text: // SPDX-License-Identifier: GPL-2.0
  
  #include <linux/signal.h>
  #include <linux/uaccess.h>
  #include <linux/syscalls.h>
  #include <linux/resume_user_mode.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 __user *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 __user *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
  #define restore_fpu_state(sigcontext)	(0)
  #define save_fpu_state(sigcontext)	(0)
  #endif
  
  struct rt_sigframe {
  	/*
  	 * pad[3] is compatible with the same struct defined in
  	 * gcc/libgcc/config/csky/linux-unwind.h
  	 */
  	int pad[3];
  	struct siginfo info;
  	struct ucontext uc;
  };
  
  static long restore_sigcontext(struct pt_regs *regs,
  	struct sigcontext __user *sc)
  {
  	int err = 0;
  	unsigned long sr = regs->sr;
  
  	/* sc_pt_regs is structured the same as the start of pt_regs */
  	err |= __copy_from_user(regs, &sc->sc_pt_regs, sizeof(struct pt_regs));
  
  	/* BIT(0) of regs->sr is Condition Code/Carry bit */
  	regs->sr = (sr & ~1) | (regs->sr & 1);
  
  	/* Restore the floating-point state. */
  	err |= restore_fpu_state(sc);
  
  	return err;
  }
  
  SYSCALL_DEFINE0(rt_sigreturn)
  {
  	struct pt_regs *regs = current_pt_regs();
  	struct rt_sigframe __user *frame;
  	sigset_t set;
  
  	/* Always make any pending restarted system calls return -EINTR */
  	current->restart_block.fn = do_no_restart_syscall;
  
  	frame = (struct rt_sigframe __user *)regs->usp;
  
  	if (!access_ok(frame, sizeof(*frame)))
  		goto badframe;
  
  	if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
  		goto badframe;
  
  	set_current_blocked(&set);
  
  	if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
  		goto badframe;
  
  	if (restore_altstack(&frame->uc.uc_stack))
  		goto badframe;
  
  	return regs->a0;
  
  badframe:
  	force_sig(SIGSEGV);
  	return 0;
  }
  
  static int setup_sigcontext(struct rt_sigframe __user *frame,
  	struct pt_regs *regs)
  {
  	struct sigcontext __user *sc = &frame->uc.uc_mcontext;
  	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 __user *get_sigframe(struct ksignal *ksig,
  	struct pt_regs *regs, size_t framesize)
  {
  	unsigned long sp;
  	/* Default to using normal stack */
  	sp = regs->usp;
  
  	/*
  	 * If we are on the alternate signal stack and would overflow it, don't.
  	 * Return an always-bogus address instead so we will die with SIGSEGV.
  	 */
  	if (on_sig_stack(sp) && !likely(on_sig_stack(sp - framesize)))
  		return (void __user __force *)(-1UL);
  
  	/* This is the X/Open sanctioned signal stack switching. */
  	sp = sigsp(sp, ksig) - framesize;
  
  	/* Align the stack frame. */
  	sp &= -8UL;
  
  	return (void __user *)sp;
  }
  
  static int
  setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
  {
  	struct rt_sigframe __user *frame;
  	int err = 0;
  
  	frame = get_sigframe(ksig, regs, 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(NULL, &frame->uc.uc_link);
  	err |= __save_altstack(&frame->uc.uc_stack, regs->usp);
  	err |= setup_sigcontext(frame, regs);
  	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
  	if (err)
  		return -EFAULT;
  
  	/* Set up to return from userspace. */
  	regs->lr = (unsigned long)VDSO_SYMBOL(
  		current->mm->context.vdso, rt_sigreturn);
  
  	/*
  	 * Set up registers for signal handler.
  	 * Registers that we don't modify keep the value they had from
  	 * user-space at the time we took the signal.
  	 * We always pass siginfo and mcontext, regardless of SA_SIGINFO,
  	 * since some things rely on this (e.g. glibc's debug/segfault.c).
  	 */
  	regs->pc  = (unsigned long)ksig->ka.sa.sa_handler;
  	regs->usp = (unsigned long)frame;
  	regs->a0  = ksig->sig;				/* a0: signal number */
  	regs->a1  = (unsigned long)(&(frame->info));	/* a1: siginfo pointer */
  	regs->a2  = (unsigned long)(&(frame->uc));	/* a2: ucontext pointer */
  
  	return 0;
  }
  
  static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
  {
  	sigset_t *oldset = sigmask_to_save();
  	int ret;
  
  	rseq_signal_deliver(ksig, regs);
  
  	/* Are we from a system call? */
  	if (in_syscall(regs)) {
  		/* Avoid additional syscall restarting via ret_from_exception */
  		forget_syscall(regs);
  
  		/* If so, check system call restarting.. */
  		switch (regs->a0) {
  		case -ERESTART_RESTARTBLOCK:
  		case -ERESTARTNOHAND:
  			regs->a0 = -EINTR;
  			break;
  
  		case -ERESTARTSYS:
  			if (!(ksig->ka.sa.sa_flags & SA_RESTART)) {
  				regs->a0 = -EINTR;
  				break;
  			}
  			fallthrough;
  		case -ERESTARTNOINTR:
  			regs->a0 = regs->orig_a0;
  			regs->pc -= TRAP0_SIZE;
  			break;
  		}
  	}
  
  	/* Set up the stack frame */
  	ret = setup_rt_frame(ksig, oldset, regs);
  
  	signal_setup_done(ret, ksig, 0);
  }
  
  static void do_signal(struct pt_regs *regs)
  {
  	struct ksignal ksig;
  
  	if (get_signal(&ksig)) {
  		/* Actually deliver the signal */
  		handle_signal(&ksig, regs);
  		return;
  	}
  
  	/* Did we come from a system call? */
  	if (in_syscall(regs)) {
  		/* Avoid additional syscall restarting via ret_from_exception */
  		forget_syscall(regs);
  
  		/* Restart the system call - no handlers present */
  		switch (regs->a0) {
  		case -ERESTARTNOHAND:
  		case -ERESTARTSYS:
  		case -ERESTARTNOINTR:
  			regs->a0 = regs->orig_a0;
  			regs->pc -= TRAP0_SIZE;
  			break;
  		case -ERESTART_RESTARTBLOCK:
  			regs->a0 = regs->orig_a0;
  			regs_syscallid(regs) = __NR_restart_syscall;
  			regs->pc -= TRAP0_SIZE;
  			break;
  		}
  	}
  
  	/*
  	 * If there is no signal to deliver, we just put the saved
  	 * sigmask back.
  	 */
  	restore_saved_sigmask();
  }
  
  /*
   * notification of userspace execution resumption
   * - triggered by the _TIF_WORK_MASK flags
   */
  asmlinkage void do_notify_resume(struct pt_regs *regs,
  	unsigned long thread_info_flags)
  {
  	if (thread_info_flags & _TIF_UPROBE)
  		uprobe_notify_resume(regs);
  
  	/* Handle pending signal delivery */
  	if (thread_info_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
  		do_signal(regs);
  
  	if (thread_info_flags & _TIF_NOTIFY_RESUME)
  		resume_user_mode_work(regs);
  }
  