1/* SPDX-License-Identifier: GPL-2.0-only */
2#ifndef _ASM_X86_ENTRY_COMMON_H
3#define _ASM_X86_ENTRY_COMMON_H
4
5#include <linux/randomize_kstack.h>
6#include <linux/user-return-notifier.h>
7
8#include <asm/nospec-branch.h>
9#include <asm/io_bitmap.h>
10#include <asm/fpu/api.h>
11
12/* Check that the stack and regs on entry from user mode are sane. */
13static __always_inline void arch_enter_from_user_mode(struct pt_regs *regs)
14{
15	if (IS_ENABLED(CONFIG_DEBUG_ENTRY)) {
16		/*
17		 * Make sure that the entry code gave us a sensible EFLAGS
18		 * register.  Native because we want to check the actual CPU
19		 * state, not the interrupt state as imagined by Xen.
20		 */
21		unsigned long flags = native_save_fl();
22		unsigned long mask = X86_EFLAGS_DF | X86_EFLAGS_NT;
23
24		/*
25		 * For !SMAP hardware we patch out CLAC on entry.
26		 */
27		if (cpu_feature_enabled(X86_FEATURE_SMAP) ||
28		    cpu_feature_enabled(X86_FEATURE_XENPV))
29			mask |= X86_EFLAGS_AC;
30
31		WARN_ON_ONCE(flags & mask);
32
33		/* We think we came from user mode. Make sure pt_regs agrees. */
34		WARN_ON_ONCE(!user_mode(regs));
35
36		/*
37		 * All entries from user mode (except #DF) should be on the
38		 * normal thread stack and should have user pt_regs in the
39		 * correct location.
40		 */
41		WARN_ON_ONCE(!on_thread_stack());
42		WARN_ON_ONCE(regs != task_pt_regs(current));
43	}
44}
45#define arch_enter_from_user_mode arch_enter_from_user_mode
46
47static inline void arch_exit_to_user_mode_prepare(struct pt_regs *regs,
48						  unsigned long ti_work)
49{
50	if (ti_work & _TIF_USER_RETURN_NOTIFY)
51		fire_user_return_notifiers();
52
53	if (unlikely(ti_work & _TIF_IO_BITMAP))
54		tss_update_io_bitmap();
55
56	fpregs_assert_state_consistent();
57	if (unlikely(ti_work & _TIF_NEED_FPU_LOAD))
58		switch_fpu_return();
59
60#ifdef CONFIG_COMPAT
61	/*
62	 * Compat syscalls set TS_COMPAT.  Make sure we clear it before
63	 * returning to user mode.  We need to clear it *after* signal
64	 * handling, because syscall restart has a fixup for compat
65	 * syscalls.  The fixup is exercised by the ptrace_syscall_32
66	 * selftest.
67	 *
68	 * We also need to clear TS_REGS_POKED_I386: the 32-bit tracer
69	 * special case only applies after poking regs and before the
70	 * very next return to user mode.
71	 */
72	current_thread_info()->status &= ~(TS_COMPAT | TS_I386_REGS_POKED);
73#endif
74
75	/*
76	 * Ultimately, this value will get limited by KSTACK_OFFSET_MAX(),
77	 * but not enough for x86 stack utilization comfort. To keep
78	 * reasonable stack head room, reduce the maximum offset to 8 bits.
79	 *
80	 * The actual entropy will be further reduced by the compiler when
81	 * applying stack alignment constraints (see cc_stack_align4/8 in
82	 * arch/x86/Makefile), which will remove the 3 (x86_64) or 2 (ia32)
83	 * low bits from any entropy chosen here.
84	 *
85	 * Therefore, final stack offset entropy will be 5 (x86_64) or
86	 * 6 (ia32) bits.
87	 */
88	choose_random_kstack_offset(rdtsc() & 0xFF);
89}
90#define arch_exit_to_user_mode_prepare arch_exit_to_user_mode_prepare
91
92static __always_inline void arch_exit_to_user_mode(void)
93{
94	amd_clear_divider();
95}
96#define arch_exit_to_user_mode arch_exit_to_user_mode
97
98#endif
99