refactor: one more step towards arch-agnostic design

[lunaix-os.git] / lunaix-os / arch / i386 / mm / gdt.c

diff --git a/lunaix-os/arch/i386/mm/gdt.c b/lunaix-os/arch/i386/mm/gdt.c
new file mode 100644 (file)
index 0000000..5d4ffe8
--- /dev/null
+++ b/lunaix-os/arch/i386/mm/gdt.c
@@ -0,0 +1,79 @@
+#include <lunaix/types.h>
+#include <sys/x86_isa.h>
+
+#define SD_TYPE(x) (x << 8)
+#define SD_CODE_DATA(x) (x << 12)
+#define SD_DPL(x) (x << 13)
+#define SD_PRESENT(x) (x << 15)
+#define SD_AVL(x) (x << 20)
+#define SD_64BITS(x) (x << 21)
+#define SD_32BITS(x) (x << 22)
+#define SD_4K_GRAN(x) (x << 23)
+
+#define SEG_LIM_L(x) (x & 0x0ffff)
+#define SEG_LIM_H(x) (x & 0xf0000)
+#define SEG_BASE_L(x) ((x & 0x0000ffff) << 16)
+#define SEG_BASE_M(x) ((x & 0x00ff0000) >> 16)
+#define SEG_BASE_H(x) (x & 0xff000000)
+
+#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
+
+#define SEG_R0_CODE                                                            \
+    SD_TYPE(SEG_CODE_EXRD) | SD_CODE_DATA(1) | SD_DPL(0) | SD_PRESENT(1) |     \
+      SD_AVL(0) | SD_64BITS(0) | SD_32BITS(1) | SD_4K_GRAN(1)
+
+#define SEG_R0_DATA                                                            \
+    SD_TYPE(SEG_DATA_RDWR) | SD_CODE_DATA(1) | SD_DPL(0) | SD_PRESENT(1) |     \
+      SD_AVL(0) | SD_64BITS(0) | SD_32BITS(1) | SD_4K_GRAN(1)
+
+#define SEG_R3_CODE                                                            \
+    SD_TYPE(SEG_CODE_EXRD) | SD_CODE_DATA(1) | SD_DPL(3) | SD_PRESENT(1) |     \
+      SD_AVL(0) | SD_64BITS(0) | SD_32BITS(1) | SD_4K_GRAN(1)
+
+#define SEG_R3_DATA                                                            \
+    SD_TYPE(SEG_DATA_RDWR) | SD_CODE_DATA(1) | SD_DPL(3) | SD_PRESENT(1) |     \
+      SD_AVL(0) | SD_64BITS(0) | SD_32BITS(1) | SD_4K_GRAN(1)
+
+#define SEG_TSS SD_TYPE(9) | SD_DPL(0) | SD_PRESENT(1)
+
+#define GDT_ENTRY 6
+
+u64_t _gdt[GDT_ENTRY];
+u16_t _gdt_limit = sizeof(_gdt) - 1;
+
+void
+_set_gdt_entry(u32_t index, u32_t base, u32_t limit, u32_t flags)
+{
+    _gdt[index] =
+      SEG_BASE_H(base) | flags | SEG_LIM_H(limit) | SEG_BASE_M(base);
+    _gdt[index] <<= 32;
+    _gdt[index] |= SEG_BASE_L(base) | SEG_LIM_L(limit);
+}
+
+extern struct x86_tss _tss;
+
+void
+_init_gdt()
+{
+    _set_gdt_entry(0, 0, 0, 0);
+    _set_gdt_entry(1, 0, 0xfffff, SEG_R0_CODE);
+    _set_gdt_entry(2, 0, 0xfffff, SEG_R0_DATA);
+    _set_gdt_entry(3, 0, 0xfffff, SEG_R3_CODE);
+    _set_gdt_entry(4, 0, 0xfffff, SEG_R3_DATA);
+    _set_gdt_entry(5, (u32_t)&_tss, sizeof(struct x86_tss) - 1, SEG_TSS);
+}
\ No newline at end of file