goto badframe;
 859
 860         set_current_blocked(&set);
 861
 862         if (restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags))
 863                 goto badframe;
 864
 865         if (compat_restore_altstack(&frame->uc.uc_stack))
 866                 goto badframe;
 867
 868         return regs->ax;
 869
 870 badframe:
 871         signal_fault(regs, frame, "x32 rt_sigreturn");
 872         return 0;
 873 }
 874 #endif