diff options
| -rw-r--r-- | baremetal/boot.bochsrc | 4 | ||||
| -rw-r--r-- | baremetal/boot.hex | 13 |
2 files changed, 9 insertions, 8 deletions
diff --git a/baremetal/boot.bochsrc b/baremetal/boot.bochsrc index 4ddd2ca1..7745d972 100644 --- a/baremetal/boot.bochsrc +++ b/baremetal/boot.bochsrc @@ -1,7 +1,7 @@ -# Configuration for the Bochs x86 CPU emulator to run the output of baremetal/boot.hex +# Configuration for the Bochs x86 CPU emulator to run baremetal Mu programs # See baremetal/boot.hex for more details. ata0-master: type=disk, path="disk.img", mode=flat, cylinders=20, heads=16, spt=63 # 10MB, 512 bytes per sector boot: disk -mouse: enabled=1, toggle=ctrl+f10 +# PS/2 mouse requires black magic that I don't know how to explain. log: - diff --git a/baremetal/boot.hex b/baremetal/boot.hex index deccff9d..47e56425 100644 --- a/baremetal/boot.hex +++ b/baremetal/boot.hex @@ -21,11 +21,11 @@ # # Since we start out in 16-bit mode, we need instructions SubX doesn't # support. -# This file contains just lowercase hex bytes and comments. It makes liberal -# use of: +# This file contains just lowercase hex bytes and comments. Programming it +# requires liberal use of: # - comments documenting expected offsets # - size checks on the emitted file (currently: 6144 bytes) -# - xxd to eyeball that offsets contain expected bytes +# - xxd to spot-check contents of specific offsets in the generated output # # Programs using this initialization: # - can't use any syscalls @@ -40,6 +40,8 @@ # a few magic constants: # Video memory: start is stored at 0x8128 # Keyboard buffer: starts at 0x8028 +# +# No mouse support. _That_ would require panicking. # Outline of this file with offsets and the addresses they map to at run-time: # -- 16-bit mode code @@ -63,7 +65,7 @@ # offset 1800 (address 9400): entrypoint for applications (don't forget to adjust survey_baremetal if this changes) # Other details of the current memory map: -# code: first two default-sized disk tracks into [0x00007c00, 0x00017800) +# code: first two default-sized disk tracks get loaded to [0x00007c00, 0x00017800) # stack grows down from 0x00070000 # see below # heap: [0x01000000, 0x02000000) @@ -76,7 +78,6 @@ # - loads the first sector (512 bytes) # from some bootable image (see the boot sector marker at the end of this file) # to the address range [0x7c00, 0x7e00) -# call this disk read #0 # - starts executing code at address 0x7c00 # offset 00 (address 0x7c00): @@ -100,7 +101,7 @@ bc 00 00 # sp <- 0x0000 # 14: - # disk read #1: load remaining sectors from first two tracks of disk into addresses [0x7e00, 0x17800) + # load remaining sectors from first two tracks of disk into addresses [0x7e00, 0x17800) b4 02 # ah <- 2 # read sectors from disk # dl comes conveniently initialized at boot time with the index of the device being booted b5 00 # ch <- 0 # cylinder 0 |