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Improve GDT entries

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This commit is contained in:
Baptiste Wicht 2013-12-15 21:03:44 +01:00
parent 8fca1bc2a0
commit 0263dceb1f
1 changed files with 61 additions and 3 deletions
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64
kernel/src/boot/boot_16.cpp
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@ -64,6 +64,14 @@ void setup_idt(){
asm volatile("lidt %0" : : "m" (null_idt));
}
constexpr uint64_t gdt_entry(uint32_t base, uint32_t limit, uint16_t flags){
return ((((base) & 0xff000000ULL) << (56-24)) |
(((flags) & 0x0000f0ffULL) << 40) |
(((limit) & 0x000f0000ULL) << (48-16)) |
(((base) & 0x00ffffffULL) << 16) |
(((limit) & 0x0000ffffULL)));
}
#define GDT_ENTRY(f1, f2) \
((static_cast<uint64_t>(0x0FFFF) << 48) | \
(((f1)) << 16) | \
@ -75,13 +83,63 @@ void setup_idt(){
#define B_10001111 0x8F
#define B_10101111 0xAF
#define SEG_DESCTYPE(x) ((x) << 0x04) // Descriptor type (0 for system, 1 for code/data)
#define SEG_PRES(x) ((x) << 0x07) // Present
#define SEG_SAVL(x) ((x) << 0x0C) // Available for system use
#define SEG_LONG(x) ((x) << 0x0D) // Long mode
#define SEG_SIZE(x) ((x) << 0x0E) // Size (0 for 16-bit, 1 for 32)
#define SEG_GRAN(x) ((x) << 0x0F) // Granularity (0 for 1B - 1MB, 1 for 4KB - 4GB)
#define SEG_PRIV(x) (((x) & 0x03) << 0x05) // Set privilege level (0 - 3)
#define SEG_DATA_RD 0x00 // Read-Only
#define SEG_DATA_RDA 0x01 // Read-Only, accessed
#define SEG_DATA_RDWR 0x02 // Read/Write
#define SEG_DATA_RDWRA 0x03 // Read/Write, accessed
#define SEG_DATA_RDEXPD 0x04 // Read-Only, expand-down
#define SEG_DATA_RDEXPDA 0x05 // Read-Only, expand-down, accessed
#define SEG_DATA_RDWREXPD 0x06 // Read/Write, expand-down
#define SEG_DATA_RDWREXPDA 0x07 // Read/Write, expand-down, accessed
#define SEG_CODE_EX 0x08 // Execute-Only
#define SEG_CODE_EXA 0x09 // Execute-Only, accessed
#define SEG_CODE_EXRD 0x0A // Execute/Read
#define SEG_CODE_EXRDA 0x0B // Execute/Read, accessed
#define SEG_CODE_EXC 0x0C // Execute-Only, conforming
#define SEG_CODE_EXCA 0x0D // Execute-Only, conforming, accessed
#define SEG_CODE_EXRDC 0x0E // Execute/Read, conforming
#define SEG_CODE_EXRDCA 0x0F // Execute/Read, conforming, accessed
constexpr uint16_t code_32_selector(){
return
SEG_DESCTYPE(1) | SEG_PRES(1) | SEG_SAVL(0) |
SEG_LONG(0) | SEG_SIZE(1) | SEG_GRAN(1) |
SEG_PRIV(0) | SEG_CODE_EXRD;
}
constexpr uint16_t code_64_selector(){
return
SEG_DESCTYPE(1) | SEG_PRES(1) | SEG_SAVL(0) |
SEG_LONG(1) | SEG_SIZE(1) | SEG_GRAN(1) |
SEG_PRIV(0) | SEG_CODE_EXRD;
}
constexpr uint16_t data_selector(){
return
SEG_DESCTYPE(1) | SEG_PRES(1) | SEG_SAVL(0) |
SEG_LONG(0) | SEG_SIZE(1) | SEG_GRAN(1) |
SEG_PRIV(0) | SEG_DATA_RDWR;
}
void setup_gdt(){
//TODO On some machines, this should be aligned to 16 bits
static const uint64_t gdt[] = {
0, //Null Selector
GDT_ENTRY(B_10011010, B_11001111), //32-bit Code Selector (ring 0)
GDT_ENTRY(B_10010010, B_10001111), //Data Selector (ring 0)
GDT_ENTRY(B_10011010, B_10101111) //64-bit Code Selector (ring 0)
gdt_entry(0, 0xFFFFF, code_32_selector()),
gdt_entry(0, 0xFFFFF, data_selector()),
gdt_entry(0, 0xFFFFF, code_64_selector())
//GDT_ENTRY(B_10011010, B_11001111), //32-bit Code Selector (ring 0)
//GDT_ENTRY(, ), //Data Selector (ring 0)
//GDT_ENTRY(, ) //64-bit Code Selector (ring 0)
};
static gdt_ptr gdtr;