added _exit system call

Author: yuvraj1803

kernel/idt/__0x80/__0x80.c

@@ -31,6 +31,7 @@ void __0x80_init()
     __0x80_add_function(__NR_3_MALLOC,__0x80_MALLOC);
     __0x80_add_function(__NR_4_FREE,  __0x80_FREE);
     __0x80_add_function(__NR_5_EXEC, __0x80_EXEC);
+    __0x80_add_function(__NR_6_EXIT, __0x80_EXIT);
 }
 
 

kernel/idt/__0x80/__0x80.h

@@ -18,7 +18,8 @@ enum __0x80_COMMANDS{
     __NR_2_PUTCH,
     __NR_3_MALLOC,
     __NR_4_FREE,
-    __NR_5_EXEC
+    __NR_5_EXEC,
+    __NR_6_EXIT
 
 };
 

kernel/idt/__0x80/process/process.c

@@ -19,9 +19,16 @@ void* __0x80_EXEC(struct interrupt_frame* iframe){
         return (void*) -ERR_PROCESS_CREATION_FAILED;
     }
 
+    process_switch(_process);
     task_switch(_process->task);
     enter_task(&_process->task->registers);
 
     return (void*) SUCCESS;
 
+}
+
+void* __0x80_EXIT(struct interrupt_frame* iframe){
+    process_kill(process_current());
+    process_back_to_gshell();
+    return (void*) SUCCESS;
 }

kernel/idt/__0x80/process/process.h

@@ -4,6 +4,7 @@
 #include "../../idt.h"
 
 void* __0x80_EXEC(struct interrupt_frame* iframe);
+void* __0x80_EXIT(struct interrupt_frame* iframe);
 
 
 #endif

kernel/task/process/process.c

@@ -164,6 +164,12 @@ void process_switch(struct process* _process){
     current_process = _process;
 }
 
+void process_back_to_gshell(){
+    process_switch(process_list[0]);
+    task_switch(process_list[0]->task);
+    enter_task(&process_list[0]->task->registers);
+}
+
 static int8_t process_map_memory(struct process* _process){
 
     // if file type is binary
@@ -312,7 +318,7 @@ int process_kill(struct process* _process){
 
     // free all data dynamically allocated by the process.
     for(int allocation = 0;allocation < PROCESS_MAX_PROCESS_MEM_ALLOCATIONS; allocation++){
-        process_free(_process->mem_allocations[allocation]);
+        if(_process->mem_allocations[allocation] != 0) _process->mem_allocations[allocation];
     }
 
     // mark pid as free to use

kernel/task/process/process.h

@@ -14,9 +14,11 @@
 struct process *process_get(uint16_t pid);
 struct process *process_new(const char *filename);
 struct process *process_current();
+void process_switch(struct process* _process);
 void* process_malloc(uint32_t size);
 void* process_free(void* base_addr);
 int process_kill(struct process* _process);
+void process_back_to_gshell();  
 
 void process_init();
 

usrspc/lib/Makefile

@@ -1,5 +1,5 @@
 OBJ = ./build/_start.s.o ./build/stdio.s.o ./build/stdlib.s.o ./build/stdio.o ./build/stdlib.o ./build/unistd.s.o \
-		./build/string.o
+		./build/string.o ./build/_exit.s.o
 INC = -I./include
 FLAGS = -g -ffreestanding -falign-jumps -falign-functions -falign-labels -falign-loops -fstrength-reduce -fomit-frame-pointer -finline-functions -Wno-unused-function -fno-builtin -Werror -Wno-unused-label -Wno-cpp -Wno-unused-parameter -Wno-unused-variable -Wno-unused-value  -nostdlib -nostartfiles -nodefaultlibs -Wall -O0 -Iinc
 
@@ -9,6 +9,9 @@ all: $(OBJ)
 ./build/_start.s.o: ./_start/_start.s
 	nasm -f elf ./_start/_start.s -o ./build/_start.s.o
 
+./build/_exit.s.o: ./_exit/_exit.s;
+	nasm -f elf ./_exit/_exit.s -o ./build/_exit.s.o
+
 ./build/stdio.s.o: ./stdio/stdio.s
 	nasm -f elf ./stdio/stdio.s  -o ./build/stdio.s.o
 

usrspc/lib/_exit/_exit.s

@@ -0,0 +1,16 @@
+[BITS 32]
+
+section .asm
+
+global _exit
+
+_exit:
+
+    push ebp
+    mov ebp, esp
+
+    mov eax, 6 ; call __0x80_EXIT system call handler
+    int 0x80
+
+    pop ebp
+    ret

usrspc/lib/_start/_start.s

@@ -4,8 +4,10 @@ section .asm
 
 global _start
 extern main
+extern _exit
 
 _start:
 
     call main
+    call _exit
     ret