Move paging related functions to paging.c

doc/13_calling_kernel_space_routines_from_user_space.md

@@ -27,3 +27,4 @@ print:
 
 - Interrupt 0x80 handler [commit](https://github.com/taikiy/kernel/commit/42c0b6374e21e096060d27e3255a2e007c55b0cd)
 - Register 0x80 handler in IDT [commit](https://github.com/taikiy/kernel/commit/2020d58d9047f2584ab03d95ccfab2b221ff2ced)
+- `sys_print` function [commit](https://github.com/taikiy/kernel/commit/459b80a2d26d9ff61d42f026305b79abbe5acf4f)

src/gdt/gdt.c

@@ -1,6 +1,7 @@
 #include "gdt.h"
 #include "config.h"
 #include "memory/memory.h"
+#include "system/sys.h"
 #include "task/tss.h"
 
 struct tss tss;

src/gdt/gdt.h

@@ -1,7 +1,6 @@
 #ifndef GDT_H
 #define GDT_H
 
-#include "kernel.h"
 #include <stdint.h>
 
 /* clang-format off

src/idt/idt.c

@@ -1,7 +1,6 @@
 #include "idt.h"
 #include "config.h"
 #include "io/io.h"
-#include "kernel.h"
 #include "memory/memory.h"
 #include "system/syscall.h"
 #include "task/task.h"

src/kernel.asm

@@ -1,7 +1,6 @@
 [BITS 32]
 
 global _start
-global set_kernel_segment_registers
 
 extern kernel_main
 
@@ -39,14 +38,6 @@ _start:
     ; cli                       ; Disables interrupts
     ; hlt                       ; This hangs the computer
 
-set_kernel_segment_registers:
-    mov ax, DATA_SEG
-    mov ds, ax
-    mov es, ax
-    mov fs, ax
-    mov gs, ax
-    ret
-
 times 512 - ($ - $$) db 0       ; Pad the kernel code sector to 512 bytes
                                 ; This ensures that any object files written in C and linked with this assembly
                                 ; will be correctly aligned.

src/kernel.c

@@ -12,44 +12,18 @@
 #include "memory/paging/paging.h"
 #include "status.h"
 #include "string/string.h"
+#include "system/sys.h"
 #include "system/syscall.h"
 #include "task/process.h"
 #include "task/task.h"
 #include "task/tss.h"
 #include "terminal/terminal.h"
 
-extern void set_kernel_segment_registers();
 void test_path_parser();
 void test_file_system();
 void test_user_space();
 void test_syscall();
 
-void
-panic(const char* message)
-{
-    print("PANIC: ");
-    print(message);
-    print("\n");
-    while (1) {};
-}
-
-static struct paging_map* kernel_page = 0;
-
-void
-initialize_kernel_space_paging()
-{
-    kernel_page = new_paging_map(PAGING_IS_WRITABLE | PAGING_IS_PRESENT | PAGING_ACCESS_FROM_ALL);
-    switch_page(kernel_page);
-    enable_paging();
-}
-
-void
-switch_to_kernel_page()
-{
-    set_kernel_segment_registers();
-    switch_page(kernel_page);
-}
-
 void
 kernel_main()
 {

src/kernel.h

@@ -2,7 +2,5 @@
 #define KERNEL_H
 
 void kernel_main();
-void switch_to_kernel_page();
-void panic(const char* message);
 
 #endif

src/memory/paging/paging.asm

@@ -4,6 +4,11 @@ section .asm
 
 global load_directory
 global enable_paging
+global set_kernel_segment_registers
+global set_user_segment_registers
+
+KERNEL_DATA_SEG equ 0x10
+USER_DATA_SEG   equ 0x23   ; user data segment | flags: 0x3
 
 load_directory:
     push ebp
@@ -25,3 +30,19 @@ enable_paging:
 
     pop ebp
     ret
+
+set_kernel_segment_registers:
+    mov ax, KERNEL_DATA_SEG
+    mov ds, ax
+    mov es, ax
+    mov fs, ax
+    mov gs, ax
+    ret
+
+set_user_segment_registers:
+    mov ax, USER_DATA_SEG
+    mov ds, ax
+    mov es, ax
+    mov fs, ax
+    mov gs, ax
+    ret

src/memory/paging/paging.c

@@ -1,65 +1,21 @@
 #include "paging.h"
 #include "memory/heap/kheap.h"
+#include "system/sys.h"
+#include "task/task.h"
 
-void load_directory(uint32_t* directory);
+extern void load_directory(uint32_t* directory);
+extern void enable_paging();
 
+static struct paging_map* kernel_page = 0;
 static uint32_t* current_directory = 0;
 
-struct paging_map*
-new_paging_map(uint8_t flags)
-{
-    // allocate a linear memory space for a page directory (1024 entries)
-    uint32_t* directory = kzalloc(sizeof(uint32_t) * PAGING_TOTAL_ENTRIES);
-    int offset = 0;
-
-    for (int i = 0; i < PAGING_TOTAL_ENTRIES; i++) {
-        // allocate a linear memory for a page table (1024 entries)
-        uint32_t* table = kzalloc(sizeof(uint32_t) * PAGING_TOTAL_ENTRIES);
-
-        for (int j = 0; j < PAGING_TOTAL_ENTRIES; j++) {
-            // set the page table entry
-            // this is the virtual address of a 4K size page which is not allocated yet
-            table[j] = (offset + j * PAGING_PAGE_SIZE_BYTES) | flags;
-        }
-
-        offset += (PAGING_TOTAL_ENTRIES * PAGING_PAGE_SIZE_BYTES);
-        // set the page directory entry
-        // this is the virtual address of the beginning of the page table at index `i`
-        directory[i] = (uint32_t)table | flags | PAGING_IS_WRITABLE;
-    }
-
-    // this points to the first page directory entry, which will be fed to CR3 registry
-    struct paging_map* map = kzalloc(sizeof(struct paging_map));
-    map->directory = directory;
-
-    return map;
-}
-
-status_t
-free_paging_map(struct paging_map* map)
+static void
+switch_page(struct paging_map* map)
 {
-    status_t result = ALL_OK;
-
-    if (!map) {
-        result = ERROR(EINVARG);
-        goto out;
+    if (!map->directory) {
+        panic("Paging map directory is null");
     }
 
-    for (int i = 0; i < PAGING_TOTAL_ENTRIES; i++) {
-        uint32_t* table = (uint32_t*)(map->directory[i] & 0xfffff000); // mask the flags to get the table address
-        kfree(table);
-    }
-
-    kfree(map->directory);
-    kfree(map);
-
-out:
-    return result;
-}
-
-void
-switch_page(struct paging_map* map)
-{
     load_directory(map->directory);
     current_directory = map->directory;
 }
@@ -130,6 +86,58 @@ map_page_frame(struct paging_map* map, uint32_t* physical_address, uint32_t* vir
     return set_page_frame(map, virtual_address, (uint32_t)physical_address | flags);
 }
 
+struct paging_map*
+new_paging_map(uint8_t flags)
+{
+    // allocate a linear memory space for a page directory (1024 entries)
+    uint32_t* directory = kzalloc(sizeof(uint32_t) * PAGING_TOTAL_ENTRIES);
+    int offset = 0;
+
+    for (int i = 0; i < PAGING_TOTAL_ENTRIES; i++) {
+        // allocate a linear memory for a page table (1024 entries)
+        uint32_t* table = kzalloc(sizeof(uint32_t) * PAGING_TOTAL_ENTRIES);
+
+        for (int j = 0; j < PAGING_TOTAL_ENTRIES; j++) {
+            // set the page table entry
+            // this is the virtual address of a 4K size page which is not allocated yet
+            table[j] = (offset + j * PAGING_PAGE_SIZE_BYTES) | flags;
+        }
+
+        offset += (PAGING_TOTAL_ENTRIES * PAGING_PAGE_SIZE_BYTES);
+        // set the page directory entry
+        // this is the virtual address of the beginning of the page table at index `i`
+        directory[i] = (uint32_t)table | flags | PAGING_IS_WRITABLE;
+    }
+
+    // this points to the first page directory entry, which will be fed to CR3 registry
+    struct paging_map* map = kzalloc(sizeof(struct paging_map));
+    map->directory = directory;
+
+    return map;
+}
+
+status_t
+free_paging_map(struct paging_map* map)
+{
+    status_t result = ALL_OK;
+
+    if (!map) {
+        result = ERROR(EINVARG);
+        goto out;
+    }
+
+    for (int i = 0; i < PAGING_TOTAL_ENTRIES; i++) {
+        uint32_t* table = (uint32_t*)(map->directory[i] & 0xfffff000); // mask the flags to get the table address
+        kfree(table);
+    }
+
+    kfree(map->directory);
+    kfree(map);
+
+out:
+    return result;
+}
+
 status_t
 map_physical_address_to_pages(
   struct paging_map* map,
@@ -174,3 +182,26 @@ map_physical_address_to_pages(
 out:
     return result;
 }
+
+void
+initialize_kernel_space_paging()
+{
+    kernel_page = new_paging_map(PAGING_IS_WRITABLE | PAGING_IS_PRESENT | PAGING_ACCESS_FROM_ALL);
+    switch_page(kernel_page);
+    enable_paging();
+}
+
+void
+switch_to_kernel_page()
+{
+    set_kernel_segment_registers();
+    switch_page(kernel_page);
+}
+
+void
+switch_to_user_page()
+{
+    set_user_segment_registers();
+    struct task* current_task = get_current_task();
+    switch_page(current_task->user_page);
+}

src/memory/paging/paging.h

@@ -20,16 +20,20 @@ struct paging_map
     uint32_t* directory;
 };
 
+extern void set_kernel_segment_registers();
+extern void set_user_segment_registers();
+
 struct paging_map* new_paging_map(uint8_t flags);
 status_t free_paging_map(struct paging_map* map);
-void switch_page(struct paging_map* map);
-void enable_paging();
 status_t map_physical_address_to_pages(
   struct paging_map* map,
   void* physical_address,
   void* virtual_address,
   uint32_t size,
   uint32_t flags
 );
+void initialize_kernel_space_paging();
+void switch_to_kernel_page();
+void switch_to_user_page();
 
 #endif

src/system/sys.c

@@ -0,0 +1,11 @@
+#include "sys.h"
+#include "terminal/terminal.h"
+
+void
+panic(const char* message)
+{
+    print("PANIC: ");
+    print(message);
+    print("\n");
+    while (1) {};
+}

src/system/sys.h

@@ -0,0 +1,6 @@
+#ifndef SYS_H
+#define SYS_H
+
+void panic(const char* message);
+
+#endif

src/system/syscall.c

@@ -1,6 +1,6 @@
 #include "syscall.h"
 #include "config.h"
-#include "kernel.h"
+#include "sys.h"
 #include "terminal/terminal.h"
 
 static SYSCALL_HANDLER syscall_handlers[TOTAL_SYSCALL_COUNT];

src/task/task.asm

@@ -2,11 +2,10 @@
 
 section .asm
 
-global return_to_task
-global set_user_segment_registers
+global return_to_user_space
 
-; void return_to_task(struct registers* registers);
-return_to_task:
+; void return_to_user_space(struct registers* registers);
+return_to_user_space:
     ; here, we don't push the base pointer because we call `iretd` at the end
     mov ebp, esp
     mov ebx, [ebp + 4] ; +4 becuase we didn't push EBP
@@ -52,11 +51,3 @@ restore_general_purpose_registers:
     mov ebx, [ebx + 20]
     pop ebp
     ret
-
-set_user_segment_registers:
-    mov ax, 0x23 ; user data segment | flags: 0x3
-    mov ds, ax
-    mov es, ax
-    mov fs, ax
-    mov gs, ax
-    ret