arch/riscv/kernel/signal.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Copyright (C) 2009 Sunplus Core Technology Co., Ltd.
   4  *  Chen Liqin <liqin.chen@sunplusct.com>
   5  *  Lennox Wu <lennox.wu@sunplusct.com>
   6  * Copyright (C) 2012 Regents of the University of California
   7  */
   8
   9 #include <linux/signal.h>
  10 #include <linux/uaccess.h>
  11 #include <linux/syscalls.h>
  12 #include <linux/tracehook.h>
  13 #include <linux/linkage.h>
  14
  15 #include <asm/ucontext.h>
  16 #include <asm/vdso.h>
  17 #include <asm/switch_to.h>
  18 #include <asm/csr.h>
  19
  20 extern u32 __user_rt_sigreturn[2];
  21
  22 #define DEBUG_SIG 0
  23
  24 struct rt_sigframe {
  25         struct siginfo info;
  26         struct ucontext uc;
  27 #ifndef CONFIG_MMU
  28         u32 sigreturn_code[2];
  29 #endif
  30 };
  31
  32 #ifdef CONFIG_FPU
  33 static long restore_fp_state(struct pt_regs *regs,
  34                              union __riscv_fp_state __user *sc_fpregs)
  35 {
  36         long err;
  37         struct __riscv_d_ext_state __user *state = &sc_fpregs->d;
  38         size_t i;
  39
  40         err = __copy_from_user(&current->thread.fstate, state, sizeof(*state));
  41         if (unlikely(err))
  42                 return err;
  43
  44         fstate_restore(current, regs);
  45
  46         /* We support no other extension state at this time. */
  47         for (i = 0; i < ARRAY_SIZE(sc_fpregs->q.reserved); i++) {
  48                 u32 value;
  49
  50                 err = __get_user(value, &sc_fpregs->q.reserved[i]);
  51                 if (unlikely(err))
  52                         break;
  53                 if (value != 0)
  54                         return -EINVAL;
  55         }
  56
  57         return err;
  58 }
  59
  60 static long save_fp_state(struct pt_regs *regs,
  61                           union __riscv_fp_state __user *sc_fpregs)
  62 {
  63         long err;
  64         struct __riscv_d_ext_state __user *state = &sc_fpregs->d;
  65         size_t i;
  66
  67         fstate_save(current, regs);
  68         err = __copy_to_user(state, &current->thread.fstate, sizeof(*state));
  69         if (unlikely(err))
  70                 return err;
  71
  72         /* We support no other extension state at this time. */
  73         for (i = 0; i < ARRAY_SIZE(sc_fpregs->q.reserved); i++) {
  74                 err = __put_user(0, &sc_fpregs->q.reserved[i]);
  75                 if (unlikely(err))
  76                         break;
  77         }
  78
  79         return err;
  80 }
  81 #else
  82 #define save_fp_state(task, regs) (0)
  83 #define restore_fp_state(task, regs) (0)
  84 #endif
  85
  86 static long restore_sigcontext(struct pt_regs *regs,
  87         struct sigcontext __user *sc)
  88 {
  89         long err;
  90         /* sc_regs is structured the same as the start of pt_regs */
  91         err = __copy_from_user(regs, &sc->sc_regs, sizeof(sc->sc_regs));
  92         /* Restore the floating-point state. */
  93         if (has_fpu)
  94                 err |= restore_fp_state(regs, &sc->sc_fpregs);
  95         return err;
  96 }
  97
  98 SYSCALL_DEFINE0(rt_sigreturn)
  99 {
 100         struct pt_regs *regs = current_pt_regs();
 101         struct rt_sigframe __user *frame;
 102         struct task_struct *task;
 103         sigset_t set;
 104
 105         /* Always make any pending restarted system calls return -EINTR */
 106         current->restart_block.fn = do_no_restart_syscall;
 107
 108         frame = (struct rt_sigframe __user *)regs->sp;
 109
 110         if (!access_ok(frame, sizeof(*frame)))
 111                 goto badframe;
 112
 113         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
 114                 goto badframe;
 115
 116         set_current_blocked(&set);
 117
 118         if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
 119                 goto badframe;
 120
 121         if (restore_altstack(&frame->uc.uc_stack))
 122                 goto badframe;
 123
 124         return regs->a0;
 125
 126 badframe:
 127         task = current;
 128         if (show_unhandled_signals) {
 129                 pr_info_ratelimited(
 130                         "%s[%d]: bad frame in %s: frame=%p pc=%p sp=%p\n",
 131                         task->comm, task_pid_nr(task), __func__,
 132                         frame, (void *)regs->epc, (void *)regs->sp);
 133         }
 134         force_sig(SIGSEGV);
 135         return 0;
 136 }
 137
 138 static long setup_sigcontext(struct rt_sigframe __user *frame,
 139         struct pt_regs *regs)
 140 {
 141         struct sigcontext __user *sc = &frame->uc.uc_mcontext;
 142         long err;
 143         /* sc_regs is structured the same as the start of pt_regs */
 144         err = __copy_to_user(&sc->sc_regs, regs, sizeof(sc->sc_regs));
 145         /* Save the floating-point state. */
 146         if (has_fpu)
 147                 err |= save_fp_state(regs, &sc->sc_fpregs);
 148         return err;
 149 }
 150
 151 static inline void __user *get_sigframe(struct ksignal *ksig,
 152         struct pt_regs *regs, size_t framesize)
 153 {
 154         unsigned long sp;
 155         /* Default to using normal stack */
 156         sp = regs->sp;
 157
 158         /*
 159          * If we are on the alternate signal stack and would overflow it, don't.
 160          * Return an always-bogus address instead so we will die with SIGSEGV.
 161          */
 162         if (on_sig_stack(sp) && !likely(on_sig_stack(sp - framesize)))
 163                 return (void __user __force *)(-1UL);
 164
 165         /* This is the X/Open sanctioned signal stack switching. */
 166         sp = sigsp(sp, ksig) - framesize;
 167
 168         /* Align the stack frame. */
 169         sp &= ~0xfUL;
 170
 171         return (void __user *)sp;
 172 }
 173
 174 static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
 175         struct pt_regs *regs)
 176 {
 177         struct rt_sigframe __user *frame;
 178         long err = 0;
 179
 180         frame = get_sigframe(ksig, regs, sizeof(*frame));
 181         if (!access_ok(frame, sizeof(*frame)))
 182                 return -EFAULT;
 183
 184         err |= copy_siginfo_to_user(&frame->info, &ksig->info);
 185
 186         /* Create the ucontext. */
 187         err |= __put_user(0, &frame->uc.uc_flags);
 188         err |= __put_user(NULL, &frame->uc.uc_link);
 189         err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
 190         err |= setup_sigcontext(frame, regs);
 191         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 192         if (err)
 193                 return -EFAULT;
 194
 195         /* Set up to return from userspace. */
 196 #ifdef CONFIG_MMU
 197         regs->ra = (unsigned long)VDSO_SYMBOL(
 198                 current->mm->context.vdso, rt_sigreturn);
 199 #else
 200         /*
 201          * For the nommu case we don't have a VDSO.  Instead we push two
 202          * instructions to call the rt_sigreturn syscall onto the user stack.
 203          */
 204         if (copy_to_user(&frame->sigreturn_code, __user_rt_sigreturn,
 205                          sizeof(frame->sigreturn_code)))
 206                 return -EFAULT;
 207         regs->ra = (unsigned long)&frame->sigreturn_code;
 208 #endif /* CONFIG_MMU */
 209
 210         /*
 211          * Set up registers for signal handler.
 212          * Registers that we don't modify keep the value they had from
 213          * user-space at the time we took the signal.
 214          * We always pass siginfo and mcontext, regardless of SA_SIGINFO,
 215          * since some things rely on this (e.g. glibc's debug/segfault.c).
 216          */
 217         regs->epc = (unsigned long)ksig->ka.sa.sa_handler;
 218         regs->sp = (unsigned long)frame;
 219         regs->a0 = ksig->sig;                     /* a0: signal number */
 220         regs->a1 = (unsigned long)(&frame->info); /* a1: siginfo pointer */
 221         regs->a2 = (unsigned long)(&frame->uc);   /* a2: ucontext pointer */
 222
 223 #if DEBUG_SIG
 224         pr_info("SIG deliver (%s:%d): sig=%d pc=%p ra=%p sp=%p\n",
 225                 current->comm, task_pid_nr(current), ksig->sig,
 226                 (void *)regs->epc, (void *)regs->ra, frame);
 227 #endif
 228
 229         return 0;
 230 }
 231
 232 static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
 233 {
 234         sigset_t *oldset = sigmask_to_save();
 235         int ret;
 236
 237         /* Are we from a system call? */
 238         if (regs->cause == EXC_SYSCALL) {
 239                 /* Avoid additional syscall restarting via ret_from_exception */
 240                 regs->cause = -1UL;
 241                 /* If so, check system call restarting.. */
 242                 switch (regs->a0) {
 243                 case -ERESTART_RESTARTBLOCK:
 244                 case -ERESTARTNOHAND:
 245                         regs->a0 = -EINTR;
 246                         break;
 247
 248                 case -ERESTARTSYS:
 249                         if (!(ksig->ka.sa.sa_flags & SA_RESTART)) {
 250                                 regs->a0 = -EINTR;
 251                                 break;
 252                         }
 253                         fallthrough;
 254                 case -ERESTARTNOINTR:
 255                         regs->a0 = regs->orig_a0;
 256                         regs->epc -= 0x4;
 257                         break;
 258                 }
 259         }
 260
 261         /* Set up the stack frame */
 262         ret = setup_rt_frame(ksig, oldset, regs);
 263
 264         signal_setup_done(ret, ksig, 0);
 265 }
 266
 267 static void do_signal(struct pt_regs *regs)
 268 {
 269         struct ksignal ksig;
 270
 271         if (get_signal(&ksig)) {
 272                 /* Actually deliver the signal */
 273                 handle_signal(&ksig, regs);
 274                 return;
 275         }
 276
 277         /* Did we come from a system call? */
 278         if (regs->cause == EXC_SYSCALL) {
 279                 /* Avoid additional syscall restarting via ret_from_exception */
 280                 regs->cause = -1UL;
 281
 282                 /* Restart the system call - no handlers present */
 283                 switch (regs->a0) {
 284                 case -ERESTARTNOHAND:
 285                 case -ERESTARTSYS:
 286                 case -ERESTARTNOINTR:
 287                         regs->a0 = regs->orig_a0;
 288                         regs->epc -= 0x4;
 289                         break;
 290                 case -ERESTART_RESTARTBLOCK:
 291                         regs->a0 = regs->orig_a0;
 292                         regs->a7 = __NR_restart_syscall;
 293                         regs->epc -= 0x4;
 294                         break;
 295                 }
 296         }
 297
 298         /*
 299          * If there is no signal to deliver, we just put the saved
 300          * sigmask back.
 301          */
 302         restore_saved_sigmask();
 303 }
 304
 305 /*
 306  * notification of userspace execution resumption
 307  * - triggered by the _TIF_WORK_MASK flags
 308  */
 309 asmlinkage __visible void do_notify_resume(struct pt_regs *regs,
 310                                            unsigned long thread_info_flags)
 311 {
 312         /* Handle pending signal delivery */
 313         if (thread_info_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
 314                 do_signal(regs);
 315
 316         if (thread_info_flags & _TIF_NOTIFY_RESUME)
 317                 tracehook_notify_resume(regs);
 318 }