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. */
13 static __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
47 static 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 * This value will get limited by KSTACK_OFFSET_MAX(), which is 10
77 * bits. The actual entropy will be further reduced by the compiler
78 * when applying stack alignment constraints (see cc_stack_align4/8 in
79 * arch/x86/Makefile), which will remove the 3 (x86_64) or 2 (ia32)
80 * low bits from any entropy chosen here.
81 *
82 * Therefore, final stack offset entropy will be 7 (x86_64) or
83 * 8 (ia32) bits.
84 */
85 choose_random_kstack_offset(rdtsc());
86 }
87 #define arch_exit_to_user_mode_prepare arch_exit_to_user_mode_prepare
88
89 static __always_inline void arch_exit_to_user_mode(void)
90 {
91 amd_clear_divider();
92 }
93 #define arch_exit_to_user_mode arch_exit_to_user_mode
94
95 #endif
96
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.