From 2b146d7fb7d0812dfcd4ac213682e947ba98051c Mon Sep 17 00:00:00 2001
From: John Tsiombikas <nuclear@member.fsf.org>
Date: Thu, 17 Dec 2020 05:34:33 +0200
Subject: [PATCH] works nicely from the floppy

---
 .gitignore      |    1 +
 Makefile        |    8 +-
 README.md       |   42 +++++++++
 bootsplash.asm  |   87 +++++++++++++++++--
 lut.inc         |  257 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 lutgen/Makefile |    8 ++
 lutgen/lutgen.c |   14 +++
 7 files changed, 408 insertions(+), 9 deletions(-)
 create mode 100644 README.md
 create mode 100644 lut.inc
 create mode 100644 lutgen/Makefile
 create mode 100644 lutgen/lutgen.c

diff --git a/.gitignore b/.gitignore
index 492e4f8..48b722b 100644
--- a/.gitignore
+++ b/.gitignore
@@ -8,3 +8,4 @@
 dis
 rle/rle
 rle/unrle
+lutgen/lutgen
diff --git a/Makefile b/Makefile
index fc3da3e..2f6fab5 100644
--- a/Makefile
+++ b/Makefile
@@ -5,12 +5,18 @@ $(img): $(bin)
 	dd if=/dev/zero of=$@ bs=512 count=2880
 	dd if=$< of=$@ bs=512 conv=notrunc
 
-$(bin): bootsplash.asm nuclear.rle
+$(bin): bootsplash.asm nuclear.rle fire.pal
 	nasm -f bin -o $@ $<
 
 nuclear.rle: nuclear.img rle/rle
 	cat $< | rle/rle >$@ 2>rle.log
 
+nuclear.img: nuclear.pgm
+	dd if=$< of=$@ bs=1 skip=61
+
+fire.pal: fire.ppm
+	dd if=$< of=$@ bs=1 skip=59
+
 rle/rle:
 	$(MAKE) -C rle
 
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..1f34f05
--- /dev/null
+++ b/README.md
@@ -0,0 +1,42 @@
+Bootsplash
+----------
+Small bootable program that shows a splash effect every time you boot it up, and
+when you hit any key on the keyboard, it proceeds to load the actual system (or
+your regular boot loader) off the hard drive.
+
+
+Author: John Tsiombikas <nuclear@member.fsf.org>
+
+Not copyrighted, public domain software. Feel free to use it any way you like.
+If public domain is not legally recognized in your country, you may instead use
+it under the terms of the Creative Commons CC0 license.
+
+Future improvements (TODO list):
+
+  - Option to load active partition instead of MBR from the selected boot device
+    to make bootsplash itself installable on the MBR (as it is, it would just
+    infinitely load itself).
+  - Add BIOS parameter block and fake partition table, to make it more likely
+    to be loadable from a USB stick.
+  - Add timeout to boot automatically if no key is pressed for a certain amount
+    of time.
+
+Build
+-----
+To build bootsplash you need the netwide assembler (nasm). If you want to
+customize the image used by the effect, you'll also need a C compiler to build
+the RLE encoder under `rle`.
+
+The data files are not in the repo. You'll need to get them from one of the
+release archives.
+
+  - `nuclear.pgm`: 320x200 greyscale image used by the effect in binary Portable
+    GreyMap format.  This is fed into the `rle` encoder to produce `nuclear.rle`
+    which is `incbin`-ed into the bootsplash program.
+  - `fire.ppm`: 256x1 RGB image in binary Portable PixMap format. The header gets
+    stripped and the resulting `fire.pal` file is `incbin`-ed into the program.
+
+If you don't want to customize the effect, simply copy the final files
+(`nuclear.rle` and `fire.pal`) and type make.
+
+To install onto a floppy, just use `dd`.
diff --git a/bootsplash.asm b/bootsplash.asm
index 5885c4d..b7f53c7 100644
--- a/bootsplash.asm
+++ b/bootsplash.asm
@@ -1,13 +1,26 @@
 	org 7c00h
 	bits 16
 
+BOOT_DEV equ 80h
+
 stacktop equ 7b00h
 boot_driveno equ 7b00h	; 1 byte
 stage2_size equ stage2_end - stage2_start
 
-spawn_rate equ 256
+spawn_rate equ 512
 framebuf equ 40000h
 
+%macro floppy_motor_off 0
+	pushf
+	and dl, 80h
+	jnz %%end	; skip if high bit is set (i.e. it's not a floppy)
+	mov dx, 3f2h
+	in al, dx
+	and al, 0fh
+	out dx, al
+%%end:	popf
+%endmacro
+
 start:
 	xor ax, ax
 	mov ds, ax
@@ -23,12 +36,13 @@ start:
 	xor ax, ax
 	mov es, ax
 	mov bx, stage2_start
-	mov ah, 2		; read sectors LBA call
+	mov ah, 2		; read sectors call
 	mov al, (stage2_size + 511) / 512  ; num sectors
 	mov cx, 2		; ch: cylinder, cl: sector
 	xor dx, dx		; dh: head
 	mov dl, [boot_driveno]
 	int 13h
+	floppy_motor_off	; turn off floppy motor (if dl is < 80h)
 	jnc stage2_start	; loaded successfully, jump to it
 
 	; failed to load second sector
@@ -52,15 +66,19 @@ printstr:
 .done:	ret
 
 str_load_fail db "Failed to load second stage!",0
-str_booting db "Booting ...",0
+str_booting db "Booting system... ",0
+str_bootfail db "failed!",0
 
 
 	times 510-($-$$) db 0
-	dw 0xaa55
+bootsig dw 0xaa55
 
 	; start of the second stage
 stage2_start:
+	pushf
+	cli
 	call splash
+	popf
 
 	xor ax, ax
 	mov es, ax
@@ -69,10 +87,39 @@ stage2_start:
 	mov ax, str_booting
 	call printstr
 
-	cli
-.hang:	hlt
+	; blank out the existing boot signature to really see if a boot sector
+	; gets loaded correctly
+	xor ax, ax
+	mov [bootsig], ax
+
+	; load from BOOT_DEV into 7c00h and jump
+	mov bx, 7c00h
+	mov ax, 0201h		; ah: call 2 (read sectors), al: count = 1
+	mov cx, 1		; ch: cylinder 0, cl: sector 1
+	mov dx, BOOT_DEV	; dh: head 0, dl: boot device number
+	int 13h
+	floppy_motor_off	; turn floppy motor off (if dl < 80h)
+
+	jc .fail		; BIOS will set the carry flag on failure
+	mov ax, [bootsig]
+	cmp ax, 0aa55h
+	jnz .fail		; fail if what we loaded is not a valid boot sect
+
+	mov ax, 0e0dh
+	mov bx, 7
+	int 10h
+	mov ax, 0e0ah
+	int 10h
+
+	jmp 7c00h		; all checks passed, jump there
+
+.fail:	mov ax, str_bootfail
+	call printstr
+.hang:	cli
+	hlt
 	jmp .hang
 
+
 	; splash screen effect
 splash:
 	mov ax, 13h
@@ -142,6 +189,15 @@ splash:
 	xor edx, edx
 	div dword [num_spawn_pos]	; edx <- rand % num_spawn_pos
 	mov bx, [es:edx * 2]		; grab one of the spawn positions
+
+	; animate the spawn position
+	xor ax, ax
+	mov al, [frameno]
+	mov bp, ax
+	movsx ax, byte [bp + sintab]
+	sar ax, 3
+	add bx, ax
+
 	mov byte [fs:bx], 0xff		; plot a pixel there
 	dec cx
 	jnz .spawn
@@ -153,13 +209,23 @@ splash:
 	xor ax, ax	; use: pixel accum
 	xor dx, dx	; use: second pixel
 .blurloop:
+	xor ax, ax
 	mov al, [bx]
 	mov dl, [bx + 320]
 	add ax, dx
-	shr ax, 1
+	mov dl, [bx + 319]
+	add ax, dx
+	mov dl, [bx + 321]
+	add ax, dx
+	mov dl, [bx + 640]
+	add ax, dx
+	xor dx, dx
+	mov cx, 5
+	div cx
 	mov [bx], al
+
 	inc bx
-	cmp bx, 64000 - 320 * 2
+	cmp bx, 64000 - 640
 	jnz .blurloop
 
 
@@ -184,6 +250,8 @@ splash:
 	xor ax, ax
 	mov ds, ax
 
+	inc word [frameno]
+
 	; check for keypress
 	in al, 64h
 	and al, 1
@@ -240,7 +308,10 @@ randval dd 0ace1h
 
 
 	; data
+%include "lut.inc"
+
 num_spawn_pos dd 0
+frameno dw 0
 	align 16
 spawn_pos:
 imgrle:	incbin "nuclear.rle"
diff --git a/lut.inc b/lut.inc
new file mode 100644
index 0000000..5dc6fdc
--- /dev/null
+++ b/lut.inc
@@ -0,0 +1,257 @@
+sintab:
+	db 0
+	db 2
+	db 5
+	db 8
+	db 11
+	db 15
+	db 18
+	db 21
+	db 24
+	db 27
+	db 30
+	db 33
+	db 36
+	db 39
+	db 42
+	db 45
+	db 48
+	db 51
+	db 54
+	db 56
+	db 59
+	db 62
+	db 65
+	db 67
+	db 70
+	db 72
+	db 75
+	db 77
+	db 80
+	db 82
+	db 85
+	db 87
+	db 89
+	db 91
+	db 93
+	db 96
+	db 98
+	db 100
+	db 101
+	db 103
+	db 105
+	db 107
+	db 108
+	db 110
+	db 111
+	db 113
+	db 114
+	db 116
+	db 117
+	db 118
+	db 119
+	db 120
+	db 121
+	db 122
+	db 123
+	db 123
+	db 124
+	db 125
+	db 125
+	db 126
+	db 126
+	db 126
+	db 126
+	db 126
+	db 127
+	db 126
+	db 126
+	db 126
+	db 126
+	db 126
+	db 125
+	db 125
+	db 124
+	db 123
+	db 123
+	db 122
+	db 121
+	db 120
+	db 119
+	db 118
+	db 117
+	db 116
+	db 114
+	db 113
+	db 111
+	db 110
+	db 108
+	db 107
+	db 105
+	db 103
+	db 101
+	db 100
+	db 98
+	db 96
+	db 93
+	db 91
+	db 89
+	db 87
+	db 85
+	db 82
+	db 80
+	db 77
+	db 75
+	db 72
+	db 70
+	db 67
+	db 65
+	db 62
+	db 59
+	db 56
+	db 54
+	db 51
+	db 48
+	db 45
+	db 42
+	db 39
+	db 36
+	db 33
+	db 30
+	db 27
+	db 24
+	db 21
+	db 18
+	db 15
+	db 11
+	db 8
+	db 5
+	db 2
+	db 0
+	db -3
+	db -6
+	db -9
+	db -12
+	db -16
+	db -19
+	db -22
+	db -25
+	db -28
+	db -31
+	db -34
+	db -37
+	db -40
+	db -43
+	db -46
+	db -49
+	db -52
+	db -55
+	db -57
+	db -60
+	db -63
+	db -66
+	db -68
+	db -71
+	db -73
+	db -76
+	db -78
+	db -81
+	db -83
+	db -86
+	db -88
+	db -90
+	db -92
+	db -94
+	db -97
+	db -99
+	db -101
+	db -102
+	db -104
+	db -106
+	db -108
+	db -109
+	db -111
+	db -112
+	db -114
+	db -115
+	db -117
+	db -118
+	db -119
+	db -120
+	db -121
+	db -122
+	db -123
+	db -124
+	db -124
+	db -125
+	db -126
+	db -126
+	db -127
+	db -127
+	db -127
+	db -127
+	db -127
+	db -128
+	db -127
+	db -127
+	db -127
+	db -127
+	db -127
+	db -126
+	db -126
+	db -125
+	db -124
+	db -124
+	db -123
+	db -122
+	db -121
+	db -120
+	db -119
+	db -118
+	db -117
+	db -115
+	db -114
+	db -112
+	db -111
+	db -109
+	db -108
+	db -106
+	db -104
+	db -102
+	db -101
+	db -99
+	db -97
+	db -94
+	db -92
+	db -90
+	db -88
+	db -86
+	db -83
+	db -81
+	db -78
+	db -76
+	db -73
+	db -71
+	db -68
+	db -66
+	db -63
+	db -60
+	db -57
+	db -55
+	db -52
+	db -49
+	db -46
+	db -43
+	db -40
+	db -37
+	db -34
+	db -31
+	db -28
+	db -25
+	db -22
+	db -19
+	db -16
+	db -12
+	db -9
+	db -6
+	db -3
diff --git a/lutgen/Makefile b/lutgen/Makefile
new file mode 100644
index 0000000..56c882c
--- /dev/null
+++ b/lutgen/Makefile
@@ -0,0 +1,8 @@
+LDFLAGS = -lm
+
+lutgen: lutgen.o
+	$(CC) -o $@ $< $(LDFLAGS)
+
+clean:
+	$(RM) lutgen
+	$(RM) lutgen.o
diff --git a/lutgen/lutgen.c b/lutgen/lutgen.c
new file mode 100644
index 0000000..2e5bf27
--- /dev/null
+++ b/lutgen/lutgen.c
@@ -0,0 +1,14 @@
+#include <stdio.h>
+#include <math.h>
+
+int main(void)
+{
+	int i;
+
+	printf("sintab:\n");
+	for(i=0; i<256; i++) {
+		float x = sin((float)i / 128.0f * M_PI);
+		printf("\tdb %d\n", (int)(x * 127.5f - 0.5f));
+	}
+	return 0;
+}
-- 
1.7.10.4