e9922e775f
The BOOT_GDT_SEGMENT_COUNT was based on USER_DATA_SEGMENT on both x86 and x86_64. However, on x86_64 the order of the segments is different, leading to a too small gBootGDT array. Move the define to the arch specific headers so they can be setup correctly in either case. Also add a STATIC_ASSERT() to check that the descriptors fit into the array. Pointed out by CID 1210898.
96 lines
2.0 KiB
C
96 lines
2.0 KiB
C
/*
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* Copyright 2012, Alex Smith, alex@alex-smith.me.uk.
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* Distributed under the terms of the MIT License.
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*/
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#ifndef _KERNEL_ARCH_X86_64_DESCRIPTORS_H
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#define _KERNEL_ARCH_X86_64_DESCRIPTORS_H
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// Segment definitions.
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// Note that the ordering of these is important to SYSCALL/SYSRET.
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#define KERNEL_CODE_SEGMENT 1
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#define KERNEL_DATA_SEGMENT 2
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#define USER_DATA_SEGMENT 3
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#define USER_CODE_SEGMENT 4
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#define BOOT_GDT_SEGMENT_COUNT (USER_CODE_SEGMENT + 1)
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#define KERNEL_CODE_SELECTOR ((KERNEL_CODE_SEGMENT << 3) | DPL_KERNEL)
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#define KERNEL_DATA_SELECTOR ((KERNEL_DATA_SEGMENT << 3) | DPL_KERNEL)
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#define USER_CODE_SELECTOR ((USER_CODE_SEGMENT << 3) | DPL_USER)
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#define USER_DATA_SELECTOR ((USER_DATA_SEGMENT << 3) | DPL_USER)
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#ifndef _ASSEMBLER
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// Structure of a segment descriptor.
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struct segment_descriptor {
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uint32 limit0 : 16;
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uint32 base0 : 24;
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uint32 type : 4;
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uint32 desc_type : 1;
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uint32 dpl : 2;
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uint32 present : 1;
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uint32 limit1 : 4;
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uint32 available : 1;
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uint32 long_mode : 1;
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uint32 d_b : 1;
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uint32 granularity : 1;
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uint32 base1 : 8;
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} _PACKED;
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struct tss {
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uint32 _reserved1;
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uint64 sp0;
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uint64 sp1;
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uint64 sp2;
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uint64 _reserved2;
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uint64 ist1;
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uint64 ist2;
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uint64 ist3;
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uint64 ist4;
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uint64 ist5;
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uint64 ist6;
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uint64 ist7;
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uint64 _reserved3;
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uint16 _reserved4;
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uint16 io_map_base;
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} _PACKED;
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static inline void
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clear_segment_descriptor(segment_descriptor* desc)
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{
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*(uint64*)desc = 0;
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}
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static inline void
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set_segment_descriptor(segment_descriptor* desc, uint8 type, uint8 dpl)
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{
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clear_segment_descriptor(desc);
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// In 64-bit mode the CPU ignores the base/limit of code/data segments,
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// it always treats base as 0 and does no limit checks.
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desc->base0 = 0;
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desc->base1 = 0;
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desc->limit0 = 0xffff;
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desc->limit1 = 0xf;
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desc->granularity = 1;
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desc->type = type;
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desc->desc_type = DT_CODE_DATA_SEGMENT;
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desc->dpl = dpl;
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desc->present = 1;
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desc->long_mode = (type & DT_CODE_EXECUTE_ONLY) ? 1 : 0;
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// Must be set to 1 for code segments only.
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}
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#endif /* _ASSEMBLER */
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#endif /* _KERNEL_ARCH_X86_64_DESCRIPTORS_H */
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