--- arch/x86/cpu/cpu.c | 2 +- arch/x86/cpu/interrupts.c | 2 +- arch/x86/cpu/start16.S | 54 +++++++++++++++++++++++++++++++++++--------- 3 files changed, 45 insertions(+), 13 deletions(-)
diff --git a/arch/x86/cpu/cpu.c b/arch/x86/cpu/cpu.c index 7ec0c12..70a864d 100644 --- a/arch/x86/cpu/cpu.c +++ b/arch/x86/cpu/cpu.c @@ -61,7 +61,7 @@ static void reload_gdt(void) * There are machines which are known to not boot with the GDT * being 8-byte unaligned. Intel recommends 16 byte alignment */ - static const u64 boot_gdt[] __attribute__((aligned(16))) = { + static const u64 boot_gdt[] __aligned(16) = { /* CS: code, read/execute, 4 GB, base 0 */ [GDT_ENTRY_32BIT_CS] = GDT_ENTRY(0xc09b, 0, 0xfffff), /* DS: data, read/write, 4 GB, base 0 */ diff --git a/arch/x86/cpu/interrupts.c b/arch/x86/cpu/interrupts.c index e0958eb..43ec3f8 100644 --- a/arch/x86/cpu/interrupts.c +++ b/arch/x86/cpu/interrupts.c @@ -174,7 +174,7 @@ struct desc_ptr { unsigned short segment; } __packed;
-struct idt_entry idt[256] __attribute__((aligned(16))); +struct idt_entry idt[256] __aligned(16);
struct desc_ptr idt_ptr;
diff --git a/arch/x86/cpu/start16.S b/arch/x86/cpu/start16.S index 33e53cd..f454827 100644 --- a/arch/x86/cpu/start16.S +++ b/arch/x86/cpu/start16.S @@ -86,7 +86,8 @@ gdt_ptr: .word 0x20 /* limit (32 bytes = 4 GDT entries) */ .long BOOT_SEG + gdt /* base */
- /* The GDT table ... + /* + * The GDT table ... * * Selector Type * 0x00 NULL @@ -96,15 +97,46 @@ gdt_ptr: */
gdt: - .word 0, 0, 0, 0 /* NULL */ - .word 0, 0, 0, 0 /* unused */ + /* The NULL Desciptor - Mandatory */ + .word 0x0000 /* limit_low */ + .word 0x0000 /* base_low */ + .byte 0x00 /* base_middle */ + .byte 0x00 /* access */ + .byte 0x00 /* flags + limit_high */ + .byte 0x00 /* base_high */ + + /* Unused Desciptor - (matches Linux) */ + .word 0x0000 /* limit_low */ + .word 0x0000 /* base_low */ + .byte 0x00 /* base_middle */ + .byte 0x00 /* access */ + .byte 0x00 /* flags + limit_high */ + .byte 0x00 /* base_high */
- .word 0xFFFF /* 4Gb - (0x100000*0x1000 = 4Gb) */ - .word 0 /* base address = 0 */ - .word 0x9B00 /* code read/exec */ - .word 0x00CF /* granularity = 4096, 386 (+5th nibble of limit) */ + /* + * The Code Segment Descriptor: + * - Base = 0x00000000 + * - Size = 4GB + * - Access = Present, Ring 0, Exec (Code), Readable + * - Flags = 4kB Granularity, 32-bit + */ + .word 0xffff /* limit_low */ + .word 0x0000 /* base_low */ + .byte 0x00 /* base_middle */ + .byte 0x9a /* access */ + .byte 0xcf /* flags + limit_high */ + .byte 0x00 /* base_high */
- .word 0xFFFF /* 4Gb - (0x100000*0x1000 = 4Gb) */ - .word 0x0 /* base address = 0 */ - .word 0x9300 /* data read/write */ - .word 0x00CF /* granularity = 4096, 386 (+5th nibble of limit) */ + /* + * The Data Segment Descriptor: + * - Base = 0x00000000 + * - Size = 4GB + * - Access = Present, Ring 0, Non-Exec (Data), Writable + * - Flags = 4kB Granularity, 32-bit + */ + .word 0xffff /* limit_low */ + .word 0x0000 /* base_low */ + .byte 0x00 /* base_middle */ + .byte 0x93 /* access */ + .byte 0xcf /* flags + limit_high */ + .byte 0x00 /* base_high */