Add Master Boot Record partition scheme support.

Makefile

@@ -3,7 +3,7 @@ MAKEFILE_NOT_MEANT_FOR_SORTIX=1
 include compiler.mak
 include version.mak
 
-MODULES=libc libm dispd games mkinitrd mxmpp utils bench ext sortix
+MODULES=libc libm dispd games mkinitrd mxmpp utils bench ext mbr sortix
 
 ifndef SYSROOT
   SYSROOT:=$(shell pwd)/sysroot

mbr/.gitignore

@@ -0,0 +1 @@
+mbrfs

mbr/Makefile

@@ -0,0 +1,31 @@
+SOFTWARE_MEANT_FOR_SORTIX=1
+include ../compiler.mak
+include ../version.mak
+include ../dirs.mak
+
+OPTLEVEL?=-g -O2
+CXXFLAGS?=$(OPTLEVEL)
+
+CXXFLAGS:=$(CXXFLAGS) -Wall -Wextra -fno-exceptions -fno-rtti
+
+BINARIES:=mbrfs
+
+INSTALLBINARIES:=$(addprefix $(DESTDIR)$(BINDIR)/,$(BINARIES))
+
+all: $(BINARIES)
+
+.PHONY: all install uninstall clean
+
+install: all
+	mkdir -p $(DESTDIR)$(BINDIR)
+	install $(BINARIES) $(DESTDIR)$(BINDIR)
+
+uninstall:
+	rm -f $(INSTALLBINARIES)
+
+%: %.cpp
+	$(CXX) -std=gnu++11 $(CPPFLAGS) $(CXXFLAGS) $< -o $@
+
+clean:
+	rm -f $(BINARIES) *.o
+

mbr/mbrfs.cpp

@@ -0,0 +1,272 @@
+/*******************************************************************************
+
+    Copyright(C) Jonas 'Sortie' Termansen 2013.
+
+    This program is free software: you can redistribute it and/or modify it
+    under the terms of the GNU General Public License as published by the Free
+    Software Foundation, either version 3 of the License, or (at your option)
+    any later version.
+
+    This program is distributed in the hope that it will be useful, but WITHOUT
+    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+    FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+    more details.
+
+    You should have received a copy of the GNU General Public License along with
+    this program. If not, see <http://www.gnu.org/licenses/>.
+
+    mbrfs.cpp
+    Creates block devices representing master boot record partitions.
+
+*******************************************************************************/
+
+#include <endian.h>
+#include <errno.h>
+#include <error.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <fsmarshall.h>
+
+struct partition
+{
+	little_uint8_t flags;
+	little_uint8_t start_head;
+	little_uint16_t start_sector_cylinder;
+	little_uint8_t system_id;
+	little_uint8_t end_head;
+	little_uint16_t end_sector_cylinder;
+	little_uint32_t start_sector;
+	little_uint32_t total_sectors;
+} __attribute__((packed));
+
+struct partition_lba48
+{
+	little_uint8_t flags;
+	little_uint8_t signature1;
+	little_uint16_t start_sector_high;
+	little_uint8_t system_id;
+	little_uint8_t signature2;
+	little_uint16_t total_sectors_high;
+	little_uint32_t start_sector;
+	little_uint32_t total_sectors;
+} __attribute__((packed));
+
+struct mbr
+{
+	uint8_t bootstrap[436];
+	uint8_t unique_disk_id[10];
+	struct partition partitions[4];
+	uint8_t signature[2];
+} __attribute__((packed));
+
+bool memiszero(const void* mem, size_t size)
+{
+	for ( size_t i = 0; i < size; i++ )
+		if ( ((const uint8_t*) mem)[i] )
+			return false;
+	return true;
+}
+
+bool is_48bit_lba_partition(const struct partition* partition)
+{
+	const struct partition_lba48* partition_lba48 =
+		(const struct partition_lba48*) partition;
+	return partition_lba48->flags & 0x1 &&
+	       partition_lba48->signature1 == 0x14 &&
+	       partition_lba48->signature2 == 0xeb;
+}
+
+bool is_extended_partition(const struct partition* partition)
+{
+	return partition->system_id == 0x5 || partition->system_id == 0xF;
+}
+
+uint64_t partition_get_start(const struct partition* partition)
+{
+	if ( !is_48bit_lba_partition(partition) )
+		return partition->start_sector * 512;
+	const struct partition_lba48* partition_lba48 =
+		(const struct partition_lba48*) partition;
+	uint64_t lower = partition_lba48->start_sector;
+	uint64_t higher = partition_lba48->start_sector_high;
+	return ((lower << 48) + higher) * 512;
+}
+
+uint64_t partition_get_length(const struct partition* partition)
+{
+	if ( !is_48bit_lba_partition(partition) )
+		return partition->total_sectors * 512;
+	const struct partition_lba48* partition_lba48 =
+		(const struct partition_lba48*) partition;
+	uint64_t lower = partition_lba48->total_sectors;
+	uint64_t higher = partition_lba48->total_sectors_high;
+	return ((lower << 48) + higher) * 512;
+}
+
+bool is_partition_used(const struct partition* partition)
+{
+	if ( memiszero(partition, sizeof(*partition)) )
+		return false;
+	if ( !partition->system_id )
+		return false;
+	if ( !partition_get_start(partition) )
+		return false;
+	if ( !partition_get_length(partition) )
+		return false;
+	return true;
+}
+
+bool verify_is_partition(const struct partition* partition)
+{
+	if ( memiszero(partition, sizeof(*partition)) )
+		return true;
+	return true;
+}
+
+bool verify_is_mbr(const struct mbr* mbr)
+{
+	if ( memiszero(mbr, sizeof(*mbr)) )
+		return false;
+	if ( !(mbr->signature[0] == 0x55 && mbr->signature[1] == 0xAA) )
+		return false;
+	bool found_extended = false;
+	for ( size_t i = 0; i < 4; i++ )
+	{
+		const struct partition* partition = &mbr->partitions[i];
+		if ( !verify_is_partition(partition) )
+			return false;
+		if ( is_extended_partition(partition) )
+		{
+			if ( found_extended )
+				return false;
+			found_extended = true;
+		}
+	}
+	return true;
+}
+
+int create_partition_block_device(const char* path, int diskfd, off_t start,
+                                  off_t length)
+{
+	int ret = -1, mountfd, partfd;
+
+	// Make sure that is a file that we can mount bind us on.
+	if ( 0 <= (mountfd = open(path, O_RDONLY | O_CREAT, 0666)) )
+	{
+		// Create a file descriptor for our new partition.
+		if ( 0 <= (partfd = mkpartition(diskfd, start, length)) )
+		{
+			ret = fsm_fsbind(partfd, mountfd, 0);
+			close(partfd);
+		}
+		close(mountfd);
+	}
+
+	return ret;
+}
+
+void Usage(FILE* fp, const char* argv0)
+{
+	fprintf(fp, "Usage: %s [--probe] DEVICE...\n", argv0);
+}
+
+void Help(FILE* fp, const char* argv0)
+{
+	Usage(fp, argv0);
+}
+
+void Version(FILE* fp, const char* argv0)
+{
+	Usage(fp, argv0);
+}
+
+int main(int argc, char* argv[])
+{
+	const char* argv0 = argv[0];
+	bool probe = false;
+	for ( int i = 1; i < argc; i++ )
+	{
+		const char* arg = argv[i];
+		if ( arg[0] != '-' )
+			continue;
+		argv[i] = NULL;
+		if ( !strcmp(arg, "--") )
+			break;
+		if ( arg[1] != '-' )
+		{
+			while ( char c = *++arg ) switch ( c )
+			{
+			default:
+				fprintf(stderr, "%s: unknown option -- '%c'\n", argv0, c);
+				Usage(stderr, argv0);
+				exit(1);
+			}
+		}
+		else if ( !strcmp(arg, "--help") ) { Help(stdout, argv0); exit(0); }
+		else if ( !strcmp(arg, "--usage") ) { Usage(stdout, argv0); exit(0); }
+		else if ( !strcmp(arg, "--version") ) { Version(stdout, argv0); exit(0); }
+		else if ( !strcmp(arg, "--probe") )
+			probe = true;
+		else
+		{
+			fprintf(stderr, "%s: unknown option: %s\n", argv0, arg);
+			Usage(stderr, argv0);
+			exit(1);
+		}
+	}
+
+	if ( argc == 1 )
+	{
+		Usage(stderr, argv0);
+		exit(0);
+	}
+
+	for ( int i = 1; i < argc; i++ )
+	{
+		if ( !argv[i] )
+			continue;
+		const char* path = argv[i];
+		size_t path_len = strlen(path);
+		int fd = open(path, O_RDWR);
+		if ( fd < 0 )
+			error(1, errno, "`%s'", path);
+		struct mbr mbr;
+		if ( preadall(fd, &mbr, sizeof(mbr), 0) != sizeof(mbr) )
+			error(1, errno, "read: `%s'", path);
+		if ( !verify_is_mbr(&mbr) )
+		{
+			if ( probe )
+				exit(1);
+			error(1, 0, "`%s': No valid master boot record detected", path);
+		}
+		for ( size_t i = 0; !probe && i < 4; i++ )
+		{
+			struct partition* partition = &mbr.partitions[i];
+			if ( !is_partition_used(partition) )
+				continue;
+			// TODO: Support extended partitions!
+			if ( is_extended_partition(partition) )
+				continue;
+			uint64_t start = partition_get_start(partition);
+			uint64_t length = partition_get_length(partition);
+
+			size_t device_name_len = path_len + 1 + sizeof(size_t) * 3;
+			char* device_name = new char[device_name_len+1];
+			snprintf(device_name, device_name_len, "%sp%zu", path, i+1);
+
+			if ( create_partition_block_device(device_name, fd, start, length) != 0 )
+				error(1, errno, "creating `%s'", device_name);
+
+			printf("%s\n", device_name);
+
+			delete[] device_name;
+		}
+		close(fd);
+	}
+	return 0;
+}