1 // Copyright 2017 The Chromium OS Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4 //
5 // For GDT details see arch/x86/include/asm/segment.h
6
7 use kvm_sys::kvm_segment;
8
9 /// Constructor for a conventional segment GDT (or LDT) entry. Derived from the kernel's segment.h.
gdt_entry(flags: u16, base: u32, limit: u32) -> u6410 pub fn gdt_entry(flags: u16, base: u32, limit: u32) -> u64 {
11 ((((base as u64) & 0xff000000u64) << (56 - 24))
12 | (((flags as u64) & 0x0000f0ffu64) << 40)
13 | (((limit as u64) & 0x000f0000u64) << (48 - 16))
14 | (((base as u64) & 0x00ffffffu64) << 16)
15 | ((limit as u64) & 0x0000ffffu64))
16 }
17
get_base(entry: u64) -> u6418 fn get_base(entry: u64) -> u64 {
19 ((((entry) & 0xFF00000000000000) >> 32)
20 | (((entry) & 0x000000FF00000000) >> 16)
21 | (((entry) & 0x00000000FFFF0000) >> 16))
22 }
23
get_limit(entry: u64) -> u3224 fn get_limit(entry: u64) -> u32 {
25 ((((entry) & 0x000F000000000000) >> 32) | ((entry) & 0x000000000000FFFF)) as u32
26 }
27
get_g(entry: u64) -> u828 fn get_g(entry: u64) -> u8 {
29 ((entry & 0x0080000000000000) >> 55) as u8
30 }
31
get_db(entry: u64) -> u832 fn get_db(entry: u64) -> u8 {
33 ((entry & 0x0040000000000000) >> 54) as u8
34 }
35
get_l(entry: u64) -> u836 fn get_l(entry: u64) -> u8 {
37 ((entry & 0x0020000000000000) >> 53) as u8
38 }
39
get_avl(entry: u64) -> u840 fn get_avl(entry: u64) -> u8 {
41 ((entry & 0x0010000000000000) >> 52) as u8
42 }
43
get_p(entry: u64) -> u844 fn get_p(entry: u64) -> u8 {
45 ((entry & 0x0000800000000000) >> 47) as u8
46 }
47
get_dpl(entry: u64) -> u848 fn get_dpl(entry: u64) -> u8 {
49 ((entry & 0x0000600000000000) >> 45) as u8
50 }
51
get_s(entry: u64) -> u852 fn get_s(entry: u64) -> u8 {
53 ((entry & 0x0000100000000000) >> 44) as u8
54 }
55
get_type(entry: u64) -> u856 fn get_type(entry: u64) -> u8 {
57 ((entry & 0x00000F0000000000) >> 40) as u8
58 }
59
60 /// Automatically build the kvm struct for SET_SREGS from the kernel bit fields.
61 ///
62 /// # Arguments
63 ///
64 /// * `entry` - The gdt entry.
65 /// * `table_index` - Index of the entry in the gdt table.
kvm_segment_from_gdt(entry: u64, table_index: u8) -> kvm_segment66 pub fn kvm_segment_from_gdt(entry: u64, table_index: u8) -> kvm_segment {
67 kvm_segment {
68 base: get_base(entry),
69 limit: get_limit(entry),
70 selector: (table_index * 8) as u16,
71 type_: get_type(entry),
72 present: get_p(entry),
73 dpl: get_dpl(entry),
74 db: get_db(entry),
75 s: get_s(entry),
76 l: get_l(entry),
77 g: get_g(entry),
78 avl: get_avl(entry),
79 padding: 0,
80 unusable: match get_p(entry) {
81 0 => 1,
82 _ => 0,
83 },
84 }
85 }
86
87 #[cfg(test)]
88 mod test {
89 use super::*;
90
91 #[test]
field_parse()92 fn field_parse() {
93 let gdt = gdt_entry(0xA09B, 0x100000, 0xfffff);
94 let seg = kvm_segment_from_gdt(gdt, 0);
95 // 0xA09B
96 // 'A'
97 assert_eq!(0x1, seg.g);
98 assert_eq!(0x0, seg.db);
99 assert_eq!(0x1, seg.l);
100 assert_eq!(0x0, seg.avl);
101 // '9'
102 assert_eq!(0x1, seg.present);
103 assert_eq!(0x0, seg.dpl);
104 assert_eq!(0x1, seg.s);
105 // 'B'
106 assert_eq!(0xB, seg.type_);
107 // base and limit
108 assert_eq!(0x100000, seg.base);
109 assert_eq!(0xfffff, seg.limit);
110 assert_eq!(0x0, seg.unusable);
111 }
112 }
113