Optimizations to kernel size

- Add kernel build flag for NO_VGA. By default this is enabled
- Re-org if statements for calls of os_debug_string
- Use 32-bit register sets in interrupt.asm where possible. This saves 5 bytes per `mov`

Author: Ian Seyler

build.sh

@@ -1,6 +1,6 @@
 #!/usr/bin/env bash
 
-BUILDFLAGS=""
+BUILDFLAGS="-dNO_VGA"
 
 # Internal
 # -dNO_VIRTIO	Remove VirtIO drivers (NVS, NET)
@@ -14,7 +14,8 @@ BUILDFLAGS=""
 # -dNO_I8259X	Remove i8259x 10-Gigabit driver
 # HID
 # -dNO_XHCI	Remove xHCI USB driver (hid)
-# -dNO_LFB	Remove LFB text driver
+# -dNO_LFB	Remove LFB graphical text output driver
+# -dNO_VGA	Remove VGA text output driver
 
 mkdir -p bin
 cd src

src/drivers.asm

@@ -55,7 +55,8 @@
 ; Video
 %ifndef NO_LFB
 %include "drivers/lfb/lfb.asm"
-%else
+%endif
+%ifndef NO_VGA
 %include "drivers/vga.asm"
 %endif
 

src/init/64.asm

@@ -115,17 +115,25 @@ make_interrupt_gate_stubs:
 	; Configure the serial port (if present)
 	call serial_init
 
+init_64_lfb:
 	; Initialize text output
 %ifndef NO_LFB
+	; Check if LFB was enabled by Pure64
+	mov rax, [os_screen_lfb]
+	cmp rax, 0
+	je init_64_vga
 	call lfb_init			; Initialize LFB for text output
-%else
+%endif
+init_64_vga:
+%ifndef NO_VGA
 	call vga_init
-	; Output progress via serial
+%endif
+
+	; Output progress via debug
 	mov rsi, msg_baremetal
 	call os_debug_string
 	mov rsi, msg_64
 	call os_debug_string
-%endif
 
 	; Initialize the APIC
 	call os_apic_init
@@ -164,11 +172,11 @@ no_more_aps:
 	; Output block to screen (2/8)
 	mov ebx, 2
 	call os_debug_block
-%else
+%endif
+
 	; Output progress via serial
 	mov rsi, msg_ok
 	call os_debug_string
-%endif
 
 	ret
 ; -----------------------------------------------------------------------------

src/init/bus.asm

@@ -29,11 +29,9 @@
 ; -----------------------------------------------------------------------------
 init_bus:
 
-%ifdef NO_LFB
 	; Output progress via serial
 	mov rsi, msg_bus
 	call os_debug_string
-%endif
 
 	mov rdi, bus_table		; Address of Bus Table in memory
 	xor edx, edx			; Register 0 for Device ID/Vendor ID
@@ -165,11 +163,11 @@ init_bus_usb_not_found:
 	; Output block to screen (4/8)
 	mov ebx, 6
 	call os_debug_block
-%else
+%endif
+
 	; Output progress via serial
 	mov rsi, msg_ok
 	call os_debug_string
-%endif
 
 	ret
 ; -----------------------------------------------------------------------------

src/init/net.asm

@@ -10,11 +10,9 @@
 ; init_net -- Configure the first network device it finds
 init_net:
 
-%ifdef NO_LFB
 	; Output progress via serial
 	mov rsi, msg_net
 	call os_debug_string
-%endif
 
 	mov ax, [NIC_DeviceVendor_ID]	; Check for NIC driver definitions
 	cmp ax, 0x0000
@@ -123,11 +121,11 @@ init_net_end:
 	; Output block to screen (6/8)
 	mov ebx, 10
 	call os_debug_block
-%else
+%endif
+
 	; Output progress via serial
 	mov rsi, msg_ok
 	call os_debug_string
-%endif
 
 	ret
 ; -----------------------------------------------------------------------------

src/init/nvs.asm

@@ -10,11 +10,9 @@
 ; init_nvs -- Configure the first non-volatile storage device it finds
 init_nvs:
 
-%ifdef NO_LFB
 	; Output progress via serial
 	mov rsi, msg_nvs
 	call os_debug_string
-%endif
 
 %ifndef NO_NVME
 	; Check Bus Table for NVMe
@@ -93,11 +91,11 @@ init_nvs_done:
 	; Output block to screen (5/8)
 	mov ebx, 8
 	call os_debug_block
-%else
+%endif
+
 	; Output progress via serial
 	mov rsi, msg_ok
 	call os_debug_string
-%endif
 
 	ret
 ; -----------------------------------------------------------------------------

src/init/sys.asm

@@ -25,11 +25,11 @@ init_sys_done:
 	; Output block to screen (8/8)
 	mov ebx, 14
 	call os_debug_block
-%else
+%endif
+
 	; Output progress via serial
 	mov rsi, msg_ready
 	call os_debug_string
-%endif
 
 	ret
 ; -----------------------------------------------------------------------------

src/interrupt.asm

@@ -10,9 +10,9 @@
 ; Default exception handler
 align 8
 exception_gate:
-	mov rsi, int_string00
+	mov esi, int_string00
 	call b_output
-	mov rsi, exc_string
+	mov esi, exc_string
 	call b_output
 	jmp $				; Hang
 ; -----------------------------------------------------------------------------
@@ -175,7 +175,7 @@ ap_wakeup:
 align 8
 ap_reset:
 	; Don't use 'os_apic_write' as we can't guarantee the state of the stack
-	mov rax, ap_clear		; Set RAX to the address of ap_clear
+	mov eax, ap_clear		; Set RAX to the address of ap_clear
 	mov [rsp], rax			; Overwrite the return address on the CPU's stack
 	mov rdi, [os_LocalAPICAddress]	; Acknowledge the IPI
 	add rdi, 0xB0
@@ -378,24 +378,24 @@ exception_gate_main:
 	push rcx			; Char counter for b_output
 	push rax			; Save RAX since b_smp_get_id clobbers it
 	call os_debug_newline
-	mov rsi, int_string00
-	mov rcx, 6
+	mov esi, int_string00
+	mov ecx, 6
 	call b_output
 	call b_smp_get_id		; Get the local CPU ID and print it
 	call os_debug_dump_ax
-	mov rsi, int_string01
-	mov rcx, 15
+	mov esi, int_string01
+	mov ecx, 15
 	call b_output
-	mov rsi, exc_string00
+	mov esi, exc_string00
 	pop rax
-	and rax, 0x00000000000000FF	; Clear out everything in RAX except for AL
+	and eax, 0x00000000000000FF	; Clear out everything in RAX except for AL
 	push rax
 	mov bl, 6			; Length of each message
 	mul bl				; AX = AL x BL
 	add rsi, rax			; Use the value in RAX as an offset to get to the right message
 	pop rax
 	mov bl, 0x0F
-	mov rcx, 6
+	mov ecx, 6
 	call b_output
 	pop rcx
 	pop rsi
@@ -420,14 +420,14 @@ exception_gate_main:
 	push rcx
 	push rbx
 	push rax
-	mov rsi, reg_string00		; Load address of first register string
+	mov esi, reg_string00		; Load address of first register string
 	mov ecx, 4			; Number of characters per reg_string
 	mov edx, 16			; Counter of registers to left to output
 	xor ebx, ebx			; Counter of registers output per line
 	call os_debug_newline
 exception_gate_main_nextreg:
 	call b_output
-	add rsi, 4
+	add esi, 4
 	pop rax
 	call os_debug_dump_rax
 	add ebx, 1
@@ -445,7 +445,7 @@ exception_gate_main_nextreg_continue:
 	mov rax, [rsp+8] 		; RIP of caller
 	call os_debug_dump_rax
 	call os_debug_space
-	add rsi, 4
+	add esi, 4
 	call b_output
 	mov rax, cr2
 	call os_debug_dump_rax

src/syscalls/debug.asm

@@ -155,7 +155,6 @@ os_debug_space:
 ; -----------------------------------------------------------------------------
 
 
-%ifdef NO_LFB
 ; -----------------------------------------------------------------------------
 ; os_debug_string - Dump a string to output
 ; IN:	RSI = String Address (null terminated)
@@ -172,14 +171,13 @@ os_debug_string:
 	not rcx
 	dec rcx
 
-	call b_output
+	call b_output_serial
 
 	pop rax
 	pop rcx
 	pop rdi
 	ret
 ; -----------------------------------------------------------------------------
-%endif
 
 
 %ifndef NO_LFB