feat: add write support to I/O stack (disk, ESP, FAT32)

.github/workflows/build.yml

@@ -29,4 +29,4 @@ jobs:
         run: podman run --rm --read-only -v "$PWD:/workspace" -w /workspace dev make all
       - name: test
         timeout-minutes: 1
-        run: podman run --rm --read-only -v "$PWD:/workspace" -w /workspace dev make test_loader emu_test test uki_test kexec_test
+        run: podman run --rm --read-only -v "$PWD:/workspace" -w /workspace dev make test

.gitignore

@@ -5,8 +5,8 @@
 bootloader_emu
 busybox
 busybox.tar.bz2
-demo.img
 demo_uki.img
+demo.img
 dependencies.make
 disk
 hello
@@ -19,5 +19,7 @@ kexec.cpio
 mini_kexec
 purgatory.h
 serial.log
+test_fat32
+test_fat32_disk
 test_loader
 uki_disk

Makefile

@@ -1,11 +1,13 @@
 MAKEFLAGS += --no-builtin-rules
 .SILENT:
-.PHONY: all clean distclean test uki_test kexec_test
+UNIT_TESTS := loader fat32
+.PHONY: all clean distclean test unit_tests qemu_test uki_test kexec_test emu_test $(UNIT_TESTS:%=run_test_%)
 
 CC := gcc
 CC_X86 := x86_64-linux-gnu-gcc
 
 CFLAGS := -std=c23 -Os -g -Wall -Wextra -Wdeclaration-after-statement -Werror -fpack-struct -fno-builtin
+CFLAGS_USER := $(CFLAGS) -DNO_STATIC_INTERNALS
 CFLAGS_M16 := $(CFLAGS) -m16 -march=i386 -nostdinc -ffreestanding -fno-pic -fno-stack-protector -fno-asynchronous-unwind-tables -fno-unwind-tables -fno-exceptions -ffunction-sections -fdata-sections
 
 LD := ld
@@ -22,14 +24,18 @@ OBJDUMP_FLAGS_M16 := -m i8086 -M intel
 
 all: disk uki.efi kexec.cpio bootloader_emu kernel
 
+test: unit_tests emu_test qemu_test uki_test kexec_test
+
+unit_tests: $(UNIT_TESTS:%=run_test_%)
+
 clean:
 	git clean -e '!kernel' -e '!kernel.tar.xz' -e '!busybox.tar.bz2' -fX
 
 distclean:
 	git clean -fX
 	rm -rf kernel_headers busybox
 
-test: disk
+qemu_test: disk
 	echo 'running $< in qemu'
 	./run_vm.sh -n '$<' | tee serial.log
 	grep -F 'Found GPT disk: 01234567-ABCD-0123-ABCD-0123456789AB' < serial.log > /dev/null
@@ -70,23 +76,37 @@ dependencies.make: *.c
 
 include dependencies.make
 
-bootloader.o: main.o io_buf.o lib.o gpt.o fat32.o loader.o linux.o
+bootloader.o: main.emu.o io_buf.emu.o lib.emu.o gpt.emu.o fat32.emu.o loader.emu.o linux.emu.o
 	echo 'linking $^ -> $@'
 	$(LD) -r -o '$@' $^
-	$(OBJCOPY) --keep-global-symbol=init '$@'
+	$(OBJCOPY) --keep-global-symbol=bootloader_init '$@'
 	$(OBJDUMP) -h '$@'
 
 bootloader_emu: bootloader.o bios_services_emu.o
 	echo 'linking $^ -> $@'
 	$(CC) -o '$@' $^
 
-test_loader: lib.o gpt.o fat32.o io_buf.o
+test_loader: lib.emu.o gpt.emu.o fat32.emu.o io_buf.emu.o loader.emu.o
+
+test_fat32: lib.emu.o gpt.emu.o fat32.emu.o io_buf.emu.o
+
+test_fat32_inputs := test_fat32_disk
+
+test_fat32_disk: make_test_fat32_disk.sh
+	echo 'creating $@'
+	./$< '$@'
 
 test_%: test_%.o
 	echo 'linking $^ -> $@'
 	$(CC) -o '$@' $^
-	echo 'running $@'
-	./'$@'
+
+define UNIT_TEST_RULE
+run_test_$(1): test_$(1) $$(test_$(1)_inputs)
+	echo 'running $$<'
+	./'$$<' $$(test_$(1)_inputs)
+endef
+
+$(foreach unit,$(UNIT_TESTS),$(eval $(call UNIT_TEST_RULE,$(unit))))
 
 disk: make_disk.sh mbr.bin bootloader.bin kernel initrd.cpio
 	echo 'creating $@'
@@ -157,7 +177,13 @@ uki.efi: pe_inject.py uki_base.efi kernel_stub.bin pe_loader.bin
 
 %.o:
 	echo 'compiling $< -> $@'
-	$(CC) $(CFLAGS) -c '$<' -o '$@'
+	$(CC) $(CFLAGS_USER) -c '$<' -o '$@'
+	$(OBJDUMP) -h '$@'
+
+%.emu.o: %.o
+	echo 'prefixing $< -> $@'
+	$(OBJCOPY) --prefix-symbols=bootloader_ '$<' '$@'
+	$(OBJCOPY) --redefine-sym bootloader_memset=memset '$@'
 	$(OBJDUMP) -h '$@'
 
 %.m16.o:

bios_services.c

@@ -78,6 +78,46 @@ int16 disk_read(uint8 *buffer, uint16 sectors, uint32 lba)
 	return 0;
 }
 
+int16 disk_write(const uint8 *buffer, uint16 sectors, uint32 lba)
+{
+	static struct disk_address_packet disk_address_packet;
+
+	uint8 result;
+	uint8 error;
+	uint16 offset;
+	uint16 segment;
+
+	if (sectors > 64) return -1;
+
+	if ((uint32) buffer > 0x000fffff) return -1;
+	offset  = ((uint32) buffer & 0x0000ffff);
+	segment = ((uint32) buffer & 0x000f0000) >> 4;
+
+	disk_address_packet = (struct disk_address_packet) {
+		.size           = 0x10,
+		.reserved       = 0x00,
+		.sectors        = sectors,
+		.buffer_offset  = offset,
+		.buffer_segment = segment,
+		.lba_low        = lba,
+		.lba_high       = 0x00000000
+	};
+
+	__asm__ __volatile__ ( "int $0x13\nsetb %[res]\nmov %%ah, %[err]"
+	                       : [res] "=r" (result), [err] "=r" (error)
+	                       : "a" (0x4300), "d" (0x0080), "S" (&disk_address_packet)
+	                       : );
+
+	if (result != 0) {
+		print_str("disk write failed with ERR ");
+		print_hex_be(&error, 0x0001);
+		print_str("\r\n");
+		return -1;
+	}
+
+	return 0;
+}
+
 int16 mem_move(uint8 *dst, const uint8 *src, uint32 len)
 {
 	static struct global_descriptor_table global_descriptor_table[6];

bios_services.h

@@ -1,6 +1,11 @@
-void halt();
-void reset();
-void print_char(char c);
-int16 disk_read(uint8 *buffer, uint16 sectors, uint32 lba);
-int16 mem_move(uint8 *dst, const uint8 *src, uint32 len);
-void exec_kernel();
+#pragma once
+
+#include "prefix.h"
+
+void PREFIX(halt)();
+void PREFIX(reset)();
+void PREFIX(print_char)(char c);
+int16 PREFIX(disk_read)(uint8 *buffer, uint16 sectors, uint32 lba);
+int16 PREFIX(disk_write)(const uint8 *buffer, uint16 sectors, uint32 lba);
+int16 PREFIX(mem_move)(uint8 *dst, const uint8 *src, uint32 len);
+void PREFIX(exec_kernel)();

bios_services_emu.c

@@ -5,6 +5,8 @@
 #include <unistd.h>
 #include <fcntl.h>
 
+#define PREFIX(name) bootloader_##name
+
 #include "types.h"
 #include "bios_services.h"
 
@@ -15,7 +17,7 @@
 static int debug = 0;
 static int disk_fd = -1;
 
-void init();
+void bootloader_init();
 
 int main(int argc, char **argv)
 {
@@ -29,34 +31,34 @@ int main(int argc, char **argv)
 		exit(1);
 	}
 
-	disk_fd = open(argv[1], O_RDONLY);
+	disk_fd = open(argv[1], O_RDWR);
 	if (disk_fd == -1) {
 		perror("open");
 		exit(1);
 	}
 
-	init();
+	bootloader_init();
 }
 
-void halt()
+void bootloader_halt()
 {
 	debug_printf();
 	while (1) pause();
 }
 
-void reset()
+void bootloader_reset()
 {
 	debug_printf();
 	exit(0);
 }
 
-void print_char(char c)
+void bootloader_print_char(char c)
 {
 	if (c != 0) fputc(c, stdout);
 	else fflush(stdout);
 }
 
-int16 disk_read(uint8 *buffer, uint16 sectors, uint32 lba)
+int16 bootloader_disk_read(uint8 *buffer, uint16 sectors, uint32 lba)
 {
 	uint32 len;
 	uint32 offset;
@@ -88,13 +90,45 @@ int16 disk_read(uint8 *buffer, uint16 sectors, uint32 lba)
 	return 0;
 }
 
-int16 mem_move(uint8 *dst, const uint8 *src, uint32 len)
+int16 bootloader_disk_write(const uint8 *buffer, uint16 sectors, uint32 lba)
+{
+	uint32 len;
+	uint32 offset;
+	ssize_t len_written;
+
+	debug_printf("buffer=0x%08lx, sectors=%u, lba=%u)", (size_t) buffer, sectors, lba);
+
+	if (sectors > 64) return -1;
+
+	len    = sectors * 0x0200;
+	offset = lba * 0x0200;
+
+	while (len) {
+		len_written = pwrite(disk_fd, buffer, len, offset);
+
+		if (len_written == -1) {
+			perror("pwrite");
+			return -1;
+		} else if (len_written == 0) {
+			fprintf(stderr, "unexpected zero-length write\n");
+			return -1;
+		}
+
+		len -= len_written;
+		offset += len_written;
+		buffer += len_written;
+	}
+
+	return 0;
+}
+
+int16 bootloader_mem_move(uint8 *dst, const uint8 *src, uint32 len)
 {
 	debug_printf("dst=0x%08lx, src=0x%08lx, len=%u)", (size_t) dst, (size_t) src, len);
 	return 0;
 }
 
-void exec_kernel()
+void bootloader_exec_kernel()
 {
 	debug_printf();
 	exit(0);