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 | * 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 | |
92 | static __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 |