5 * The layout of the per-CPU GDT under Linux:
12 * 4 - unused <==== new cacheline
15 * ------- start of TLS (Thread-Local Storage) segments:
17 * 6 - TLS segment #1 [ glibc's TLS segment ]
18 * 7 - TLS segment #2 [ Wine's %fs Win32 segment ]
24 * ------- start of kernel segments:
26 * 12 - kernel code segment <==== new cacheline
27 * 13 - kernel data segment
28 * 14 - default user CS
29 * 15 - default user DS
32 * 18 - PNPBIOS support (16->32 gate)
33 * 19 - PNPBIOS support
34 * 20 - PNPBIOS support
35 * 21 - PNPBIOS support
36 * 22 - PNPBIOS support
37 * 23 - APM BIOS support
38 * 24 - APM BIOS support
39 * 25 - APM BIOS support
41 * 26 - ESPFIX small SS
42 * 27 - per-cpu [ offset to per-cpu data area ]
46 * 31 - TSS for double fault handler
48 #define GDT_ENTRY_TLS_MIN 6
49 #define GDT_ENTRY_TLS_MAX (GDT_ENTRY_TLS_MIN + GDT_ENTRY_TLS_ENTRIES - 1)
51 #define GDT_ENTRY_DEFAULT_USER_CS 14
52 #define __USER_CS (GDT_ENTRY_DEFAULT_USER_CS * 8 + 3)
54 #define GDT_ENTRY_DEFAULT_USER_DS 15
55 #define __USER_DS (GDT_ENTRY_DEFAULT_USER_DS * 8 + 3)
57 #define GDT_ENTRY_KERNEL_BASE 12
59 #define GDT_ENTRY_KERNEL_CS (GDT_ENTRY_KERNEL_BASE + 0)
60 #define __KERNEL_CS (GDT_ENTRY_KERNEL_CS * 8)
62 #define GDT_ENTRY_KERNEL_DS (GDT_ENTRY_KERNEL_BASE + 1)
63 #define __KERNEL_DS (GDT_ENTRY_KERNEL_DS * 8)
65 #define GDT_ENTRY_TSS (GDT_ENTRY_KERNEL_BASE + 4)
66 #define GDT_ENTRY_LDT (GDT_ENTRY_KERNEL_BASE + 5)
68 #define GDT_ENTRY_PNPBIOS_BASE (GDT_ENTRY_KERNEL_BASE + 6)
69 #define GDT_ENTRY_APMBIOS_BASE (GDT_ENTRY_KERNEL_BASE + 11)
71 #define GDT_ENTRY_ESPFIX_SS (GDT_ENTRY_KERNEL_BASE + 14)
72 #define __ESPFIX_SS (GDT_ENTRY_ESPFIX_SS * 8)
74 #define GDT_ENTRY_PERCPU (GDT_ENTRY_KERNEL_BASE + 15)
76 #define __KERNEL_PERCPU (GDT_ENTRY_PERCPU * 8)
78 #define __KERNEL_PERCPU 0
81 #define GDT_ENTRY_DOUBLEFAULT_TSS 31
84 * The GDT has 32 entries
86 #define GDT_ENTRIES 32
88 /* Simple and small GDT entries for booting only */
90 #define GDT_ENTRY_BOOT_CS 2
91 #define __BOOT_CS (GDT_ENTRY_BOOT_CS * 8)
93 #define GDT_ENTRY_BOOT_DS (GDT_ENTRY_BOOT_CS + 1)
94 #define __BOOT_DS (GDT_ENTRY_BOOT_DS * 8)
96 /* The PnP BIOS entries in the GDT */
97 #define GDT_ENTRY_PNPBIOS_CS32 (GDT_ENTRY_PNPBIOS_BASE + 0)
98 #define GDT_ENTRY_PNPBIOS_CS16 (GDT_ENTRY_PNPBIOS_BASE + 1)
99 #define GDT_ENTRY_PNPBIOS_DS (GDT_ENTRY_PNPBIOS_BASE + 2)
100 #define GDT_ENTRY_PNPBIOS_TS1 (GDT_ENTRY_PNPBIOS_BASE + 3)
101 #define GDT_ENTRY_PNPBIOS_TS2 (GDT_ENTRY_PNPBIOS_BASE + 4)
103 /* The PnP BIOS selectors */
104 #define PNP_CS32 (GDT_ENTRY_PNPBIOS_CS32 * 8) /* segment for calling fn */
105 #define PNP_CS16 (GDT_ENTRY_PNPBIOS_CS16 * 8) /* code segment for BIOS */
106 #define PNP_DS (GDT_ENTRY_PNPBIOS_DS * 8) /* data segment for BIOS */
107 #define PNP_TS1 (GDT_ENTRY_PNPBIOS_TS1 * 8) /* transfer data segment */
108 #define PNP_TS2 (GDT_ENTRY_PNPBIOS_TS2 * 8) /* another data segment */
111 * Matching rules for certain types of segments.
114 /* Matches only __KERNEL_CS, ignoring PnP / USER / APM segments */
115 #define SEGMENT_IS_KERNEL_CODE(x) (((x) & 0xfc) == GDT_ENTRY_KERNEL_CS * 8)
117 /* Matches __KERNEL_CS and __USER_CS (they must be 2 entries apart) */
118 #define SEGMENT_IS_FLAT_CODE(x) (((x) & 0xec) == GDT_ENTRY_KERNEL_CS * 8)
120 /* Matches PNP_CS32 and PNP_CS16 (they must be consecutive) */
121 #define SEGMENT_IS_PNP_CODE(x) (((x) & 0xf4) == GDT_ENTRY_PNPBIOS_BASE * 8)