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/tracehook.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 #define DEBUG_SIG 0 32 33 extern struct task_struct *coproc_owners[]; 34 35 struct rt_sigframe 36 { 37 struct siginfo info; 38 struct ucontext uc; 39 struct { 40 xtregs_opt_t opt; 41 xtregs_user_t user; 42 #if XTENSA_HAVE_COPROCESSORS 43 xtregs_coprocessor_t cp; 44 #endif 45 } xtregs; 46 unsigned char retcode[6]; 47 unsigned int window[4]; 48 }; 49 50 /* 51 * Flush register windows stored in pt_regs to stack. 52 * Returns 1 for errors. 53 */ 54 55 int 56 flush_window_regs_user(struct pt_regs *regs) 57 { 58 const unsigned long ws = regs->windowstart; 59 const unsigned long wb = regs->windowbase; 60 unsigned long sp = 0; 61 unsigned long wm; 62 int err = 1; 63 int base; 64 65 /* Return if no other frames. */ 66 67 if (regs->wmask == 1) 68 return 0; 69 70 /* Rotate windowmask and skip empty frames. */ 71 72 wm = (ws >> wb) | (ws << (XCHAL_NUM_AREGS / 4 - wb)); 73 base = (XCHAL_NUM_AREGS / 4) - (regs->wmask >> 4); 74 75 /* For call8 or call12 frames, we need the previous stack pointer. */ 76 77 if ((regs->wmask & 2) == 0) 78 if (__get_user(sp, (int*)(regs->areg[base * 4 + 1] - 12))) 79 goto errout; 80 81 /* Spill frames to stack. */ 82 83 while (base < XCHAL_NUM_AREGS / 4) { 84 85 int m = (wm >> base); 86 int inc = 0; 87 88 /* Save registers a4..a7 (call8) or a4...a11 (call12) */ 89 90 if (m & 2) { /* call4 */ 91 inc = 1; 92 93 } else if (m & 4) { /* call8 */ 94 if (copy_to_user(&SPILL_SLOT_CALL8(sp, 4), 95 ®s->areg[(base + 1) * 4], 16)) 96 goto errout; 97 inc = 2; 98 99 } else if (m & 8) { /* call12 */ 100 if (copy_to_user(&SPILL_SLOT_CALL12(sp, 4), 101 ®s->areg[(base + 1) * 4], 32)) 102 goto errout; 103 inc = 3; 104 } 105 106 /* Save current frame a0..a3 under next SP */ 107 108 sp = regs->areg[((base + inc) * 4 + 1) % XCHAL_NUM_AREGS]; 109 if (copy_to_user(&SPILL_SLOT(sp, 0), ®s->areg[base * 4], 16)) 110 goto errout; 111 112 /* Get current stack pointer for next loop iteration. */ 113 114 sp = regs->areg[base * 4 + 1]; 115 base += inc; 116 } 117 118 regs->wmask = 1; 119 regs->windowstart = 1 << wb; 120 121 return 0; 122 123 errout: 124 return err; 125 } 126 127 /* 128 * Note: We don't copy double exception 'regs', we have to finish double exc. 129 * first before we return to signal handler! This dbl.exc.handler might cause 130 * another double exception, but I think we are fine as the situation is the 131 * same as if we had returned to the signal handerl and got an interrupt 132 * immediately... 133 */ 134 135 static int 136 setup_sigcontext(struct rt_sigframe __user *frame, struct pt_regs *regs) 137 { 138 struct sigcontext __user *sc = &frame->uc.uc_mcontext; 139 struct thread_info *ti = current_thread_info(); 140 int err = 0; 141 142 #define COPY(x) err |= __put_user(regs->x, &sc->sc_##x) 143 COPY(pc); 144 COPY(ps); 145 COPY(lbeg); 146 COPY(lend); 147 COPY(lcount); 148 COPY(sar); 149 #undef COPY 150 151 err |= flush_window_regs_user(regs); 152 err |= __copy_to_user (sc->sc_a, regs->areg, 16 * 4); 153 err |= __put_user(0, &sc->sc_xtregs); 154 155 if (err) 156 return err; 157 158 #if XTENSA_HAVE_COPROCESSORS 159 coprocessor_flush_all(ti); 160 coprocessor_release_all(ti); 161 err |= __copy_to_user(&frame->xtregs.cp, &ti->xtregs_cp, 162 sizeof (frame->xtregs.cp)); 163 #endif 164 err |= __copy_to_user(&frame->xtregs.opt, ®s->xtregs_opt, 165 sizeof (xtregs_opt_t)); 166 err |= __copy_to_user(&frame->xtregs.user, &ti->xtregs_user, 167 sizeof (xtregs_user_t)); 168 169 err |= __put_user(err ? NULL : &frame->xtregs, &sc->sc_xtregs); 170 171 return err; 172 } 173 174 static int 175 restore_sigcontext(struct pt_regs *regs, struct rt_sigframe __user *frame) 176 { 177 struct sigcontext __user *sc = &frame->uc.uc_mcontext; 178 struct thread_info *ti = current_thread_info(); 179 unsigned int err = 0; 180 unsigned long ps; 181 182 #define COPY(x) err |= __get_user(regs->x, &sc->sc_##x) 183 COPY(pc); 184 COPY(lbeg); 185 COPY(lend); 186 COPY(lcount); 187 COPY(sar); 188 #undef COPY 189 190 /* All registers were flushed to stack. Start with a prestine frame. */ 191 192 regs->wmask = 1; 193 regs->windowbase = 0; 194 regs->windowstart = 1; 195 196 regs->syscall = -1; /* disable syscall checks */ 197 198 /* For PS, restore only PS.CALLINC. 199 * Assume that all other bits are either the same as for the signal 200 * handler, or the user mode value doesn't matter (e.g. PS.OWB). 201 */ 202 err |= __get_user(ps, &sc->sc_ps); 203 regs->ps = (regs->ps & ~PS_CALLINC_MASK) | (ps & PS_CALLINC_MASK); 204 205 /* Additional corruption checks */ 206 207 if ((regs->lcount > 0) 208 && ((regs->lbeg > TASK_SIZE) || (regs->lend > TASK_SIZE)) ) 209 err = 1; 210 211 err |= __copy_from_user(regs->areg, sc->sc_a, 16 * 4); 212 213 if (err) 214 return err; 215 216 /* The signal handler may have used coprocessors in which 217 * case they are still enabled. We disable them to force a 218 * reloading of the original task's CP state by the lazy 219 * context-switching mechanisms of CP exception handling. 220 * Also, we essentially discard any coprocessor state that the 221 * signal handler created. */ 222 223 #if XTENSA_HAVE_COPROCESSORS 224 coprocessor_release_all(ti); 225 err |= __copy_from_user(&ti->xtregs_cp, &frame->xtregs.cp, 226 sizeof (frame->xtregs.cp)); 227 #endif 228 err |= __copy_from_user(&ti->xtregs_user, &frame->xtregs.user, 229 sizeof (xtregs_user_t)); 230 err |= __copy_from_user(®s->xtregs_opt, &frame->xtregs.opt, 231 sizeof (xtregs_opt_t)); 232 233 return err; 234 } 235 236 237 /* 238 * Do a signal return; undo the signal stack. 239 */ 240 241 asmlinkage long xtensa_rt_sigreturn(long a0, long a1, long a2, long a3, 242 long a4, long a5, struct pt_regs *regs) 243 { 244 struct rt_sigframe __user *frame; 245 sigset_t set; 246 int ret; 247 248 /* Always make any pending restarted system calls return -EINTR */ 249 current->restart_block.fn = do_no_restart_syscall; 250 251 if (regs->depc > 64) 252 panic("rt_sigreturn in double exception!\n"); 253 254 frame = (struct rt_sigframe __user *) regs->areg[1]; 255 256 if (!access_ok(VERIFY_READ, frame, sizeof(*frame))) 257 goto badframe; 258 259 if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set))) 260 goto badframe; 261 262 set_current_blocked(&set); 263 264 if (restore_sigcontext(regs, frame)) 265 goto badframe; 266 267 ret = regs->areg[2]; 268 269 if (restore_altstack(&frame->uc.uc_stack)) 270 goto badframe; 271 272 return ret; 273 274 badframe: 275 force_sig(SIGSEGV, current); 276 return 0; 277 } 278 279 280 281 /* 282 * Set up a signal frame. 283 */ 284 285 static int 286 gen_return_code(unsigned char *codemem) 287 { 288 int err = 0; 289 290 /* 291 * The 12-bit immediate is really split up within the 24-bit MOVI 292 * instruction. As long as the above system call numbers fit within 293 * 8-bits, the following code works fine. See the Xtensa ISA for 294 * details. 295 */ 296 297 #if __NR_rt_sigreturn > 255 298 # error Generating the MOVI instruction below breaks! 299 #endif 300 301 #ifdef __XTENSA_EB__ /* Big Endian version */ 302 /* Generate instruction: MOVI a2, __NR_rt_sigreturn */ 303 err |= __put_user(0x22, &codemem[0]); 304 err |= __put_user(0x0a, &codemem[1]); 305 err |= __put_user(__NR_rt_sigreturn, &codemem[2]); 306 /* Generate instruction: SYSCALL */ 307 err |= __put_user(0x00, &codemem[3]); 308 err |= __put_user(0x05, &codemem[4]); 309 err |= __put_user(0x00, &codemem[5]); 310 311 #elif defined __XTENSA_EL__ /* Little Endian version */ 312 /* Generate instruction: MOVI a2, __NR_rt_sigreturn */ 313 err |= __put_user(0x22, &codemem[0]); 314 err |= __put_user(0xa0, &codemem[1]); 315 err |= __put_user(__NR_rt_sigreturn, &codemem[2]); 316 /* Generate instruction: SYSCALL */ 317 err |= __put_user(0x00, &codemem[3]); 318 err |= __put_user(0x50, &codemem[4]); 319 err |= __put_user(0x00, &codemem[5]); 320 #else 321 # error Must use compiler for Xtensa processors. 322 #endif 323 324 /* Flush generated code out of the data cache */ 325 326 if (err == 0) { 327 __invalidate_icache_range((unsigned long)codemem, 6UL); 328 __flush_invalidate_dcache_range((unsigned long)codemem, 6UL); 329 } 330 331 return err; 332 } 333 334 335 static int setup_frame(struct ksignal *ksig, sigset_t *set, 336 struct pt_regs *regs) 337 { 338 struct rt_sigframe *frame; 339 int err = 0, sig = ksig->sig; 340 unsigned long sp, ra, tp; 341 342 sp = regs->areg[1]; 343 344 if ((ksig->ka.sa.sa_flags & SA_ONSTACK) != 0 && sas_ss_flags(sp) == 0) { 345 sp = current->sas_ss_sp + current->sas_ss_size; 346 } 347 348 frame = (void *)((sp - sizeof(*frame)) & -16ul); 349 350 if (regs->depc > 64) 351 panic ("Double exception sys_sigreturn\n"); 352 353 if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame))) { 354 return -EFAULT; 355 } 356 357 if (ksig->ka.sa.sa_flags & SA_SIGINFO) { 358 err |= copy_siginfo_to_user(&frame->info, &ksig->info); 359 } 360 361 /* Create the user context. */ 362 363 err |= __put_user(0, &frame->uc.uc_flags); 364 err |= __put_user(0, &frame->uc.uc_link); 365 err |= __save_altstack(&frame->uc.uc_stack, regs->areg[1]); 366 err |= setup_sigcontext(frame, regs); 367 err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set)); 368 369 if (ksig->ka.sa.sa_flags & SA_RESTORER) { 370 ra = (unsigned long)ksig->ka.sa.sa_restorer; 371 } else { 372 373 /* Create sys_rt_sigreturn syscall in stack frame */ 374 375 err |= gen_return_code(frame->retcode); 376 377 if (err) { 378 return -EFAULT; 379 } 380 ra = (unsigned long) frame->retcode; 381 } 382 383 /* 384 * Create signal handler execution context. 385 * Return context not modified until this point. 386 */ 387 388 /* Set up registers for signal handler; preserve the threadptr */ 389 tp = regs->threadptr; 390 start_thread(regs, (unsigned long) ksig->ka.sa.sa_handler, 391 (unsigned long) frame); 392 393 /* Set up a stack frame for a call4 394 * Note: PS.CALLINC is set to one by start_thread 395 */ 396 regs->areg[4] = (((unsigned long) ra) & 0x3fffffff) | 0x40000000; 397 regs->areg[6] = (unsigned long) sig; 398 regs->areg[7] = (unsigned long) &frame->info; 399 regs->areg[8] = (unsigned long) &frame->uc; 400 regs->threadptr = tp; 401 402 #if DEBUG_SIG 403 printk("SIG rt deliver (%s:%d): signal=%d sp=%p pc=%08x\n", 404 current->comm, current->pid, sig, frame, regs->pc); 405 #endif 406 407 return 0; 408 } 409 410 /* 411 * Note that 'init' is a special process: it doesn't get signals it doesn't 412 * want to handle. Thus you cannot kill init even with a SIGKILL even by 413 * mistake. 414 * 415 * Note that we go through the signals twice: once to check the signals that 416 * the kernel can handle, and then we build all the user-level signal handling 417 * stack-frames in one go after that. 418 */ 419 static void do_signal(struct pt_regs *regs) 420 { 421 struct ksignal ksig; 422 423 task_pt_regs(current)->icountlevel = 0; 424 425 if (get_signal(&ksig)) { 426 int ret; 427 428 /* Are we from a system call? */ 429 430 if ((signed)regs->syscall >= 0) { 431 432 /* If so, check system call restarting.. */ 433 434 switch (regs->areg[2]) { 435 case -ERESTARTNOHAND: 436 case -ERESTART_RESTARTBLOCK: 437 regs->areg[2] = -EINTR; 438 break; 439 440 case -ERESTARTSYS: 441 if (!(ksig.ka.sa.sa_flags & SA_RESTART)) { 442 regs->areg[2] = -EINTR; 443 break; 444 } 445 /* fallthrough */ 446 case -ERESTARTNOINTR: 447 regs->areg[2] = regs->syscall; 448 regs->pc -= 3; 449 break; 450 451 default: 452 /* nothing to do */ 453 if (regs->areg[2] != 0) 454 break; 455 } 456 } 457 458 /* Whee! Actually deliver the signal. */ 459 /* Set up the stack frame */ 460 ret = setup_frame(&ksig, sigmask_to_save(), regs); 461 signal_setup_done(ret, &ksig, 0); 462 if (current->ptrace & PT_SINGLESTEP) 463 task_pt_regs(current)->icountlevel = 1; 464 465 return; 466 } 467 468 /* Did we come from a system call? */ 469 if ((signed) regs->syscall >= 0) { 470 /* Restart the system call - no handlers present */ 471 switch (regs->areg[2]) { 472 case -ERESTARTNOHAND: 473 case -ERESTARTSYS: 474 case -ERESTARTNOINTR: 475 regs->areg[2] = regs->syscall; 476 regs->pc -= 3; 477 break; 478 case -ERESTART_RESTARTBLOCK: 479 regs->areg[2] = __NR_restart_syscall; 480 regs->pc -= 3; 481 break; 482 } 483 } 484 485 /* If there's no signal to deliver, we just restore the saved mask. */ 486 restore_saved_sigmask(); 487 488 if (current->ptrace & PT_SINGLESTEP) 489 task_pt_regs(current)->icountlevel = 1; 490 return; 491 } 492 493 void do_notify_resume(struct pt_regs *regs) 494 { 495 if (test_thread_flag(TIF_SIGPENDING)) 496 do_signal(regs); 497 498 if (test_and_clear_thread_flag(TIF_NOTIFY_RESUME)) 499 tracehook_notify_resume(regs); 500 } 501