text: // SPDX-License-Identifier: GPL-2.0
  /*
   *  Copyright (C) 1991, 1992  Linus Torvalds
   *  Copyright (C) 2000, 2001, 2002 Andi Kleen SuSE Labs
   *
   *  1997-11-28  Modified for POSIX.1b signals by Richard Henderson
   *  2000-06-20  Pentium III FXSR, SSE support by Gareth Hughes
   *  2000-2002   x86-64 support by Andi Kleen
   */
  
  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  
  #include <linux/sched.h>
  #include <linux/sched/task_stack.h>
  #include <linux/mm.h>
  #include <linux/smp.h>
  #include <linux/kernel.h>
  #include <linux/errno.h>
  #include <linux/wait.h>
  #include <linux/tracehook.h>
  #include <linux/unistd.h>
  #include <linux/stddef.h>
  #include <linux/personality.h>
  #include <linux/uaccess.h>
  #include <linux/user-return-notifier.h>
  #include <linux/uprobes.h>
  #include <linux/context_tracking.h>
  #include <linux/syscalls.h>
  
  #include <asm/processor.h>
  #include <asm/ucontext.h>
  #include <asm/fpu/internal.h>
  #include <asm/fpu/signal.h>
  #include <asm/vdso.h>
  #include <asm/mce.h>
  #include <asm/sighandling.h>
  #include <asm/vm86.h>
  
  #ifdef CONFIG_X86_64
  #include <asm/proto.h>
  #include <asm/ia32_unistd.h>
  #endif /* CONFIG_X86_64 */
  
  #include <asm/syscall.h>
  #include <asm/syscalls.h>
  
  #include <asm/sigframe.h>
  #include <asm/signal.h>
  
  #define COPY(x)			do {			\
  	get_user_ex(regs->x, &sc->x);			\
  } while (0)
  
  #define GET_SEG(seg)		({			\
  	unsigned short tmp;				\
  	get_user_ex(tmp, &sc->seg);			\
  	tmp;						\
  })
  
  #define COPY_SEG(seg)		do {			\
  	regs->seg = GET_SEG(seg);			\
  } while (0)
  
  #define COPY_SEG_CPL3(seg)	do {			\
  	regs->seg = GET_SEG(seg) | 3;			\
  } while (0)
  
  #ifdef CONFIG_X86_64
  /*
   * If regs->ss will cause an IRET fault, change it.  Otherwise leave it
   * alone.  Using this generally makes no sense unless
   * user_64bit_mode(regs) would return true.
   */
  static void force_valid_ss(struct pt_regs *regs)
  {
  	u32 ar;
  	asm volatile ("lar %[old_ss], %[ar]\n\t"
  		      "jz 1f\n\t"		/* If invalid: */
  		      "xorl %[ar], %[ar]\n\t"	/* set ar = 0 */
  		      "1:"
  		      : [ar] "=r" (ar)
  		      : [old_ss] "rm" ((u16)regs->ss));
  
  	/*
  	 * For a valid 64-bit user context, we need DPL 3, type
  	 * read-write data or read-write exp-down data, and S and P
  	 * set.  We can't use VERW because VERW doesn't check the
  	 * P bit.
  	 */
  	ar &= AR_DPL_MASK | AR_S | AR_P | AR_TYPE_MASK;
  	if (ar != (AR_DPL3 | AR_S | AR_P | AR_TYPE_RWDATA) &&
  	    ar != (AR_DPL3 | AR_S | AR_P | AR_TYPE_RWDATA_EXPDOWN))
  		regs->ss = __USER_DS;
  }
  #endif
  
  static int restore_sigcontext(struct pt_regs *regs,
  			      struct sigcontext __user *sc,
  			      unsigned long uc_flags)
  {
  	unsigned long buf_val;
  	void __user *buf;
  	unsigned int tmpflags;
  	unsigned int err = 0;
  
  	/* Always make any pending restarted system calls return -EINTR */
  	current->restart_block.fn = do_no_restart_syscall;
  
  	get_user_try {
  
  #ifdef CONFIG_X86_32
  		set_user_gs(regs, GET_SEG(gs));
  		COPY_SEG(fs);
  		COPY_SEG(es);
  		COPY_SEG(ds);
  #endif /* CONFIG_X86_32 */
  
  		COPY(di); COPY(si); COPY(bp); COPY(sp); COPY(bx);
  		COPY(dx); COPY(cx); COPY(ip); COPY(ax);
  
  #ifdef CONFIG_X86_64
  		COPY(r8);
  		COPY(r9);
  		COPY(r10);
  		COPY(r11);
  		COPY(r12);
  		COPY(r13);
  		COPY(r14);
  		COPY(r15);
  #endif /* CONFIG_X86_64 */
  
  		COPY_SEG_CPL3(cs);
  		COPY_SEG_CPL3(ss);
  
  		get_user_ex(tmpflags, &sc->flags);
  		regs->flags = (regs->flags & ~FIX_EFLAGS) | (tmpflags & FIX_EFLAGS);
  		regs->orig_ax = -1;		/* disable syscall checks */
  
  		get_user_ex(buf_val, &sc->fpstate);
  		buf = (void __user *)buf_val;
  	} get_user_catch(err);
  
  #ifdef CONFIG_X86_64
  	/*
  	 * Fix up SS if needed for the benefit of old DOSEMU and
  	 * CRIU.
  	 */
  	if (unlikely(!(uc_flags & UC_STRICT_RESTORE_SS) && user_64bit_mode(regs)))
  		force_valid_ss(regs);
  #endif
  
  	err |= fpu__restore_sig(buf, IS_ENABLED(CONFIG_X86_32));
  
  	force_iret();
  
  	return err;
  }
  
  int setup_sigcontext(struct sigcontext __user *sc, void __user *fpstate,
  		     struct pt_regs *regs, unsigned long mask)
  {
  	int err = 0;
  
  	put_user_try {
  
  #ifdef CONFIG_X86_32
  		put_user_ex(get_user_gs(regs), (unsigned int __user *)&sc->gs);
  		put_user_ex(regs->fs, (unsigned int __user *)&sc->fs);
  		put_user_ex(regs->es, (unsigned int __user *)&sc->es);
  		put_user_ex(regs->ds, (unsigned int __user *)&sc->ds);
  #endif /* CONFIG_X86_32 */
  
  		put_user_ex(regs->di, &sc->di);
  		put_user_ex(regs->si, &sc->si);
  		put_user_ex(regs->bp, &sc->bp);
  		put_user_ex(regs->sp, &sc->sp);
  		put_user_ex(regs->bx, &sc->bx);
  		put_user_ex(regs->dx, &sc->dx);
  		put_user_ex(regs->cx, &sc->cx);
  		put_user_ex(regs->ax, &sc->ax);
  #ifdef CONFIG_X86_64
  		put_user_ex(regs->r8, &sc->r8);
  		put_user_ex(regs->r9, &sc->r9);
  		put_user_ex(regs->r10, &sc->r10);
  		put_user_ex(regs->r11, &sc->r11);
  		put_user_ex(regs->r12, &sc->r12);
  		put_user_ex(regs->r13, &sc->r13);
  		put_user_ex(regs->r14, &sc->r14);
  		put_user_ex(regs->r15, &sc->r15);
  #endif /* CONFIG_X86_64 */
  
  		put_user_ex(current->thread.trap_nr, &sc->trapno);
  		put_user_ex(current->thread.error_code, &sc->err);
  		put_user_ex(regs->ip, &sc->ip);
  #ifdef CONFIG_X86_32
  		put_user_ex(regs->cs, (unsigned int __user *)&sc->cs);
  		put_user_ex(regs->flags, &sc->flags);
  		put_user_ex(regs->sp, &sc->sp_at_signal);
  		put_user_ex(regs->ss, (unsigned int __user *)&sc->ss);
  #else /* !CONFIG_X86_32 */
  		put_user_ex(regs->flags, &sc->flags);
  		put_user_ex(regs->cs, &sc->cs);
  		put_user_ex(0, &sc->gs);
  		put_user_ex(0, &sc->fs);
  		put_user_ex(regs->ss, &sc->ss);
  #endif /* CONFIG_X86_32 */
  
  		put_user_ex(fpstate, &sc->fpstate);
  
  		/* non-iBCS2 extensions.. */
  		put_user_ex(mask, &sc->oldmask);
  		put_user_ex(current->thread.cr2, &sc->cr2);
  	} put_user_catch(err);
  
  	return err;
  }
  
  /*
   * Set up a signal frame.
   */
  
  /*
   * Determine which stack to use..
   */
  static unsigned long align_sigframe(unsigned long sp)
  {
  #ifdef CONFIG_X86_32
  	/*
  	 * Align the stack pointer according to the i386 ABI,
  	 * i.e. so that on function entry ((sp + 4) & 15) == 0.
  	 */
  	sp = ((sp + 4) & -16ul) - 4;
  #else /* !CONFIG_X86_32 */
  	sp = round_down(sp, 16) - 8;
  #endif
  	return sp;
  }
  
  static void __user *
  get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size,
  	     void __user **fpstate)
  {
  	/* Default to using normal stack */
  	unsigned long math_size = 0;
  	unsigned long sp = regs->sp;
  	unsigned long buf_fx = 0;
  	int onsigstack = on_sig_stack(sp);
  	struct fpu *fpu = &current->thread.fpu;
  
  	/* redzone */
  	if (IS_ENABLED(CONFIG_X86_64))
  		sp -= 128;
  
  	/* This is the X/Open sanctioned signal stack switching.  */
  	if (ka->sa.sa_flags & SA_ONSTACK) {
  		if (sas_ss_flags(sp) == 0)
  			sp = current->sas_ss_sp + current->sas_ss_size;
  	} else if (IS_ENABLED(CONFIG_X86_32) &&
  		   !onsigstack &&
  		   regs->ss != __USER_DS &&
  		   !(ka->sa.sa_flags & SA_RESTORER) &&
  		   ka->sa.sa_restorer) {
  		/* This is the legacy signal stack switching. */
  		sp = (unsigned long) ka->sa.sa_restorer;
  	}
  
  	if (fpu->initialized) {
  		sp = fpu__alloc_mathframe(sp, IS_ENABLED(CONFIG_X86_32),
  					  &buf_fx, &math_size);
  		*fpstate = (void __user *)sp;
  	}
  
  	sp = align_sigframe(sp - frame_size);
  
  	/*
  	 * 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 (onsigstack && !likely(on_sig_stack(sp)))
  		return (void __user *)-1L;
  
  	/* save i387 and extended state */
  	if (fpu->initialized &&
  	    copy_fpstate_to_sigframe(*fpstate, (void __user *)buf_fx, math_size) < 0)
  		return (void __user *)-1L;
  
  	return (void __user *)sp;
  }
  
  #ifdef CONFIG_X86_32
  static const struct {
  	u16 poplmovl;
  	u32 val;
  	u16 int80;
  } __attribute__((packed)) retcode = {
  	0xb858,		/* popl %eax; movl $..., %eax */
  	__NR_sigreturn,
  	0x80cd,		/* int $0x80 */
  };
  
  static const struct {
  	u8  movl;
  	u32 val;
  	u16 int80;
  	u8  pad;
  } __attribute__((packed)) rt_retcode = {
  	0xb8,		/* movl $..., %eax */
  	__NR_rt_sigreturn,
  	0x80cd,		/* int $0x80 */
  	0
  };
  
  static int
  __setup_frame(int sig, struct ksignal *ksig, sigset_t *set,
  	      struct pt_regs *regs)
  {
  	struct sigframe __user *frame;
  	void __user *restorer;
  	int err = 0;
  	void __user *fpstate = NULL;
  
  	frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fpstate);
  
  	if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
  		return -EFAULT;
  
  	if (__put_user(sig, &frame->sig))
  		return -EFAULT;
  
  	if (setup_sigcontext(&frame->sc, fpstate, regs, set->sig[0]))
  		return -EFAULT;
  
  	if (_NSIG_WORDS > 1) {
  		if (__copy_to_user(&frame->extramask, &set->sig[1],
  				   sizeof(frame->extramask)))
  			return -EFAULT;
  	}
  
  	if (current->mm->context.vdso)
  		restorer = current->mm->context.vdso +
  			vdso_image_32.sym___kernel_sigreturn;
  	else
  		restorer = &frame->retcode;
  	if (ksig->ka.sa.sa_flags & SA_RESTORER)
  		restorer = ksig->ka.sa.sa_restorer;
  
  	/* Set up to return from userspace.  */
  	err |= __put_user(restorer, &frame->pretcode);
  
  	/*
  	 * This is popl %eax ; movl $__NR_sigreturn, %eax ; int $0x80
  	 *
  	 * WE DO NOT USE IT ANY MORE! It's only left here for historical
  	 * reasons and because gdb uses it as a signature to notice
  	 * signal handler stack frames.
  	 */
  	err |= __put_user(*((u64 *)&retcode), (u64 *)frame->retcode);
  
  	if (err)
  		return -EFAULT;
  
  	/* Set up registers for signal handler */
  	regs->sp = (unsigned long)frame;
  	regs->ip = (unsigned long)ksig->ka.sa.sa_handler;
  	regs->ax = (unsigned long)sig;
  	regs->dx = 0;
  	regs->cx = 0;
  
  	regs->ds = __USER_DS;
  	regs->es = __USER_DS;
  	regs->ss = __USER_DS;
  	regs->cs = __USER_CS;
  
  	return 0;
  }
  
  static int __setup_rt_frame(int sig, struct ksignal *ksig,
  			    sigset_t *set, struct pt_regs *regs)
  {
  	struct rt_sigframe __user *frame;
  	void __user *restorer;
  	int err = 0;
  	void __user *fpstate = NULL;
  
  	frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fpstate);
  
  	if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
  		return -EFAULT;
  
  	put_user_try {
  		put_user_ex(sig, &frame->sig);
  		put_user_ex(&frame->info, &frame->pinfo);
  		put_user_ex(&frame->uc, &frame->puc);
  
  		/* Create the ucontext.  */
  		if (boot_cpu_has(X86_FEATURE_XSAVE))
  			put_user_ex(UC_FP_XSTATE, &frame->uc.uc_flags);
  		else
  			put_user_ex(0, &frame->uc.uc_flags);
  		put_user_ex(0, &frame->uc.uc_link);
  		save_altstack_ex(&frame->uc.uc_stack, regs->sp);
  
  		/* Set up to return from userspace.  */
  		restorer = current->mm->context.vdso +
  			vdso_image_32.sym___kernel_rt_sigreturn;
  		if (ksig->ka.sa.sa_flags & SA_RESTORER)
  			restorer = ksig->ka.sa.sa_restorer;
  		put_user_ex(restorer, &frame->pretcode);
  
  		/*
  		 * This is movl $__NR_rt_sigreturn, %ax ; int $0x80
  		 *
  		 * WE DO NOT USE IT ANY MORE! It's only left here for historical
  		 * reasons and because gdb uses it as a signature to notice
  		 * signal handler stack frames.
  		 */
  		put_user_ex(*((u64 *)&rt_retcode), (u64 *)frame->retcode);
  	} put_user_catch(err);
  	
  	err |= copy_siginfo_to_user(&frame->info, &ksig->info);
  	err |= setup_sigcontext(&frame->uc.uc_mcontext, fpstate,
  				regs, set->sig[0]);
  	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
  
  	if (err)
  		return -EFAULT;
  
  	/* Set up registers for signal handler */
  	regs->sp = (unsigned long)frame;
  	regs->ip = (unsigned long)ksig->ka.sa.sa_handler;
  	regs->ax = (unsigned long)sig;
  	regs->dx = (unsigned long)&frame->info;
  	regs->cx = (unsigned long)&frame->uc;
  
  	regs->ds = __USER_DS;
  	regs->es = __USER_DS;
  	regs->ss = __USER_DS;
  	regs->cs = __USER_CS;
  
  	return 0;
  }
  #else /* !CONFIG_X86_32 */
  static unsigned long frame_uc_flags(struct pt_regs *regs)
  {
  	unsigned long flags;
  
  	if (boot_cpu_has(X86_FEATURE_XSAVE))
  		flags = UC_FP_XSTATE | UC_SIGCONTEXT_SS;
  	else
  		flags = UC_SIGCONTEXT_SS;
  
  	if (likely(user_64bit_mode(regs)))
  		flags |= UC_STRICT_RESTORE_SS;
  
  	return flags;
  }
  
  static int __setup_rt_frame(int sig, struct ksignal *ksig,
  			    sigset_t *set, struct pt_regs *regs)
  {
  	struct rt_sigframe __user *frame;
  	void __user *fp = NULL;
  	unsigned long uc_flags;
  	int err = 0;
  
  	frame = get_sigframe(&ksig->ka, regs, sizeof(struct rt_sigframe), &fp);
  
  	if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
  		return -EFAULT;
  
  	if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
  		if (copy_siginfo_to_user(&frame->info, &ksig->info))
  			return -EFAULT;
  	}
  
  	uc_flags = frame_uc_flags(regs);
  
  	put_user_try {
  		/* Create the ucontext.  */
  		put_user_ex(uc_flags, &frame->uc.uc_flags);
  		put_user_ex(0, &frame->uc.uc_link);
  		save_altstack_ex(&frame->uc.uc_stack, regs->sp);
  
  		/* Set up to return from userspace.  If provided, use a stub
  		   already in userspace.  */
  		/* x86-64 should always use SA_RESTORER. */
  		if (ksig->ka.sa.sa_flags & SA_RESTORER) {
  			put_user_ex(ksig->ka.sa.sa_restorer, &frame->pretcode);
  		} else {
  			/* could use a vstub here */
  			err |= -EFAULT;
  		}
  	} put_user_catch(err);
  
  	err |= setup_sigcontext(&frame->uc.uc_mcontext, fp, regs, set->sig[0]);
  	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
  
  	if (err)
  		return -EFAULT;
  
  	/* Set up registers for signal handler */
  	regs->di = sig;
  	/* In case the signal handler was declared without prototypes */
  	regs->ax = 0;
  
  	/* This also works for non SA_SIGINFO handlers because they expect the
  	   next argument after the signal number on the stack. */
  	regs->si = (unsigned long)&frame->info;
  	regs->dx = (unsigned long)&frame->uc;
  	regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
  
  	regs->sp = (unsigned long)frame;
  
  	/*
  	 * Set up the CS and SS registers to run signal handlers in
  	 * 64-bit mode, even if the handler happens to be interrupting
  	 * 32-bit or 16-bit code.
  	 *
  	 * SS is subtle.  In 64-bit mode, we don't need any particular
  	 * SS descriptor, but we do need SS to be valid.  It's possible
  	 * that the old SS is entirely bogus -- this can happen if the
  	 * signal we're trying to deliver is #GP or #SS caused by a bad
  	 * SS value.  We also have a compatbility issue here: DOSEMU
  	 * relies on the contents of the SS register indicating the
  	 * SS value at the time of the signal, even though that code in
  	 * DOSEMU predates sigreturn's ability to restore SS.  (DOSEMU
  	 * avoids relying on sigreturn to restore SS; instead it uses
  	 * a trampoline.)  So we do our best: if the old SS was valid,
  	 * we keep it.  Otherwise we replace it.
  	 */
  	regs->cs = __USER_CS;
  
  	if (unlikely(regs->ss != __USER_DS))
  		force_valid_ss(regs);
  
  	return 0;
  }
  #endif /* CONFIG_X86_32 */
  
  static int x32_setup_rt_frame(struct ksignal *ksig,
  			      compat_sigset_t *set,
  			      struct pt_regs *regs)
  {
  #ifdef CONFIG_X86_X32_ABI
  	struct rt_sigframe_x32 __user *frame;
  	unsigned long uc_flags;
  	void __user *restorer;
  	int err = 0;
  	void __user *fpstate = NULL;
  
  	frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fpstate);
  
  	if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
  		return -EFAULT;
  
  	if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
  		if (__copy_siginfo_to_user32(&frame->info, &ksig->info, true))
  			return -EFAULT;
  	}
  
  	uc_flags = frame_uc_flags(regs);
  
  	put_user_try {
  		/* Create the ucontext.  */
  		put_user_ex(uc_flags, &frame->uc.uc_flags);
  		put_user_ex(0, &frame->uc.uc_link);
  		compat_save_altstack_ex(&frame->uc.uc_stack, regs->sp);
  		put_user_ex(0, &frame->uc.uc__pad0);
  
  		if (ksig->ka.sa.sa_flags & SA_RESTORER) {
  			restorer = ksig->ka.sa.sa_restorer;
  		} else {
  			/* could use a vstub here */
  			restorer = NULL;
  			err |= -EFAULT;
  		}
  		put_user_ex(restorer, &frame->pretcode);
  	} put_user_catch(err);
  
  	err |= setup_sigcontext(&frame->uc.uc_mcontext, fpstate,
  				regs, set->sig[0]);
  	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
  
  	if (err)
  		return -EFAULT;
  
  	/* Set up registers for signal handler */
  	regs->sp = (unsigned long) frame;
  	regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
  
  	/* We use the x32 calling convention here... */
  	regs->di = ksig->sig;
  	regs->si = (unsigned long) &frame->info;
  	regs->dx = (unsigned long) &frame->uc;
  
  	loadsegment(ds, __USER_DS);
  	loadsegment(es, __USER_DS);
  
  	regs->cs = __USER_CS;
  	regs->ss = __USER_DS;
  #endif	/* CONFIG_X86_X32_ABI */
  
  	return 0;
  }
  
  /*
   * Do a signal return; undo the signal stack.
   */
  #ifdef CONFIG_X86_32
  SYSCALL_DEFINE0(sigreturn)
  {
  	struct pt_regs *regs = current_pt_regs();
  	struct sigframe __user *frame;
  	sigset_t set;
  
  	frame = (struct sigframe __user *)(regs->sp - 8);
  
  	if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
  		goto badframe;
  	if (__get_user(set.sig[0], &frame->sc.oldmask) || (_NSIG_WORDS > 1
  		&& __copy_from_user(&set.sig[1], &frame->extramask,
  				    sizeof(frame->extramask))))
  		goto badframe;
  
  	set_current_blocked(&set);
  
  	/*
  	 * x86_32 has no uc_flags bits relevant to restore_sigcontext.
  	 * Save a few cycles by skipping the __get_user.
  	 */
  	if (restore_sigcontext(regs, &frame->sc, 0))
  		goto badframe;
  	return regs->ax;
  
  badframe:
  	signal_fault(regs, frame, "sigreturn");
  
  	return 0;
  }
  #endif /* CONFIG_X86_32 */
  
  SYSCALL_DEFINE0(rt_sigreturn)
  {
  	struct pt_regs *regs = current_pt_regs();
  	struct rt_sigframe __user *frame;
  	sigset_t set;
  	unsigned long uc_flags;
  
  	frame = (struct rt_sigframe __user *)(regs->sp - sizeof(long));
  	if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
  		goto badframe;
  	if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
  		goto badframe;
  	if (__get_user(uc_flags, &frame->uc.uc_flags))
  		goto badframe;
  
  	set_current_blocked(&set);
  
  	if (restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags))
  		goto badframe;
  
  	if (restore_altstack(&frame->uc.uc_stack))
  		goto badframe;
  
  	return regs->ax;
  
  badframe:
  	signal_fault(regs, frame, "rt_sigreturn");
  	return 0;
  }
  
  static inline int is_ia32_compat_frame(struct ksignal *ksig)
  {
  	return IS_ENABLED(CONFIG_IA32_EMULATION) &&
  		ksig->ka.sa.sa_flags & SA_IA32_ABI;
  }
  
  static inline int is_ia32_frame(struct ksignal *ksig)
  {
  	return IS_ENABLED(CONFIG_X86_32) || is_ia32_compat_frame(ksig);
  }
  
  static inline int is_x32_frame(struct ksignal *ksig)
  {
  	return IS_ENABLED(CONFIG_X86_X32_ABI) &&
  		ksig->ka.sa.sa_flags & SA_X32_ABI;
  }
  
  static int
  setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs)
  {
  	int usig = ksig->sig;
  	sigset_t *set = sigmask_to_save();
  	compat_sigset_t *cset = (compat_sigset_t *) set;
  
  	/*
  	 * Increment event counter and perform fixup for the pre-signal
  	 * frame.
  	 */
  	rseq_signal_deliver(ksig, regs);
  
  	/* Set up the stack frame */
  	if (is_ia32_frame(ksig)) {
  		if (ksig->ka.sa.sa_flags & SA_SIGINFO)
  			return ia32_setup_rt_frame(usig, ksig, cset, regs);
  		else
  			return ia32_setup_frame(usig, ksig, cset, regs);
  	} else if (is_x32_frame(ksig)) {
  		return x32_setup_rt_frame(ksig, cset, regs);
  	} else {
  		return __setup_rt_frame(ksig->sig, ksig, set, regs);
  	}
  }
  
  static void
  handle_signal(struct ksignal *ksig, struct pt_regs *regs)
  {
  	bool stepping, failed;
  	struct fpu *fpu = &current->thread.fpu;
  
  	if (v8086_mode(regs))
  		save_v86_state((struct kernel_vm86_regs *) regs, VM86_SIGNAL);
  
  	/* Are we from a system call? */
  	if (syscall_get_nr(current, regs) >= 0) {
  		/* If so, check system call restarting.. */
  		switch (syscall_get_error(current, regs)) {
  		case -ERESTART_RESTARTBLOCK:
  		case -ERESTARTNOHAND:
  			regs->ax = -EINTR;
  			break;
  
  		case -ERESTARTSYS:
  			if (!(ksig->ka.sa.sa_flags & SA_RESTART)) {
  				regs->ax = -EINTR;
  				break;
  			}
  		/* fallthrough */
  		case -ERESTARTNOINTR:
  			regs->ax = regs->orig_ax;
  			regs->ip -= 2;
  			break;
  		}
  	}
  
  	/*
  	 * If TF is set due to a debugger (TIF_FORCED_TF), clear TF now
  	 * so that register information in the sigcontext is correct and
  	 * then notify the tracer before entering the signal handler.
  	 */
  	stepping = test_thread_flag(TIF_SINGLESTEP);
  	if (stepping)
  		user_disable_single_step(current);
  
  	failed = (setup_rt_frame(ksig, regs) < 0);
  	if (!failed) {
  		/*
  		 * Clear the direction flag as per the ABI for function entry.
  		 *
  		 * Clear RF when entering the signal handler, because
  		 * it might disable possible debug exception from the
  		 * signal handler.
  		 *
  		 * Clear TF for the case when it wasn't set by debugger to
  		 * avoid the recursive send_sigtrap() in SIGTRAP handler.
  		 */
  		regs->flags &= ~(X86_EFLAGS_DF|X86_EFLAGS_RF|X86_EFLAGS_TF);
  		/*
  		 * Ensure the signal handler starts with the new fpu state.
  		 */
  		if (fpu->initialized)
  			fpu__clear(fpu);
  	}
  	signal_setup_done(failed, ksig, stepping);
  }
  
  static inline unsigned long get_nr_restart_syscall(const struct pt_regs *regs)
  {
  	/*
  	 * This function is fundamentally broken as currently
  	 * implemented.
  	 *
  	 * The idea is that we want to trigger a call to the
  	 * restart_block() syscall and that we want in_ia32_syscall(),
  	 * in_x32_syscall(), etc. to match whatever they were in the
  	 * syscall being restarted.  We assume that the syscall
  	 * instruction at (regs->ip - 2) matches whatever syscall
  	 * instruction we used to enter in the first place.
  	 *
  	 * The problem is that we can get here when ptrace pokes
  	 * syscall-like values into regs even if we're not in a syscall
  	 * at all.
  	 *
  	 * For now, we maintain historical behavior and guess based on
  	 * stored state.  We could do better by saving the actual
  	 * syscall arch in restart_block or (with caveats on x32) by
  	 * checking if regs->ip points to 'int $0x80'.  The current
  	 * behavior is incorrect if a tracer has a different bitness
  	 * than the tracee.
  	 */
  #ifdef CONFIG_IA32_EMULATION
  	if (current_thread_info()->status & (TS_COMPAT|TS_I386_REGS_POKED))
  		return __NR_ia32_restart_syscall;
  #endif
  #ifdef CONFIG_X86_X32_ABI
  	return __NR_restart_syscall | (regs->orig_ax & __X32_SYSCALL_BIT);
  #else
  	return __NR_restart_syscall;
  #endif
  }
  
  /*
   * 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.
   */
  void do_signal(struct pt_regs *regs)
  {
  	struct ksignal ksig;
  
  	if (get_signal(&ksig)) {
  		/* Whee! Actually deliver the signal.  */
  		handle_signal(&ksig, regs);
  		return;
  	}
  
  	/* Did we come from a system call? */
  	if (syscall_get_nr(current, regs) >= 0) {
  		/* Restart the system call - no handlers present */
  		switch (syscall_get_error(current, regs)) {
  		case -ERESTARTNOHAND:
  		case -ERESTARTSYS:
  		case -ERESTARTNOINTR:
  			regs->ax = regs->orig_ax;
  			regs->ip -= 2;
  			break;
  
  		case -ERESTART_RESTARTBLOCK:
  			regs->ax = get_nr_restart_syscall(regs);
  			regs->ip -= 2;
  			break;
  		}
  	}
  
  	/*
  	 * If there's no signal to deliver, we just put the saved sigmask
  	 * back.
  	 */
  	restore_saved_sigmask();
  }
  
  void signal_fault(struct pt_regs *regs, void __user *frame, char *where)
  {
  	struct task_struct *me = current;
  
  	if (show_unhandled_signals && printk_ratelimit()) {
  		printk("%s"
  		       "%s[%d] bad frame in %s frame:%p ip:%lx sp:%lx orax:%lx",
  		       task_pid_nr(current) > 1 ? KERN_INFO : KERN_EMERG,
  		       me->comm, me->pid, where, frame,
  		       regs->ip, regs->sp, regs->orig_ax);
  		print_vma_addr(KERN_CONT " in ", regs->ip);
  		pr_cont("\n");
  	}
  
  	force_sig(SIGSEGV, me);
  }
  
  #ifdef CONFIG_X86_X32_ABI
  asmlinkage long sys32_x32_rt_sigreturn(void)
  {
  	struct pt_regs *regs = current_pt_regs();
  	struct rt_sigframe_x32 __user *frame;
  	sigset_t set;
  	unsigned long uc_flags;
  
  	frame = (struct rt_sigframe_x32 __user *)(regs->sp - 8);
  
  	if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
  		goto badframe;
  	if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
  		goto badframe;
  	if (__get_user(uc_flags, &frame->uc.uc_flags))
  		goto badframe;
  
  	set_current_blocked(&set);
  
  	if (restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags))
  		goto badframe;
  
  	if (compat_restore_altstack(&frame->uc.uc_stack))
  		goto badframe;
  
  	return regs->ax;
  
  badframe:
  	signal_fault(regs, frame, "x32 rt_sigreturn");
  	return 0;
  }
  #endif
  