1 /* 2 * arch/xtensa/kernel/signal.c 3 * 4 * Default platform functions. 5 * 6 * This file is subject to the terms and conditions of the GNU General Public 7 * License. See the file "COPYING" in the main directory of this archive 8 * for more details. 9 * 10 * Copyright (C) 2005, 2006 Tensilica Inc. 11 * Copyright (C) 1991, 1992 Linus Torvalds 12 * 1997-11-28 Modified for POSIX.1b signals by Richard Henderson 13 * 14 * Chris Zankel <chris@zankel.net> 15 * Joe Taylor <joe@tensilica.com> 16 */ 17 18 #include <linux/signal.h> 19 #include <linux/errno.h> 20 #include <linux/ptrace.h> 21 #include <linux/personality.h> 22 #include <linux/resume_user_mode.h> 23 #include <linux/sched/task_stack.h> 24 25 #include <asm/ucontext.h> 26 #include <linux/uaccess.h> 27 #include <asm/cacheflush.h> 28 #include <asm/coprocessor.h> 29 #include <asm/unistd.h> 30 31 extern struct task_struct *coproc_owners[]; 32 33 struct rt_sigframe 34 { 35 struct siginfo info; 36 struct ucontext uc; 37 struct { 38 xtregs_opt_t opt; 39 xtregs_user_t user; 40 #if XTENSA_HAVE_COPROCESSORS 41 xtregs_coprocessor_t cp; 42 #endif 43 } xtregs; 44 unsigned char retcode[6]; 45 unsigned int window[4]; 46 }; 47 48 #if defined(USER_SUPPORT_WINDOWED) 49 /* 50 * Flush register windows stored in pt_regs to stack. 51 * Returns 1 for errors. 52 */ 53 54 static int 55 flush_window_regs_user(struct pt_regs *regs) 56 { 57 const unsigned long ws = regs->windowstart; 58 const unsigned long wb = regs->windowbase; 59 unsigned long sp = 0; 60 unsigned long wm; 61 int err = 1; 62 int base; 63 64 /* Return if no other frames. */ 65 66 if (regs->wmask == 1) 67 return 0; 68 69 /* Rotate windowmask and skip empty frames. */ 70 71 wm = (ws >> wb) | (ws << (XCHAL_NUM_AREGS / 4 - wb)); 72 base = (XCHAL_NUM_AREGS / 4) - (regs->wmask >> 4); 73 74 /* For call8 or call12 frames, we need the previous stack pointer. */ 75 76 if ((regs->wmask & 2) == 0) 77 if (__get_user(sp, (int*)(regs->areg[base * 4 + 1] - 12))) 78 goto errout; 79 80 /* Spill frames to stack. */ 81 82 while (base < XCHAL_NUM_AREGS / 4) { 83 84 int m = (wm >> base); 85 int inc = 0; 86 87 /* Save registers a4..a7 (call8) or a4...a11 (call12) */ 88 89 if (m & 2) { /* call4 */ 90 inc = 1; 91 92 } else if (m & 4) { /* call8 */ 93 if (copy_to_user(&SPILL_SLOT_CALL8(sp, 4), 94 ®s->areg[(base + 1) * 4], 16)) 95 goto errout; 96 inc = 2; 97 98 } else if (m & 8) { /* call12 */ 99 if (copy_to_user(&SPILL_SLOT_CALL12(sp, 4), 100 ®s->areg[(base + 1) * 4], 32)) 101 goto errout; 102 inc = 3; 103 } 104 105 /* Save current frame a0..a3 under next SP */ 106 107 sp = regs->areg[((base + inc) * 4 + 1) % XCHAL_NUM_AREGS]; 108 if (copy_to_user(&SPILL_SLOT(sp, 0), ®s->areg[base * 4], 16)) 109 goto errout; 110 111 /* Get current stack pointer for next loop iteration. */ 112 113 sp = regs->areg[base * 4 + 1]; 114 base += inc; 115 } 116 117 regs->wmask = 1; 118 regs->windowstart = 1 << wb; 119 120 return 0; 121 122 errout: 123 return err; 124 } 125 #else 126 static int 127 flush_window_regs_user(struct pt_regs *regs) 128 { 129 return 0; 130 } 131 #endif 132 133 /* 134 * Note: We don't copy double exception 'regs', we have to finish double exc. 135 * first before we return to signal handler! This dbl.exc.handler might cause 136 * another double exception, but I think we are fine as the situation is the 137 * same as if we had returned to the signal handerl and got an interrupt 138 * immediately... 139 */ 140 141 static int 142 setup_sigcontext(struct rt_sigframe __user *frame, struct pt_regs *regs) 143 { 144 struct sigcontext __user *sc = &frame->uc.uc_mcontext; 145 struct thread_info *ti = current_thread_info(); 146 int err = 0; 147 148 #define COPY(x) err |= __put_user(regs->x, &sc->sc_##x) 149 COPY(pc); 150 COPY(ps); 151 COPY(lbeg); 152 COPY(lend); 153 COPY(lcount); 154 COPY(sar); 155 #undef COPY 156 157 err |= flush_window_regs_user(regs); 158 err |= __copy_to_user (sc->sc_a, regs->areg, 16 * 4); 159 err |= __put_user(0, &sc->sc_xtregs); 160 161 if (err) 162 return err; 163 164 #if XTENSA_HAVE_COPROCESSORS 165 coprocessor_flush_release_all(ti); 166 err |= __copy_to_user(&frame->xtregs.cp, &ti->xtregs_cp, 167 sizeof (frame->xtregs.cp)); 168 #endif 169 err |= __copy_to_user(&frame->xtregs.opt, ®s->xtregs_opt, 170 sizeof (xtregs_opt_t)); 171 err |= __copy_to_user(&frame->xtregs.user, &ti->xtregs_user, 172 sizeof (xtregs_user_t)); 173 174 err |= __put_user(err ? NULL : &frame->xtregs, &sc->sc_xtregs); 175 176 return err; 177 } 178 179 static int 180 restore_sigcontext(struct pt_regs *regs, struct rt_sigframe __user *frame) 181 { 182 struct sigcontext __user *sc = &frame->uc.uc_mcontext; 183 struct thread_info *ti = current_thread_info(); 184 unsigned int err = 0; 185 unsigned long ps; 186 187 #define COPY(x) err |= __get_user(regs->x, &sc->sc_##x) 188 COPY(pc); 189 COPY(lbeg); 190 COPY(lend); 191 COPY(lcount); 192 COPY(sar); 193 #undef COPY 194 195 /* All registers were flushed to stack. Start with a pristine frame. */ 196 197 regs->wmask = 1; 198 regs->windowbase = 0; 199 regs->windowstart = 1; 200 201 regs->syscall = NO_SYSCALL; /* disable syscall checks */ 202 203 /* For PS, restore only PS.CALLINC. 204 * Assume that all other bits are either the same as for the signal 205 * handler, or the user mode value doesn't matter (e.g. PS.OWB). 206 */ 207 err |= __get_user(ps, &sc->sc_ps); 208 regs->ps = (regs->ps & ~PS_CALLINC_MASK) | (ps & PS_CALLINC_MASK); 209 210 /* Additional corruption checks */ 211 212 if ((regs->lcount > 0) 213 && ((regs->lbeg > TASK_SIZE) || (regs->lend > TASK_SIZE)) ) 214 err = 1; 215 216 err |= __copy_from_user(regs->areg, sc->sc_a, 16 * 4); 217 218 if (err) 219 return err; 220 221 /* The signal handler may have used coprocessors in which 222 * case they are still enabled. We disable them to force a 223 * reloading of the original task's CP state by the lazy 224 * context-switching mechanisms of CP exception handling. 225 * Also, we essentially discard any coprocessor state that the 226 * signal handler created. */ 227 228 #if XTENSA_HAVE_COPROCESSORS 229 coprocessor_release_all(ti); 230 err |= __copy_from_user(&ti->xtregs_cp, &frame->xtregs.cp, 231 sizeof (frame->xtregs.cp)); 232 #endif 233 err |= __copy_from_user(&ti->xtregs_user, &frame->xtregs.user, 234 sizeof (xtregs_user_t)); 235 err |= __copy_from_user(®s->xtregs_opt, &frame->xtregs.opt, 236 sizeof (xtregs_opt_t)); 237 238 return err; 239 } 240 241 242 /* 243 * Do a signal return; undo the signal stack. 244 */ 245 246 asmlinkage long xtensa_rt_sigreturn(void) 247 { 248 struct pt_regs *regs = current_pt_regs(); 249 struct rt_sigframe __user *frame; 250 sigset_t set; 251 int ret; 252 253 /* Always make any pending restarted system calls return -EINTR */ 254 current->restart_block.fn = do_no_restart_syscall; 255 256 if (regs->depc > 64) 257 panic("rt_sigreturn in double exception!\n"); 258 259 frame = (struct rt_sigframe __user *) regs->areg[1]; 260 261 if (!access_ok(frame, sizeof(*frame))) 262 goto badframe; 263 264 if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set))) 265 goto badframe; 266 267 set_current_blocked(&set); 268 269 if (restore_sigcontext(regs, frame)) 270 goto badframe; 271 272 ret = regs->areg[2]; 273 274 if (restore_altstack(&frame->uc.uc_stack)) 275 goto badframe; 276 277 return ret; 278 279 badframe: 280 force_sig(SIGSEGV); 281 return 0; 282 } 283 284 285 286 /* 287 * Set up a signal frame. 288 */ 289 290 static int 291 gen_return_code(unsigned char *codemem) 292 { 293 int err = 0; 294 295 /* 296 * The 12-bit immediate is really split up within the 24-bit MOVI 297 * instruction. As long as the above system call numbers fit within 298 * 8-bits, the following code works fine. See the Xtensa ISA for 299 * details. 300 */ 301 302 #if __NR_rt_sigreturn > 255 303 # error Generating the MOVI instruction below breaks! 304 #endif 305 306 #ifdef __XTENSA_EB__ /* Big Endian version */ 307 /* Generate instruction: MOVI a2, __NR_rt_sigreturn */ 308 err |= __put_user(0x22, &codemem[0]); 309 err |= __put_user(0x0a, &codemem[1]); 310 err |= __put_user(__NR_rt_sigreturn, &codemem[2]); 311 /* Generate instruction: SYSCALL */ 312 err |= __put_user(0x00, &codemem[3]); 313 err |= __put_user(0x05, &codemem[4]); 314 err |= __put_user(0x00, &codemem[5]); 315 316 #elif defined __XTENSA_EL__ /* Little Endian version */ 317 /* Generate instruction: MOVI a2, __NR_rt_sigreturn */ 318 err |= __put_user(0x22, &codemem[0]); 319 err |= __put_user(0xa0, &codemem[1]); 320 err |= __put_user(__NR_rt_sigreturn, &codemem[2]); 321 /* Generate instruction: SYSCALL */ 322 err |= __put_user(0x00, &codemem[3]); 323 err |= __put_user(0x50, &codemem[4]); 324 err |= __put_user(0x00, &codemem[5]); 325 #else 326 # error Must use compiler for Xtensa processors. 327 #endif 328 329 /* Flush generated code out of the data cache */ 330 331 if (err == 0) { 332 __invalidate_icache_range((unsigned long)codemem, 6UL); 333 __flush_invalidate_dcache_range((unsigned long)codemem, 6UL); 334 } 335 336 return err; 337 } 338 339 340 static int setup_frame(struct ksignal *ksig, sigset_t *set, 341 struct pt_regs *regs) 342 { 343 struct rt_sigframe *frame; 344 int err = 0, sig = ksig->sig; 345 unsigned long sp, ra, tp, ps; 346 unsigned long handler = (unsigned long)ksig->ka.sa.sa_handler; 347 unsigned long handler_fdpic_GOT = 0; 348 unsigned int base; 349 bool fdpic = IS_ENABLED(CONFIG_BINFMT_ELF_FDPIC) && 350 (current->personality & FDPIC_FUNCPTRS); 351 352 if (fdpic) { 353 unsigned long __user *fdpic_func_desc = 354 (unsigned long __user *)handler; 355 if (__get_user(handler, &fdpic_func_desc[0]) || 356 __get_user(handler_fdpic_GOT, &fdpic_func_desc[1])) 357 return -EFAULT; 358 } 359 360 sp = regs->areg[1]; 361 362 if ((ksig->ka.sa.sa_flags & SA_ONSTACK) != 0 && sas_ss_flags(sp) == 0) { 363 sp = current->sas_ss_sp + current->sas_ss_size; 364 } 365 366 frame = (void *)((sp - sizeof(*frame)) & -16ul); 367 368 if (regs->depc > 64) 369 panic ("Double exception sys_sigreturn\n"); 370 371 if (!access_ok(frame, sizeof(*frame))) { 372 return -EFAULT; 373 } 374 375 if (ksig->ka.sa.sa_flags & SA_SIGINFO) { 376 err |= copy_siginfo_to_user(&frame->info, &ksig->info); 377 } 378 379 /* Create the user context. */ 380 381 err |= __put_user(0, &frame->uc.uc_flags); 382 err |= __put_user(0, &frame->uc.uc_link); 383 err |= __save_altstack(&frame->uc.uc_stack, regs->areg[1]); 384 err |= setup_sigcontext(frame, regs); 385 err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set)); 386 387 if (ksig->ka.sa.sa_flags & SA_RESTORER) { 388 if (fdpic) { 389 unsigned long __user *fdpic_func_desc = 390 (unsigned long __user *)ksig->ka.sa.sa_restorer; 391 392 err |= __get_user(ra, fdpic_func_desc); 393 } else { 394 ra = (unsigned long)ksig->ka.sa.sa_restorer; 395 } 396 } else { 397 398 /* Create sys_rt_sigreturn syscall in stack frame */ 399 400 err |= gen_return_code(frame->retcode); 401 ra = (unsigned long) frame->retcode; 402 } 403 404 if (err) 405 return -EFAULT; 406 407 /* 408 * Create signal handler execution context. 409 * Return context not modified until this point. 410 */ 411 412 /* Set up registers for signal handler; preserve the threadptr */ 413 tp = regs->threadptr; 414 ps = regs->ps; 415 start_thread(regs, handler, (unsigned long)frame); 416 417 /* Set up a stack frame for a call4 if userspace uses windowed ABI */ 418 if (ps & PS_WOE_MASK) { 419 base = 4; 420 regs->areg[base] = 421 (((unsigned long) ra) & 0x3fffffff) | 0x40000000; 422 ps = (ps & ~(PS_CALLINC_MASK | PS_OWB_MASK)) | 423 (1 << PS_CALLINC_SHIFT); 424 } else { 425 base = 0; 426 regs->areg[base] = (unsigned long) ra; 427 } 428 regs->areg[base + 2] = (unsigned long) sig; 429 regs->areg[base + 3] = (unsigned long) &frame->info; 430 regs->areg[base + 4] = (unsigned long) &frame->uc; 431 regs->threadptr = tp; 432 regs->ps = ps; 433 if (fdpic) 434 regs->areg[base + 11] = handler_fdpic_GOT; 435 436 pr_debug("SIG rt deliver (%s:%d): signal=%d sp=%p pc=%08lx\n", 437 current->comm, current->pid, sig, frame, regs->pc); 438 439 return 0; 440 } 441 442 /* 443 * Note that 'init' is a special process: it doesn't get signals it doesn't 444 * want to handle. Thus you cannot kill init even with a SIGKILL even by 445 * mistake. 446 * 447 * Note that we go through the signals twice: once to check the signals that 448 * the kernel can handle, and then we build all the user-level signal handling 449 * stack-frames in one go after that. 450 */ 451 static void do_signal(struct pt_regs *regs) 452 { 453 struct ksignal ksig; 454 455 task_pt_regs(current)->icountlevel = 0; 456 457 if (get_signal(&ksig)) { 458 int ret; 459 460 /* Are we from a system call? */ 461 462 if (regs->syscall != NO_SYSCALL) { 463 464 /* If so, check system call restarting.. */ 465 466 switch (regs->areg[2]) { 467 case -ERESTARTNOHAND: 468 case -ERESTART_RESTARTBLOCK: 469 regs->areg[2] = -EINTR; 470 break; 471 472 case -ERESTARTSYS: 473 if (!(ksig.ka.sa.sa_flags & SA_RESTART)) { 474 regs->areg[2] = -EINTR; 475 break; 476 } 477 fallthrough; 478 case -ERESTARTNOINTR: 479 regs->areg[2] = regs->syscall; 480 regs->pc -= 3; 481 break; 482 483 default: 484 /* nothing to do */ 485 if (regs->areg[2] != 0) 486 break; 487 } 488 } 489 490 /* Whee! Actually deliver the signal. */ 491 /* Set up the stack frame */ 492 ret = setup_frame(&ksig, sigmask_to_save(), regs); 493 signal_setup_done(ret, &ksig, 0); 494 if (test_thread_flag(TIF_SINGLESTEP)) 495 task_pt_regs(current)->icountlevel = 1; 496 497 return; 498 } 499 500 /* Did we come from a system call? */ 501 if (regs->syscall != NO_SYSCALL) { 502 /* Restart the system call - no handlers present */ 503 switch (regs->areg[2]) { 504 case -ERESTARTNOHAND: 505 case -ERESTARTSYS: 506 case -ERESTARTNOINTR: 507 regs->areg[2] = regs->syscall; 508 regs->pc -= 3; 509 break; 510 case -ERESTART_RESTARTBLOCK: 511 regs->areg[2] = __NR_restart_syscall; 512 regs->pc -= 3; 513 break; 514 } 515 } 516 517 /* If there's no signal to deliver, we just restore the saved mask. */ 518 restore_saved_sigmask(); 519 520 if (test_thread_flag(TIF_SINGLESTEP)) 521 task_pt_regs(current)->icountlevel = 1; 522 return; 523 } 524 525 void do_notify_resume(struct pt_regs *regs) 526 { 527 if (test_thread_flag(TIF_SIGPENDING) || 528 test_thread_flag(TIF_NOTIFY_SIGNAL)) 529 do_signal(regs); 530 531 if (test_thread_flag(TIF_NOTIFY_RESUME)) 532 resume_user_mode_work(regs); 533 } 534