From 74057dac1d460574f0b7edb89e9e4125a69c885a Mon Sep 17 00:00:00 2001
From: iximeow <me@iximeow.net>
Date: Mon, 28 Sep 2015 03:33:19 -0700
Subject: add awful support for non-0x7e00 start, prefix real start address to
 kernel

---
 bootloader.asm           | 13 +++++++------
 build_helpers/compile.sh | 14 ++++++++++++--
 2 files changed, 19 insertions(+), 8 deletions(-)

diff --git a/bootloader.asm b/bootloader.asm
index c9ed98b..7d218eb 100644
--- a/bootloader.asm
+++ b/bootloader.asm
@@ -13,7 +13,7 @@ start:
   call verify_read
   mov si, READ_NERR
   call write_str
-  jmp 0x7e00
+  jmp word [0x7dfc]
   jmp hang
 
 read_err:
@@ -23,17 +23,18 @@ hang:
   jmp hang
 
 verify_read:
+  mov bx, word [0x7dfc]
   mov al, 0x66
-  cmp al, [0x7e00]
+  cmp al, byte [bx]
   jne read_err
   mov al, 0x55
-  cmp al, [0x7e01]
+  cmp al, byte [bx+1]
   jne read_err
   mov al, 0x66
-  cmp al, [0x7e02]
+  cmp al, byte [bx+2]
   jne read_err
   mov al, 0x89
-  cmp al, [0x7e03]
+  cmp al, byte [bx+3]
   jne read_err
   ret
 
@@ -106,7 +107,7 @@ LBA_DISK_READ_PACKET:
   db 0x10
   db 0
   dw 32     ; number of blocks to read, reset to # actually read when done
-  dw 0x7e00 ; read destination address
+  dw 0x7dfc ; read destination address
   dw 0x0000
   dd 1      ; lba to read from
   dd 0      ; for extended lba adresses (not really used here)
diff --git a/build_helpers/compile.sh b/build_helpers/compile.sh
index 40cd293..f00549f 100755
--- a/build_helpers/compile.sh
+++ b/build_helpers/compile.sh
@@ -10,8 +10,18 @@ OUTNAME="src._kernel._main"
 echo -n "[*] Building '$INPATH' to 'tmp/$OUTNAME'... "
 gcc -T linker.ld -m32 -Wl,--build-id=none -nostartfiles -nostdlib -ffreestanding $INPATH -o "tmp/$OUTNAME".o
 echo " OK!"
+echo -n "[+] Start address is... "
+BIN_START=$(objdump tmp/src._kernel._main.o -f | grep start | cut -b 15-)
+echo "$BIN_START"
+# this actually writes three extra nulls, not sure why...
+echo "$BIN_START" | xxd -r - | od -t x --endian=little | head | xxd -r - > "bin/$OUTNAME".bin
 echo -n "[+] Stripping unnecessary sections... "
-objcopy -R .note.gnu.build-id -R .comment -O binary "tmp/$OUTNAME".o "bin/$OUTNAME".bin
+objcopy -R .note.gnu.build-id -R .comment -O binary "tmp/$OUTNAME".o "tmp/converted_$OUTNAME".bin
 echo " OK!"
-rm "tmp/$OUTNAME".o
+
+echo -n "[+] Joining kernel and start address... "
+# adjust for the three extra nulls above
+dd if="tmp/converted_$OUTNAME".bin of="bin/$OUTNAME".bin seek=4 oflag=seek_bytes conv=notrunc 2>/dev/null
+echo " OK!"
+#rm "tmp/$OUTNAME".o
 
-- 
cgit v1.1