arch/x86/kernel/signal.c - linux - Git at Google

 // 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/kstrtox.h>
 #include <linux/errno.h>
 #include <linux/wait.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/entry-common.h>
 #include <linux/syscalls.h>
 #include <linux/rseq.h>

 #include <asm/processor.h>
 #include <asm/ucontext.h>
 #include <asm/fpu/signal.h>
 #include <asm/fpu/xstate.h>
 #include <asm/vdso.h>
 #include <asm/mce.h>
 #include <asm/sighandling.h>
 #include <asm/vm86.h>

 #include <asm/syscall.h>
 #include <asm/sigframe.h>
 #include <asm/signal.h>
 #include <asm/shstk.h>

 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;
 }

 /*
  * Enable all pkeys temporarily, so as to ensure that both the current
  * execution stack as well as the alternate signal stack are writeable.
  * The application can use any of the available pkeys to protect the
  * alternate signal stack, and we don't know which one it is, so enable
  * all. The PKRU register will be reset to init_pkru later in the flow,
  * in fpu__clear_user_states(), and it is the application's responsibility
  * to enable the appropriate pkey as the first step in the signal handler
  * so that the handler does not segfault.
  */
 static inline u32 sig_prepare_pkru(void)
 {
 	u32 orig_pkru = read_pkru();

 	write_pkru(0);
 	return orig_pkru;
 }

 /*
  * Set up a signal frame.
  */

 /* x86 ABI requires 16-byte alignment */
 #define FRAME_ALIGNMENT	16UL

 #define MAX_FRAME_PADDING	(FRAME_ALIGNMENT - 1)

 /*
  * Determine which stack to use..
  */
 void __user *
 get_sigframe(struct ksignal *ksig, struct pt_regs *regs, size_t frame_size,
 	     void __user **fpstate)
 {
 	struct k_sigaction *ka = &ksig->ka;
 	int ia32_frame = is_ia32_frame(ksig);
 	/* Default to using normal stack */
 	bool nested_altstack = on_sig_stack(regs->sp);
 	bool entering_altstack = false;
 	unsigned long math_size = 0;
 	unsigned long sp = regs->sp;
 	unsigned long buf_fx = 0;
 	u32 pkru;

 	/* redzone */
 	if (!ia32_frame)
 		sp -= 128;

 	/* This is the X/Open sanctioned signal stack switching.  */
 	if (ka->sa.sa_flags & SA_ONSTACK) {
 		/*
 		 * This checks nested_altstack via sas_ss_flags(). Sensible
 		 * programs use SS_AUTODISARM, which disables that check, and
 		 * programs that don't use SS_AUTODISARM get compatible.
 		 */
 		if (sas_ss_flags(sp) == 0) {
 			sp = current->sas_ss_sp + current->sas_ss_size;
 			entering_altstack = true;
 		}
 	} else if (ia32_frame &&
 		   !nested_altstack &&
 		   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;
 		entering_altstack = true;
 	}

 	sp = fpu__alloc_mathframe(sp, ia32_frame, &buf_fx, &math_size);
 	*fpstate = (void __user *)sp;

 	sp -= frame_size;

 	if (ia32_frame)
 		/*
 		 * Align the stack pointer according to the i386 ABI,
 		 * i.e. so that on function entry ((sp + 4) & 15) == 0.
 		 */
 		sp = ((sp + 4) & -FRAME_ALIGNMENT) - 4;
 	else
 		sp = round_down(sp, FRAME_ALIGNMENT) - 8;

 	/*
 	 * 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 (unlikely((nested_altstack || entering_altstack) &&
 		     !__on_sig_stack(sp))) {

 		if (show_unhandled_signals && printk_ratelimit())
 			pr_info("%s[%d] overflowed sigaltstack\n",
 				current->comm, task_pid_nr(current));

 		return (void __user *)-1L;
 	}

 	/* Update PKRU to enable access to the alternate signal stack. */
 	pkru = sig_prepare_pkru();
 	/* save i387 and extended state */
 	if (!copy_fpstate_to_sigframe(*fpstate, (void __user *)buf_fx, math_size, pkru)) {
 		/*
 		 * Restore PKRU to the original, user-defined value; disable
 		 * extra pkeys enabled for the alternate signal stack, if any.
 		 */
 		write_pkru(pkru);
 		return (void __user *)-1L;
 	}

 	return (void __user *)sp;
 }

 /*
  * There are four different struct types for signal frame: sigframe_ia32,
  * rt_sigframe_ia32, rt_sigframe_x32, and rt_sigframe. Use the worst case
  * -- the largest size. It means the size for 64-bit apps is a bit more
  * than needed, but this keeps the code simple.
  */
 #if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
 # define MAX_FRAME_SIGINFO_UCTXT_SIZE	sizeof(struct sigframe_ia32)
 #else
 # define MAX_FRAME_SIGINFO_UCTXT_SIZE	sizeof(struct rt_sigframe)
 #endif

 /*
  * The FP state frame contains an XSAVE buffer which must be 64-byte aligned.
  * If a signal frame starts at an unaligned address, extra space is required.
  * This is the max alignment padding, conservatively.
  */
 #define MAX_XSAVE_PADDING	63UL

 /*
  * The frame data is composed of the following areas and laid out as:
  *
  * -------------------------
  * | alignment padding     |
  * -------------------------
  * | (f)xsave frame        |
  * -------------------------
  * | fsave header          |
  * -------------------------
  * | alignment padding     |
  * -------------------------
  * | siginfo + ucontext    |
  * -------------------------
  */

 /* max_frame_size tells userspace the worst case signal stack size. */
 static unsigned long __ro_after_init max_frame_size;
 static unsigned int __ro_after_init fpu_default_state_size;

 static int __init init_sigframe_size(void)
 {
 	fpu_default_state_size = fpu__get_fpstate_size();

 	max_frame_size = MAX_FRAME_SIGINFO_UCTXT_SIZE + MAX_FRAME_PADDING;

 	max_frame_size += fpu_default_state_size + MAX_XSAVE_PADDING;

 	/* Userspace expects an aligned size. */
 	max_frame_size = round_up(max_frame_size, FRAME_ALIGNMENT);

 	pr_info("max sigframe size: %lu\n", max_frame_size);
 	return 0;
 }
 early_initcall(init_sigframe_size);

 unsigned long get_sigframe_size(void)
 {
 	return max_frame_size;
 }

 static int
 setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs)
 {
 	/* 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(ksig, regs);
 		else
 			return ia32_setup_frame(ksig, regs);
 	} else if (is_x32_frame(ksig)) {
 		return x32_setup_rt_frame(ksig, regs);
 	} else {
 		return x64_setup_rt_frame(ksig, 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) != -1) {
 		/* 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.
 		 */
 		fpu__clear_user_states(fpu);
 	}
 	signal_setup_done(failed, ksig, stepping);
 }

 static inline unsigned long get_nr_restart_syscall(const struct pt_regs *regs)
 {
 #ifdef CONFIG_IA32_EMULATION
 	if (current->restart_block.arch_data & TS_COMPAT)
 		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 arch_do_signal_or_restart(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) != -1) {
 		/* 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);
 }

 #ifdef CONFIG_DYNAMIC_SIGFRAME
 #ifdef CONFIG_STRICT_SIGALTSTACK_SIZE
 static bool strict_sigaltstack_size __ro_after_init = true;
 #else
 static bool strict_sigaltstack_size __ro_after_init = false;
 #endif

 static int __init strict_sas_size(char *arg)
 {
 	return kstrtobool(arg, &strict_sigaltstack_size) == 0;
 }
 __setup("strict_sas_size", strict_sas_size);

 /*
  * MINSIGSTKSZ is 2048 and can't be changed despite the fact that AVX512
  * exceeds that size already. As such programs might never use the
  * sigaltstack they just continued to work. While always checking against
  * the real size would be correct, this might be considered a regression.
  *
  * Therefore avoid the sanity check, unless enforced by kernel
  * configuration or command line option.
  *
  * When dynamic FPU features are supported, the check is also enforced when
  * the task has permissions to use dynamic features. Tasks which have no
  * permission are checked against the size of the non-dynamic feature set
  * if strict checking is enabled. This avoids forcing all tasks on the
  * system to allocate large sigaltstacks even if they are never going
  * to use a dynamic feature. As this is serialized via sighand::siglock
  * any permission request for a dynamic feature either happened already
  * or will see the newly install sigaltstack size in the permission checks.
  */
 bool sigaltstack_size_valid(size_t ss_size)
 {
 	unsigned long fsize = max_frame_size - fpu_default_state_size;
 	u64 mask;

 	lockdep_assert_held(&current->sighand->siglock);

 	if (!fpu_state_size_dynamic() && !strict_sigaltstack_size)
 		return true;

 	fsize += current->group_leader->thread.fpu.perm.__user_state_size;
 	if (likely(ss_size > fsize))
 		return true;

 	if (strict_sigaltstack_size)
 		return ss_size > fsize;

 	mask = current->group_leader->thread.fpu.perm.__state_perm;
 	if (mask & XFEATURE_MASK_USER_DYNAMIC)
 		return ss_size > fsize;

 	return true;
 }
 #endif /* CONFIG_DYNAMIC_SIGFRAME */
	// 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/kstrtox.h>
	#include <linux/errno.h>
	#include <linux/wait.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/entry-common.h>
	#include <linux/syscalls.h>
	#include <linux/rseq.h>

	#include <asm/processor.h>
	#include <asm/ucontext.h>
	#include <asm/fpu/signal.h>
	#include <asm/fpu/xstate.h>
	#include <asm/vdso.h>
	#include <asm/mce.h>
	#include <asm/sighandling.h>
	#include <asm/vm86.h>

	#include <asm/syscall.h>
	#include <asm/sigframe.h>
	#include <asm/signal.h>
	#include <asm/shstk.h>

	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;
	}

	/*
	* Enable all pkeys temporarily, so as to ensure that both the current
	* execution stack as well as the alternate signal stack are writeable.
	* The application can use any of the available pkeys to protect the
	* alternate signal stack, and we don't know which one it is, so enable
	* all. The PKRU register will be reset to init_pkru later in the flow,
	* in fpu__clear_user_states(), and it is the application's responsibility
	* to enable the appropriate pkey as the first step in the signal handler
	* so that the handler does not segfault.
	*/
	static inline u32 sig_prepare_pkru(void)
	{
	u32 orig_pkru = read_pkru();

	write_pkru(0);
	return orig_pkru;
	}

	/*
	* Set up a signal frame.
	*/

	/* x86 ABI requires 16-byte alignment */
	#define FRAME_ALIGNMENT 16UL

	#define MAX_FRAME_PADDING (FRAME_ALIGNMENT - 1)

	/*
	* Determine which stack to use..
	*/
	void __user *
	get_sigframe(struct ksignal ksig, struct pt_regs regs, size_t frame_size,
	void __user **fpstate)
	{
	struct k_sigaction *ka = &ksig->ka;
	int ia32_frame = is_ia32_frame(ksig);
	/* Default to using normal stack */
	bool nested_altstack = on_sig_stack(regs->sp);
	bool entering_altstack = false;
	unsigned long math_size = 0;
	unsigned long sp = regs->sp;
	unsigned long buf_fx = 0;
	u32 pkru;

	/* redzone */
	if (!ia32_frame)
	sp -= 128;

	/* This is the X/Open sanctioned signal stack switching. */
	if (ka->sa.sa_flags & SA_ONSTACK) {
	/*
	* This checks nested_altstack via sas_ss_flags(). Sensible
	* programs use SS_AUTODISARM, which disables that check, and
	* programs that don't use SS_AUTODISARM get compatible.
	*/
	if (sas_ss_flags(sp) == 0) {
	sp = current->sas_ss_sp + current->sas_ss_size;
	entering_altstack = true;
	}
	} else if (ia32_frame &&
	!nested_altstack &&
	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;
	entering_altstack = true;
	}

	sp = fpu__alloc_mathframe(sp, ia32_frame, &buf_fx, &math_size);
	fpstate = (void __user )sp;

	sp -= frame_size;

	if (ia32_frame)
	/*
	* Align the stack pointer according to the i386 ABI,
	* i.e. so that on function entry ((sp + 4) & 15) == 0.
	*/
	sp = ((sp + 4) & -FRAME_ALIGNMENT) - 4;
	else
	sp = round_down(sp, FRAME_ALIGNMENT) - 8;

	/*
	* 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 (unlikely((nested_altstack \|\| entering_altstack) &&
	!__on_sig_stack(sp))) {

	if (show_unhandled_signals && printk_ratelimit())
	pr_info("%s[%d] overflowed sigaltstack\n",
	current->comm, task_pid_nr(current));

	return (void __user *)-1L;
	}

	/* Update PKRU to enable access to the alternate signal stack. */
	pkru = sig_prepare_pkru();
	/* save i387 and extended state */
	if (!copy_fpstate_to_sigframe(fpstate, (void __user )buf_fx, math_size, pkru)) {
	/*
	* Restore PKRU to the original, user-defined value; disable
	* extra pkeys enabled for the alternate signal stack, if any.
	*/
	write_pkru(pkru);
	return (void __user *)-1L;
	}

	return (void __user *)sp;
	}

	/*
	* There are four different struct types for signal frame: sigframe_ia32,
	* rt_sigframe_ia32, rt_sigframe_x32, and rt_sigframe. Use the worst case
	* -- the largest size. It means the size for 64-bit apps is a bit more
	* than needed, but this keeps the code simple.
	*/
	#if defined(CONFIG_X86_32) \|\| defined(CONFIG_IA32_EMULATION)
	# define MAX_FRAME_SIGINFO_UCTXT_SIZE sizeof(struct sigframe_ia32)
	#else
	# define MAX_FRAME_SIGINFO_UCTXT_SIZE sizeof(struct rt_sigframe)
	#endif

	/*
	* The FP state frame contains an XSAVE buffer which must be 64-byte aligned.
	* If a signal frame starts at an unaligned address, extra space is required.
	* This is the max alignment padding, conservatively.
	*/
	#define MAX_XSAVE_PADDING 63UL

	/*
	* The frame data is composed of the following areas and laid out as:
	*
	* -------------------------
	* \| alignment padding \|
	* -------------------------
	* \| (f)xsave frame \|
	* -------------------------
	* \| fsave header \|
	* -------------------------
	* \| alignment padding \|
	* -------------------------
	* \| siginfo + ucontext \|
	* -------------------------
	*/

	/* max_frame_size tells userspace the worst case signal stack size. */
	static unsigned long __ro_after_init max_frame_size;
	static unsigned int __ro_after_init fpu_default_state_size;

	static int __init init_sigframe_size(void)
	{
	fpu_default_state_size = fpu__get_fpstate_size();

	max_frame_size = MAX_FRAME_SIGINFO_UCTXT_SIZE + MAX_FRAME_PADDING;

	max_frame_size += fpu_default_state_size + MAX_XSAVE_PADDING;

	/* Userspace expects an aligned size. */
	max_frame_size = round_up(max_frame_size, FRAME_ALIGNMENT);

	pr_info("max sigframe size: %lu\n", max_frame_size);
	return 0;
	}
	early_initcall(init_sigframe_size);

	unsigned long get_sigframe_size(void)
	{
	return max_frame_size;
	}

	static int
	setup_rt_frame(struct ksignal ksig, struct pt_regs regs)
	{
	/* 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(ksig, regs);
	else
	return ia32_setup_frame(ksig, regs);
	} else if (is_x32_frame(ksig)) {
	return x32_setup_rt_frame(ksig, regs);
	} else {
	return x64_setup_rt_frame(ksig, 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) != -1) {
	/* 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.
	*/
	fpu__clear_user_states(fpu);
	}
	signal_setup_done(failed, ksig, stepping);
	}

	static inline unsigned long get_nr_restart_syscall(const struct pt_regs *regs)
	{
	#ifdef CONFIG_IA32_EMULATION
	if (current->restart_block.arch_data & TS_COMPAT)
	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 arch_do_signal_or_restart(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) != -1) {
	/* 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);
	}

	#ifdef CONFIG_DYNAMIC_SIGFRAME
	#ifdef CONFIG_STRICT_SIGALTSTACK_SIZE
	static bool strict_sigaltstack_size __ro_after_init = true;
	#else
	static bool strict_sigaltstack_size __ro_after_init = false;
	#endif

	static int __init strict_sas_size(char *arg)
	{
	return kstrtobool(arg, &strict_sigaltstack_size) == 0;
	}
	__setup("strict_sas_size", strict_sas_size);

	/*
	* MINSIGSTKSZ is 2048 and can't be changed despite the fact that AVX512
	* exceeds that size already. As such programs might never use the
	* sigaltstack they just continued to work. While always checking against
	* the real size would be correct, this might be considered a regression.
	*
	* Therefore avoid the sanity check, unless enforced by kernel
	* configuration or command line option.
	*
	* When dynamic FPU features are supported, the check is also enforced when
	* the task has permissions to use dynamic features. Tasks which have no
	* permission are checked against the size of the non-dynamic feature set
	* if strict checking is enabled. This avoids forcing all tasks on the
	* system to allocate large sigaltstacks even if they are never going
	* to use a dynamic feature. As this is serialized via sighand::siglock
	* any permission request for a dynamic feature either happened already
	* or will see the newly install sigaltstack size in the permission checks.
	*/
	bool sigaltstack_size_valid(size_t ss_size)
	{
	unsigned long fsize = max_frame_size - fpu_default_state_size;
	u64 mask;

	lockdep_assert_held(&current->sighand->siglock);

	if (!fpu_state_size_dynamic() && !strict_sigaltstack_size)
	return true;

	fsize += current->group_leader->thread.fpu.perm.__user_state_size;
	if (likely(ss_size > fsize))
	return true;

	if (strict_sigaltstack_size)
	return ss_size > fsize;

	mask = current->group_leader->thread.fpu.perm.__state_perm;
	if (mask & XFEATURE_MASK_USER_DYNAMIC)
	return ss_size > fsize;

	return true;
	}
	#endif /* CONFIG_DYNAMIC_SIGFRAME */