arch/arm64/kernel/signal.c

   1 /*
   2  * Based on arch/arm/kernel/signal.c
   3  *
   4  * Copyright (C) 1995-2009 Russell King
   5  * Copyright (C) 2012 ARM Ltd.
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include <linux/errno.h>
  21 #include <linux/signal.h>
  22 #include <linux/personality.h>
  23 #include <linux/freezer.h>
  24 #include <linux/uaccess.h>
  25 #include <linux/tracehook.h>
  26 #include <linux/ratelimit.h>
  27
  28 #include <asm/compat.h>
  29 #include <asm/debug-monitors.h>
  30 #include <asm/elf.h>
  31 #include <asm/cacheflush.h>
  32 #include <asm/ucontext.h>
  33 #include <asm/unistd.h>
  34 #include <asm/fpsimd.h>
  35 #include <asm/signal32.h>
  36 #include <asm/vdso.h>
  37
  38 /*
  39  * Do a signal return; undo the signal stack. These are aligned to 128-bit.
  40  */
  41 struct rt_sigframe {
  42         struct siginfo info;
  43         struct ucontext uc;
  44         u64 fp;
  45         u64 lr;
  46 };
  47
  48 static int preserve_fpsimd_context(struct fpsimd_context __user *ctx)
  49 {
  50         struct fpsimd_state *fpsimd = &current->thread.fpsimd_state;
  51         int err;
  52
  53         /* dump the hardware registers to the fpsimd_state structure */
  54         fpsimd_save_state(fpsimd);
  55
  56         /* copy the FP and status/control registers */
  57         err = __copy_to_user(ctx->vregs, fpsimd->vregs, sizeof(fpsimd->vregs));
  58         __put_user_error(fpsimd->fpsr, &ctx->fpsr, err);
  59         __put_user_error(fpsimd->fpcr, &ctx->fpcr, err);
  60
  61         /* copy the magic/size information */
  62         __put_user_error(FPSIMD_MAGIC, &ctx->head.magic, err);
  63         __put_user_error(sizeof(struct fpsimd_context), &ctx->head.size, err);
  64
  65         return err ? -EFAULT : 0;
  66 }
  67
  68 static int restore_fpsimd_context(struct fpsimd_context __user *ctx)
  69 {
  70         struct fpsimd_state fpsimd;
  71         __u32 magic, size;
  72         int err = 0;
  73
  74         /* check the magic/size information */
  75         __get_user_error(magic, &ctx->head.magic, err);
  76         __get_user_error(size, &ctx->head.size, err);
  77         if (err)
  78                 return -EFAULT;
  79         if (magic != FPSIMD_MAGIC || size != sizeof(struct fpsimd_context))
  80                 return -EINVAL;
  81
  82         /* copy the FP and status/control registers */
  83         err = __copy_from_user(fpsimd.vregs, ctx->vregs,
  84                                sizeof(fpsimd.vregs));
  85         __get_user_error(fpsimd.fpsr, &ctx->fpsr, err);
  86         __get_user_error(fpsimd.fpcr, &ctx->fpcr, err);
  87
  88         /* load the hardware registers from the fpsimd_state structure */
  89         if (!err) {
  90                 preempt_disable();
  91                 fpsimd_load_state(&fpsimd);
  92                 preempt_enable();
  93         }
  94
  95         return err ? -EFAULT : 0;
  96 }
  97
  98 static int restore_sigframe(struct pt_regs *regs,
  99                             struct rt_sigframe __user *sf)
 100 {
 101         sigset_t set;
 102         int i, err;
 103         struct aux_context __user *aux =
 104                 (struct aux_context __user *)sf->uc.uc_mcontext.__reserved;
 105
 106         err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
 107         if (err == 0)
 108                 set_current_blocked(&set);
 109
 110         for (i = 0; i < 31; i++)
 111                 __get_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i],
 112                                  err);
 113         __get_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err);
 114         __get_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err);
 115         __get_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err);
 116
 117         /*
 118          * Avoid sys_rt_sigreturn() restarting.
 119          */
 120         regs->syscallno = ~0UL;
 121
 122         err |= !valid_user_regs(&regs->user_regs);
 123
 124         if (err == 0)
 125                 err |= restore_fpsimd_context(&aux->fpsimd);
 126
 127         return err;
 128 }
 129
 130 asmlinkage long sys_rt_sigreturn(struct pt_regs *regs)
 131 {
 132         struct rt_sigframe __user *frame;
 133
 134         /* Always make any pending restarted system calls return -EINTR */
 135         current_thread_info()->restart_block.fn = do_no_restart_syscall;
 136
 137         /*
 138          * Since we stacked the signal on a 128-bit boundary, then 'sp' should
 139          * be word aligned here.
 140          */
 141         if (regs->sp & 15)
 142                 goto badframe;
 143
 144         frame = (struct rt_sigframe __user *)regs->sp;
 145
 146         if (!access_ok(VERIFY_READ, frame, sizeof (*frame)))
 147                 goto badframe;
 148
 149         if (restore_sigframe(regs, frame))
 150                 goto badframe;
 151
 152         if (do_sigaltstack(&frame->uc.uc_stack,
 153                            NULL, regs->sp) == -EFAULT)
 154                 goto badframe;
 155
 156         return regs->regs[0];
 157
 158 badframe:
 159         if (show_unhandled_signals)
 160                 pr_info_ratelimited("%s[%d]: bad frame in %s: pc=%08llx sp=%08llx\n",
 161                                     current->comm, task_pid_nr(current), __func__,
 162                                     regs->pc, regs->sp);
 163         force_sig(SIGSEGV, current);
 164         return 0;
 165 }
 166
 167 asmlinkage long sys_sigaltstack(const stack_t __user *uss, stack_t __user *uoss,
 168                                 unsigned long sp)
 169 {
 170         return do_sigaltstack(uss, uoss, sp);
 171 }
 172
 173 static int setup_sigframe(struct rt_sigframe __user *sf,
 174                           struct pt_regs *regs, sigset_t *set)
 175 {
 176         int i, err = 0;
 177         struct aux_context __user *aux =
 178                 (struct aux_context __user *)sf->uc.uc_mcontext.__reserved;
 179
 180         /* set up the stack frame for unwinding */
 181         __put_user_error(regs->regs[29], &sf->fp, err);
 182         __put_user_error(regs->regs[30], &sf->lr, err);
 183
 184         for (i = 0; i < 31; i++)
 185                 __put_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i],
 186                                  err);
 187         __put_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err);
 188         __put_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err);
 189         __put_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err);
 190
 191         __put_user_error(current->thread.fault_address, &sf->uc.uc_mcontext.fault_address, err);
 192
 193         err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(*set));
 194
 195         if (err == 0)
 196                 err |= preserve_fpsimd_context(&aux->fpsimd);
 197
 198         /* set the "end" magic */
 199         __put_user_error(0, &aux->end.magic, err);
 200         __put_user_error(0, &aux->end.size, err);
 201
 202         return err;
 203 }
 204
 205 static void __user *get_sigframe(struct k_sigaction *ka, struct pt_regs *regs,
 206                                  int framesize)
 207 {
 208         unsigned long sp, sp_top;
 209         void __user *frame;
 210
 211         sp = sp_top = regs->sp;
 212
 213         /*
 214          * This is the X/Open sanctioned signal stack switching.
 215          */
 216         if ((ka->sa.sa_flags & SA_ONSTACK) && !sas_ss_flags(sp))
 217                 sp = sp_top = current->sas_ss_sp + current->sas_ss_size;
 218
 219         sp = (sp - framesize) & ~15;
 220         frame = (void __user *)sp;
 221
 222         /*
 223          * Check that we can actually write to the signal frame.
 224          */
 225         if (!access_ok(VERIFY_WRITE, frame, sp_top - sp))
 226                 frame = NULL;
 227
 228         return frame;
 229 }
 230
 231 static void setup_return(struct pt_regs *regs, struct k_sigaction *ka,
 232                          void __user *frame, int usig)
 233 {
 234         __sigrestore_t sigtramp;
 235
 236         regs->regs[0] = usig;
 237         regs->sp = (unsigned long)frame;
 238         regs->regs[29] = regs->sp + offsetof(struct rt_sigframe, fp);
 239         regs->pc = (unsigned long)ka->sa.sa_handler;
 240
 241         if (ka->sa.sa_flags & SA_RESTORER)
 242                 sigtramp = ka->sa.sa_restorer;
 243         else
 244                 sigtramp = VDSO_SYMBOL(current->mm->context.vdso, sigtramp);
 245
 246         regs->regs[30] = (unsigned long)sigtramp;
 247 }
 248
 249 static int setup_rt_frame(int usig, struct k_sigaction *ka, siginfo_t *info,
 250                           sigset_t *set, struct pt_regs *regs)
 251 {
 252         struct rt_sigframe __user *frame;
 253         stack_t stack;
 254         int err = 0;
 255
 256         frame = get_sigframe(ka, regs, sizeof(*frame));
 257         if (!frame)
 258                 return 1;
 259
 260         __put_user_error(0, &frame->uc.uc_flags, err);
 261         __put_user_error(NULL, &frame->uc.uc_link, err);
 262
 263         memset(&stack, 0, sizeof(stack));
 264         stack.ss_sp = (void __user *)current->sas_ss_sp;
 265         stack.ss_flags = sas_ss_flags(regs->sp);
 266         stack.ss_size = current->sas_ss_size;
 267         err |= __copy_to_user(&frame->uc.uc_stack, &stack, sizeof(stack));
 268
 269         err |= setup_sigframe(frame, regs, set);
 270         if (err == 0) {
 271                 setup_return(regs, ka, frame, usig);
 272                 if (ka->sa.sa_flags & SA_SIGINFO) {
 273                         err |= copy_siginfo_to_user(&frame->info, info);
 274                         regs->regs[1] = (unsigned long)&frame->info;
 275                         regs->regs[2] = (unsigned long)&frame->uc;
 276                 }
 277         }
 278
 279         return err;
 280 }
 281
 282 static void setup_restart_syscall(struct pt_regs *regs)
 283 {
 284         if (is_compat_task())
 285                 compat_setup_restart_syscall(regs);
 286         else
 287                 regs->regs[8] = __NR_restart_syscall;
 288 }
 289
 290 /*
 291  * OK, we're invoking a handler
 292  */
 293 static void handle_signal(unsigned long sig, struct k_sigaction *ka,
 294                           siginfo_t *info, struct pt_regs *regs)
 295 {
 296         struct thread_info *thread = current_thread_info();
 297         struct task_struct *tsk = current;
 298         sigset_t *oldset = sigmask_to_save();
 299         int usig = sig;
 300         int ret;
 301
 302         /*
 303          * translate the signal
 304          */
 305         if (usig < 32 && thread->exec_domain && thread->exec_domain->signal_invmap)
 306                 usig = thread->exec_domain->signal_invmap[usig];
 307
 308         /*
 309          * Set up the stack frame
 310          */
 311         if (is_compat_task()) {
 312                 if (ka->sa.sa_flags & SA_SIGINFO)
 313                         ret = compat_setup_rt_frame(usig, ka, info, oldset,
 314                                                     regs);
 315                 else
 316                         ret = compat_setup_frame(usig, ka, oldset, regs);
 317         } else {
 318                 ret = setup_rt_frame(usig, ka, info, oldset, regs);
 319         }
 320
 321         /*
 322          * Check that the resulting registers are actually sane.
 323          */
 324         ret |= !valid_user_regs(&regs->user_regs);
 325
 326         if (ret != 0) {
 327                 force_sigsegv(sig, tsk);
 328                 return;
 329         }
 330
 331         /*
 332          * Fast forward the stepping logic so we step into the signal
 333          * handler.
 334          */
 335         user_fastforward_single_step(tsk);
 336
 337         signal_delivered(sig, info, ka, regs, 0);
 338 }
 339
 340 /*
 341  * Note that 'init' is a special process: it doesn't get signals it doesn't
 342  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 343  * mistake.
 344  *
 345  * Note that we go through the signals twice: once to check the signals that
 346  * the kernel can handle, and then we build all the user-level signal handling
 347  * stack-frames in one go after that.
 348  */
 349 static void do_signal(struct pt_regs *regs)
 350 {
 351         unsigned long continue_addr = 0, restart_addr = 0;
 352         struct k_sigaction ka;
 353         siginfo_t info;
 354         int signr, retval = 0;
 355         int syscall = (int)regs->syscallno;
 356
 357         /*
 358          * If we were from a system call, check for system call restarting...
 359          */
 360         if (syscall >= 0) {
 361                 continue_addr = regs->pc;
 362                 restart_addr = continue_addr - (compat_thumb_mode(regs) ? 2 : 4);
 363                 retval = regs->regs[0];
 364
 365                 /*
 366                  * Avoid additional syscall restarting via ret_to_user.
 367                  */
 368                 regs->syscallno = ~0UL;
 369
 370                 /*
 371                  * Prepare for system call restart. We do this here so that a
 372                  * debugger will see the already changed PC.
 373                  */
 374                 switch (retval) {
 375                 case -ERESTARTNOHAND:
 376                 case -ERESTARTSYS:
 377                 case -ERESTARTNOINTR:
 378                 case -ERESTART_RESTARTBLOCK:
 379                         regs->regs[0] = regs->orig_x0;
 380                         regs->pc = restart_addr;
 381                         break;
 382                 }
 383         }
 384
 385         /*
 386          * Get the signal to deliver. When running under ptrace, at this point
 387          * the debugger may change all of our registers.
 388          */
 389         signr = get_signal_to_deliver(&info, &ka, regs, NULL);
 390         if (signr > 0) {
 391                 /*
 392                  * Depending on the signal settings, we may need to revert the
 393                  * decision to restart the system call, but skip this if a
 394                  * debugger has chosen to restart at a different PC.
 395                  */
 396                 if (regs->pc == restart_addr &&
 397                     (retval == -ERESTARTNOHAND ||
 398                      retval == -ERESTART_RESTARTBLOCK ||
 399                      (retval == -ERESTARTSYS &&
 400                       !(ka.sa.sa_flags & SA_RESTART)))) {
 401                         regs->regs[0] = -EINTR;
 402                         regs->pc = continue_addr;
 403                 }
 404
 405                 handle_signal(signr, &ka, &info, regs);
 406                 return;
 407         }
 408
 409         /*
 410          * Handle restarting a different system call. As above, if a debugger
 411          * has chosen to restart at a different PC, ignore the restart.
 412          */
 413         if (syscall >= 0 && regs->pc == restart_addr) {
 414                 if (retval == -ERESTART_RESTARTBLOCK)
 415                         setup_restart_syscall(regs);
 416                 user_rewind_single_step(current);
 417         }
 418
 419         restore_saved_sigmask();
 420 }
 421
 422 asmlinkage void do_notify_resume(struct pt_regs *regs,
 423                                  unsigned int thread_flags)
 424 {
 425         if (thread_flags & _TIF_SIGPENDING)
 426                 do_signal(regs);
 427
 428         if (thread_flags & _TIF_NOTIFY_RESUME) {
 429                 clear_thread_flag(TIF_NOTIFY_RESUME);
 430                 tracehook_notify_resume(regs);
 431         }
 432 }