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 58struct rt_sigframe { 59 struct siginfo info; 60 struct ucontext uc; 61#define MAGIC_SIGALTSTK 0x07302004 62 unsigned int sigret_magic; 63}; 64 65static int 66stash_usr_regs(struct rt_sigframe __user *sf, struct pt_regs *regs, 67 sigset_t *set) 68{ 69 int err; 70 err = __copy_to_user(&(sf->uc.uc_mcontext.regs.scratch), regs, 71 sizeof(sf->uc.uc_mcontext.regs.scratch)); 72 err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(sigset_t)); 73 74 return err; 75} 76 77static int restore_usr_regs(struct pt_regs *regs, struct rt_sigframe __user *sf) 78{ 79 sigset_t set; 80 int err; 81 82 err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set)); 83 if (!err) 84 set_current_blocked(&set); 85 86 err |= __copy_from_user(regs, &(sf->uc.uc_mcontext.regs.scratch), 87 sizeof(sf->uc.uc_mcontext.regs.scratch)); 88 89 return err; 90} 91 92static inline int is_do_ss_needed(unsigned int magic) 93{ 94 if (MAGIC_SIGALTSTK == magic) 95 return 1; 96 else 97 return 0; 98} 99 100SYSCALL_DEFINE0(rt_sigreturn) 101{ 102 struct rt_sigframe __user *sf; 103 unsigned int magic; 104 struct pt_regs *regs = current_pt_regs(); 105 106 /* Always make any pending restarted system calls return -EINTR */ 107 current->restart_block.fn = do_no_restart_syscall; 108 109 /* Since we stacked the signal on a word boundary, 110 * then 'sp' should be word aligned here. If it's 111 * not, then the user is trying to mess with us. 112 */ 113 if (regs->sp & 3) 114 goto badframe; 115 116 sf = (struct rt_sigframe __force __user *)(regs->sp); 117 118 if (!access_ok(VERIFY_READ, sf, sizeof(*sf))) 119 goto badframe; 120 121 if (__get_user(magic, &sf->sigret_magic)) 122 goto badframe; 123 124 if (unlikely(is_do_ss_needed(magic))) 125 if (restore_altstack(&sf->uc.uc_stack)) 126 goto badframe; 127 128 if (restore_usr_regs(regs, sf)) 129 goto badframe; 130 131 /* Don't restart from sigreturn */ 132 syscall_wont_restart(regs); 133 134 /* 135 * Ensure that sigreturn always returns to user mode (in case the 136 * regs saved on user stack got fudged between save and sigreturn) 137 * Otherwise it is easy to panic the kernel with a custom 138 * signal handler and/or restorer which clobberes the status32/ret 139 * to return to a bogus location in kernel mode. 140 */ 141 regs->status32 |= STATUS_U_MASK; 142 143 return regs->r0; 144 145badframe: 146 force_sig(SIGSEGV, current); 147 return 0; 148} 149 150/* 151 * Determine which stack to use.. 152 */ 153static inline void __user *get_sigframe(struct ksignal *ksig, 154 struct pt_regs *regs, 155 unsigned long framesize) 156{ 157 unsigned long sp = sigsp(regs->sp, ksig); 158 void __user *frame; 159 160 /* No matter what happens, 'sp' must be word 161 * aligned otherwise nasty things could happen 162 */ 163 164 /* ATPCS B01 mandates 8-byte alignment */ 165 frame = (void __user *)((sp - framesize) & ~7); 166 167 /* Check that we can actually write to the signal frame */ 168 if (!access_ok(VERIFY_WRITE, frame, framesize)) 169 frame = NULL; 170 171 return frame; 172} 173 174static int 175setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs) 176{ 177 struct rt_sigframe __user *sf; 178 unsigned int magic = 0; 179 int err = 0; 180 181 sf = get_sigframe(ksig, regs, sizeof(struct rt_sigframe)); 182 if (!sf) 183 return 1; 184 185 /* 186 * w/o SA_SIGINFO, struct ucontext is partially populated (only 187 * uc_mcontext/uc_sigmask) for kernel's normal user state preservation 188 * during signal handler execution. This works for SA_SIGINFO as well 189 * although the semantics are now overloaded (the same reg state can be 190 * inspected by userland: but are they allowed to fiddle with it ? 191 */ 192 err |= stash_usr_regs(sf, regs, set); 193 194 /* 195 * SA_SIGINFO requires 3 args to signal handler: 196 * #1: sig-no (common to any handler) 197 * #2: struct siginfo 198 * #3: struct ucontext (completely populated) 199 */ 200 if (unlikely(ksig->ka.sa.sa_flags & SA_SIGINFO)) { 201 err |= copy_siginfo_to_user(&sf->info, &ksig->info); 202 err |= __put_user(0, &sf->uc.uc_flags); 203 err |= __put_user(NULL, &sf->uc.uc_link); 204 err |= __save_altstack(&sf->uc.uc_stack, regs->sp); 205 206 /* setup args 2 and 3 for user mode handler */ 207 regs->r1 = (unsigned long)&sf->info; 208 regs->r2 = (unsigned long)&sf->uc; 209 210 /* 211 * small optim to avoid unconditonally calling do_sigaltstack 212 * in sigreturn path, now that we only have rt_sigreturn 213 */ 214 magic = MAGIC_SIGALTSTK; 215 } 216 217 err |= __put_user(magic, &sf->sigret_magic); 218 if (err) 219 return err; 220 221 /* #1 arg to the user Signal handler */ 222 regs->r0 = ksig->sig; 223 224 /* setup PC of user space signal handler */ 225 regs->ret = (unsigned long)ksig->ka.sa.sa_handler; 226 227 /* 228 * handler returns using sigreturn stub provided already by userpsace 229 * If not, nuke the process right away 230 */ 231 if(!(ksig->ka.sa.sa_flags & SA_RESTORER)) 232 return 1; 233 234 regs->blink = (unsigned long)ksig->ka.sa.sa_restorer; 235 236 /* User Stack for signal handler will be above the frame just carved */ 237 regs->sp = (unsigned long)sf; 238 239 /* 240 * Bug 94183, Clear the DE bit, so that when signal handler 241 * starts to run, it doesn't use BTA 242 */ 243 regs->status32 &= ~STATUS_DE_MASK; 244 regs->status32 |= STATUS_L_MASK; 245 246 return err; 247} 248 249static void arc_restart_syscall(struct k_sigaction *ka, struct pt_regs *regs) 250{ 251 switch (regs->r0) { 252 case -ERESTART_RESTARTBLOCK: 253 case -ERESTARTNOHAND: 254 /* 255 * ERESTARTNOHAND means that the syscall should 256 * only be restarted if there was no handler for 257 * the signal, and since we only get here if there 258 * is a handler, we don't restart 259 */ 260 regs->r0 = -EINTR; /* ERESTART_xxx is internal */ 261 break; 262 263 case -ERESTARTSYS: 264 /* 265 * ERESTARTSYS means to restart the syscall if 266 * there is no handler or the handler was 267 * registered with SA_RESTART 268 */ 269 if (!(ka->sa.sa_flags & SA_RESTART)) { 270 regs->r0 = -EINTR; 271 break; 272 } 273 /* fallthrough */ 274 275 case -ERESTARTNOINTR: 276 /* 277 * ERESTARTNOINTR means that the syscall should 278 * be called again after the signal handler returns. 279 * Setup reg state just as it was before doing the trap 280 * r0 has been clobbered with sys call ret code thus it 281 * needs to be reloaded with orig first arg to syscall 282 * in orig_r0. Rest of relevant reg-file: 283 * r8 (syscall num) and (r1 - r7) will be reset to 284 * their orig user space value when we ret from kernel 285 */ 286 regs->r0 = regs->orig_r0; 287 regs->ret -= 4; 288 break; 289 } 290} 291 292/* 293 * OK, we're invoking a handler 294 */ 295static void 296handle_signal(struct ksignal *ksig, struct pt_regs *regs) 297{ 298 sigset_t *oldset = sigmask_to_save(); 299 int failed; 300 301 /* Set up the stack frame */ 302 failed = setup_rt_frame(ksig, oldset, regs); 303 304 signal_setup_done(failed, ksig, 0); 305} 306 307void do_signal(struct pt_regs *regs) 308{ 309 struct ksignal ksig; 310 int restart_scall; 311 312 restart_scall = in_syscall(regs) && syscall_restartable(regs); 313 314 if (get_signal(&ksig)) { 315 if (restart_scall) { 316 arc_restart_syscall(&ksig.ka, regs); 317 syscall_wont_restart(regs); /* No more restarts */ 318 } 319 handle_signal(&ksig, regs); 320 return; 321 } 322 323 if (restart_scall) { 324 /* No handler for syscall: restart it */ 325 if (regs->r0 == -ERESTARTNOHAND || 326 regs->r0 == -ERESTARTSYS || regs->r0 == -ERESTARTNOINTR) { 327 regs->r0 = regs->orig_r0; 328 regs->ret -= 4; 329 } else if (regs->r0 == -ERESTART_RESTARTBLOCK) { 330 regs->r8 = __NR_restart_syscall; 331 regs->ret -= 4; 332 } 333 syscall_wont_restart(regs); /* No more restarts */ 334 } 335 336 /* If there's no signal to deliver, restore the saved sigmask back */ 337 restore_saved_sigmask(); 338} 339 340void do_notify_resume(struct pt_regs *regs) 341{ 342 /* 343 * ASM glue gaurantees that this is only called when returning to 344 * user mode 345 */ 346 if (test_and_clear_thread_flag(TIF_NOTIFY_RESUME)) 347 tracehook_notify_resume(regs); 348} 349