arch: i386: gdt.c: fix a bug in userspace jump

Fix a bug in the GDT that prevented the kernel from jumping to userspace
correctly.

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

1 files changed, 12 insertions, 52 deletions

diff --git a/arch/i386/boot/gdt.c b/arch/i386/boot/gdt.c
index f84c767..c0cf127 100644
--- a/arch/i386/boot/gdt.c
+++ b/arch/i386/boot/gdt.c
@@ -1,55 +1,11 @@
+#include <kernel/gdt.h>
+#include <kernel/asm.h>
 #include <kernel/string.h>
-#include <stdint.h>
-
-struct gdt_entry {
-        uint16_t limit_low;
-        uint16_t base_low;
-        uint8_t base_middle;
-        uint8_t access;
-        uint8_t gran;
-        uint8_t base_high;
-} __attribute__((packed));
-
-struct gdt_ptr {
-        uint16_t limit;
-        uint32_t base;
-} __attribute__((packed));
-
-struct tss_entry {
-        uint32_t link;
-        uint32_t esp0;
-        uint32_t ss0;
-        uint32_t esp1;
-        uint32_t ss2;
-        uint32_t cr3;
-        uint32_t eip;
-        uint32_t eflags;
-        uint32_t eax;
-        uint32_t ecx;
-        uint32_t edx;
-        uint32_t ebx;
-        uint32_t esp;
-        uint32_t ebp;
-        uint32_t esi;
-        uint32_t edi;
-        uint32_t es;
-        uint32_t cs;
-        uint32_t ss;
-        uint32_t ds;
-        uint32_t fs;
-        uint32_t gs;
-        uint32_t ldtr;
-        uint16_t trap;
-        uint16_t iomap_base;
-} __attribute__((packed));
 
 struct gdt_entry desc[6];
 struct gdt_ptr gp;
 struct tss_entry tss_entry;
 
-extern void flush_gdt(void);
-extern void flush_tss(void);
-
 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;
@@ -61,11 +17,11 @@ void gdt_set_gate(int num, uint32_t base, uint32_t limit, uint8_t access, uint8_
         desc[num].access = access;
 }
 
-void write_tss(int num, uint16_t ss0, uint16_t esp0) {
+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, 0xE9, 0x00);
+        gdt_set_gate(num, base, limit, 0x89, 0x00);
         memset(&tss_entry, 0x0, sizeof(tss_entry));
         
         tss_entry.ss0 = ss0;
@@ -79,15 +35,19 @@ void write_tss(int num, uint16_t ss0, uint16_t esp0) {
         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, 0xFFFFFFFF, 0x9A, 0xCF);
-        gdt_set_gate(2, 0, 0xFFFFFFFF, 0x92, 0xCF);
-        gdt_set_gate(3, 0, 0xFFFFFFFF, 0xFA, 0xCF);
-        gdt_set_gate(4, 0, 0xFFFFFFFF, 0xF2, 0xCF);
+        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));