Implemented a custom executable called, ForstWing Deployed Executable

source/desktop-manager/Makefile

@@ -33,12 +33,15 @@ override HEADER_DEPS := $(addprefix obj/,$(CFILES:.c=.c.d))
 .PHONY: all
 
 all:
-	@make clean desktop-manager.bin
+	@make clean desktop-manager.bin finalize
 
 clean:
 	@rm -rf obj
 	@rm -rf desktop-manager.bin
 
+finalize:
+	@python ./tools/signature.py
+
 desktop-manager.bin: x86_64-dm-linker.ld $(OBJ)
 	@mkdir -p "$$(dirname $@)"
 	@ld $(OBJ) $(LDFLAGS) -o $@

source/desktop-manager/dm_main.c

@@ -34,14 +34,15 @@ Replace [SYSCALL ID] to appropriate syscall numbers.
 void send_alive_msg(){
     asm volatile("movq %0, %%rax" :: "r"((int64)0x3));
     asm volatile("int $0x80");
+    asm volatile("movq %0, %%rax" :: "r"((int64)0x0)); // ! Always revert the RAX register after an syscall
 }
 
 /**
  * @attention Don't rename this function, if you wanted to rename it, u must change the linker also.
  * 
  */
-void dw_main(){
+int dw_main(){
     send_alive_msg();
 
-    return; // Safe to do.
+    return 0; // status code
 }

source/desktop-manager/tools/signature.py

@@ -0,0 +1,53 @@
+import struct
+import os
+
+def check_endian(file_path):
+    with open(file_path, 'rb') as file:
+        data = file.read(4)
+
+    if len(data) == 4:
+        little_endian_value = int.from_bytes(data, byteorder='little')
+        big_endian_value = int.from_bytes(data, byteorder='big')
+
+        if little_endian_value == big_endian_value:
+            print(f"The file '{file_path}' has an indeterminate endian.")
+            exit(1)
+        elif little_endian_value < big_endian_value:
+            print(f"The file '{file_path}' is little-endian.")
+            return 1
+        else:
+            print(f"The file '{file_path}' is big-endian.")
+            return 2
+    else:
+        print(f"The file '{file_path}' does not contain enough data to determine its endian.")
+        exit(1)
+
+def append_header(file_path, architecture, file_size):
+    """
+    Appends a custom header to a binary file.
+
+    Args:
+        file_path (str): Path to the binary file.
+        architecture (int): Architecture information (32 or 64 bits).
+        file_size (int): Size of the file in bytes.
+    """
+    signature = b'FWDE' # stands for Frost Wing Deployed Executable
+    architecture_byte = struct.pack('B', architecture)  # 'B' format code packs an unsigned char (1 byte)
+    size_byte = struct.pack('B', file_size)  # 'B' format code packs an unsigned char (1 byte)
+
+    endian = check_endian(file_path) # 0 = error; 1 = little; 2 = big
+
+    endian_byte = struct.pack('B', endian)  # 'B' format code packs an unsigned char (1 byte)
+
+    with open(file_path, 'rb') as file:
+        existing_content = file.read()
+
+    with open(file_path, 'wb') as file:
+        file.write(signature + architecture_byte + size_byte + endian_byte)
+        file.write(existing_content)
+
+file_path = 'desktop-manager.bin'
+architecture = 1  # 1 = 64 bits; 2 = 32 bits; 3 = 16 bits; 4 = 8 bits
+file_size = os.path.getsize(file_path)
+
+append_header(file_path, architecture, file_size)

source/includes/executables/fwde.h

@@ -0,0 +1,21 @@
+/**
+ * @file fwde.h
+ * @author Pradosh ([email protected])
+ * @brief The executor header for FrostWing Deployed Executable - 64 bits
+ * @version 0.1
+ * @date 2024-01-07
+ * 
+ * @copyright Copyright (c) Pradosh 2024
+ * 
+ */
+#include <basics.h>
+#include <stdbool.h>
+
+typedef struct {
+    char signature[4]; // FWDE
+    int8 architecture; // 1 = 64 bits; 2 = 32 bits; 3 = 16 bits; 4 = 8 bits
+    int8 raw_size; // size of just the executable part and not the header
+    int8 endian; // 0 = error; 1 = little; 2 = big
+} fwde_header;
+
+void execute_fwde(int64* addr);

source/includes/kernel.h

@@ -40,7 +40,7 @@
 #include <linkedlist.h>
 #include <ps2-mouse.h>
 #include <image/targa.h>
-#include <executables/binary.h>
+#include <executables/fwde.h>
 
 /**
  * @brief The memory address pointer where the kernel ends.

source/kernel/C/executables/fwde.c

@@ -0,0 +1,65 @@
+/**
+ * @file fwde.c
+ * @author Pradosh ([email protected])
+ * @brief The executor code for FrostWing Deployed Executable - 64 bits
+ * @version 0.1
+ * @date 2024-01-07
+ * 
+ * @copyright Copyright (c) Pradosh 2024
+ * 
+ */
+
+#include <executables/fwde.h>
+
+bool verify_signature(char* signature){
+    if(signature[0] == 'F' &&
+       signature[1] == 'W' &&
+       signature[2] == 'D' &&
+       signature[3] == 'E'){
+        return true;
+    }
+    else
+        return false;
+}
+
+void execute_fwde(int64* addr){
+    info("Verifying the FrostWing deployed executable!", __FILE__);
+
+    int8* local = (int8*)addr;
+
+    fwde_header* header = (fwde_header*)local;
+
+    if(verify_signature(header->signature)){
+        info("Signature is correct!", __FILE__);
+    }else{
+        error("Wrong signature! Abort.", __FILE__);
+        return;
+    }
+
+    if(header->endian != 1 && header->endian != 2){
+        error("Undetermined endian executable! Abort.", __FILE__);
+        return;
+    }
+
+    if(header->architecture == 1){ // 64 bits
+        local += sizeof(fwde_header);
+        if(*(local + header->raw_size) == 0){
+            info("Valid executable! and ready for execution!", __FILE__);
+        }
+        info("Starting executing the FrostWing deployed executable...", __FILE__);
+        int (*execute_binary)() = (int (*)())local;
+        info("Function is ready!", __FILE__);
+        int status_code = execute_binary();
+        if(status_code != 0){
+            error("Executable returned an non zero status code! (something went wrong on the executable side)", __FILE__);
+            printf("Status code : 0x%x (%d)", status_code, status_code);
+            return;
+        }
+    }else{
+        error("Unsupported architecture!", __FILE__);
+        return;
+    }
+
+
+    done("Completed successfully!", __FILE__);
+}

source/kernel/C/kernel.c

@@ -382,7 +382,7 @@ void main(void) {
 
     font_address = module_request.response->modules[1]->address;
 
-    execute_bin(module_request.response->modules[2]->address);
+    execute_fwde(module_request.response->modules[2]->address);
 
     print("press F10 for (ACPI) Shutdown.\n");
     print("press F9 for (ACPI/Hard) Reboot/Reset.\n");