arch/openrisc/kernel/signal.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * OpenRISC signal.c
   4  *
   5  * Linux architectural port borrowing liberally from similar works of
   6  * others.  All original copyrights apply as per the original source
   7  * declaration.
   8  *
   9  * Modifications for the OpenRISC architecture:
  10  * Copyright (C) 2003 Matjaz Breskvar <phoenix@bsemi.com>
  11  * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
  12  */
  13
  14 #include <linux/sched.h>
  15 #include <linux/mm.h>
  16 #include <linux/smp.h>
  17 #include <linux/kernel.h>
  18 #include <linux/signal.h>
  19 #include <linux/errno.h>
  20 #include <linux/wait.h>
  21 #include <linux/ptrace.h>
  22 #include <linux/unistd.h>
  23 #include <linux/stddef.h>
  24 #include <linux/resume_user_mode.h>
  25
  26 #include <asm/fpu.h>
  27 #include <asm/processor.h>
  28 #include <asm/syscall.h>
  29 #include <asm/ucontext.h>
  30 #include <linux/uaccess.h>
  31
  32 struct rt_sigframe {
  33         struct siginfo info;
  34         struct ucontext uc;
  35         unsigned char retcode[16];      /* trampoline code */
  36 };
  37
  38 asmlinkage long _sys_rt_sigreturn(struct pt_regs *regs);
  39
  40 asmlinkage int do_work_pending(struct pt_regs *regs, unsigned int thread_flags,
  41                                int syscall);
  42
  43 #ifdef CONFIG_FPU
  44 static long restore_fp_state(struct sigcontext __user *sc)
  45 {
  46         long err;
  47
  48         err = __copy_from_user(&current->thread.fpcsr, &sc->fpcsr, sizeof(unsigned long));
  49         if (unlikely(err))
  50                 return err;
  51
  52         /* Restore the FPU state */
  53         restore_fpu(current);
  54
  55         return 0;
  56 }
  57
  58 static long save_fp_state(struct sigcontext __user *sc)
  59 {
  60         long err;
  61
  62         /* Sync the user FPU state so we can copy to sigcontext */
  63         save_fpu(current);
  64
  65         err = __copy_to_user(&sc->fpcsr, &current->thread.fpcsr, sizeof(unsigned long));
  66
  67         return err;
  68 }
  69 #else
  70 #define save_fp_state(sc) (0)
  71 #define restore_fp_state(sc) (0)
  72 #endif
  73
  74 static int restore_sigcontext(struct pt_regs *regs,
  75                               struct sigcontext __user *sc)
  76 {
  77         int err = 0;
  78
  79         /* Always make any pending restarted system calls return -EINTR */
  80         current->restart_block.fn = do_no_restart_syscall;
  81
  82         /*
  83          * Restore the regs from &sc->regs.
  84          * (sc is already checked since the sigframe was
  85          *  checked in sys_sigreturn previously)
  86          */
  87         err |= __copy_from_user(regs, sc->regs.gpr, 32 * sizeof(unsigned long));
  88         err |= __copy_from_user(&regs->pc, &sc->regs.pc, sizeof(unsigned long));
  89         err |= __copy_from_user(&regs->sr, &sc->regs.sr, sizeof(unsigned long));
  90         err |= restore_fp_state(sc);
  91
  92         /* make sure the SM-bit is cleared so user-mode cannot fool us */
  93         regs->sr &= ~SPR_SR_SM;
  94
  95         regs->orig_gpr11 = -1;  /* Avoid syscall restart checks */
  96
  97         /* TODO: the other ports use regs->orig_XX to disable syscall checks
  98          * after this completes, but we don't use that mechanism. maybe we can
  99          * use it now ?
 100          */
 101
 102         return err;
 103 }
 104
 105 asmlinkage long _sys_rt_sigreturn(struct pt_regs *regs)
 106 {
 107         struct rt_sigframe __user *frame = (struct rt_sigframe __user *)regs->sp;
 108         sigset_t set;
 109
 110         /*
 111          * Since we stacked the signal on a dword boundary,
 112          * then frame should be dword aligned here.  If it's
 113          * not, then the user is trying to mess with us.
 114          */
 115         if (((unsigned long)frame) & 3)
 116                 goto badframe;
 117
 118         if (!access_ok(frame, sizeof(*frame)))
 119                 goto badframe;
 120         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
 121                 goto badframe;
 122
 123         set_current_blocked(&set);
 124
 125         if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
 126                 goto badframe;
 127
 128         if (restore_altstack(&frame->uc.uc_stack))
 129                 goto badframe;
 130
 131         return regs->gpr[11];
 132
 133 badframe:
 134         force_sig(SIGSEGV);
 135         return 0;
 136 }
 137
 138 /*
 139  * Set up a signal frame.
 140  */
 141
 142 static int setup_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
 143 {
 144         int err = 0;
 145
 146         /* copy the regs */
 147         /* There should be no need to save callee-saved registers here...
 148          * ...but we save them anyway.  Revisit this
 149          */
 150         err |= __copy_to_user(sc->regs.gpr, regs, 32 * sizeof(unsigned long));
 151         err |= __copy_to_user(&sc->regs.pc, &regs->pc, sizeof(unsigned long));
 152         err |= __copy_to_user(&sc->regs.sr, &regs->sr, sizeof(unsigned long));
 153         err |= save_fp_state(sc);
 154
 155         return err;
 156 }
 157
 158 static inline unsigned long align_sigframe(unsigned long sp)
 159 {
 160         return sp & ~3UL;
 161 }
 162
 163 /*
 164  * Work out where the signal frame should go.  It's either on the user stack
 165  * or the alternate stack.
 166  */
 167
 168 static inline void __user *get_sigframe(struct ksignal *ksig,
 169                                         struct pt_regs *regs, size_t frame_size)
 170 {
 171         unsigned long sp = regs->sp;
 172
 173         /* redzone */
 174         sp -= STACK_FRAME_OVERHEAD;
 175         sp = sigsp(sp, ksig);
 176         sp = align_sigframe(sp - frame_size);
 177
 178         return (void __user *)sp;
 179 }
 180
 181 /* grab and setup a signal frame.
 182  *
 183  * basically we stack a lot of state info, and arrange for the
 184  * user-mode program to return to the kernel using either a
 185  * trampoline which performs the syscall sigreturn, or a provided
 186  * user-mode trampoline.
 187  */
 188 static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
 189                           struct pt_regs *regs)
 190 {
 191         struct rt_sigframe __user *frame;
 192         unsigned long return_ip;
 193         int err = 0;
 194
 195         frame = get_sigframe(ksig, regs, sizeof(*frame));
 196
 197         if (!access_ok(frame, sizeof(*frame)))
 198                 return -EFAULT;
 199
 200         /* Create siginfo.  */
 201         if (ksig->ka.sa.sa_flags & SA_SIGINFO)
 202                 err |= copy_siginfo_to_user(&frame->info, &ksig->info);
 203
 204         /* Create the ucontext.  */
 205         err |= __put_user(0, &frame->uc.uc_flags);
 206         err |= __put_user(NULL, &frame->uc.uc_link);
 207         err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
 208         err |= setup_sigcontext(regs, &frame->uc.uc_mcontext);
 209
 210         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 211
 212         if (err)
 213                 return -EFAULT;
 214
 215         /* trampoline - the desired return ip is the retcode itself */
 216         return_ip = (unsigned long)&frame->retcode;
 217         /* This is:
 218                 l.ori r11,r0,__NR_sigreturn
 219                 l.sys 1
 220          */
 221         err |= __put_user(0xa960,             (short __user *)(frame->retcode + 0));
 222         err |= __put_user(__NR_rt_sigreturn,  (short __user *)(frame->retcode + 2));
 223         err |= __put_user(0x20000001, (unsigned long __user *)(frame->retcode + 4));
 224         err |= __put_user(0x15000000, (unsigned long __user *)(frame->retcode + 8));
 225
 226         if (err)
 227                 return -EFAULT;
 228
 229         /* Set up registers for signal handler */
 230         regs->pc = (unsigned long)ksig->ka.sa.sa_handler; /* what we enter NOW */
 231         regs->gpr[9] = (unsigned long)return_ip;     /* what we enter LATER */
 232         regs->gpr[3] = (unsigned long)ksig->sig;           /* arg 1: signo */
 233         regs->gpr[4] = (unsigned long)&frame->info;  /* arg 2: (siginfo_t*) */
 234         regs->gpr[5] = (unsigned long)&frame->uc;    /* arg 3: ucontext */
 235
 236         /* actually move the usp to reflect the stacked frame */
 237         regs->sp = (unsigned long)frame;
 238
 239         return 0;
 240 }
 241
 242 static inline void
 243 handle_signal(struct ksignal *ksig, struct pt_regs *regs)
 244 {
 245         int ret;
 246
 247         ret = setup_rt_frame(ksig, sigmask_to_save(), regs);
 248
 249         signal_setup_done(ret, ksig, test_thread_flag(TIF_SINGLESTEP));
 250 }
 251
 252 /*
 253  * Note that 'init' is a special process: it doesn't get signals it doesn't
 254  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 255  * mistake.
 256  *
 257  * Also note that the regs structure given here as an argument, is the latest
 258  * pushed pt_regs. It may or may not be the same as the first pushed registers
 259  * when the initial usermode->kernelmode transition took place. Therefore
 260  * we can use user_mode(regs) to see if we came directly from kernel or user
 261  * mode below.
 262  */
 263
 264 static int do_signal(struct pt_regs *regs, int syscall)
 265 {
 266         struct ksignal ksig;
 267         unsigned long continue_addr = 0;
 268         unsigned long restart_addr = 0;
 269         unsigned long retval = 0;
 270         int restart = 0;
 271
 272         if (syscall) {
 273                 continue_addr = regs->pc;
 274                 restart_addr = continue_addr - 4;
 275                 retval = regs->gpr[11];
 276
 277                 /*
 278                  * Setup syscall restart here so that a debugger will
 279                  * see the already changed PC.
 280                  */
 281                 switch (retval) {
 282                 case -ERESTART_RESTARTBLOCK:
 283                         restart = -2;
 284                         fallthrough;
 285                 case -ERESTARTNOHAND:
 286                 case -ERESTARTSYS:
 287                 case -ERESTARTNOINTR:
 288                         restart++;
 289                         regs->gpr[11] = regs->orig_gpr11;
 290                         regs->pc = restart_addr;
 291                         break;
 292                 }
 293         }
 294
 295         /*
 296          * Get the signal to deliver.  During the call to get_signal the
 297          * debugger may change all our registers so we may need to revert
 298          * the decision to restart the syscall; specifically, if the PC is
 299          * changed, don't restart the syscall.
 300          */
 301         if (get_signal(&ksig)) {
 302                 if (unlikely(restart) && regs->pc == restart_addr) {
 303                         if (retval == -ERESTARTNOHAND ||
 304                             retval == -ERESTART_RESTARTBLOCK
 305                             || (retval == -ERESTARTSYS
 306                                 && !(ksig.ka.sa.sa_flags & SA_RESTART))) {
 307                                 /* No automatic restart */
 308                                 regs->gpr[11] = -EINTR;
 309                                 regs->pc = continue_addr;
 310                         }
 311                 }
 312                 handle_signal(&ksig, regs);
 313         } else {
 314                 /* no handler */
 315                 restore_saved_sigmask();
 316                 /*
 317                  * Restore pt_regs PC as syscall restart will be handled by
 318                  * kernel without return to userspace
 319                  */
 320                 if (unlikely(restart) && regs->pc == restart_addr) {
 321                         regs->pc = continue_addr;
 322                         return restart;
 323                 }
 324         }
 325
 326         return 0;
 327 }
 328
 329 asmlinkage int
 330 do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
 331 {
 332         do {
 333                 if (likely(thread_flags & _TIF_NEED_RESCHED)) {
 334                         schedule();
 335                 } else {
 336                         if (unlikely(!user_mode(regs)))
 337                                 return 0;
 338                         local_irq_enable();
 339                         if (thread_flags & (_TIF_SIGPENDING|_TIF_NOTIFY_SIGNAL)) {
 340                                 int restart = do_signal(regs, syscall);
 341                                 if (unlikely(restart)) {
 342                                         /*
 343                                          * Restart without handlers.
 344                                          * Deal with it without leaving
 345                                          * the kernel space.
 346                                          */
 347                                         return restart;
 348                                 }
 349                                 syscall = 0;
 350                         } else {
 351                                 resume_user_mode_work(regs);
 352                         }
 353                 }
 354                 local_irq_disable();
 355                 thread_flags = read_thread_flags();
 356         } while (thread_flags & _TIF_WORK_MASK);
 357         return 0;
 358 }