arch/x86/kernel/signal.c

/* [<][>][^][v][top][bottom][index][help] */
This source file includes following definitions.
force_valid_ss
restore_sigcontext
setup_sigcontext
align_sigframe
get_sigframe
__setup_frame
__setup_rt_frame
frame_uc_flags
__setup_rt_frame
x32_setup_rt_frame
SYSCALL_DEFINE0
SYSCALL_DEFINE0
is_ia32_compat_frame
is_ia32_frame
is_x32_frame
setup_rt_frame
handle_signal
get_nr_restart_syscall
do_signal
signal_fault
sys32_x32_rt_sigreturn
   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 #define COPY(x)                 do {                    \
  51         get_user_ex(regs->x, &sc->x);                   \
  52 } while (0)
  53 
  54 #define GET_SEG(seg)            ({                      \
  55         unsigned short tmp;                             \
  56         get_user_ex(tmp, &sc->seg);                     \
  57         tmp;                                            \
  58 })
  59 
  60 #define COPY_SEG(seg)           do {                    \
  61         regs->seg = GET_SEG(seg);                       \
  62 } while (0)
  63 
  64 #define COPY_SEG_CPL3(seg)      do {                    \
  65         regs->seg = GET_SEG(seg) | 3;                   \
  66 } while (0)
  67 
  68 #ifdef CONFIG_X86_64
  69 /*
  70  * If regs->ss will cause an IRET fault, change it.  Otherwise leave it
  71  * alone.  Using this generally makes no sense unless
  72  * user_64bit_mode(regs) would return true.
  73  */
  74 static void force_valid_ss(struct pt_regs *regs)
  75 {
  76         u32 ar;
  77         asm volatile ("lar %[old_ss], %[ar]\n\t"
  78                       "jz 1f\n\t"               /* If invalid: */
  79                       "xorl %[ar], %[ar]\n\t"   /* set ar = 0 */
  80                       "1:"
  81                       : [ar] "=r" (ar)
  82                       : [old_ss] "rm" ((u16)regs->ss));
  83 
  84         /*
  85          * For a valid 64-bit user context, we need DPL 3, type
  86          * read-write data or read-write exp-down data, and S and P
  87          * set.  We can't use VERW because VERW doesn't check the
  88          * P bit.
  89          */
  90         ar &= AR_DPL_MASK | AR_S | AR_P | AR_TYPE_MASK;
  91         if (ar != (AR_DPL3 | AR_S | AR_P | AR_TYPE_RWDATA) &&
  92             ar != (AR_DPL3 | AR_S | AR_P | AR_TYPE_RWDATA_EXPDOWN))
  93                 regs->ss = __USER_DS;
  94 }
  95 #endif
  96 
  97 static int restore_sigcontext(struct pt_regs *regs,
  98                               struct sigcontext __user *sc,
  99                               unsigned long uc_flags)
 100 {
 101         unsigned long buf_val;
 102         void __user *buf;
 103         unsigned int tmpflags;
 104         unsigned int err = 0;
 105 
 106         /* Always make any pending restarted system calls return -EINTR */
 107         current->restart_block.fn = do_no_restart_syscall;
 108 
 109         get_user_try {
 110 
 111 #ifdef CONFIG_X86_32
 112                 set_user_gs(regs, GET_SEG(gs));
 113                 COPY_SEG(fs);
 114                 COPY_SEG(es);
 115                 COPY_SEG(ds);
 116 #endif /* CONFIG_X86_32 */
 117 
 118                 COPY(di); COPY(si); COPY(bp); COPY(sp); COPY(bx);
 119                 COPY(dx); COPY(cx); COPY(ip); COPY(ax);
 120 
 121 #ifdef CONFIG_X86_64
 122                 COPY(r8);
 123                 COPY(r9);
 124                 COPY(r10);
 125                 COPY(r11);
 126                 COPY(r12);
 127                 COPY(r13);
 128                 COPY(r14);
 129                 COPY(r15);
 130 #endif /* CONFIG_X86_64 */
 131 
 132                 COPY_SEG_CPL3(cs);
 133                 COPY_SEG_CPL3(ss);
 134 
 135                 get_user_ex(tmpflags, &sc->flags);
 136                 regs->flags = (regs->flags & ~FIX_EFLAGS) | (tmpflags & FIX_EFLAGS);
 137                 regs->orig_ax = -1;             /* disable syscall checks */
 138 
 139                 get_user_ex(buf_val, &sc->fpstate);
 140                 buf = (void __user *)buf_val;
 141         } get_user_catch(err);
 142 
 143 #ifdef CONFIG_X86_64
 144         /*
 145          * Fix up SS if needed for the benefit of old DOSEMU and
 146          * CRIU.
 147          */
 148         if (unlikely(!(uc_flags & UC_STRICT_RESTORE_SS) && user_64bit_mode(regs)))
 149                 force_valid_ss(regs);
 150 #endif
 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, (unsigned long __user *)&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         int ret;
 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         sp = fpu__alloc_mathframe(sp, IS_ENABLED(CONFIG_X86_32),
 268                                   &buf_fx, &math_size);
 269         *fpstate = (void __user *)sp;
 270 
 271         sp = align_sigframe(sp - frame_size);
 272 
 273         /*
 274          * If we are on the alternate signal stack and would overflow it, don't.
 275          * Return an always-bogus address instead so we will die with SIGSEGV.
 276          */
 277         if (onsigstack && !likely(on_sig_stack(sp)))
 278                 return (void __user *)-1L;
 279 
 280         /* save i387 and extended state */
 281         ret = copy_fpstate_to_sigframe(*fpstate, (void __user *)buf_fx, math_size);
 282         if (ret < 0)
 283                 return (void __user *)-1L;
 284 
 285         return (void __user *)sp;
 286 }
 287 
 288 #ifdef CONFIG_X86_32
 289 static const struct {
 290         u16 poplmovl;
 291         u32 val;
 292         u16 int80;
 293 } __attribute__((packed)) retcode = {
 294         0xb858,         /* popl %eax; movl $..., %eax */
 295         __NR_sigreturn,
 296         0x80cd,         /* int $0x80 */
 297 };
 298 
 299 static const struct {
 300         u8  movl;
 301         u32 val;
 302         u16 int80;
 303         u8  pad;
 304 } __attribute__((packed)) rt_retcode = {
 305         0xb8,           /* movl $..., %eax */
 306         __NR_rt_sigreturn,
 307         0x80cd,         /* int $0x80 */
 308         0
 309 };
 310 
 311 static int
 312 __setup_frame(int sig, struct ksignal *ksig, sigset_t *set,
 313               struct pt_regs *regs)
 314 {
 315         struct sigframe __user *frame;
 316         void __user *restorer;
 317         int err = 0;
 318         void __user *fpstate = NULL;
 319 
 320         frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fpstate);
 321 
 322         if (!access_ok(frame, sizeof(*frame)))
 323                 return -EFAULT;
 324 
 325         if (__put_user(sig, &frame->sig))
 326                 return -EFAULT;
 327 
 328         if (setup_sigcontext(&frame->sc, fpstate, regs, set->sig[0]))
 329                 return -EFAULT;
 330 
 331         if (_NSIG_WORDS > 1) {
 332                 if (__copy_to_user(&frame->extramask, &set->sig[1],
 333                                    sizeof(frame->extramask)))
 334                         return -EFAULT;
 335         }
 336 
 337         if (current->mm->context.vdso)
 338                 restorer = current->mm->context.vdso +
 339                         vdso_image_32.sym___kernel_sigreturn;
 340         else
 341                 restorer = &frame->retcode;
 342         if (ksig->ka.sa.sa_flags & SA_RESTORER)
 343                 restorer = ksig->ka.sa.sa_restorer;
 344 
 345         /* Set up to return from userspace.  */
 346         err |= __put_user(restorer, &frame->pretcode);
 347 
 348         /*
 349          * This is popl %eax ; movl $__NR_sigreturn, %eax ; int $0x80
 350          *
 351          * WE DO NOT USE IT ANY MORE! It's only left here for historical
 352          * reasons and because gdb uses it as a signature to notice
 353          * signal handler stack frames.
 354          */
 355         err |= __put_user(*((u64 *)&retcode), (u64 *)frame->retcode);
 356 
 357         if (err)
 358                 return -EFAULT;
 359 
 360         /* Set up registers for signal handler */
 361         regs->sp = (unsigned long)frame;
 362         regs->ip = (unsigned long)ksig->ka.sa.sa_handler;
 363         regs->ax = (unsigned long)sig;
 364         regs->dx = 0;
 365         regs->cx = 0;
 366 
 367         regs->ds = __USER_DS;
 368         regs->es = __USER_DS;
 369         regs->ss = __USER_DS;
 370         regs->cs = __USER_CS;
 371 
 372         return 0;
 373 }
 374 
 375 static int __setup_rt_frame(int sig, struct ksignal *ksig,
 376                             sigset_t *set, struct pt_regs *regs)
 377 {
 378         struct rt_sigframe __user *frame;
 379         void __user *restorer;
 380         int err = 0;
 381         void __user *fpstate = NULL;
 382 
 383         frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fpstate);
 384 
 385         if (!access_ok(frame, sizeof(*frame)))
 386                 return -EFAULT;
 387 
 388         put_user_try {
 389                 put_user_ex(sig, &frame->sig);
 390                 put_user_ex(&frame->info, &frame->pinfo);
 391                 put_user_ex(&frame->uc, &frame->puc);
 392 
 393                 /* Create the ucontext.  */
 394                 if (static_cpu_has(X86_FEATURE_XSAVE))
 395                         put_user_ex(UC_FP_XSTATE, &frame->uc.uc_flags);
 396                 else
 397                         put_user_ex(0, &frame->uc.uc_flags);
 398                 put_user_ex(0, &frame->uc.uc_link);
 399                 save_altstack_ex(&frame->uc.uc_stack, regs->sp);
 400 
 401                 /* Set up to return from userspace.  */
 402                 restorer = current->mm->context.vdso +
 403                         vdso_image_32.sym___kernel_rt_sigreturn;
 404                 if (ksig->ka.sa.sa_flags & SA_RESTORER)
 405                         restorer = ksig->ka.sa.sa_restorer;
 406                 put_user_ex(restorer, &frame->pretcode);
 407 
 408                 /*
 409                  * This is movl $__NR_rt_sigreturn, %ax ; int $0x80
 410                  *
 411                  * WE DO NOT USE IT ANY MORE! It's only left here for historical
 412                  * reasons and because gdb uses it as a signature to notice
 413                  * signal handler stack frames.
 414                  */
 415                 put_user_ex(*((u64 *)&rt_retcode), (u64 *)frame->retcode);
 416         } put_user_catch(err);
 417         
 418         err |= copy_siginfo_to_user(&frame->info, &ksig->info);
 419         err |= setup_sigcontext(&frame->uc.uc_mcontext, fpstate,
 420                                 regs, set->sig[0]);
 421         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 422 
 423         if (err)
 424                 return -EFAULT;
 425 
 426         /* Set up registers for signal handler */
 427         regs->sp = (unsigned long)frame;
 428         regs->ip = (unsigned long)ksig->ka.sa.sa_handler;
 429         regs->ax = (unsigned long)sig;
 430         regs->dx = (unsigned long)&frame->info;
 431         regs->cx = (unsigned long)&frame->uc;
 432 
 433         regs->ds = __USER_DS;
 434         regs->es = __USER_DS;
 435         regs->ss = __USER_DS;
 436         regs->cs = __USER_CS;
 437 
 438         return 0;
 439 }
 440 #else /* !CONFIG_X86_32 */
 441 static unsigned long frame_uc_flags(struct pt_regs *regs)
 442 {
 443         unsigned long flags;
 444 
 445         if (boot_cpu_has(X86_FEATURE_XSAVE))
 446                 flags = UC_FP_XSTATE | UC_SIGCONTEXT_SS;
 447         else
 448                 flags = UC_SIGCONTEXT_SS;
 449 
 450         if (likely(user_64bit_mode(regs)))
 451                 flags |= UC_STRICT_RESTORE_SS;
 452 
 453         return flags;
 454 }
 455 
 456 static int __setup_rt_frame(int sig, struct ksignal *ksig,
 457                             sigset_t *set, struct pt_regs *regs)
 458 {
 459         struct rt_sigframe __user *frame;
 460         void __user *fp = NULL;
 461         unsigned long uc_flags;
 462         int err = 0;
 463 
 464         frame = get_sigframe(&ksig->ka, regs, sizeof(struct rt_sigframe), &fp);
 465 
 466         if (!access_ok(frame, sizeof(*frame)))
 467                 return -EFAULT;
 468 
 469         if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
 470                 if (copy_siginfo_to_user(&frame->info, &ksig->info))
 471                         return -EFAULT;
 472         }
 473 
 474         uc_flags = frame_uc_flags(regs);
 475 
 476         put_user_try {
 477                 /* Create the ucontext.  */
 478                 put_user_ex(uc_flags, &frame->uc.uc_flags);
 479                 put_user_ex(0, &frame->uc.uc_link);
 480                 save_altstack_ex(&frame->uc.uc_stack, regs->sp);
 481 
 482                 /* Set up to return from userspace.  If provided, use a stub
 483                    already in userspace.  */
 484                 /* x86-64 should always use SA_RESTORER. */
 485                 if (ksig->ka.sa.sa_flags & SA_RESTORER) {
 486                         put_user_ex(ksig->ka.sa.sa_restorer, &frame->pretcode);
 487                 } else {
 488                         /* could use a vstub here */
 489                         err |= -EFAULT;
 490                 }
 491         } put_user_catch(err);
 492 
 493         err |= setup_sigcontext(&frame->uc.uc_mcontext, fp, regs, set->sig[0]);
 494         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 495 
 496         if (err)
 497                 return -EFAULT;
 498 
 499         /* Set up registers for signal handler */
 500         regs->di = sig;
 501         /* In case the signal handler was declared without prototypes */
 502         regs->ax = 0;
 503 
 504         /* This also works for non SA_SIGINFO handlers because they expect the
 505            next argument after the signal number on the stack. */
 506         regs->si = (unsigned long)&frame->info;
 507         regs->dx = (unsigned long)&frame->uc;
 508         regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
 509 
 510         regs->sp = (unsigned long)frame;
 511 
 512         /*
 513          * Set up the CS and SS registers to run signal handlers in
 514          * 64-bit mode, even if the handler happens to be interrupting
 515          * 32-bit or 16-bit code.
 516          *
 517          * SS is subtle.  In 64-bit mode, we don't need any particular
 518          * SS descriptor, but we do need SS to be valid.  It's possible
 519          * that the old SS is entirely bogus -- this can happen if the
 520          * signal we're trying to deliver is #GP or #SS caused by a bad
 521          * SS value.  We also have a compatbility issue here: DOSEMU
 522          * relies on the contents of the SS register indicating the
 523          * SS value at the time of the signal, even though that code in
 524          * DOSEMU predates sigreturn's ability to restore SS.  (DOSEMU
 525          * avoids relying on sigreturn to restore SS; instead it uses
 526          * a trampoline.)  So we do our best: if the old SS was valid,
 527          * we keep it.  Otherwise we replace it.
 528          */
 529         regs->cs = __USER_CS;
 530 
 531         if (unlikely(regs->ss != __USER_DS))
 532                 force_valid_ss(regs);
 533 
 534         return 0;
 535 }
 536 #endif /* CONFIG_X86_32 */
 537 
 538 static int x32_setup_rt_frame(struct ksignal *ksig,
 539                               compat_sigset_t *set,
 540                               struct pt_regs *regs)
 541 {
 542 #ifdef CONFIG_X86_X32_ABI
 543         struct rt_sigframe_x32 __user *frame;
 544         unsigned long uc_flags;
 545         void __user *restorer;
 546         int err = 0;
 547         void __user *fpstate = NULL;
 548 
 549         frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fpstate);
 550 
 551         if (!access_ok(frame, sizeof(*frame)))
 552                 return -EFAULT;
 553 
 554         if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
 555                 if (__copy_siginfo_to_user32(&frame->info, &ksig->info, true))
 556                         return -EFAULT;
 557         }
 558 
 559         uc_flags = frame_uc_flags(regs);
 560 
 561         put_user_try {
 562                 /* Create the ucontext.  */
 563                 put_user_ex(uc_flags, &frame->uc.uc_flags);
 564                 put_user_ex(0, &frame->uc.uc_link);
 565                 compat_save_altstack_ex(&frame->uc.uc_stack, regs->sp);
 566                 put_user_ex(0, &frame->uc.uc__pad0);
 567 
 568                 if (ksig->ka.sa.sa_flags & SA_RESTORER) {
 569                         restorer = ksig->ka.sa.sa_restorer;
 570                 } else {
 571                         /* could use a vstub here */
 572                         restorer = NULL;
 573                         err |= -EFAULT;
 574                 }
 575                 put_user_ex(restorer, (unsigned long __user *)&frame->pretcode);
 576         } put_user_catch(err);
 577 
 578         err |= setup_sigcontext(&frame->uc.uc_mcontext, fpstate,
 579                                 regs, set->sig[0]);
 580         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 581 
 582         if (err)
 583                 return -EFAULT;
 584 
 585         /* Set up registers for signal handler */
 586         regs->sp = (unsigned long) frame;
 587         regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
 588 
 589         /* We use the x32 calling convention here... */
 590         regs->di = ksig->sig;
 591         regs->si = (unsigned long) &frame->info;
 592         regs->dx = (unsigned long) &frame->uc;
 593 
 594         loadsegment(ds, __USER_DS);
 595         loadsegment(es, __USER_DS);
 596 
 597         regs->cs = __USER_CS;
 598         regs->ss = __USER_DS;
 599 #endif  /* CONFIG_X86_X32_ABI */
 600 
 601         return 0;
 602 }
 603 
 604 /*
 605  * Do a signal return; undo the signal stack.
 606  */
 607 #ifdef CONFIG_X86_32
 608 SYSCALL_DEFINE0(sigreturn)
 609 {
 610         struct pt_regs *regs = current_pt_regs();
 611         struct sigframe __user *frame;
 612         sigset_t set;
 613 
 614         frame = (struct sigframe __user *)(regs->sp - 8);
 615 
 616         if (!access_ok(frame, sizeof(*frame)))
 617                 goto badframe;
 618         if (__get_user(set.sig[0], &frame->sc.oldmask) || (_NSIG_WORDS > 1
 619                 && __copy_from_user(&set.sig[1], &frame->extramask,
 620                                     sizeof(frame->extramask))))
 621                 goto badframe;
 622 
 623         set_current_blocked(&set);
 624 
 625         /*
 626          * x86_32 has no uc_flags bits relevant to restore_sigcontext.
 627          * Save a few cycles by skipping the __get_user.
 628          */
 629         if (restore_sigcontext(regs, &frame->sc, 0))
 630                 goto badframe;
 631         return regs->ax;
 632 
 633 badframe:
 634         signal_fault(regs, frame, "sigreturn");
 635 
 636         return 0;
 637 }
 638 #endif /* CONFIG_X86_32 */
 639 
 640 SYSCALL_DEFINE0(rt_sigreturn)
 641 {
 642         struct pt_regs *regs = current_pt_regs();
 643         struct rt_sigframe __user *frame;
 644         sigset_t set;
 645         unsigned long uc_flags;
 646 
 647         frame = (struct rt_sigframe __user *)(regs->sp - sizeof(long));
 648         if (!access_ok(frame, sizeof(*frame)))
 649                 goto badframe;
 650         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
 651                 goto badframe;
 652         if (__get_user(uc_flags, &frame->uc.uc_flags))
 653                 goto badframe;
 654 
 655         set_current_blocked(&set);
 656 
 657         if (restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags))
 658                 goto badframe;
 659 
 660         if (restore_altstack(&frame->uc.uc_stack))
 661                 goto badframe;
 662 
 663         return regs->ax;
 664 
 665 badframe:
 666         signal_fault(regs, frame, "rt_sigreturn");
 667         return 0;
 668 }
 669 
 670 static inline int is_ia32_compat_frame(struct ksignal *ksig)
 671 {
 672         return IS_ENABLED(CONFIG_IA32_EMULATION) &&
 673                 ksig->ka.sa.sa_flags & SA_IA32_ABI;
 674 }
 675 
 676 static inline int is_ia32_frame(struct ksignal *ksig)
 677 {
 678         return IS_ENABLED(CONFIG_X86_32) || is_ia32_compat_frame(ksig);
 679 }
 680 
 681 static inline int is_x32_frame(struct ksignal *ksig)
 682 {
 683         return IS_ENABLED(CONFIG_X86_X32_ABI) &&
 684                 ksig->ka.sa.sa_flags & SA_X32_ABI;
 685 }
 686 
 687 static int
 688 setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs)
 689 {
 690         int usig = ksig->sig;
 691         sigset_t *set = sigmask_to_save();
 692         compat_sigset_t *cset = (compat_sigset_t *) set;
 693 
 694         /* Perform fixup for the pre-signal frame. */
 695         rseq_signal_deliver(ksig, regs);
 696 
 697         /* Set up the stack frame */
 698         if (is_ia32_frame(ksig)) {
 699                 if (ksig->ka.sa.sa_flags & SA_SIGINFO)
 700                         return ia32_setup_rt_frame(usig, ksig, cset, regs);
 701                 else
 702                         return ia32_setup_frame(usig, ksig, cset, regs);
 703         } else if (is_x32_frame(ksig)) {
 704                 return x32_setup_rt_frame(ksig, cset, regs);
 705         } else {
 706                 return __setup_rt_frame(ksig->sig, ksig, set, regs);
 707         }
 708 }
 709 
 710 static void
 711 handle_signal(struct ksignal *ksig, struct pt_regs *regs)
 712 {
 713         bool stepping, failed;
 714         struct fpu *fpu = &current->thread.fpu;
 715 
 716         if (v8086_mode(regs))
 717                 save_v86_state((struct kernel_vm86_regs *) regs, VM86_SIGNAL);
 718 
 719         /* Are we from a system call? */
 720         if (syscall_get_nr(current, regs) >= 0) {
 721                 /* If so, check system call restarting.. */
 722                 switch (syscall_get_error(current, regs)) {
 723                 case -ERESTART_RESTARTBLOCK:
 724                 case -ERESTARTNOHAND:
 725                         regs->ax = -EINTR;
 726                         break;
 727 
 728                 case -ERESTARTSYS:
 729                         if (!(ksig->ka.sa.sa_flags & SA_RESTART)) {
 730                                 regs->ax = -EINTR;
 731                                 break;
 732                         }
 733                 /* fallthrough */
 734                 case -ERESTARTNOINTR:
 735                         regs->ax = regs->orig_ax;
 736                         regs->ip -= 2;
 737                         break;
 738                 }
 739         }
 740 
 741         /*
 742          * If TF is set due to a debugger (TIF_FORCED_TF), clear TF now
 743          * so that register information in the sigcontext is correct and
 744          * then notify the tracer before entering the signal handler.
 745          */
 746         stepping = test_thread_flag(TIF_SINGLESTEP);
 747         if (stepping)
 748                 user_disable_single_step(current);
 749 
 750         failed = (setup_rt_frame(ksig, regs) < 0);
 751         if (!failed) {
 752                 /*
 753                  * Clear the direction flag as per the ABI for function entry.
 754                  *
 755                  * Clear RF when entering the signal handler, because
 756                  * it might disable possible debug exception from the
 757                  * signal handler.
 758                  *
 759                  * Clear TF for the case when it wasn't set by debugger to
 760                  * avoid the recursive send_sigtrap() in SIGTRAP handler.
 761                  */
 762                 regs->flags &= ~(X86_EFLAGS_DF|X86_EFLAGS_RF|X86_EFLAGS_TF);
 763                 /*
 764                  * Ensure the signal handler starts with the new fpu state.
 765                  */
 766                 fpu__clear(fpu);
 767         }
 768         signal_setup_done(failed, ksig, stepping);
 769 }
 770 
 771 static inline unsigned long get_nr_restart_syscall(const struct pt_regs *regs)
 772 {
 773         /*
 774          * This function is fundamentally broken as currently
 775          * implemented.
 776          *
 777          * The idea is that we want to trigger a call to the
 778          * restart_block() syscall and that we want in_ia32_syscall(),
 779          * in_x32_syscall(), etc. to match whatever they were in the
 780          * syscall being restarted.  We assume that the syscall
 781          * instruction at (regs->ip - 2) matches whatever syscall
 782          * instruction we used to enter in the first place.
 783          *
 784          * The problem is that we can get here when ptrace pokes
 785          * syscall-like values into regs even if we're not in a syscall
 786          * at all.
 787          *
 788          * For now, we maintain historical behavior and guess based on
 789          * stored state.  We could do better by saving the actual
 790          * syscall arch in restart_block or (with caveats on x32) by
 791          * checking if regs->ip points to 'int $0x80'.  The current
 792          * behavior is incorrect if a tracer has a different bitness
 793          * than the tracee.
 794          */
 795 #ifdef CONFIG_IA32_EMULATION
 796         if (current_thread_info()->status & (TS_COMPAT|TS_I386_REGS_POKED))
 797                 return __NR_ia32_restart_syscall;
 798 #endif
 799 #ifdef CONFIG_X86_X32_ABI
 800         return __NR_restart_syscall | (regs->orig_ax & __X32_SYSCALL_BIT);
 801 #else
 802         return __NR_restart_syscall;
 803 #endif
 804 }
 805 
 806 /*
 807  * Note that 'init' is a special process: it doesn't get signals it doesn't
 808  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 809  * mistake.
 810  */
 811 void do_signal(struct pt_regs *regs)
 812 {
 813         struct ksignal ksig;
 814 
 815         if (get_signal(&ksig)) {
 816                 /* Whee! Actually deliver the signal.  */
 817                 handle_signal(&ksig, regs);
 818                 return;
 819         }
 820 
 821         /* Did we come from a system call? */
 822         if (syscall_get_nr(current, regs) >= 0) {
 823                 /* Restart the system call - no handlers present */
 824                 switch (syscall_get_error(current, regs)) {
 825                 case -ERESTARTNOHAND:
 826                 case -ERESTARTSYS:
 827                 case -ERESTARTNOINTR:
 828                         regs->ax = regs->orig_ax;
 829                         regs->ip -= 2;
 830                         break;
 831 
 832                 case -ERESTART_RESTARTBLOCK:
 833                         regs->ax = get_nr_restart_syscall(regs);
 834                         regs->ip -= 2;
 835                         break;
 836                 }
 837         }
 838 
 839         /*
 840          * If there's no signal to deliver, we just put the saved sigmask
 841          * back.
 842          */
 843         restore_saved_sigmask();
 844 }
 845 
 846 void signal_fault(struct pt_regs *regs, void __user *frame, char *where)
 847 {
 848         struct task_struct *me = current;
 849 
 850         if (show_unhandled_signals && printk_ratelimit()) {
 851                 printk("%s"
 852                        "%s[%d] bad frame in %s frame:%p ip:%lx sp:%lx orax:%lx",
 853                        task_pid_nr(current) > 1 ? KERN_INFO : KERN_EMERG,
 854                        me->comm, me->pid, where, frame,
 855                        regs->ip, regs->sp, regs->orig_ax);
 856                 print_vma_addr(KERN_CONT " in ", regs->ip);
 857                 pr_cont("\n");
 858         }
 859 
 860         force_sig(SIGSEGV);
 861 }
 862 
 863 #ifdef CONFIG_X86_X32_ABI
 864 asmlinkage long sys32_x32_rt_sigreturn(void)
 865 {
 866         struct pt_regs *regs = current_pt_regs();
 867         struct rt_sigframe_x32 __user *frame;
 868         sigset_t set;
 869         unsigned long uc_flags;
 870 
 871         frame = (struct rt_sigframe_x32 __user *)(regs->sp - 8);
 872 
 873         if (!access_ok(frame, sizeof(*frame)))
 874                 goto badframe;
 875         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
 876                 goto badframe;
 877         if (__get_user(uc_flags, &frame->uc.uc_flags))
 878                 goto badframe;
 879 
 880         set_current_blocked(&set);
 881 
 882         if (restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags))
 883                 goto badframe;
 884 
 885         if (compat_restore_altstack(&frame->uc.uc_stack))
 886                 goto badframe;
 887 
 888         return regs->ax;
 889 
 890 badframe:
 891         signal_fault(regs, frame, "x32 rt_sigreturn");
 892         return 0;
 893 }
 894 #endif
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root/arch/x86/kernel/signal.c

DEFINITIONS
