fixing GDT

2024-11-03 19:34:35 -03:00
parent 16bf9bfa91
commit e6db640d7d
4 changed files with 58 additions and 52 deletions
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -3,10 +3,10 @@ cmake_policy(VERSION 3.30)

 project(appa-os LANGUAGES C ASM)

-enable_language(ASM-ATT)
 set(CMAKE_C_STANDARD 99)
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)

+enable_language(ASM-ATT)
 option(BUILD_DOCS "Build documentation" ON)

 if(BUILD_DOCS)
--- a/src/kernel/arch/i386/gdt.c
+++ b/src/kernel/arch/i386/gdt.c
@@ -2,9 +2,9 @@
 #include <stdio.h>
 #include <stdlib.h>

-#define GDT_SIZE 5
+#define GDT_ENTRY_SIZE 5

-static gdt_segment_descriptor_t gdt_descriptors[GDT_SIZE];
+static gdt_segment_descriptor_t gdt_descriptors[GDT_ENTRY_SIZE];
 static gdt_entry_t gdt;

 // https://forum.osdev.org/viewtopic.php?t=37245
@@ -24,40 +24,38 @@ void gdt_flush() {
               "movw  %%ax, %%fs \n\t"
               "movw  %%ax, %%gs \n\t"
               "movw  %%ax, %%ss \n\t"
-               "ljmp $0x08,$boing%=\n\t"
-               "boing%=:"
+               "ljmp $0x0008,$.gdt_flush_end%=\n\t"
+               ".gdt_flush_end%=:"
               :
               : "r"(ptr)
               : "eax");
-  // asm volatile("lgdtl %0                 \n\t"
-  //              "ljmp $0x08,$.L%= \n\t"
-  //              ".L%=:                     \n\t"
-  //              "mov %1, %%ds        \n\t"
-  //              "mov %1, %%es        \n\t"
-  //              "mov %1, %%fs        \n\t"
-  //              "mov %1, %%gs       \n\t"
-  //              "mov %1, %%ss       \n\t" ::"m"(gdt),
-  //              "r"(0x10));
 }

 void gdt_init() {
  // This is setting up 4 large seguments overlapped to use paging
  // https://stackoverflow.com/a/23979175
-  gdt.limit = sizeof(gdt_segment_descriptor_t) * GDT_SIZE - 1;
-  gdt.base = (uint32_t)&gdt_descriptors;
+  gdt.limit = (sizeof(struct gdt_segment_descriptor) * 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
-  gdt_descriptors[1] = gdt_create_segment_descriptor(0, 0xFFFFFFFF, (uint8_t)(SEG_GRAN(1) | SEG_SIZE(1)),
-                                                     SEG_PRES(1) | SEG_PRIV(0) | SEG_DESCTYPE(1) | SEG_CODE_EXRD);
-  gdt_descriptors[2] = gdt_create_segment_descriptor(0, 0xFFFFFFFF, (uint8_t)(SEG_GRAN(1) | SEG_SIZE(1)),
-                                                     SEG_PRES(1) | SEG_PRIV(0) | SEG_DESCTYPE(1) | SEG_DATA_RDWR);
-  gdt_descriptors[3] = gdt_create_segment_descriptor(0, 0xFFFFFFFF, (uint8_t)(SEG_GRAN(1) | SEG_SIZE(1)),
-                                                     SEG_PRES(1) | SEG_PRIV(3) | SEG_DESCTYPE(1) | SEG_CODE_EXRD);
-  gdt_descriptors[4] = gdt_create_segment_descriptor(0, 0xFFFFFFFF, (uint8_t)(SEG_GRAN(1) | SEG_SIZE(1)),
-                                                     SEG_PRES(1) | SEG_PRIV(3) | SEG_DESCTYPE(1) | SEG_DATA_RDWR);
+  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);
+
+  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);
+
+  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);
+
+  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
  // Load and flush the GDT
  gdt_flush();
--- a/src/kernel/include/gdt.h
+++ b/src/kernel/include/gdt.h
@@ -9,32 +9,40 @@
 // Refer to the intel documentation for a description of what each one does.

 // Descriptor type (0 for system, 1 for code/data)
-#define SEG_DESCTYPE(x) ((x) << 0x04)
-#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
-// Size (0 for 16-bit, 1 for 32)
-#define SEG_SIZE(x) ((x) << 0x0E)
-// Granularity (0 for 1B - 1MB, 1 for 4KB - 4GB)
-#define SEG_GRAN(x) ((x) << 0x0F)
-#define SEG_PRIV(x) (((x) & 0x03) << 0x05) // Set privilege level (0 - 3)
+#define GDT_ACCESS_DESCRIPTOR_TYPE(x) ((x) << 0x04)

-#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
+// Present
+#define GDT_ACCESS_PRESENT(x) ((x) << 0x07)
+
+// Set privilege level (0 - 3)
+#define GDT_ACCESS_PRIVILEGE(x) (((x) & 0x03) << 0x05) 
+
+// Long mode
+#define GDT_FLAG_LONG_MODE(x) ((x) << 0x01) 
+
+// Size (0 for 16-bit, 1 for 32)
+#define GDT_FLAG_SIZE(x) ((x) << 0x02)
+
+// Granularity (0 for 1B - 1MB, 1 for 4KB - 4GB)
+#define GDT_FLAG_GRANULARITY(x) ((x) << 0x03)
+
+
+#define GDT_DATA_RD 0x00        // Read-Only
+#define GDT_DATA_RDA 0x01       // Read-Only, accessed
+#define GDT_DATA_RDWR 0x02      // Read/Write
+#define GDT_DATA_RDWRA 0x03     // Read/Write, accessed
+#define GDT_DATA_RDEXPD 0x04    // Read-Only, expand-down
+#define GDT_DATA_RDEXPDA 0x05   // Read-Only, expand-down, accessed
+#define GDT_DATA_RDWREXPD 0x06  // Read/Write, expand-down
+#define GDT_DATA_RDWREXPDA 0x07 // Read/Write, expand-down, accessed
+#define GDT_CODE_EX 0x08        // Execute-Only
+#define GDT_CODE_EXA 0x09       // Execute-Only, accessed
+#define GDT_CODE_EXRD 0x0A      // Execute/Read
+#define GDT_CODE_EXRDA 0x0B     // Execute/Read, accessed
+#define GDT_CODE_EXC 0x0C       // Execute-Only, conforming
+#define GDT_CODE_EXCA 0x0D      // Execute-Only, conforming, accessed
+#define GDT_CODE_EXRDC 0x0E     // Execute/Read, conforming
+#define GDT_CODE_EXRDCA 0x0F    // Execute/Read, conforming, accessed

 struct gdt_segment_descriptor {
  uint16_t limit;
@@ -43,7 +51,7 @@ struct gdt_segment_descriptor {
  uint8_t access_byte;
  uint8_t flags;
  uint8_t high_base;
-} __attribute__((packed));
+} __attribute__((packed, aligned(4)));

 typedef struct gdt_segment_descriptor gdt_segment_descriptor_t;

--- a/src/kernel/version.h
+++ b/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 132
+#define APPA_OS_VERSION_PATCH 150
 #define APPA_OS_COMMIT_HASH cd01d7d8d36862bc00ae88f7cd185c352a7b7eda
-#define APPA_OS_BUILD_TIMESTAMP 1730655451
+#define APPA_OS_BUILD_TIMESTAMP 1730673250

 #endif  // INCLUDE_APPA_OS_VERSION_H_