path: root/arch/x86/kernel/signal.c

// 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/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/entry-common.h>
#include <linux/syscalls.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>

#ifdef CONFIG_X86_64
#include <linux/compat.h>
#include <asm/proto.h>
#include <asm/ia32_unistd.h>
#include <asm/fpu/xstate.h>
#endif /* CONFIG_X86_64 */

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

#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;
}
# define CONTEXT_COPY_SIZE	offsetof(struct sigcontext, reserved1)
#else
# define CONTEXT_COPY_SIZE	sizeof(struct sigcontext)
#endif

static bool restore_sigcontext(struct pt_regs *regs,
			       struct sigcontext __user *usc,
			       unsigned long uc_flags)
{
	struct sigcontext sc;

	/* Always make any pending restarted system calls return -EINTR */
	current->restart_block.fn = do_no_restart_syscall;

	if (copy_from_user(&sc, usc, CONTEXT_COPY_SIZE))
		return false;

#ifdef CONFIG_X86_32
	set_user_gs(regs, sc.gs);
	regs->fs = sc.fs;
	regs->es = sc.es;
	regs->ds = sc.ds;
#endif /* CONFIG_X86_32 */

	regs->bx = sc.bx;
	regs->cx = sc.cx;
	regs->dx = sc.dx;
	regs->si = sc.si;
	regs->di = sc.di;
	regs->bp = sc.bp;
	regs->ax = sc.ax;
	regs->sp = sc.sp;
	regs->ip = sc.ip;

#ifdef CONFIG_X86_64
	regs->r8 = sc.r8;
	regs->r9 = sc.r9;
	regs->r10 = sc.r10;
	regs->r11 = sc.r11;
	regs->r12 = sc.r12;
	regs->r13 = sc.r13;
	regs->r14 = sc.r14;
	regs->r15 = sc.r15;
#endif /* CONFIG_X86_64 */

	/* Get CS/SS and force CPL3 */
	regs->cs = sc.cs | 0x03;
	regs->ss = sc.ss | 0x03;

	regs->flags = (regs->flags & ~FIX_EFLAGS) | (sc.flags & FIX_EFLAGS);
	/* disable syscall checks */
	regs->orig_ax = -1;

#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

	return fpu__restore_sig((void __user *)sc.fpstate,
			       IS_ENABLED(CONFIG_X86_32));
}

static __always_inline int
__unsafe_setup_sigcontext(struct sigcontext __user *sc, void __user *fpstate,
		     struct pt_regs *regs, unsigned long mask)
{
#ifdef CONFIG_X86_32
	unsafe_put_user(get_user_gs(regs),
				  (unsigned int __user *)&sc->gs, Efault);
	unsafe_put_user(regs->fs, (unsigned int __user *)&sc->fs, Efault);
	unsafe_put_user(regs->es, (unsigned int __user *)&sc->es, Efault);
	unsafe_put_user(regs->ds, (unsigned int __user *)&sc->ds, Efault);
#endif /* CONFIG_X86_32 */

	unsafe_put_user(regs->di, &sc->di, Efault);
	unsafe_put_user(regs->si, &sc->si, Efault);
	unsafe_put_user(regs->bp, &sc->bp, Efault);
	unsafe_put_user(regs->sp, &sc->sp, Efault);
	unsafe_put_user(regs->bx, &sc->bx, Efault);
	unsafe_put_user(regs->dx, &sc->dx, Efault);
	unsafe_put_user(regs->cx, &sc->cx, Efault);
	unsafe_put_user(regs->ax, &sc->ax, Efault);
#ifdef CONFIG_X86_64
	unsafe_put_user(regs->r8, &sc->r