From 902512d8c05a065968581c65a50c22cfc591012a Mon Sep 17 00:00:00 2001
From: jesings <34111484+jesings@users.noreply.github.com>
Date: Fri, 9 Apr 2021 12:16:04 -0500
Subject: [PATCH] Mitigated odd bug not allowing linkage of data labels,
 updated credit

---
 bootsweeper.S | 33 +++++++++++++++------------------
 makefile      |  3 ++-
 miner.ld      | 15 ++++++++++++++-
 readme.md     |  6 +++---
 4 files changed, 34 insertions(+), 23 deletions(-)

diff --git a/bootsweeper.S b/bootsweeper.S
index c8d678e..d322b84 100644
--- a/bootsweeper.S
+++ b/bootsweeper.S
@@ -1,32 +1,27 @@
-.code16
 #60 free bytes to play with
 .global _start
-#16x16 board, each tile is a single bit, mine or not
-.data
-    x: .short 0
-    y: .byte 0
-#The first byte here is technically part of y, but I use it here to simplify memory access
-    minecolors: .byte 0, 0x79, 0x72, 0x74, 0x71, 0x76, 0x73, 0x78
-.text
+.code16
 .macro getrand #Credit goes to https://b2d-f9r.blogspot.com/2010/08/16-bit-xorshift-rng-now-with-more.html for the xorshift algorithm
 #static uint16_t x=1,y=1;
 #uint16_t t=(x^(x<<5)); 
-    movw x, %cx
+    movw (0x7df3), %cx
     shlw $5, %cx
-    xorw x, %cx
+    xorw (0x7df3), %cx
 #x=y;
-    movw y, %ax
-    movw %ax, x
+    movw (0x7df5), %ax
+    movw %ax, (0x7df3)
 #return y=(y^(y>>1))^(t^(t>>3));
     shrw %ax
-    xorw y, %ax
+    xorw (0x7df5), %ax
     movw %cx, %bx
     shrw $3, %bx
     xorw %bx, %cx
     xorw %ax, %cx
-    movw %cx, y
+    movw %cx, (0x7df5)
 #Random number is now in %cx
 .endm
+#16x16 board, each tile is a single bit, mine or not
+.text
 
 _start:
     xorw %ax, %ax
@@ -37,8 +32,8 @@ _start:
     movw %ax, %ds
     movb $0x02, %ah 
     int $0x1A #Read RTC value
-    movw %cx, x #Seed RNG
-    movw %dx, y #Seed RNG
+    movw %cx, (0x7df3) #Seed RNG
+    movw %dx, (0x7df5) #Seed RNG
 newgame:
 #initialize screen
     xorw %ax, %ax
@@ -53,7 +48,9 @@ newgame:
     movw $0xAB1, %ax
     int $0x10 #print out 16 dummy characters for each row
     getrand
-    andw x, %cx #And 2 random-ish numbers, making it so that on average 25% of tiles will be mines
+    mov %cx, %si
+    getrand
+    andw %si, %cx #And 2 random-ish numbers, making it so that on average 25% of tiles will be mines
     movzxb %dh, %di
     subw $0x5, %di#di is used for index in 16 bit
     shlw %di
@@ -207,7 +204,7 @@ uncover3: #Print correct character for tile at cursor, if it is 0 call the flood
     int $0x10
     ret
     nonzero:
-    leaw minecolors, %bx
+    leaw (0x7df6), %bx
     movzx %al, %di
     movb (%bx, %di), %bl
     xorb %bh, %bh
diff --git a/makefile b/makefile
index ed90f6b..a201c28 100644
--- a/makefile
+++ b/makefile
@@ -6,4 +6,5 @@ dosboxmine: mine
 	dosbox
 mine:
 	as bootsweeper.S -o mine.o
-	ld -o mine.bin --oformat binary -e _start mine.o -T miner.ld
+	strip --remove-section=.note.gnu.property mine.o
+	ld -o mine.bin --oformat binary mine.o -T miner.ld
diff --git a/miner.ld b/miner.ld
index 712ee07..e31596a 100644
--- a/miner.ld
+++ b/miner.ld
@@ -3,7 +3,20 @@ SECTIONS
     . = 0x7c00;
     .text :
     {
-        mine.o (.*)
+        mine.o (.text)
+        . = 0x1FE - 0xb;
+        SHORT(0x0)
+        . = 0x1FE - 0x9;
+        BYTE(0x0)
+        . = 0x1FE - 0x8;
+        BYTE(0x0)
+        BYTE(0x79)
+        BYTE(0x72)
+        BYTE(0x74)
+        BYTE(0x71)
+        BYTE(0x76)
+        BYTE(0x73)
+        BYTE(0x78)
         . = 0x1FE;
         SHORT(0xAA55)
     }
diff --git a/readme.md b/readme.md
index bc31600..4f9afa4 100644
--- a/readme.md
+++ b/readme.md
@@ -10,7 +10,7 @@ The game features stunning 16 color text mode graphics, colored numbers, cursor
 
 ## How do I play?
 
-In order to run the program, you must have the qemu, bochs, or DOSBox emulator installed (if you want to use a different emulator, feel free to configure that on your own). To run with qemu, simply use `make` and the program will compile and run! To run with bochs, use `make bochsmine` and then type `c` into the bottom input on the debug window. For DOSBox, run `dosboxmine` and then in the DOSBox command prompt type `boot mine.bin`.
+In order to run the program, you must have the qemu, bochs, or DOSBox emulator installed (if you want to use a different emulator, feel free to configure that on your own). To run with qemu, simply use `make` and the program will compile and run! To run with bochs, use `make bochsmine` and then type `c` into the bottom input on the debug window. For DOSBox, run `dosboxmine` and then in the DOSBox command prompt, mount your host system directory as the C drive, go to the C drive, and `boot mine.bin`.
 
 NOTE: In order to get arrow keys support on DOSBox (on my linux system), I needed to change usescancodes to false in ~/.dosbox/dosbox-0.74-3.conf (replace 0.74-3 with your version number).
 
@@ -26,9 +26,9 @@ NOTE: In order to get arrow keys support on DOSBox (on my linux system), I neede
 
 ## Also check out 
 
-https://gitlab.com/blevy/boot-sector-minesweeper
+https://github.com/io12/bootmine
 
-This is another minesweeper clone in the bootsector, it's got some interesting differences to this version, please check it out!
+This is another minesweeper clone in the bootsector, it's got some interesting differences to this version (being 40x25, a slightly easier difficulty, it makes use of rdtsc), please check it out!
 
 https://github.com/nanochess/bootOS