implementation of TSS

src/kernel/CMakeLists.txt

@@ -10,6 +10,14 @@ add_custom_target(
   COMMENT "Running versioning script")
 add_dependencies(${PROJECT_NAME} run_versioning_script-kernel)
 
+add_custom_target(
+  generate-iso ALL
+  COMMAND "${PROJECT_SOURCE_DIR}/scripts/create_iso.sh"
+  WORKING_DIRECTORY ${PROJECT_SOURCE_DIR}
+  BYPRODUCTS "${PROJECT_SOURCE_DIR}/appa-os.iso"
+  COMMENT "Creating ISO")
+add_dependencies(generate-iso ${PROJECT_NAME})
+
 # Set target name to be "${PROJECT_NAME}.bin"
 set_target_properties(${PROJECT_NAME} PROPERTIES PREFIX "")
 set_target_properties(${PROJECT_NAME} PROPERTIES OUTPUT_NAME "${PROJECT_NAME}")

src/kernel/arch/i386/gdt.c

@@ -1,15 +1,31 @@
 #include "gdt.h"
+#include "tss.h"
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 
-#define GDT_ENTRY_SIZE 5
+#define GDT_ENTRY_SIZE 6
 
 static gdt_segment_descriptor_t gdt_descriptors[GDT_ENTRY_SIZE];
 static gdt_entry_t gdt;
+static tss_descriptor_t tss;
+
+// https://github.com/szhou42/osdev/blob/52c02f0d4327442493459253a5c6c83c5f378765/src/kernel/descriptor_tables/tss_helper.asm#L3
+void tss_flush() {
+  // TSS is the last entry on our gdt table
+  const uint32_t tss_offset = sizeof(gdt_segment_descriptor_t) * (GDT_ENTRY_SIZE - 1);
+
+  asm volatile("mov %0, %%eax\n\t"
+               "ltr %%eax\n\t" // Load the Task Register with the TSS selector in AX
+               "ret\n\t"       // Return to the caller
+               :
+               : "r"(tss_offset)
+               : "eax");
+}
 
 // https://forum.osdev.org/viewtopic.php?t=37245
 void gdt_flush() {
-  uint32_t ptr = (uint32_t)&gdt;
+  const uint32_t ptr = (uint32_t)&gdt;
 
   asm volatile("movl %0,%%eax    \n\t"
                "lgdt (%%eax)     \n\t"
@@ -25,45 +41,68 @@ void gdt_flush() {
                "movw  %%ax, %%gs \n\t"
                "movw  %%ax, %%ss \n\t"
                "ljmp $0x0008,$.gdt_flush_end%=\n\t"
-               ".gdt_flush_end%=:"
+               ".gdt_flush_end%=:\n\t"
+               "ret\n\t"
                :
                : "r"(ptr)
                : "eax");
 }
 
+void tss_init() {
+  const uint32_t tss_base = (uint32_t)&tss;
+  const uint32_t tss_limit = tss_base + sizeof(tss_descriptor_t);
+
+  // TODO: Somehow setting TSS to 0 crashes the system, why?
+  // memset(&tss, 0, sizeof(tss));
+
+  // 0x10 corresponds to Kernel Mode Data Segment (gdt_descriptors[2]), 3rd entry on gdt table
+  tss.ss0 = (uint16_t)(sizeof(gdt_segment_descriptor_t) * (2));
+  tss.esp0 = (uint32_t)0x00;
+  tss.iopb = (uint16_t)sizeof(tss_descriptor_t);
+
+  gdt_descriptors[5] = gdt_create_segment_descriptor(tss_base, tss_limit, 0x00, GDT_ACCESS_PRESENT(1) | GDT_CODE_EXA);
+}
+
 void gdt_init() {
   // This is setting up 4 large seguments overlapped to use paging
   // https://stackoverflow.com/a/23979175
-  gdt.limit = (sizeof(struct gdt_segment_descriptor) * GDT_ENTRY_SIZE) - 1;
+  gdt.limit = (sizeof(gdt_segment_descriptor_t) * GDT_ENTRY_SIZE) - 1;
   gdt.base = (uint32_t)gdt_descriptors;
 
   // Null Segment
   gdt_descriptors[0] = gdt_create_segment_descriptor(0, 0, 0, 0);
 
-  // Kernel Mode Code Segment with 4 megabytes
+  // Kernel Mode Code Segment
   gdt_descriptors[1] = gdt_create_segment_descriptor(0, 0xFFFFFFFF, (GDT_FLAG_GRANULARITY(1) | GDT_FLAG_SIZE(1)) << 4,
                                                      GDT_ACCESS_PRESENT(1) | GDT_ACCESS_PRIVILEGE(0) |
                                                          GDT_ACCESS_DESCRIPTOR_TYPE(1) | GDT_CODE_EXRD);
 
+  // Kernel Mode Data Segment
   gdt_descriptors[2] = gdt_create_segment_descriptor(0, 0xFFFFFFFF, (GDT_FLAG_GRANULARITY(1) | GDT_FLAG_SIZE(1)) << 4,
                                                      GDT_ACCESS_PRESENT(1) | GDT_ACCESS_PRIVILEGE(0) |
                                                          GDT_ACCESS_DESCRIPTOR_TYPE(1) | GDT_DATA_RDWR);
 
+  // User Mode Code Segment
   gdt_descriptors[3] = gdt_create_segment_descriptor(0, 0xFFFFFFFF, (GDT_FLAG_GRANULARITY(1) | GDT_FLAG_SIZE(1)) << 4,
                                                      GDT_ACCESS_PRESENT(1) | GDT_ACCESS_PRIVILEGE(3) |
                                                          GDT_ACCESS_DESCRIPTOR_TYPE(1) | GDT_CODE_EXRD);
 
+  // User Mode Data Segment
   gdt_descriptors[4] = gdt_create_segment_descriptor(0, 0xFFFFFFFF, (GDT_FLAG_GRANULARITY(1) | GDT_FLAG_SIZE(1)) << 4,
                                                      GDT_ACCESS_PRESENT(1) | GDT_ACCESS_PRIVILEGE(3) |
                                                          GDT_ACCESS_DESCRIPTOR_TYPE(1) | GDT_DATA_RDWR);
-  // TODO: add Task State Segment
+  tss_init();
+
   // Load and flush the GDT
   gdt_flush();
+
+  // Load the TSS
+  tss_flush();
 }
 
 gdt_segment_descriptor_t gdt_create_segment_descriptor(uint32_t base, uint32_t limit, uint8_t flags, uint8_t access) {
   if (limit > UINT32_MAX) {
-    printf("GDT cannot encode limits larger than 0xFFFFF");
+    printf("GDT cannot encode limits larger than %X", UINT32_MAX);
     abort();
   }
 

src/kernel/arch/i386/gdt.h

@@ -65,6 +65,7 @@ gdt_segment_descriptor_t gdt_create_segment_descriptor(uint32_t base, uint32_t l
 
 void gdt_init();
 
-void gdt_flush();
+extern void gdt_flush();
+extern void tts_flush();
 
 #endif // INCLUDE_GDT_H_

src/kernel/arch/i386/tss.h

@@ -0,0 +1,57 @@
+#ifndef INCLUDE_INCLUDE_TSS_H_
+#define INCLUDE_INCLUDE_TSS_H_
+
+#include <stdint.h>
+
+struct tss_descriptor {
+  uint32_t link;
+  uint32_t esp0;
+  uint32_t ss0;
+  uint32_t esp1;
+  uint32_t ss1;
+  uint32_t esp2;
+  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;
+  // Some places place those two below as uint16_t? // http://www.brokenthorn.com/Resources/OSDev23.html
+  uint16_t iopb;
+  uint16_t ssp;
+} __attribute__((packed));
+
+typedef struct tss_descriptor tss_descriptor_t;
+
+void tss_flush();
+
+#endif // INCLUDE_INCLUDE_TSS_H_
+ 
+
+
+  
+
+
+  
+ 
+
+
+  
+
+
+  
+ 
+ 

src/kernel/kernel.c

@@ -1,4 +1,4 @@
-#include "gdt.h"
+#include "arch/i386/gdt.h"
 #include "kernel/tty.h"
 #include "version.h"
 #include <stdint.h>
@@ -23,7 +23,6 @@ void kprintf(const char *format, ...) {
   }
 }
 
-
 void __attribute__((noinline)) kernel_main(void) {
   tty_initialize();
   kprintf("Appa-OS version %s\n", VERSION);

src/kernel/kernel.h

@@ -1,6 +1,6 @@
 #ifndef INCLUDE_KERNEL_KERNEL_H_
 #define INCLUDE_KERNEL_KERNEL_H_
 
-void kprintf(const char *format, ...)
+void kprintf(const char *format, ...);
 
 #endif // INCLUDE_KERNEL_KERNEL_H_

src/kernel/version.h

@@ -8,9 +8,9 @@
 
 #define APPA_OS_VERSION_MAJOR 0
 #define APPA_OS_VERSION_MINOR 0
-#define APPA_OS_VERSION_PATCH 154
+#define APPA_OS_VERSION_PATCH 233
 #define APPA_OS_COMMIT_HASH cd01d7d8d36862bc00ae88f7cd185c352a7b7eda
-#define APPA_OS_BUILD_TIMESTAMP 1730732925
+#define APPA_OS_BUILD_TIMESTAMP 1730754533
 
 #endif  // INCLUDE_APPA_OS_VERSION_H_
 

src/libc/version.h

@@ -8,9 +8,9 @@
 
 #define LIB_C_VERSION_MAJOR 0
 #define LIB_C_VERSION_MINOR 0
-#define LIB_C_VERSION_PATCH 148
+#define LIB_C_VERSION_PATCH 227
 #define LIB_C_COMMIT_HASH cd01d7d8d36862bc00ae88f7cd185c352a7b7eda
-#define LIB_C_BUILD_TIMESTAMP 1730732925
+#define LIB_C_BUILD_TIMESTAMP 1730754533
 
 #endif  // INCLUDE_LIB_C_VERSION_H_