Move user and kernel stack init as constant

Author: scopeInfinity

Makefile

@@ -75,7 +75,7 @@ endif
 # Tools
 HOST_CC = gcc -std=c11 -Iinclude
 
-NASM=nasm -f elf32 $(NASM_DEBUG)
+NASM=nasm -f elf32 -i include/ $(NASM_DEBUG)
 
 CC=gcc -std=c11 -fno-builtin -Os -nostartfiles -nostdlib -static $(CC_DEBUG)
 KERNEL_CC = $(CC) -m32 -fno-pie -Isrc --sysroot=$(BUILD_DIR) -Iinclude -Isrc/usr/include

include/fuzzy/kernel/interrupts/timer.h

@@ -4,4 +4,4 @@ void interrupt_pit_enable();
 
 void interrupt_register_0x20_irq0_pit();
 
-void create_infant_process_irq0_stack(int ds_ss_es_fs);
+int create_infant_process_irq0_stack(int ds_ss_es_fs);

include/fuzzy/memmgr/layout.asm

@@ -0,0 +1,9 @@
+; constants only
+
+; Kernel core is app with pid 0
+; Kernel event is trigged via IRQ0 or syscall,
+
+STACKINIT_APP EQU 0xFFF0
+STACKINIT_KERNEL_CORE EQU STACKINIT_APP
+STACKINIT_KERNEL_EVENT EQU 0xC000
+

src/kernel/core.asm

@@ -1,3 +1,5 @@
+%include "fuzzy/memmgr/layout.asm"
+
 [BITS 32]
 
 extern kernel_core_entry
@@ -14,9 +16,7 @@ global kernel_core_entry_asm
         mov fs, ax
         mov gs, ax
 
-        ; TODO: Increase kernel code stack memory size
-        ; The value also depends on kernel handler stack size
-        mov esp, 0xC000  ; init stack pointer
+        mov esp, STACKINIT_KERNEL_CORE  ; init stack pointer
         jmp kernel_core_entry
 
         ; kernel_core_entry_asm currently exists only for tests.

src/kernel/interrupts/timer.asm

@@ -1,3 +1,5 @@
+%include "fuzzy/memmgr/layout.asm"
+
 [BITS 32]
 
 global irq0_pit_handler_low
@@ -25,7 +27,7 @@ global create_infant_process_irq0_stack
         mov esi, esp
 
         ; new stack and segment area
-        mov esp, 0xFFF0  ; keep offset in sync with process_create(...) and create_infant_process_irq0_stack
+        mov esp, STACKINIT_KERNEL_EVENT
         mov eax, 0x10
         mov ss, eax
         mov ds, eax
@@ -82,6 +84,8 @@ global create_infant_process_irq0_stack
         iret
 
     create_infant_process_irq0_stack:
+        ; keep in sync with _int_irq0_start
+        ; return the esp for user stack
         push ebp
         mov ebp, esp
 
@@ -95,9 +99,8 @@ global create_infant_process_irq0_stack
 
         mov ds, ecx
 
-        ; user stack creation start
         ; user initial stack
-        mov eax, 0xFFF0 ; keep in sync with _int_irq0_start
+        mov eax, STACKINIT_APP
         ; kernel offset
         xor ecx, ecx
         mov [eax-0], ecx    ; user: eflag
@@ -116,9 +119,7 @@ global create_infant_process_irq0_stack
         mov [eax-52], ecx       ; user: fs
         mov [eax-56], ecx       ; user: gs
 
-        ; user: esp = eax-56 = 0xFFF0-56
-        ; should be compatible with process_create
-        ; user stack creation end
+        sub eax, 56 ; user stack pointer
 
         pop ds
 

src/kernel/process/allocation.c

@@ -106,15 +106,6 @@ int process_create() {
     int idt_cs_entry = get_idt_cs_entry(pid);
     int idt_ds_entry = get_idt_ds_entry(pid);
 
-    process->state = STATE_LOADING;
-    process->cs = get_gdt_number_from_entry_id(idt_cs_entry);
-    process->ip = 0; //
-    // initially ds == ss
-    process->ss = get_gdt_number_from_entry_id(idt_ds_entry);
-    // should be compatible with create_infant_process_irq0_stack
-    process->sp = 0xFFF0-56;  // keep offset in sync with _int_irq0_start
-
-
     // Potential improvement:
     // - avoid populating GDT entry if already exists.
 
@@ -130,7 +121,15 @@ int process_create() {
         memory_location, memory_location+memory_size-1,
         0b0100,  // 32-bit protected mode
         0x92);
-    create_infant_process_irq0_stack(process->ss);
+
+
+    // update process state
+    process->state = STATE_LOADING;
+    process->cs = get_gdt_number_from_entry_id(idt_cs_entry);
+    process->ip = 0;
+    // initially ds == ss
+    process->ss = get_gdt_number_from_entry_id(idt_ds_entry);
+    process->sp = create_infant_process_irq0_stack(process->ss);
     return pid;
 }
 

src/kernel/process/process.asm

@@ -1,71 +1,10 @@
 [BITS 32]
 
-global call_main
 global syscall_strncpy_user_to_kernel
 global syscall_strncpy_kernel_to_user
 
 [SECTION .text]
 
-    call_main:
-        ; TODO: write assumptions and constraints
-        ; TODO: function needs to be verified for exit case.
-        push ebp
-        mov ebp, esp
-        ; callee save register
-        push ebx
-        push esi
-        push edi
-
-        mov eax, [ebp + 0x10]         ; (argc)
-        mov eax, [ebp + 0x14]         ; (argv)
-
-        ; bx and cx are used below.
-        mov ebx, [ebp + 0x08]         ; (CS)
-        mov ecx, [ebp + 0x0c]         ; (DS)
-
-        mov eax, esp
-        mov [kernel_saved_stack_top], eax
-
-
-        ; Preparing for exec.
-
-        ; assigning segment registers
-        mov es, cx
-        mov ss, cx
-        mov ds, cx
-        mov fs, cx
-        mov gs, cx
-
-        ; assign kernel stack
-        mov eax, 0xFFFC
-        mov esp, eax
-
-        ; far jump to main()
-        push ebx    ; CS, 2 bytes
-        xor ebx, ebx
-        push ebx    ; IP: 4 bytes
-        call far [esp]
-
-        ; eax should contain the program return value.
-
-        ; Returned from exec.
-
-        mov bx, 0x10
-        mov es, bx
-        mov ss, bx
-        mov ds, bx
-        mov fs, bx
-        mov gs, bx
-
-        mov ebx, [kernel_saved_stack_top]
-        mov esp, ebx
-
-        pop edi
-        pop esi
-        pop ebx
-        pop ebp
-        ret
-
     syscall_strncpy_user_to_kernel:
         push ebp
         mov ebp, esp