arch/arc/kernel/signal.c

   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         err = __copy_to_user(&(sf->uc.uc_mcontext.regs), 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
  77 static 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),
  87                                 sizeof(sf->uc.uc_mcontext.regs.scratch));
  88
  89         return err;
  90 }
  91
  92 static 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
 100 SYSCALL_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         return regs->r0;
 135
 136 badframe:
 137         force_sig(SIGSEGV, current);
 138         return 0;
 139 }
 140
 141 /*
 142  * Determine which stack to use..
 143  */
 144 static inline void __user *get_sigframe(struct ksignal *ksig,
 145                                         struct pt_regs *regs,
 146                                         unsigned long framesize)
 147 {
 148         unsigned long sp = sigsp(regs->sp, ksig);
 149         void __user *frame;
 150
 151         /* No matter what happens, 'sp' must be word
 152          * aligned otherwise nasty things could happen
 153          */
 154
 155         /* ATPCS B01 mandates 8-byte alignment */
 156         frame = (void __user *)((sp - framesize) & ~7);
 157
 158         /* Check that we can actually write to the signal frame */
 159         if (!access_ok(VERIFY_WRITE, frame, framesize))
 160                 frame = NULL;
 161
 162         return frame;
 163 }
 164
 165 /*
 166  * translate the signal
 167  */
 168 static inline int map_sig(int sig)
 169 {
 170         struct thread_info *thread = current_thread_info();
 171         if (thread->exec_domain && thread->exec_domain->signal_invmap
 172             && sig < 32)
 173                 sig = thread->exec_domain->signal_invmap[sig];
 174         return sig;
 175 }
 176
 177 static int
 178 setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
 179 {
 180         struct rt_sigframe __user *sf;
 181         unsigned int magic = 0;
 182         int err = 0;
 183
 184         sf = get_sigframe(ksig, regs, sizeof(struct rt_sigframe));
 185         if (!sf)
 186                 return 1;
 187
 188         /*
 189          * w/o SA_SIGINFO, struct ucontext is partially populated (only
 190          * uc_mcontext/uc_sigmask) for kernel's normal user state preservation
 191          * during signal handler execution. This works for SA_SIGINFO as well
 192          * although the semantics are now overloaded (the same reg state can be
 193          * inspected by userland: but are they allowed to fiddle with it ?
 194          */
 195         err |= stash_usr_regs(sf, regs, set);
 196
 197         /*
 198          * SA_SIGINFO requires 3 args to signal handler:
 199          *  #1: sig-no (common to any handler)
 200          *  #2: struct siginfo
 201          *  #3: struct ucontext (completely populated)
 202          */
 203         if (unlikely(ksig->ka.sa.sa_flags & SA_SIGINFO)) {
 204                 err |= copy_siginfo_to_user(&sf->info, &ksig->info);
 205                 err |= __put_user(0, &sf->uc.uc_flags);
 206                 err |= __put_user(NULL, &sf->uc.uc_link);
 207                 err |= __save_altstack(&sf->uc.uc_stack, regs->sp);
 208
 209                 /* setup args 2 and 3 for user mode handler */
 210                 regs->r1 = (unsigned long)&sf->info;
 211                 regs->r2 = (unsigned long)&sf->uc;
 212
 213                 /*
 214                  * small optim to avoid unconditonally calling do_sigaltstack
 215                  * in sigreturn path, now that we only have rt_sigreturn
 216                  */
 217                 magic = MAGIC_SIGALTSTK;
 218         }
 219
 220         err |= __put_user(magic, &sf->sigret_magic);
 221         if (err)
 222                 return err;
 223
 224         /* #1 arg to the user Signal handler */
 225         regs->r0 = map_sig(ksig->sig);
 226
 227         /* setup PC of user space signal handler */
 228         regs->ret = (unsigned long)ksig->ka.sa.sa_handler;
 229
 230         /*
 231          * handler returns using sigreturn stub provided already by userpsace
 232          */
 233         BUG_ON(!(ksig->ka.sa.sa_flags & SA_RESTORER));
 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
 249 static 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  */
 295 static void
 296 handle_signal(struct ksignal *ksig, struct pt_regs *regs)
 297 {
 298         sigset_t *oldset = sigmask_to_save();
 299         int ret;
 300
 301         /* Set up the stack frame */
 302         ret = setup_rt_frame(ksig, oldset, regs);
 303
 304         signal_setup_done(ret, ksig, 0);
 305 }
 306
 307 void 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
 340 void 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 }