text: // SPDX-License-Identifier: GPL-2.0
  // Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd.
  
  #include <linux/sched.h>
  #include <linux/mm.h>
  #include <linux/kernel.h>
  #include <linux/signal.h>
  #include <linux/syscalls.h>
  #include <linux/errno.h>
  #include <linux/wait.h>
  #include <linux/ptrace.h>
  #include <linux/unistd.h>
  #include <linux/stddef.h>
  #include <linux/highuid.h>
  #include <linux/personality.h>
  #include <linux/tty.h>
  #include <linux/binfmts.h>
  #include <linux/tracehook.h>
  #include <linux/freezer.h>
  #include <linux/uaccess.h>
  
  #include <asm/setup.h>
  #include <asm/pgtable.h>
  #include <asm/traps.h>
  #include <asm/ucontext.h>
  #include <asm/vdso.h>
  
  #include <abi/regdef.h>
  
  #ifdef CONFIG_CPU_HAS_FPU
  #include <abi/fpu.h>
  
  static int restore_fpu_state(struct sigcontext *sc)
  {
  	int err = 0;
  	struct user_fp user_fp;
  
  	err = copy_from_user(&user_fp, &sc->sc_user_fp, sizeof(user_fp));
  
  	restore_from_user_fp(&user_fp);
  
  	return err;
  }
  
  static int save_fpu_state(struct sigcontext *sc)
  {
  	struct user_fp user_fp;
  
  	save_to_user_fp(&user_fp);
  
  	return copy_to_user(&sc->sc_user_fp, &user_fp, sizeof(user_fp));
  }
  #else
  static inline int restore_fpu_state(struct sigcontext *sc) { return 0; }
  static inline int save_fpu_state(struct sigcontext *sc) { return 0; }
  #endif
  
  struct rt_sigframe {
  	int sig;
  	struct siginfo *pinfo;
  	void *puc;
  	struct siginfo info;
  	struct ucontext uc;
  };
  
  static int
  restore_sigframe(struct pt_regs *regs,
  		 struct sigcontext *sc, int *pr2)
  {
  	int err = 0;
  
  	/* Always make any pending restarted system calls return -EINTR */
  	current_thread_info()->task->restart_block.fn = do_no_restart_syscall;
  
  	err |= copy_from_user(regs, &sc->sc_pt_regs, sizeof(struct pt_regs));
  
  	err |= restore_fpu_state(sc);
  
  	*pr2 = regs->a0;
  	return err;
  }
  
  asmlinkage int
  do_rt_sigreturn(void)
  {
  	sigset_t set;
  	int a0;
  	struct pt_regs *regs = current_pt_regs();
  	struct rt_sigframe *frame = (struct rt_sigframe *)(regs->usp);
  
  	if (verify_area(VERIFY_READ, frame, sizeof(*frame)))
  		goto badframe;
  	if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
  		goto badframe;
  
  	sigdelsetmask(&set, (sigmask(SIGKILL) | sigmask(SIGSTOP)));
  	spin_lock_irq(&current->sighand->siglock);
  	current->blocked = set;
  	recalc_sigpending();
  	spin_unlock_irq(&current->sighand->siglock);
  
  	if (restore_sigframe(regs, &frame->uc.uc_mcontext, &a0))
  		goto badframe;
  
  	return a0;
  
  badframe:
  	force_sig(SIGSEGV, current);
  	return 0;
  }
  
  static int setup_sigframe(struct sigcontext *sc, struct pt_regs *regs)
  {
  	int err = 0;
  
  	err |= copy_to_user(&sc->sc_pt_regs, regs, sizeof(struct pt_regs));
  	err |= save_fpu_state(sc);
  
  	return err;
  }
  
  static inline void *
  get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size)
  {
  	unsigned long usp;
  
  	/* Default to using normal stack.  */
  	usp = regs->usp;
  
  	/* This is the X/Open sanctioned signal stack switching.  */
  	if ((ka->sa.sa_flags & SA_ONSTACK) && !sas_ss_flags(usp)) {
  		if (!on_sig_stack(usp))
  			usp = current->sas_ss_sp + current->sas_ss_size;
  	}
  	return (void *)((usp - frame_size) & -8UL);
  }
  
  static int
  setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
  {
  	struct rt_sigframe *frame;
  	int err = 0;
  
  	struct csky_vdso *vdso = current->mm->context.vdso;
  
  	frame = get_sigframe(&ksig->ka, regs, sizeof(*frame));
  	if (!frame)
  		return 1;
  
  	err |= __put_user(ksig->sig, &frame->sig);
  	err |= __put_user(&frame->info, &frame->pinfo);
  	err |= __put_user(&frame->uc, &frame->puc);
  	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((void *)current->sas_ss_sp,
  			&frame->uc.uc_stack.ss_sp);
  	err |= __put_user(sas_ss_flags(regs->usp),
  			&frame->uc.uc_stack.ss_flags);
  	err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
  	err |= setup_sigframe(&frame->uc.uc_mcontext, regs);
  	err |= copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
  
  	if (err)
  		goto give_sigsegv;
  
  	/* Set up registers for signal handler */
  	regs->usp = (unsigned long)frame;
  	regs->pc = (unsigned long)ksig->ka.sa.sa_handler;
  	regs->lr = (unsigned long)vdso->rt_signal_retcode;
  
  adjust_stack:
  	regs->a0 = ksig->sig; /* first arg is signo */
  	regs->a1 = (unsigned long)(&(frame->info));
  	regs->a2 = (unsigned long)(&(frame->uc));
  	return err;
  
  give_sigsegv:
  	if (ksig->sig == SIGSEGV)
  		ksig->ka.sa.sa_handler = SIG_DFL;
  	force_sig(SIGSEGV, current);
  	goto adjust_stack;
  }
  
  /*
   * OK, we're invoking a handler
   */
  static int
  handle_signal(struct ksignal *ksig, struct pt_regs *regs)
  {
  	int ret;
  	sigset_t *oldset = sigmask_to_save();
  
  	/*
  	 * set up the stack frame, regardless of SA_SIGINFO,
  	 * and pass info anyway.
  	 */
  	ret = setup_rt_frame(ksig, oldset, regs);
  
  	if (ret != 0) {
  		force_sigsegv(ksig->sig, current);
  		return ret;
  	}
  
  	/* Block the signal if we were successful. */
  	spin_lock_irq(&current->sighand->siglock);
  	sigorsets(&current->blocked, &current->blocked, &ksig->ka.sa.sa_mask);
  	if (!(ksig->ka.sa.sa_flags & SA_NODEFER))
  		sigaddset(&current->blocked, ksig->sig);
  	recalc_sigpending();
  	spin_unlock_irq(&current->sighand->siglock);
  
  	return 0;
  }
  
  /*
   * 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.
   */
  static void do_signal(struct pt_regs *regs, int syscall)
  {
  	unsigned int retval = 0, continue_addr = 0, restart_addr = 0;
  	struct ksignal ksig;
  
  	/*
  	 * We want the common case to go fast, which
  	 * is why we may in certain cases get here from
  	 * kernel mode. Just return without doing anything
  	 * if so.
  	 */
  	if (!user_mode(regs))
  		return;
  
  	current->thread.esp0 = (unsigned long)regs;
  
  	/*
  	 * If we were from a system call, check for system call restarting...
  	 */
  	if (syscall) {
  		continue_addr = regs->pc;
  #if defined(__CSKYABIV2__)
  		restart_addr = continue_addr - 4;
  #else
  		restart_addr = continue_addr - 2;
  #endif
  		retval = regs->a0;
  
  		/*
  		 * Prepare for system call restart.  We do this here so that a
  		 * debugger will see the already changed.
  		 */
  		switch (retval) {
  		case -ERESTARTNOHAND:
  		case -ERESTARTSYS:
  		case -ERESTARTNOINTR:
  			regs->a0 = regs->orig_a0;
  			regs->pc = restart_addr;
  			break;
  		case -ERESTART_RESTARTBLOCK:
  			regs->a0 = -EINTR;
  			break;
  		}
  	}
  
  	if (try_to_freeze())
  		goto no_signal;
  
  	/*
  	 * Get the signal to deliver.  When running under ptrace, at this
  	 * point the debugger may change all our registers ...
  	 */
  	if (get_signal(&ksig)) {
  		/*
  		 * Depending on the signal settings we may need to revert the
  		 * decision to restart the system call.  But skip this if a
  		 * debugger has chosen to restart at a different PC.
  		 */
  		if (regs->pc == restart_addr) {
  			if (retval == -ERESTARTNOHAND ||
  			    (retval == -ERESTARTSYS &&
  			     !(ksig.ka.sa.sa_flags & SA_RESTART))) {
  				regs->a0 = -EINTR;
  				regs->pc = continue_addr;
  			}
  		}
  
  		/* Whee!  Actually deliver the signal.  */
  		if (handle_signal(&ksig, regs) == 0) {
  			/*
  			 * A signal was successfully delivered; the saved
  			 * sigmask will have been stored in the signal frame,
  			 * and will be restored by sigreturn, so we can simply
  			 * clear the TIF_RESTORE_SIGMASK flag.
  			 */
  			if (test_thread_flag(TIF_RESTORE_SIGMASK))
  				clear_thread_flag(TIF_RESTORE_SIGMASK);
  		}
  		return;
  	}
  
  no_signal:
  	if (syscall) {
  		/*
  		 * Handle restarting a different system call.  As above,
  		 * if a debugger has chosen to restart at a different PC,
  		 * ignore the restart.
  		 */
  		if (retval == -ERESTART_RESTARTBLOCK
  				&& regs->pc == continue_addr) {
  #if defined(__CSKYABIV2__)
  			regs->regs[3] = __NR_restart_syscall;
  			regs->pc -= 4;
  #else
  			regs->regs[9] = __NR_restart_syscall;
  			regs->pc -= 2;
  #endif
  		}
  
  		/*
  		 * If there's no signal to deliver, we just put the saved
  		 * sigmask back.
  		 */
  		if (test_thread_flag(TIF_RESTORE_SIGMASK)) {
  			clear_thread_flag(TIF_RESTORE_SIGMASK);
  			sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
  		}
  	}
  }
  
  asmlinkage void
  do_notify_resume(unsigned int thread_flags, struct pt_regs *regs, int syscall)
  {
  	if (thread_flags & _TIF_SIGPENDING)
  		do_signal(regs, syscall);
  
  	if (thread_flags & _TIF_NOTIFY_RESUME) {
  		clear_thread_flag(TIF_NOTIFY_RESUME);
  		tracehook_notify_resume(regs);
  	}
  }
  