text: // SPDX-License-Identifier: GPL-2.0
  /*
   *  linux/arch/alpha/kernel/signal.c
   *
   *  Copyright (C) 1995  Linus Torvalds
   *
   *  1997-11-02  Modified for POSIX.1b signals by Richard Henderson
   */
  
  #include <linux/sched/signal.h>
  #include <linux/sched/task_stack.h>
  #include <linux/kernel.h>
  #include <linux/signal.h>
  #include <linux/errno.h>
  #include <linux/wait.h>
  #include <linux/ptrace.h>
  #include <linux/unistd.h>
  #include <linux/mm.h>
  #include <linux/smp.h>
  #include <linux/stddef.h>
  #include <linux/tty.h>
  #include <linux/binfmts.h>
  #include <linux/bitops.h>
  #include <linux/syscalls.h>
  #include <linux/tracehook.h>
  
  #include <linux/uaccess.h>
  #include <asm/sigcontext.h>
  #include <asm/ucontext.h>
  
  #include "proto.h"
  
  
  #define DEBUG_SIG 0
  
  #define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
  
  asmlinkage void ret_from_sys_call(void);
  
  /*
   * The OSF/1 sigprocmask calling sequence is different from the
   * C sigprocmask() sequence..
   */
  SYSCALL_DEFINE2(osf_sigprocmask, int, how, unsigned long, newmask)
  {
  	sigset_t oldmask;
  	sigset_t mask;
  	unsigned long res;
  
  	siginitset(&mask, newmask & _BLOCKABLE);
  	res = sigprocmask(how, &mask, &oldmask);
  	if (!res) {
  		force_successful_syscall_return();
  		res = oldmask.sig[0];
  	}
  	return res;
  }
  
  SYSCALL_DEFINE3(osf_sigaction, int, sig,
  		const struct osf_sigaction __user *, act,
  		struct osf_sigaction __user *, oact)
  {
  	struct k_sigaction new_ka, old_ka;
  	int ret;
  
  	if (act) {
  		old_sigset_t mask;
  		if (!access_ok(act, sizeof(*act)) ||
  		    __get_user(new_ka.sa.sa_handler, &act->sa_handler) ||
  		    __get_user(new_ka.sa.sa_flags, &act->sa_flags) ||
  		    __get_user(mask, &act->sa_mask))
  			return -EFAULT;
  		siginitset(&new_ka.sa.sa_mask, mask);
  		new_ka.ka_restorer = NULL;
  	}
  
  	ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
  
  	if (!ret && oact) {
  		if (!access_ok(oact, sizeof(*oact)) ||
  		    __put_user(old_ka.sa.sa_handler, &oact->sa_handler) ||
  		    __put_user(old_ka.sa.sa_flags, &oact->sa_flags) ||
  		    __put_user(old_ka.sa.sa_mask.sig[0], &oact->sa_mask))
  			return -EFAULT;
  	}
  
  	return ret;
  }
  
  SYSCALL_DEFINE5(rt_sigaction, int, sig, const struct sigaction __user *, act,
  		struct sigaction __user *, oact,
  		size_t, sigsetsize, void __user *, restorer)
  {
  	struct k_sigaction new_ka, old_ka;
  	int ret;
  
  	/* XXX: Don't preclude handling different sized sigset_t's.  */
  	if (sigsetsize != sizeof(sigset_t))
  		return -EINVAL;
  
  	if (act) {
  		new_ka.ka_restorer = restorer;
  		if (copy_from_user(&new_ka.sa, act, sizeof(*act)))
  			return -EFAULT;
  	}
  
  	ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
  
  	if (!ret && oact) {
  		if (copy_to_user(oact, &old_ka.sa, sizeof(*oact)))
  			return -EFAULT;
  	}
  
  	return ret;
  }
  
  /*
   * Do a signal return; undo the signal stack.
   */
  
  #if _NSIG_WORDS > 1
  # error "Non SA_SIGINFO frame needs rearranging"
  #endif
  
  struct sigframe
  {
  	struct sigcontext sc;
  	unsigned int retcode[3];
  };
  
  struct rt_sigframe
  {
  	struct siginfo info;
  	struct ucontext uc;
  	unsigned int retcode[3];
  };
  
  /* If this changes, userland unwinders that Know Things about our signal
     frame will break.  Do not undertake lightly.  It also implies an ABI
     change wrt the size of siginfo_t, which may cause some pain.  */
  extern char compile_time_assert
          [offsetof(struct rt_sigframe, uc.uc_mcontext) == 176 ? 1 : -1];
  
  #define INSN_MOV_R30_R16	0x47fe0410
  #define INSN_LDI_R0		0x201f0000
  #define INSN_CALLSYS		0x00000083
  
  static long
  restore_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs)
  {
  	unsigned long usp;
  	struct switch_stack *sw = (struct switch_stack *)regs - 1;
  	long i, err = __get_user(regs->pc, &sc->sc_pc);
  
  	current->restart_block.fn = do_no_restart_syscall;
  
  	sw->r26 = (unsigned long) ret_from_sys_call;
  
  	err |= __get_user(regs->r0, sc->sc_regs+0);
  	err |= __get_user(regs->r1, sc->sc_regs+1);
  	err |= __get_user(regs->r2, sc->sc_regs+2);
  	err |= __get_user(regs->r3, sc->sc_regs+3);
  	err |= __get_user(regs->r4, sc->sc_regs+4);
  	err |= __get_user(regs->r5, sc->sc_regs+5);
  	err |= __get_user(regs->r6, sc->sc_regs+6);
  	err |= __get_user(regs->r7, sc->sc_regs+7);
  	err |= __get_user(regs->r8, sc->sc_regs+8);
  	err |= __get_user(sw->r9, sc->sc_regs+9);
  	err |= __get_user(sw->r10, sc->sc_regs+10);
  	err |= __get_user(sw->r11, sc->sc_regs+11);
  	err |= __get_user(sw->r12, sc->sc_regs+12);
  	err |= __get_user(sw->r13, sc->sc_regs+13);
  	err |= __get_user(sw->r14, sc->sc_regs+14);
  	err |= __get_user(sw->r15, sc->sc_regs+15);
  	err |= __get_user(regs->r16, sc->sc_regs+16);
  	err |= __get_user(regs->r17, sc->sc_regs+17);
  	err |= __get_user(regs->r18, sc->sc_regs+18);
  	err |= __get_user(regs->r19, sc->sc_regs+19);
  	err |= __get_user(regs->r20, sc->sc_regs+20);
  	err |= __get_user(regs->r21, sc->sc_regs+21);
  	err |= __get_user(regs->r22, sc->sc_regs+22);
  	err |= __get_user(regs->r23, sc->sc_regs+23);
  	err |= __get_user(regs->r24, sc->sc_regs+24);
  	err |= __get_user(regs->r25, sc->sc_regs+25);
  	err |= __get_user(regs->r26, sc->sc_regs+26);
  	err |= __get_user(regs->r27, sc->sc_regs+27);
  	err |= __get_user(regs->r28, sc->sc_regs+28);
  	err |= __get_user(regs->gp, sc->sc_regs+29);
  	err |= __get_user(usp, sc->sc_regs+30);
  	wrusp(usp);
  
  	for (i = 0; i < 31; i++)
  		err |= __get_user(sw->fp[i], sc->sc_fpregs+i);
  	err |= __get_user(sw->fp[31], &sc->sc_fpcr);
  
  	return err;
  }
  
  /* Note that this syscall is also used by setcontext(3) to install
     a given sigcontext.  This because it's impossible to set *all*
     registers and transfer control from userland.  */
  
  asmlinkage void
  do_sigreturn(struct sigcontext __user *sc)
  {
  	struct pt_regs *regs = current_pt_regs();
  	sigset_t set;
  
  	/* Verify that it's a good sigcontext before using it */
  	if (!access_ok(sc, sizeof(*sc)))
  		goto give_sigsegv;
  	if (__get_user(set.sig[0], &sc->sc_mask))
  		goto give_sigsegv;
  
  	set_current_blocked(&set);
  
  	if (restore_sigcontext(sc, regs))
  		goto give_sigsegv;
  
  	/* Send SIGTRAP if we're single-stepping: */
  	if (ptrace_cancel_bpt (current)) {
  		send_sig_fault(SIGTRAP, TRAP_BRKPT, (void __user *) regs->pc, 0,
  			       current);
  	}
  	return;
  
  give_sigsegv:
  	force_sig(SIGSEGV);
  }
  
  asmlinkage void
  do_rt_sigreturn(struct rt_sigframe __user *frame)
  {
  	struct pt_regs *regs = current_pt_regs();
  	sigset_t set;
  
  	/* Verify that it's a good ucontext_t before using it */
  	if (!access_ok(&frame->uc, sizeof(frame->uc)))
  		goto give_sigsegv;
  	if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
  		goto give_sigsegv;
  
  	set_current_blocked(&set);
  
  	if (restore_sigcontext(&frame->uc.uc_mcontext, regs))
  		goto give_sigsegv;
  
  	/* Send SIGTRAP if we're single-stepping: */
  	if (ptrace_cancel_bpt (current)) {
  		send_sig_fault(SIGTRAP, TRAP_BRKPT, (void __user *) regs->pc, 0,
  			       current);
  	}
  	return;
  
  give_sigsegv:
  	force_sig(SIGSEGV);
  }
  
  
  /*
   * Set up a signal frame.
   */
  
  static inline void __user *
  get_sigframe(struct ksignal *ksig, unsigned long sp, size_t frame_size)
  {
  	return (void __user *)((sigsp(sp, ksig) - frame_size) & -32ul);
  }
  
  static long
  setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs, 
  		 unsigned long mask, unsigned long sp)
  {
  	struct switch_stack *sw = (struct switch_stack *)regs - 1;
  	long i, err = 0;
  
  	err |= __put_user(on_sig_stack((unsigned long)sc), &sc->sc_onstack);
  	err |= __put_user(mask, &sc->sc_mask);
  	err |= __put_user(regs->pc, &sc->sc_pc);
  	err |= __put_user(8, &sc->sc_ps);
  
  	err |= __put_user(regs->r0 , sc->sc_regs+0);
  	err |= __put_user(regs->r1 , sc->sc_regs+1);
  	err |= __put_user(regs->r2 , sc->sc_regs+2);
  	err |= __put_user(regs->r3 , sc->sc_regs+3);
  	err |= __put_user(regs->r4 , sc->sc_regs+4);
  	err |= __put_user(regs->r5 , sc->sc_regs+5);
  	err |= __put_user(regs->r6 , sc->sc_regs+6);
  	err |= __put_user(regs->r7 , sc->sc_regs+7);
  	err |= __put_user(regs->r8 , sc->sc_regs+8);
  	err |= __put_user(sw->r9   , sc->sc_regs+9);
  	err |= __put_user(sw->r10  , sc->sc_regs+10);
  	err |= __put_user(sw->r11  , sc->sc_regs+11);
  	err |= __put_user(sw->r12  , sc->sc_regs+12);
  	err |= __put_user(sw->r13  , sc->sc_regs+13);
  	err |= __put_user(sw->r14  , sc->sc_regs+14);
  	err |= __put_user(sw->r15  , sc->sc_regs+15);
  	err |= __put_user(regs->r16, sc->sc_regs+16);
  	err |= __put_user(regs->r17, sc->sc_regs+17);
  	err |= __put_user(regs->r18, sc->sc_regs+18);
  	err |= __put_user(regs->r19, sc->sc_regs+19);
  	err |= __put_user(regs->r20, sc->sc_regs+20);
  	err |= __put_user(regs->r21, sc->sc_regs+21);
  	err |= __put_user(regs->r22, sc->sc_regs+22);
  	err |= __put_user(regs->r23, sc->sc_regs+23);
  	err |= __put_user(regs->r24, sc->sc_regs+24);
  	err |= __put_user(regs->r25, sc->sc_regs+25);
  	err |= __put_user(regs->r26, sc->sc_regs+26);
  	err |= __put_user(regs->r27, sc->sc_regs+27);
  	err |= __put_user(regs->r28, sc->sc_regs+28);
  	err |= __put_user(regs->gp , sc->sc_regs+29);
  	err |= __put_user(sp, sc->sc_regs+30);
  	err |= __put_user(0, sc->sc_regs+31);
  
  	for (i = 0; i < 31; i++)
  		err |= __put_user(sw->fp[i], sc->sc_fpregs+i);
  	err |= __put_user(0, sc->sc_fpregs+31);
  	err |= __put_user(sw->fp[31], &sc->sc_fpcr);
  
  	err |= __put_user(regs->trap_a0, &sc->sc_traparg_a0);
  	err |= __put_user(regs->trap_a1, &sc->sc_traparg_a1);
  	err |= __put_user(regs->trap_a2, &sc->sc_traparg_a2);
  
  	return err;
  }
  
  static int
  setup_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
  {
  	unsigned long oldsp, r26, err = 0;
  	struct sigframe __user *frame;
  
  	oldsp = rdusp();
  	frame = get_sigframe(ksig, oldsp, sizeof(*frame));
  	if (!access_ok(frame, sizeof(*frame)))
  		return -EFAULT;
  
  	err |= setup_sigcontext(&frame->sc, regs, set->sig[0], oldsp);
  	if (err)
  		return -EFAULT;
  
  	/* Set up to return from userspace.  If provided, use a stub
  	   already in userspace.  */
  	r26 = (unsigned long) ksig->ka.ka_restorer;
  	if (!r26) {
  		err |= __put_user(INSN_MOV_R30_R16, frame->retcode+0);
  		err |= __put_user(INSN_LDI_R0+__NR_sigreturn, frame->retcode+1);
  		err |= __put_user(INSN_CALLSYS, frame->retcode+2);
  		imb();
  		r26 = (unsigned long) frame->retcode;
  	}
  
  	/* Check that everything was written properly.  */
  	if (err)
  		return err;
  
  	/* "Return" to the handler */
  	regs->r26 = r26;
  	regs->r27 = regs->pc = (unsigned long) ksig->ka.sa.sa_handler;
  	regs->r16 = ksig->sig;			/* a0: signal number */
  	regs->r17 = 0;				/* a1: exception code */
  	regs->r18 = (unsigned long) &frame->sc;	/* a2: sigcontext pointer */
  	wrusp((unsigned long) frame);
  	
  #if DEBUG_SIG
  	printk("SIG deliver (%s:%d): sp=%p pc=%p ra=%p\n",
  		current->comm, current->pid, frame, regs->pc, regs->r26);
  #endif
  	return 0;
  }
  
  static int
  setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
  {
  	unsigned long oldsp, r26, err = 0;
  	struct rt_sigframe __user *frame;
  
  	oldsp = rdusp();
  	frame = get_sigframe(ksig, oldsp, sizeof(*frame));
  	if (!access_ok(frame, sizeof(*frame)))
  		return -EFAULT;
  
  	err |= copy_siginfo_to_user(&frame->info, &ksig->info);
  
  	/* Create the ucontext.  */
  	err |= __put_user(0, &frame->uc.uc_flags);
  	err |= __put_user(0, &frame->uc.uc_link);
  	err |= __put_user(set->sig[0], &frame->uc.uc_osf_sigmask);
  	err |= __save_altstack(&frame->uc.uc_stack, oldsp);
  	err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, 
  				set->sig[0], oldsp);
  	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
  	if (err)
  		return -EFAULT;
  
  	/* Set up to return from userspace.  If provided, use a stub
  	   already in userspace.  */
  	r26 = (unsigned long) ksig->ka.ka_restorer;
  	if (!r26) {
  		err |= __put_user(INSN_MOV_R30_R16, frame->retcode+0);
  		err |= __put_user(INSN_LDI_R0+__NR_rt_sigreturn,
  				  frame->retcode+1);
  		err |= __put_user(INSN_CALLSYS, frame->retcode+2);
  		imb();
  		r26 = (unsigned long) frame->retcode;
  	}
  
  	if (err)
  		return -EFAULT;
  
  	/* "Return" to the handler */
  	regs->r26 = r26;
  	regs->r27 = regs->pc = (unsigned long) ksig->ka.sa.sa_handler;
  	regs->r16 = ksig->sig;			  /* a0: signal number */
  	regs->r17 = (unsigned long) &frame->info; /* a1: siginfo pointer */
  	regs->r18 = (unsigned long) &frame->uc;	  /* a2: ucontext pointer */
  	wrusp((unsigned long) frame);
  
  #if DEBUG_SIG
  	printk("SIG deliver (%s:%d): sp=%p pc=%p ra=%p\n",
  		current->comm, current->pid, frame, regs->pc, regs->r26);
  #endif
  
  	return 0;
  }
  
  
  /*
   * OK, we're invoking a handler.
   */
  static inline void
  handle_signal(struct ksignal *ksig, struct pt_regs *regs)
  {
  	sigset_t *oldset = sigmask_to_save();
  	int ret;
  
  	if (ksig->ka.sa.sa_flags & SA_SIGINFO)
  		ret = setup_rt_frame(ksig, oldset, regs);
  	else
  		ret = setup_frame(ksig, oldset, regs);
  
  	signal_setup_done(ret, ksig, 0);
  }
  
  static inline void
  syscall_restart(unsigned long r0, unsigned long r19,
  		struct pt_regs *regs, struct k_sigaction *ka)
  {
  	switch (regs->r0) {
  	case ERESTARTSYS:
  		if (!(ka->sa.sa_flags & SA_RESTART)) {
  		case ERESTARTNOHAND:
  			regs->r0 = EINTR;
  			break;
  		}
  		/* fallthrough */
  	case ERESTARTNOINTR:
  		regs->r0 = r0;	/* reset v0 and a3 and replay syscall */
  		regs->r19 = r19;
  		regs->pc -= 4;
  		break;
  	case ERESTART_RESTARTBLOCK:
  		regs->r0 = EINTR;
  		break;
  	}
  }
  
  
  /*
   * Note that 'init' is a special process: it doesn't get signals it doesn't
   * want to handle. Thus you cannot kill init even with a SIGKILL even by
   * mistake.
   *
   * Note that we go through the signals twice: once to check the signals that
   * the kernel can handle, and then we build all the user-level signal handling
   * stack-frames in one go after that.
   *
   * "r0" and "r19" are the registers we need to restore for system call
   * restart. "r0" is also used as an indicator whether we can restart at
   * all (if we get here from anything but a syscall return, it will be 0)
   */
  static void
  do_signal(struct pt_regs *regs, unsigned long r0, unsigned long r19)
  {
  	unsigned long single_stepping = ptrace_cancel_bpt(current);
  	struct ksignal ksig;
  
  	/* This lets the debugger run, ... */
  	if (get_signal(&ksig)) {
  		/* ... so re-check the single stepping. */
  		single_stepping |= ptrace_cancel_bpt(current);
  		/* Whee!  Actually deliver the signal.  */
  		if (r0)
  			syscall_restart(r0, r19, regs, &ksig.ka);
  		handle_signal(&ksig, regs);
  	} else {
  		single_stepping |= ptrace_cancel_bpt(current);
  		if (r0) {
  			switch (regs->r0) {
  			case ERESTARTNOHAND:
  			case ERESTARTSYS:
  			case ERESTARTNOINTR:
  				/* Reset v0 and a3 and replay syscall.  */
  				regs->r0 = r0;
  				regs->r19 = r19;
  				regs->pc -= 4;
  				break;
  			case ERESTART_RESTARTBLOCK:
  				/* Set v0 to the restart_syscall and replay */
  				regs->r0 = __NR_restart_syscall;
  				regs->pc -= 4;
  				break;
  			}
  		}
  		restore_saved_sigmask();
  	}
  	if (single_stepping)
  		ptrace_set_bpt(current);	/* re-set breakpoint */
  }
  
  void
  do_work_pending(struct pt_regs *regs, unsigned long thread_flags,
  		 unsigned long r0, unsigned long r19)
  {
  	do {
  		if (thread_flags & _TIF_NEED_RESCHED) {
  			schedule();
  		} else {
  			local_irq_enable();
  			if (thread_flags & _TIF_SIGPENDING) {
  				do_signal(regs, r0, r19);
  				r0 = 0;
  			} else {
  				clear_thread_flag(TIF_NOTIFY_RESUME);
  				tracehook_notify_resume(regs);
  			}
  		}
  		local_irq_disable();
  		thread_flags = current_thread_info()->flags;
  	} while (thread_flags & _TIF_WORK_MASK);
  }
  