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Replace bios with bootloader, don't use bootsector

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Instead of using the bootsector to load a bootloader, just put the
bootloader in the ROM and call it a day. It looks for a file on the SD
card in the root directory named `kernel.bin` and loads it into memory.

This is not a perfect solution, as the kernel will grow larger and the
kernel load address will have to change. At this point I could add back
the bootloader, but that is for later.

Also the bootloader is just a copy of the kernel, so that can be trimmed
down a lot.
This commit is contained in:
Byron Lathi
2022-04-19 10:34:19 -05:00
parent f664d59497
commit f3c7ac9696
42 changed files with 1295 additions and 232 deletions
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34
sw/bootloader/link.ld
View File

@@ -1,17 +1,35 @@
MEMORY
{
ZP: start = $0, size = $100, type = rw, define = yes;
BOOTSECT: start = $1000, size = $200, file = %O;
SDRAM: start = $200, size = $7cf0, type = rw, define = yes;
ROM: start = $8000, size = $8000, file = %O;
}
SEGMENTS {
ZEROPAGE: load = ZP, type = zp, define = yes;
DATA: load = BOOTSECT, type = rw, define = yes;
BSS: load = BOOTSECT, type = bss, define = yes;
HEAP: load = BOOTSECT, type = bss, optional = yes;
STARTUP: load = BOOTSECT, type = ro, start = $1000;
CODE: load = BOOTSECT, type = ro, start = $105a;
RODATA: load = BOOTSECT, type = ro;
SIGN: load = BOOTSECT, type = ro, start = $11fe;
DATA: load = ROM, type = rw, define = yes, run = SDRAM;
BSS: load = SDRAM, type = bss, define = yes;
HEAP: load = SDRAM, type = bss, optional = yes;
STARTUP: load = ROM, type = ro;
ONCE: load = ROM, type = ro, optional = yes;
CODE: load = ROM, type = ro;
RODATA: load = ROM, type = ro;
VECTORS: load = ROM, type = ro, start = $FFFA;
}
FEATURES {
CONDES: segment = STARTUP,
type = constructor,
label = __CONSTRUCTOR_TABLE__,
count = __CONSTRUCTOR_COUNT__;
CONDES: segment = STARTUP,
type = destructor,
label = __DESTRUCTOR_TABLE__,
count = __DESTRUCTOR_COUNT__;
}
SYMBOLS {
# Define the stack size for the application
__STACKSIZE__: value = $0200, type = weak;
__STACKSTART__: type = weak, value = $0800; # 2k stack
}