1 /* 2 * Signal Handling for ARC 3 * 4 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com) 5 * 6 * This program is free software; you can redistribute it and/or modify 7 * it under the terms of the GNU General Public License version 2 as 8 * published by the Free Software Foundation. 9 * 10 * vineetg: Jan 2010 (Restarting of timer related syscalls) 11 * 12 * vineetg: Nov 2009 (Everything needed for TIF_RESTORE_SIGMASK) 13 * -do_signal() supports TIF_RESTORE_SIGMASK 14 * -do_signal() no loner needs oldset, required by OLD sys_sigsuspend 15 * -sys_rt_sigsuspend() now comes from generic code, so discard arch implemen 16 * -sys_sigsuspend() no longer needs to fudge ptregs, hence that arg removed 17 * -sys_sigsuspend() no longer loops for do_signal(), sets TIF_xxx and leaves 18 * the job to do_signal() 19 * 20 * vineetg: July 2009 21 * -Modified Code to support the uClibc provided userland sigreturn stub 22 * to avoid kernel synthesing it on user stack at runtime, costing TLB 23 * probes and Cache line flushes. 24 * 25 * vineetg: July 2009 26 * -In stash_usr_regs( ) and restore_usr_regs( ), save/restore of user regs 27 * in done in block copy rather than one word at a time. 28 * This saves around 2K of code and improves LMBench lat_sig <catch> 29 * 30 * rajeshwarr: Feb 2009 31 * - Support for Realtime Signals 32 * 33 * vineetg: Aug 11th 2008: Bug #94183 34 * -ViXS were still seeing crashes when using insmod to load drivers. 35 * It turned out that the code to change Execute permssions for TLB entries 36 * of user was not guarded for interrupts (mod_tlb_permission) 37 * This was cauing TLB entries to be overwritten on unrelated indexes 38 * 39 * Vineetg: July 15th 2008: Bug #94183 40 * -Exception happens in Delay slot of a JMP, and before user space resumes, 41 * Signal is delivered (Ctrl + C) = >SIGINT. 42 * setup_frame( ) sets up PC,SP,BLINK to enable user space signal handler 43 * to run, but doesn't clear the Delay slot bit from status32. As a result, 44 * on resuming user mode, signal handler branches off to BTA of orig JMP 45 * -FIX: clear the DE bit from status32 in setup_frame( ) 46 * 47 * Rahul Trivedi, Kanika Nema: Codito Technologies 2004 48 */ 49 50 #include <linux/signal.h> 51 #include <linux/ptrace.h> 52 #include <linux/personality.h> 53 #include <linux/uaccess.h> 54 #include <linux/syscalls.h> 55 #include <linux/tracehook.h> 56 #include <asm/ucontext.h> 57 58 struct rt_sigframe { 59 struct siginfo info; 60 struct ucontext uc; 61 #define MAGIC_SIGALTSTK 0x07302004 62 unsigned int sigret_magic; 63 }; 64 65 static int 66 stash_usr_regs(struct rt_sigframe __user *sf, struct pt_regs *regs, 67 sigset_t *set) 68 { 69 int err; 70 struct user_regs_struct uregs; 71 72 uregs.scratch.bta = regs->bta; 73 uregs.scratch.lp_start = regs->lp_start; 74 uregs.scratch.lp_end = regs->lp_end; 75 uregs.scratch.lp_count = regs->lp_count; 76 uregs.scratch.status32 = regs->status32; 77 uregs.scratch.ret = regs->ret; 78 uregs.scratch.blink = regs->blink; 79 uregs.scratch.fp = regs->fp; 80 uregs.scratch.gp = regs->r26; 81 uregs.scratch.r12 = regs->r12; 82 uregs.scratch.r11 = regs->r11; 83 uregs.scratch.r10 = regs->r10; 84 uregs.scratch.r9 = regs->r9; 85 uregs.scratch.r8 = regs->r8; 86 uregs.scratch.r7 = regs->r7; 87 uregs.scratch.r6 = regs->r6; 88 uregs.scratch.r5 = regs->r5; 89 uregs.scratch.r4 = regs->r4; 90 uregs.scratch.r3 = regs->r3; 91 uregs.scratch.r2 = regs->r2; 92 uregs.scratch.r1 = regs->r1; 93 uregs.scratch.r0 = regs->r0; 94 uregs.scratch.sp = regs->sp; 95 96 err = __copy_to_user(&(sf->uc.uc_mcontext.regs.scratch), &uregs.scratch, 97 sizeof(sf->uc.uc_mcontext.regs.scratch)); 98 err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(sigset_t)); 99 100 return err; 101 } 102 103 static int restore_usr_regs(struct pt_regs *regs, struct rt_sigframe __user *sf) 104 { 105 sigset_t set; 106 int err; 107 struct user_regs_struct uregs; 108 109 err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set)); 110 if (!err) 111 set_current_blocked(&set); 112 113 err |= __copy_from_user(&uregs.scratch, 114 &(sf->uc.uc_mcontext.regs.scratch), 115 sizeof(sf->uc.uc_mcontext.regs.scratch)); 116 117 regs->bta = uregs.scratch.bta; 118 regs->lp_start = uregs.scratch.lp_start; 119 regs->lp_end = uregs.scratch.lp_end; 120 regs->lp_count = uregs.scratch.lp_count; 121 regs->status32 = uregs.scratch.status32; 122 regs->ret = uregs.scratch.ret; 123 regs->blink = uregs.scratch.blink; 124 regs->fp = uregs.scratch.fp; 125 regs->r26 = uregs.scratch.gp; 126 regs->r12 = uregs.scratch.r12; 127 regs->r11 = uregs.scratch.r11; 128 regs->r10 = uregs.scratch.r10; 129 regs->r9 = uregs.scratch.r9; 130 regs->r8 = uregs.scratch.r8; 131 regs->r7 = uregs.scratch.r7; 132 regs->r6 = uregs.scratch.r6; 133 regs->r5 = uregs.scratch.r5; 134 regs->r4 = uregs.scratch.r4; 135 regs->r3 = uregs.scratch.r3; 136 regs->r2 = uregs.scratch.r2; 137 regs->r1 = uregs.scratch.r1; 138 regs->r0 = uregs.scratch.r0; 139 regs->sp = uregs.scratch.sp; 140 141 return err; 142 } 143 144 static inline int is_do_ss_needed(unsigned int magic) 145 { 146 if (MAGIC_SIGALTSTK == magic) 147 return 1; 148 else 149 return 0; 150 } 151 152 SYSCALL_DEFINE0(rt_sigreturn) 153 { 154 struct rt_sigframe __user *sf; 155 unsigned int magic; 156 struct pt_regs *regs = current_pt_regs(); 157 158 /* Always make any pending restarted system calls return -EINTR */ 159 current->restart_block.fn = do_no_restart_syscall; 160 161 /* Since we stacked the signal on a word boundary, 162 * then 'sp' should be word aligned here. If it's 163 * not, then the user is trying to mess with us. 164 */ 165 if (regs->sp & 3) 166 goto badframe; 167 168 sf = (struct rt_sigframe __force __user *)(regs->sp); 169 170 if (!access_ok(VERIFY_READ, sf, sizeof(*sf))) 171 goto badframe; 172 173 if (__get_user(magic, &sf->sigret_magic)) 174 goto badframe; 175 176 if (unlikely(is_do_ss_needed(magic))) 177 if (restore_altstack(&sf->uc.uc_stack)) 178 goto badframe; 179 180 if (restore_usr_regs(regs, sf)) 181 goto badframe; 182 183 /* Don't restart from sigreturn */ 184 syscall_wont_restart(regs); 185 186 /* 187 * Ensure that sigreturn always returns to user mode (in case the 188 * regs saved on user stack got fudged between save and sigreturn) 189 * Otherwise it is easy to panic the kernel with a custom 190 * signal handler and/or restorer which clobberes the status32/ret 191 * to return to a bogus location in kernel mode. 192 */ 193 regs->status32 |= STATUS_U_MASK; 194 195 return regs->r0; 196 197 badframe: 198 force_sig(SIGSEGV, current); 199 return 0; 200 } 201 202 /* 203 * Determine which stack to use.. 204 */ 205 static inline void __user *get_sigframe(struct ksignal *ksig, 206 struct pt_regs *regs, 207 unsigned long framesize) 208 { 209 unsigned long sp = sigsp(regs->sp, ksig); 210 void __user *frame; 211 212 /* No matter what happens, 'sp' must be word 213 * aligned otherwise nasty things could happen 214 */ 215 216 /* ATPCS B01 mandates 8-byte alignment */ 217 frame = (void __user *)((sp - framesize) & ~7); 218 219 /* Check that we can actually write to the signal frame */ 220 if (!access_ok(VERIFY_WRITE, frame, framesize)) 221 frame = NULL; 222 223 return frame; 224 } 225 226 static int 227 setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs) 228 { 229 struct rt_sigframe __user *sf; 230 unsigned int magic = 0; 231 int err = 0; 232 233 sf = get_sigframe(ksig, regs, sizeof(struct rt_sigframe)); 234 if (!sf) 235 return 1; 236 237 /* 238 * w/o SA_SIGINFO, struct ucontext is partially populated (only 239 * uc_mcontext/uc_sigmask) for kernel's normal user state preservation 240 * during signal handler execution. This works for SA_SIGINFO as well 241 * although the semantics are now overloaded (the same reg state can be 242 * inspected by userland: but are they allowed to fiddle with it ? 243 */ 244 err |= stash_usr_regs(sf, regs, set); 245 246 /* 247 * SA_SIGINFO requires 3 args to signal handler: 248 * #1: sig-no (common to any handler) 249 * #2: struct siginfo 250 * #3: struct ucontext (completely populated) 251 */ 252 if (unlikely(ksig->ka.sa.sa_flags & SA_SIGINFO)) { 253 err |= copy_siginfo_to_user(&sf->info, &ksig->info); 254 err |= __put_user(0, &sf->uc.uc_flags); 255 err |= __put_user(NULL, &sf->uc.uc_link); 256 err |= __save_altstack(&sf->uc.uc_stack, regs->sp); 257 258 /* setup args 2 and 3 for user mode handler */ 259 regs->r1 = (unsigned long)&sf->info; 260 regs->r2 = (unsigned long)&sf->uc; 261 262 /* 263 * small optim to avoid unconditonally calling do_sigaltstack 264 * in sigreturn path, now that we only have rt_sigreturn 265 */ 266 magic = MAGIC_SIGALTSTK; 267 } 268 269 err |= __put_user(magic, &sf->sigret_magic); 270 if (err) 271 return err; 272 273 /* #1 arg to the user Signal handler */ 274 regs->r0 = ksig->sig; 275 276 /* setup PC of user space signal handler */ 277 regs->ret = (unsigned long)ksig->ka.sa.sa_handler; 278 279 /* 280 * handler returns using sigreturn stub provided already by userpsace 281 * If not, nuke the process right away 282 */ 283 if(!(ksig->ka.sa.sa_flags & SA_RESTORER)) 284 return 1; 285 286 regs->blink = (unsigned long)ksig->ka.sa.sa_restorer; 287 288 /* User Stack for signal handler will be above the frame just carved */ 289 regs->sp = (unsigned long)sf; 290 291 /* 292 * Bug 94183, Clear the DE bit, so that when signal handler 293 * starts to run, it doesn't use BTA 294 */ 295 regs->status32 &= ~STATUS_DE_MASK; 296 regs->status32 |= STATUS_L_MASK; 297 298 return err; 299 } 300 301 static void arc_restart_syscall(struct k_sigaction *ka, struct pt_regs *regs) 302 { 303 switch (regs->r0) { 304 case -ERESTART_RESTARTBLOCK: 305 case -ERESTARTNOHAND: 306 /* 307 * ERESTARTNOHAND means that the syscall should 308 * only be restarted if there was no handler for 309 * the signal, and since we only get here if there 310 * is a handler, we don't restart 311 */ 312 regs->r0 = -EINTR; /* ERESTART_xxx is internal */ 313 break; 314 315 case -ERESTARTSYS: 316 /* 317 * ERESTARTSYS means to restart the syscall if 318 * there is no handler or the handler was 319 * registered with SA_RESTART 320 */ 321 if (!(ka->sa.sa_flags & SA_RESTART)) { 322 regs->r0 = -EINTR; 323 break; 324 } 325 /* fallthrough */ 326 327 case -ERESTARTNOINTR: 328 /* 329 * ERESTARTNOINTR means that the syscall should 330 * be called again after the signal handler returns. 331 * Setup reg state just as it was before doing the trap 332 * r0 has been clobbered with sys call ret code thus it 333 * needs to be reloaded with orig first arg to syscall 334 * in orig_r0. Rest of relevant reg-file: 335 * r8 (syscall num) and (r1 - r7) will be reset to 336 * their orig user space value when we ret from kernel 337 */ 338 regs->r0 = regs->orig_r0; 339 regs->ret -= is_isa_arcv2() ? 2 : 4; 340 break; 341 } 342 } 343 344 /* 345 * OK, we're invoking a handler 346 */ 347 static void 348 handle_signal(struct ksignal *ksig, struct pt_regs *regs) 349 { 350 sigset_t *oldset = sigmask_to_save(); 351 int failed; 352 353 /* Set up the stack frame */ 354 failed = setup_rt_frame(ksig, oldset, regs); 355 356 signal_setup_done(failed, ksig, 0); 357 } 358 359 void do_signal(struct pt_regs *regs) 360 { 361 struct ksignal ksig; 362 int restart_scall; 363 364 restart_scall = in_syscall(regs) && syscall_restartable(regs); 365 366 if (get_signal(&ksig)) { 367 if (restart_scall) { 368 arc_restart_syscall(&ksig.ka, regs); 369 syscall_wont_restart(regs); /* No more restarts */ 370 } 371 handle_signal(&ksig, regs); 372 return; 373 } 374 375 if (restart_scall) { 376 /* No handler for syscall: restart it */ 377 if (regs->r0 == -ERESTARTNOHAND || 378 regs->r0 == -ERESTARTSYS || regs->r0 == -ERESTARTNOINTR) { 379 regs->r0 = regs->orig_r0; 380 regs->ret -= is_isa_arcv2() ? 2 : 4; 381 } else if (regs->r0 == -ERESTART_RESTARTBLOCK) { 382 regs->r8 = __NR_restart_syscall; 383 regs->ret -= is_isa_arcv2() ? 2 : 4; 384 } 385 syscall_wont_restart(regs); /* No more restarts */ 386 } 387 388 /* If there's no signal to deliver, restore the saved sigmask back */ 389 restore_saved_sigmask(); 390 } 391 392 void do_notify_resume(struct pt_regs *regs) 393 { 394 /* 395 * ASM glue gaurantees that this is only called when returning to 396 * user mode 397 */ 398 if (test_and_clear_thread_flag(TIF_NOTIFY_RESUME)) 399 tracehook_notify_resume(regs); 400 } 401