Add preliminary bootloader

This bootloader right now just prints the letter A, but should be
capable of reading blocks from the SD card into memory.

sw/bootloader/Makefile

@@ -0,0 +1,41 @@
+CC=cl65
+CFLAGS=-T -t none -I. --cpu "65C02" -DNO_SD_INIT
+test: CFLAGS=-T -t sim65c02 -I.
+LDFLAGS=-C link.ld -m $(NAME).map
+SIM=sim65
+SIMARGS=-v -c -x 1000000
+
+NAME=bootloader
+
+BIN=$(NAME).bin
+HEX=$(NAME).hex
+
+LISTS=lists
+
+SRCS=$(wildcard *.s) $(wildcard *.c)
+SRCS+=$(filter-out $(wildcard tests/*), $(wildcard **/*.s)) $(filter-out $(wildcard tests/*), $(wildcard **/*.c))
+OBJS+=$(patsubst %.s,%.o,$(filter %s,$(SRCS)))
+OBJS+=$(patsubst %.c,%.o,$(filter %c,$(SRCS)))
+
+all: $(HEX)
+
+$(HEX): $(BIN)
+	objcopy --input-target=binary --output-target=ihex $(BIN) $(HEX)
+	
+
+$(BIN): $(OBJS)
+	$(CC) $(CFLAGS) $(LDFLAGS) $(OBJS) -o $@
+
+%.o: %.c $(LISTS)
+	$(CC) $(CFLAGS) -l $(LISTS)/$<.list -c $< -o $@
+
+%.o: %.s $(LISTS)
+	$(CC) $(CFLAGS) -l $(LISTS)/$<.list -c $< -o $@
+
+$(LISTS):
+	mkdir -p $(addprefix $(LISTS)/,$(sort $(dir $(SRCS))))
+
+.PHONY: clean
+clean:
+	rm -rf $(OBJS) $(BIN) $(HEX) $(LISTS) $(NAME).map
+

sw/bootloader/bios_calls.h

@@ -0,0 +1,8 @@
+#ifndef _BIOS_CALLS_H
+#define _BIOS_CALLS_H
+
+#include <stdint.h>
+
+void sd_readblock(uint16_t addr, void* buf);
+
+#endif

sw/bootloader/bios_calls.s

@@ -0,0 +1,23 @@
+.export _sd_readblock
+
+.autoimport
+
+.importzp sreg
+
+; sreg is the pointer to store the data
+; a/y is the block address
+; send command 17 with the block address of 00/y/a
+
+; void sd_readblock(uint16_t addr, void* buf);
+
+_sd_readblock:
+    sta sreg        ; move buf pointer to sreg
+    stx sreg+1
+
+    jsr popax       ; move addr to a/y
+    tya
+
+    ldx #$1         ; call interrupt 1
+    brk
+
+    rts

sw/bootloader/boot.s

@@ -0,0 +1,26 @@
+; We need to to read the boot sector from the
+; SD card, verify the last 2 bytes, then jump to the
+; beginning of it.
+
+.include "zeropage.inc"
+
+.import _load_bootsect
+
+.export _init, _boot
+
+.segment "STARTUP"
+
+_init:  jmp _boot
+
+.segment "CODE"
+
+_boot:  ldx #$ff
+        txs
+        cld
+
+        jsr _load_bootsect
+        jmp $1000
+
+.segment "SIGN"
+.byte $55
+.byte $aa

sw/bootloader/io.inc65

@@ -0,0 +1 @@
+../kernel/devices/io.inc65

sw/bootloader/link.ld

@@ -0,0 +1,17 @@
+MEMORY
+{
+  ZP:  start = $0,    size = $100,  type = rw, define = yes;
+  BOOTSECT: start = $1000, size = $200, 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;
+}
+

sw/bootloader/main.c

@@ -0,0 +1,11 @@
+#include <stdint.h>
+
+#include "bios_calls.h"
+#include "uart.h"
+
+//Should probably do this in asm
+void load_bootsect() {
+    uart_txb_block('A');
+    for (;;);
+    return;
+}

sw/bootloader/uart.h

@@ -0,0 +1 @@
+../kernel/devices/uart.h

sw/bootloader/uart.s

@@ -0,0 +1 @@
+../kernel/devices/uart.s