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 7 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 8 9 #include <linux/kernel.h> 10 #include <linux/errno.h> 11 #include <linux/unistd.h> 12 #include <linux/uaccess.h> 13 #include <linux/syscalls.h> 14 15 #include <asm/ucontext.h> 16 #include <asm/fpu/signal.h> 17 #include <asm/sighandling.h> 18 19 #include <asm/syscall.h> 20 #include <asm/sigframe.h> 21 #include <asm/signal.h> 22 23 /* 24 * If regs->ss will cause an IRET fault, change it. Otherwise leave it 25 * alone. Using this generally makes no sense unless 26 * user_64bit_mode(regs) would return true. 27 */ 28 static void force_valid_ss(struct pt_regs *regs) 29 { 30 u32 ar; 31 asm volatile ("lar %[old_ss], %[ar]\n\t" 32 "jz 1f\n\t" /* If invalid: */ 33 "xorl %[ar], %[ar]\n\t" /* set ar = 0 */ 34 "1:" 35 : [ar] "=r" (ar) 36 : [old_ss] "rm" ((u16)regs->ss)); 37 38 /* 39 * For a valid 64-bit user context, we need DPL 3, type 40 * read-write data or read-write exp-down data, and S and P 41 * set. We can't use VERW because VERW doesn't check the 42 * P bit. 43 */ 44 ar &= AR_DPL_MASK | AR_S | AR_P | AR_TYPE_MASK; 45 if (ar != (AR_DPL3 | AR_S | AR_P | AR_TYPE_RWDATA) && 46 ar != (AR_DPL3 | AR_S | AR_P | AR_TYPE_RWDATA_EXPDOWN)) 47 regs->ss = __USER_DS; 48 } 49 50 static bool restore_sigcontext(struct pt_regs *regs, 51 struct sigcontext __user *usc, 52 unsigned long uc_flags) 53 { 54 struct sigcontext sc; 55 56 /* Always make any pending restarted system calls return -EINTR */ 57 current->restart_block.fn = do_no_restart_syscall; 58 59 if (copy_from_user(&sc, usc, offsetof(struct sigcontext, reserved1))) 60 return false; 61 62 regs->bx = sc.bx; 63 regs->cx = sc.cx; 64 regs->dx = sc.dx; 65 regs->si = sc.si; 66 regs->di = sc.di; 67 regs->bp = sc.bp; 68 regs->ax = sc.ax; 69 regs->sp = sc.sp; 70 regs->ip = sc.ip; 71 regs->r8 = sc.r8; 72 regs->r9 = sc.r9; 73 regs->r10 = sc.r10; 74 regs->r11 = sc.r11; 75 regs->r12 = sc.r12; 76 regs->r13 = sc.r13; 77 regs->r14 = sc.r14; 78 regs->r15 = sc.r15; 79 80 /* Get CS/SS and force CPL3 */ 81 regs->cs = sc.cs | 0x03; 82 regs->ss = sc.ss | 0x03; 83 84 regs->flags = (regs->flags & ~FIX_EFLAGS) | (sc.flags & FIX_EFLAGS); 85 /* disable syscall checks */ 86 regs->orig_ax = -1; 87 88 /* 89 * Fix up SS if needed for the benefit of old DOSEMU and 90 * CRIU. 91 */ 92 if (unlikely(!(uc_flags & UC_STRICT_RESTORE_SS) && user_64bit_mode(regs))) 93 force_valid_ss(regs); 94 95 return fpu__restore_sig((void __user *)sc.fpstate, 0); 96 } 97 98 static __always_inline int 99 __unsafe_setup_sigcontext(struct sigcontext __user *sc, void __user *fpstate, 100 struct pt_regs *regs, unsigned long mask) 101 { 102 unsafe_put_user(regs->di, &sc->di, Efault); 103 unsafe_put_user(regs->si, &sc->si, Efault); 104 unsafe_put_user(regs->bp, &sc->bp, Efault); 105 unsafe_put_user(regs->sp, &sc->sp, Efault); 106 unsafe_put_user(regs->bx, &sc->bx, Efault); 107 unsafe_put_user(regs->dx, &sc->dx, Efault); 108 unsafe_put_user(regs->cx, &sc->cx, Efault); 109 unsafe_put_user(regs->ax, &sc->ax, Efault); 110 unsafe_put_user(regs->r8, &sc->r8, Efault); 111 unsafe_put_user(regs->r9, &sc->r9, Efault); 112 unsafe_put_user(regs->r10, &sc->r10, Efault); 113 unsafe_put_user(regs->r11, &sc->r11, Efault); 114 unsafe_put_user(regs->r12, &sc->r12, Efault); 115 unsafe_put_user(regs->r13, &sc->r13, Efault); 116 unsafe_put_user(regs->r14, &sc->r14, Efault); 117 unsafe_put_user(regs->r15, &sc->r15, Efault); 118 119 unsafe_put_user(current->thread.trap_nr, &sc->trapno, Efault); 120 unsafe_put_user(current->thread.error_code, &sc->err, Efault); 121 unsafe_put_user(regs->ip, &sc->ip, Efault); 122 unsafe_put_user(regs->flags, &sc->flags, Efault); 123 unsafe_put_user(regs->cs, &sc->cs, Efault); 124 unsafe_put_user(0, &sc->gs, Efault); 125 unsafe_put_user(0, &sc->fs, Efault); 126 unsafe_put_user(regs->ss, &sc->ss, Efault); 127 128 unsafe_put_user(fpstate, (unsigned long __user *)&sc->fpstate, Efault); 129 130 /* non-iBCS2 extensions.. */ 131 unsafe_put_user(mask, &sc->oldmask, Efault); 132 unsafe_put_user(current->thread.cr2, &sc->cr2, Efault); 133 return 0; 134 Efault: 135 return -EFAULT; 136 } 137 138 #define unsafe_put_sigcontext(sc, fp, regs, set, label) \ 139 do { \ 140 if (__unsafe_setup_sigcontext(sc, fp, regs, set->sig[0])) \ 141 goto label; \ 142 } while(0); 143 144 #define unsafe_put_sigmask(set, frame, label) \ 145 unsafe_put_user(*(__u64 *)(set), \ 146 (__u64 __user *)&(frame)->uc.uc_sigmask, \ 147 label) 148 149 static unsigned long frame_uc_flags(struct pt_regs *regs) 150 { 151 unsigned long flags; 152 153 if (boot_cpu_has(X86_FEATURE_XSAVE)) 154 flags = UC_FP_XSTATE | UC_SIGCONTEXT_SS; 155 else 156 flags = UC_SIGCONTEXT_SS; 157 158 if (likely(user_64bit_mode(regs))) 159 flags |= UC_STRICT_RESTORE_SS; 160 161 return flags; 162 } 163 164 int x64_setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs) 165 { 166 sigset_t *set = sigmask_to_save(); 167 struct rt_sigframe __user *frame; 168 void __user *fp = NULL; 169 unsigned long uc_flags; 170 171 /* x86-64 should always use SA_RESTORER. */ 172 if (!(ksig->ka.sa.sa_flags & SA_RESTORER)) 173 return -EFAULT; 174 175 frame = get_sigframe(ksig, regs, sizeof(struct rt_sigframe), &fp); 176 uc_flags = frame_uc_flags(regs); 177 178 if (!user_access_begin(frame, sizeof(*frame))) 179 return -EFAULT; 180 181 /* Create the ucontext. */ 182 unsafe_put_user(uc_flags, &frame->uc.uc_flags, Efault); 183 unsafe_put_user(0, &frame->uc.uc_link, Efault); 184 unsafe_save_altstack(&frame->uc.uc_stack, regs->sp, Efault); 185 186 /* Set up to return from userspace. If provided, use a stub 187 already in userspace. */ 188 unsafe_put_user(ksig->ka.sa.sa_restorer, &frame->pretcode, Efault); 189 unsafe_put_sigcontext(&frame->uc.uc_mcontext, fp, regs, set, Efault); 190 unsafe_put_sigmask(set, frame, Efault); 191 user_access_end(); 192 193 if (ksig->ka.sa.sa_flags & SA_SIGINFO) { 194 if (copy_siginfo_to_user(&frame->info, &ksig->info)) 195 return -EFAULT; 196 } 197 198 if (setup_signal_shadow_stack(ksig)) 199 return -EFAULT; 200 201 /* Set up registers for signal handler */ 202 regs->di = ksig->sig; 203 /* In case the signal handler was declared without prototypes */ 204 regs->ax = 0; 205 206 /* This also works for non SA_SIGINFO handlers because they expect the 207 next argument after the signal number on the stack. */ 208 regs->si = (unsigned long)&frame->info; 209 regs->dx = (unsigned long)&frame->uc; 210 regs->ip = (unsigned long) ksig->ka.sa.sa_handler; 211 212 regs->sp = (unsigned long)frame; 213 214 /* 215 * Set up the CS and SS registers to run signal handlers in 216 * 64-bit mode, even if the handler happens to be interrupting 217 * 32-bit or 16-bit code. 218 * 219 * SS is subtle. In 64-bit mode, we don't need any particular 220 * SS descriptor, but we do need SS to be valid. It's possible 221 * that the old SS is entirely bogus -- this can happen if the 222 * signal we're trying to deliver is #GP or #SS caused by a bad 223 * SS value. We also have a compatibility issue here: DOSEMU 224 * relies on the contents of the SS register indicating the 225 * SS value at the time of the signal, even though that code in 226 * DOSEMU predates sigreturn's ability to restore SS. (DOSEMU 227 * avoids relying on sigreturn to restore SS; instead it uses 228 * a trampoline.) So we do our best: if the old SS was valid, 229 * we keep it. Otherwise we replace it. 230 */ 231 regs->cs = __USER_CS; 232 233 if (unlikely(regs->ss != __USER_DS)) 234 force_valid_ss(regs); 235 236 return 0; 237 238 Efault: 239 user_access_end(); 240 return -EFAULT; 241 } 242 243 /* 244 * Do a signal return; undo the signal stack. 245 */ 246 SYSCALL_DEFINE0(rt_sigreturn) 247 { 248 struct pt_regs *regs = current_pt_regs(); 249 struct rt_sigframe __user *frame; 250 sigset_t set; 251 unsigned long uc_flags; 252 253 frame = (struct rt_sigframe __user *)(regs->sp - sizeof(long)); 254 if (!access_ok(frame, sizeof(*frame))) 255 goto badframe; 256 if (__get_user(*(__u64 *)&set, (__u64 __user *)&frame->uc.uc_sigmask)) 257 goto badframe; 258 if (__get_user(uc_flags, &frame->uc.uc_flags)) 259 goto badframe; 260 261 set_current_blocked(&set); 262 263 if (!restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags)) 264 goto badframe; 265 266 if (restore_signal_shadow_stack()) 267 goto badframe; 268 269 if (restore_altstack(&frame->uc.uc_stack)) 270 goto badframe; 271 272 return regs->ax; 273 274 badframe: 275 signal_fault(regs, frame, "rt_sigreturn"); 276 return 0; 277 } 278 279 #ifdef CONFIG_X86_X32_ABI 280 static int x32_copy_siginfo_to_user(struct compat_siginfo __user *to, 281 const struct kernel_siginfo *from) 282 { 283 struct compat_siginfo new; 284 285 copy_siginfo_to_external32(&new, from); 286 if (from->si_signo == SIGCHLD) { 287 new._sifields._sigchld_x32._utime = from->si_utime; 288 new._sifields._sigchld_x32._stime = from->si_stime; 289 } 290 if (copy_to_user(to, &new, sizeof(struct compat_siginfo))) 291 return -EFAULT; 292 return 0; 293 } 294 295 int copy_siginfo_to_user32(struct compat_siginfo __user *to, 296 const struct kernel_siginfo *from) 297 { 298 if (in_x32_syscall()) 299 return x32_copy_siginfo_to_user(to, from); 300 return __copy_siginfo_to_user32(to, from); 301 } 302 303 int x32_setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs) 304 { 305 compat_sigset_t *set = (compat_sigset_t *) sigmask_to_save(); 306 struct rt_sigframe_x32 __user *frame; 307 unsigned long uc_flags; 308 void __user *restorer; 309 void __user *fp = NULL; 310 311 if (!(ksig->ka.sa.sa_flags & SA_RESTORER)) 312 return -EFAULT; 313 314 frame = get_sigframe(ksig, regs, sizeof(*frame), &fp); 315 316 uc_flags = frame_uc_flags(regs); 317 318 if (setup_signal_shadow_stack(ksig)) 319 return -EFAULT; 320 321 if (!user_access_begin(frame, sizeof(*frame))) 322 return -EFAULT; 323 324 /* Create the ucontext. */ 325 unsafe_put_user(uc_flags, &frame->uc.uc_flags, Efault); 326 unsafe_put_user(0, &frame->uc.uc_link, Efault); 327 unsafe_compat_save_altstack(&frame->uc.uc_stack, regs->sp, Efault); 328 unsafe_put_user(0, &frame->uc.uc__pad0, Efault); 329 restorer = ksig->ka.sa.sa_restorer; 330 unsafe_put_user(restorer, (unsigned long __user *)&frame->pretcode, Efault); 331 unsafe_put_sigcontext(&frame->uc.uc_mcontext, fp, regs, set, Efault); 332 unsafe_put_sigmask(set, frame, Efault); 333 user_access_end(); 334 335 if (ksig->ka.sa.sa_flags & SA_SIGINFO) { 336 if (x32_copy_siginfo_to_user(&frame->info, &ksig->info)) 337 return -EFAULT; 338 } 339 340 /* Set up registers for signal handler */ 341 regs->sp = (unsigned long) frame; 342 regs->ip = (unsigned long) ksig->ka.sa.sa_handler; 343 344 /* We use the x32 calling convention here... */ 345 regs->di = ksig->sig; 346 regs->si = (unsigned long) &frame->info; 347 regs->dx = (unsigned long) &frame->uc; 348 349 loadsegment(ds, __USER_DS); 350 loadsegment(es, __USER_DS); 351 352 regs->cs = __USER_CS; 353 regs->ss = __USER_DS; 354 355 return 0; 356 357 Efault: 358 user_access_end(); 359 return -EFAULT; 360 } 361 362 COMPAT_SYSCALL_DEFINE0(x32_rt_sigreturn) 363 { 364 struct pt_regs *regs = current_pt_regs(); 365 struct rt_sigframe_x32 __user *frame; 366 sigset_t set; 367 unsigned long uc_flags; 368 369 frame = (struct rt_sigframe_x32 __user *)(regs->sp - 8); 370 371 if (!access_ok(frame, sizeof(*frame))) 372 goto badframe; 373 if (__get_user(set.sig[0], (__u64 __user *)&frame->uc.uc_sigmask)) 374 goto badframe; 375 if (__get_user(uc_flags, &frame->uc.uc_flags)) 376 goto badframe; 377 378 set_current_blocked(&set); 379 380 if (!restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags)) 381 goto badframe; 382 383 if (restore_signal_shadow_stack()) 384 goto badframe; 385 386 if (compat_restore_altstack(&frame->uc.uc_stack)) 387 goto badframe; 388 389 return regs->ax; 390 391 badframe: 392 signal_fault(regs, frame, "x32 rt_sigreturn"); 393 return 0; 394 } 395 #endif /* CONFIG_X86_X32_ABI */ 396 397 #ifdef CONFIG_COMPAT 398 void sigaction_compat_abi(struct k_sigaction *act, struct k_sigaction *oact) 399 { 400 if (!act) 401 return; 402 403 if (in_ia32_syscall()) 404 act->sa.sa_flags |= SA_IA32_ABI; 405 if (in_x32_syscall()) 406 act->sa.sa_flags |= SA_X32_ABI; 407 } 408 #endif /* CONFIG_COMPAT */ 409 410 /* 411 * If adding a new si_code, there is probably new data in 412 * the siginfo. Make sure folks bumping the si_code 413 * limits also have to look at this code. Make sure any 414 * new fields are handled in copy_siginfo_to_user32()! 415 */ 416 static_assert(NSIGILL == 11); 417 static_assert(NSIGFPE == 15); 418 static_assert(NSIGSEGV == 10); 419 static_assert(NSIGBUS == 5); 420 static_assert(NSIGTRAP == 6); 421 static_assert(NSIGCHLD == 6); 422 static_assert(NSIGSYS == 2); 423 424 /* This is part of the ABI and can never change in size: */ 425 static_assert(sizeof(siginfo_t) == 128); 426 427 /* This is a part of the ABI and can never change in alignment */ 428 static_assert(__alignof__(siginfo_t) == 8); 429 430 /* 431 * The offsets of all the (unioned) si_fields are fixed 432 * in the ABI, of course. Make sure none of them ever 433 * move and are always at the beginning: 434 */ 435 static_assert(offsetof(siginfo_t, si_signo) == 0); 436 static_assert(offsetof(siginfo_t, si_errno) == 4); 437 static_assert(offsetof(siginfo_t, si_code) == 8); 438 439 /* 440 * Ensure that the size of each si_field never changes. 441 * If it does, it is a sign that the 442 * copy_siginfo_to_user32() code below needs to updated 443 * along with the size in the CHECK_SI_SIZE(). 444 * 445 * We repeat this check for both the generic and compat 446 * siginfos. 447 * 448 * Note: it is OK for these to grow as long as the whole 449 * structure stays within the padding size (checked 450 * above). 451 */ 452 453 #define CHECK_SI_OFFSET(name) \ 454 static_assert(offsetof(siginfo_t, _sifields) == \ 455 offsetof(siginfo_t, _sifields.name)) 456 #define CHECK_SI_SIZE(name, size) \ 457 static_assert(sizeof_field(siginfo_t, _sifields.name) == size) 458 459 CHECK_SI_OFFSET(_kill); 460 CHECK_SI_SIZE (_kill, 2*sizeof(int)); 461 static_assert(offsetof(siginfo_t, si_pid) == 0x10); 462 static_assert(offsetof(siginfo_t, si_uid) == 0x14); 463 464 CHECK_SI_OFFSET(_timer); 465 CHECK_SI_SIZE (_timer, 6*sizeof(int)); 466 static_assert(offsetof(siginfo_t, si_tid) == 0x10); 467 static_assert(offsetof(siginfo_t, si_overrun) == 0x14); 468 static_assert(offsetof(siginfo_t, si_value) == 0x18); 469 470 CHECK_SI_OFFSET(_rt); 471 CHECK_SI_SIZE (_rt, 4*sizeof(int)); 472 static_assert(offsetof(siginfo_t, si_pid) == 0x10); 473 static_assert(offsetof(siginfo_t, si_uid) == 0x14); 474 static_assert(offsetof(siginfo_t, si_value) == 0x18); 475 476 CHECK_SI_OFFSET(_sigchld); 477 CHECK_SI_SIZE (_sigchld, 8*sizeof(int)); 478 static_assert(offsetof(siginfo_t, si_pid) == 0x10); 479 static_assert(offsetof(siginfo_t, si_uid) == 0x14); 480 static_assert(offsetof(siginfo_t, si_status) == 0x18); 481 static_assert(offsetof(siginfo_t, si_utime) == 0x20); 482 static_assert(offsetof(siginfo_t, si_stime) == 0x28); 483 484 #ifdef CONFIG_X86_X32_ABI 485 /* no _sigchld_x32 in the generic siginfo_t */ 486 static_assert(sizeof_field(compat_siginfo_t, _sifields._sigchld_x32) == 487 7*sizeof(int)); 488 static_assert(offsetof(compat_siginfo_t, _sifields) == 489 offsetof(compat_siginfo_t, _sifields._sigchld_x32)); 490 static_assert(offsetof(compat_siginfo_t, _sifields._sigchld_x32._utime) == 0x18); 491 static_assert(offsetof(compat_siginfo_t, _sifields._sigchld_x32._stime) == 0x20); 492 #endif 493 494 CHECK_SI_OFFSET(_sigfault); 495 CHECK_SI_SIZE (_sigfault, 8*sizeof(int)); 496 static_assert(offsetof(siginfo_t, si_addr) == 0x10); 497 498 static_assert(offsetof(siginfo_t, si_trapno) == 0x18); 499 500 static_assert(offsetof(siginfo_t, si_addr_lsb) == 0x18); 501 502 static_assert(offsetof(siginfo_t, si_lower) == 0x20); 503 static_assert(offsetof(siginfo_t, si_upper) == 0x28); 504 505 static_assert(offsetof(siginfo_t, si_pkey) == 0x20); 506 507 static_assert(offsetof(siginfo_t, si_perf_data) == 0x18); 508 static_assert(offsetof(siginfo_t, si_perf_type) == 0x20); 509 static_assert(offsetof(siginfo_t, si_perf_flags) == 0x24); 510 511 CHECK_SI_OFFSET(_sigpoll); 512 CHECK_SI_SIZE (_sigpoll, 4*sizeof(int)); 513 static_assert(offsetof(siginfo_t, si_band) == 0x10); 514 static_assert(offsetof(siginfo_t, si_fd) == 0x18); 515 516 CHECK_SI_OFFSET(_sigsys); 517 CHECK_SI_SIZE (_sigsys, 4*sizeof(int)); 518 static_assert(offsetof(siginfo_t, si_call_addr) == 0x10); 519 static_assert(offsetof(siginfo_t, si_syscall) == 0x18); 520 static_assert(offsetof(siginfo_t, si_arch) == 0x1C); 521 522 /* any new si_fields should be added here */ 523