arch: i386: cleanup everything and reorganize

Clean up everything in the i386 arch directory. This code has been in
dire need of refactoring for a long while. All the inline assembly
functions and the data structures related to the architecture should be
placed into their own header file. Now the scheduler can access
registers and ISRs without having to deal with arch-specific code.

Signed-off-by: Danny Holman <dholman@gymli.org>

1 files changed, 58 insertions, 0 deletions

diff --git a/arch/i386/kernel/gdt.c b/arch/i386/kernel/gdt.c
new file mode 100644
index 0000000..c0cf127
--- /dev/null
+++ b/arch/i386/kernel/gdt.c
@@ -0,0 +1,58 @@
+#include <kernel/gdt.h>
+#include <kernel/asm.h>
+#include <kernel/string.h>
+
+struct gdt_entry desc[6];
+struct gdt_ptr gp;
+struct tss_entry tss_entry;
+
+void gdt_set_gate(int num, uint32_t base, uint32_t limit, uint8_t access, uint8_t gran) {
+        desc[num].base_low = (base & 0xFFFF);
+        desc[num].base_middle = (base >> 16) & 0xFF;
+        desc[num].base_high = (base >> 24) & 0xFF;
+
+        desc[num].limit_low = (limit & 0xFFFF);
+        desc[num].gran = (limit >> 16) & 0x0F;
+        desc[num].gran |= (gran & 0xF0);
+        desc[num].access = access;
+}
+
+void write_tss(int num, uint32_t ss0, uint32_t esp0) {
+        uint32_t base = (uint32_t)&tss_entry;
+        uint32_t limit = base + sizeof(struct tss_entry);
+
+        gdt_set_gate(num, base, limit, 0x89, 0x00);
+        memset(&tss_entry, 0x0, sizeof(tss_entry));
+        
+        tss_entry.ss0 = ss0;
+        tss_entry.esp0 = esp0;
+        tss_entry.cs = 0x0B;
+        tss_entry.ss = 0x13;
+        tss_entry.ds = 0x13;
+        tss_entry.es = 0x13;
+        tss_entry.fs = 0x13;
+        tss_entry.gs = 0x13;
+        tss_entry.iomap_base = sizeof(tss_entry);
+}
+
+void set_kernel_esp(uint32_t esp) {
+        tss_entry.esp0 = esp;
+}
+
+void gdt_install(void) {
+        gp.limit = (sizeof(struct gdt_entry) * 6) - 1;
+        gp.base = (uint32_t)&desc;
+
+        gdt_set_gate(0, 0, 0, 0, 0);
+        gdt_set_gate(1, 0, 0xFFFFF, 0x9A, 0xCF);
+        gdt_set_gate(2, 0, 0xFFFFF, 0x92, 0xCF);
+        gdt_set_gate(3, 0, 0xFFFFF, 0xFA, 0xCF);
+        gdt_set_gate(4, 0, 0xFFFFF, 0xF2, 0xCF);
+        
+        uint32_t esp;
+        __asm__ volatile("movl %%esp, %0" : "=r"(esp));
+        write_tss(5, 0x10, esp);
+
+        flush_gdt();
+        flush_tss();
+}