From 79f2fa136f26a0b87917336e089485712ee49bd6 Mon Sep 17 00:00:00 2001
From: Marvin Borner
Date: Fri, 7 Aug 2020 21:14:20 +0200
Subject: Dual-tasking works.
I don't know why triple-tasking doesn't though...
---
src/Makefile | 1 +
src/entry.asm | 29 ++++++++---------------------
src/features/load.c | 1 +
src/features/proc.asm | 25 +++++++++++++++++++++++++
src/features/proc.c | 36 +++++++++++++++++++++---------------
src/inc/proc.h | 4 ++--
6 files changed, 58 insertions(+), 38 deletions(-)
create mode 100644 src/features/proc.asm
(limited to 'src')
diff --git a/src/Makefile b/src/Makefile
index d568901..e917981 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -14,6 +14,7 @@ COBJS = main.o \
features/gui.o \
features/load.o \
features/proc.o \
+ features/proc_asm.o \
features/syscall.o \
lib/str.o \
lib/mem.o \
diff --git a/src/entry.asm b/src/entry.asm
index 67b5ffd..ac70091 100644
--- a/src/entry.asm
+++ b/src/entry.asm
@@ -4,14 +4,17 @@
; Definitions
-%define LOCATION 0x7c00 ; Bootloader location
-
; General configurations
; TODO: Find out why 2560x1600 doesn't work
%define VIDEO_WIDTH 1920
%define VIDEO_HEIGHT 1200
%define VIDEO_BPP 4
+; Boot constants
+%define LOCATION 0x7c00 ; Bootloader location
+%define SECTOR_END 0xaa55 ; Bootsector end signature
+%define SECTOR_SIZE 510 ; 512 bytes minus signature
+
; Interrupts
%define VIDEO_INT 0x10 ; Video BIOS Interrupt
%define DISK_INT 0x13 ; Disk BIOS Interrupt
@@ -158,8 +161,6 @@ lba_error:
; Video map routine
video_map:
- xor eax, eax
- mov es, ax
mov bx, VESA_START ; Set load address
mov di, bx
mov ax, VESA_GET_MODES ; Get video modes
@@ -187,7 +188,6 @@ video_map:
cmp ax, VESA_SUCCESS_SIG ; Check if call succeeded
jne .error ; Nope, jump to error!
- xor ax, ax
mov ax, [es:di + VESA_FRAMEBUFFER_OFFSET] ; Save framebuffer
mov [.framebuffer], ax ; Move fb address to struct
@@ -209,7 +209,6 @@ video_map:
lea ax, [es:di - 0x100]
mov [vid_info.array], ax
.set_mode:
- xor ax, ax
mov ax, VESA_SET_MODE ; Set VBE mode
mov bx, [.mode] ; Set mode address
mov [vid_info], bx ; Move mode information to array
@@ -257,8 +256,8 @@ lba:
dd 0 ; More storage bytes
; End of boot sector
-times 510 - ($ - $$) db 0
-dw 0xAA55
+times SECTOR_SIZE - ($ - $$) db 0
+dw SECTOR_END
; This is the second stage. It tries to load the kernel (inode 5) into memory.
; To do this, it first checks the integrity of the ext2 fs. Then it has to find
@@ -297,9 +296,6 @@ stage_two:
jmp protected_mode_enter
kernel_load:
- xor ax, ax ; Clear ax
- mov dx, ax ; Clear dx
-
; TODO: Add singly pointer support (until ~12KiB)
;cmp cx, EXT2_DIRECT_POINTER_COUNT ; Indirect pointer needed?
;jge .indirect ; Singly indirect pointer
@@ -316,8 +312,6 @@ kernel_load:
; push bx
; push cx
;
-; xor ebx, ebx
-;
; ; Read singly indirect pointer
; mov bx, EXT2_GET_ADDRESS(EXT2_KERNEL_INODE) ; First block
; lea di, [bx + EXT2_IND_POINTER_OFFSET] ; Address of singly indirect pointer
@@ -363,13 +357,6 @@ protected_mode_enter:
out A20_GATE, al
.a20_enabled:
- ; Clear registers
- xor ax, ax
- mov ds, ax
- mov es, ax
- mov fs, ax
- mov gs, ax
-
lgdt [gdt_desc] ; Load GDT
; Set protected mode via cr0
@@ -390,7 +377,7 @@ protected_mode:
mov esp, STACK_POINTER ; Move stack pointer
- mov ax, gdt_tss - gdt ; Load TSS
+ mov ax, (gdt_tss - gdt) | 0b11 ; Load TSS in ring 3
ltr ax
mov eax, vid_info ; Pass VBE struct to kernel
diff --git a/src/features/load.c b/src/features/load.c
index 5382c77..cc1a094 100644
--- a/src/features/load.c
+++ b/src/features/load.c
@@ -14,5 +14,6 @@ void bin_load(char *path, struct proc *proc)
proc->regs.ebp = (u32)stack;
proc->regs.esp = (u32)stack;
+ proc->regs.useresp = (u32)stack;
proc->regs.eip = (u32)data;
}
diff --git a/src/features/proc.asm b/src/features/proc.asm
new file mode 100644
index 0000000..3d6bbc4
--- /dev/null
+++ b/src/features/proc.asm
@@ -0,0 +1,25 @@
+%define USER_CODE_SEGMENT 0x18
+%define USER_DATA_SEGMENT 0x20
+%define RING3_MASK 0b11
+
+global proc_jump_userspace
+extern _esp
+extern _eip
+proc_jump_userspace:
+ mov ax, USER_DATA_SEGMENT | RING3_MASK
+ mov ds, ax
+ mov es, ax
+ mov fs, ax
+ mov gs, ax
+
+ mov eax, dword [_esp]
+ push USER_DATA_SEGMENT | RING3_MASK
+ push eax
+ pushf
+
+ sti
+
+ push USER_CODE_SEGMENT | RING3_MASK
+ push dword [_eip]
+
+ iret
diff --git a/src/features/proc.c b/src/features/proc.c
index 46b55fb..a14aaea 100644
--- a/src/features/proc.c
+++ b/src/features/proc.c
@@ -16,10 +16,8 @@ struct proc *last;
void scheduler(struct regs *regs)
{
- if (current) {
- printf("%d", current->pid);
+ if (current)
memcpy(¤t->regs, regs, sizeof(struct regs));
- }
timer_handler();
@@ -34,7 +32,19 @@ void scheduler(struct regs *regs)
else
current = current->next;
+ /* proc_print(); */
memcpy(regs, ¤t->regs, sizeof(struct regs));
+
+ if (regs->cs != GDT_USER_CODE_OFFSET) {
+ regs->gs = GDT_USER_DATA_OFFSET;
+ regs->fs = GDT_USER_DATA_OFFSET;
+ regs->es = GDT_USER_DATA_OFFSET;
+ regs->ds = GDT_USER_DATA_OFFSET;
+ regs->ss = GDT_USER_DATA_OFFSET;
+ regs->cs = GDT_USER_CODE_OFFSET;
+ regs->eflags = EFLAGS_ALWAYS | EFLAGS_INTERRUPTS;
+ }
+ printf("%d", current->pid);
}
void proc_print()
@@ -64,19 +74,10 @@ void proc_attach(struct proc *proc)
struct proc *proc_make()
{
- /* if (current) */
- /* current->state = PROC_ASLEEP; */
struct proc *proc = malloc(sizeof(*proc));
proc->pid = pid++;
proc->state = PROC_RUNNING;
-
- // Configure registers (default data)
- proc->regs.ds = GDT_DATA_OFFSET;
- proc->regs.es = GDT_DATA_OFFSET;
- proc->regs.fs = GDT_DATA_OFFSET;
- proc->regs.gs = GDT_DATA_OFFSET;
- proc->regs.cs = GDT_CODE_OFFSET;
- proc->regs.eflags = EFLAGS_ALWAYS | EFLAGS_INTERRUPTS;
+ proc->next = NULL;
if (current)
proc_attach(proc);
@@ -84,6 +85,9 @@ struct proc *proc_make()
return proc;
}
+extern void proc_jump_userspace();
+
+u32 _esp, _eip;
void proc_init()
{
cli();
@@ -93,6 +97,8 @@ void proc_init()
bin_load("/init", root);
strcpy(root->name, "root");
proc_print();
- sti();
- hlt();
+
+ _eip = root->regs.eip;
+ _esp = root->regs.esp;
+ proc_jump_userspace();
}
diff --git a/src/inc/proc.h b/src/inc/proc.h
index 8231810..39ba704 100644
--- a/src/inc/proc.h
+++ b/src/inc/proc.h
@@ -9,8 +9,8 @@
#define EFLAGS_ALWAYS 0x2 // Always one
#define EFLAGS_INTERRUPTS 0x200 // Enable interrupts
-#define GDT_DATA_OFFSET 0x10 // Data segment offset in GDT
-#define GDT_CODE_OFFSET 0x8 // Code segment offset in GDT
+#define GDT_USER_CODE_OFFSET 0x1b // User code segment offset in GDT (with ring3 mask)
+#define GDT_USER_DATA_OFFSET 0x23 // User data segment offset in GDT (with ring3 mask)
enum state { PROC_RUNNING, PROC_ASLEEP };
--
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