Command line 'writembr' tool implemented

* Implemented writembr tool used to update MBR area with easy boot
  loader starting the system from currently active partition;
* This work fixes #5595;
* This is result of GCI2011 task.

Signed-off-by: Siarzhuk Zharski <zharik@gmx.li>

build/jam/HaikuImage

@@ -60,7 +60,8 @@ SYSTEM_BIN = "[" addattr alert arp base64 basename bash bc beep bzip2
 	tput tr traceroute translate trash true truncate tsort tty
 	uname unchop unexpand unmount uniq unlink unrar unshar unzip unzipsfx
 	<bin>updatedb uptime urlwrapper useradd uudecode uuencode
-	vdir version vmstat waitfor watch wc wget whoami xargs xres yes
+	vdir version vmstat
+	waitfor watch wc wget whoami $(X86_ONLY)writembr xargs xres yes
 	zdiff zforce zgrep zip zipcloak <bin>zipgrep zipnote zipsplit zmore znew
 ;
 

src/bin/Jamfile

@@ -276,6 +276,7 @@ SubInclude HAIKU_TOP src bin screen_blanker ;
 SubInclude HAIKU_TOP src bin screenmode ;
 SubInclude HAIKU_TOP src bin sharutils ;
 SubInclude HAIKU_TOP src bin unrar ;
+SubInclude HAIKU_TOP src bin writembr ;
 SubInclude HAIKU_TOP src bin zic ;
 
 # RCS commands

src/bin/writembr/Jamfile

@@ -0,0 +1,28 @@
+SubDir HAIKU_TOP src bin writembr ;
+
+UsePrivateHeaders shared storage ;
+
+Application writembr :
+	writembr.cpp
+
+	: be $(TARGET_LIBSUPC+++) $(TARGET_LIBSTDC++)
+;
+
+# Assemble the MBR code, and convert it into a header file
+
+rule AssembleYasmBin object : source
+{
+	SEARCH on $(source) = $(SUBDIR) ;
+	MakeLocateDebug $(object) ;
+	Depends $(object) : $(source) ;
+}
+
+actions AssembleYasmBin
+{
+	$(HAIKU_YASM) -f bin -O5 -o $(1) $(2)
+}
+
+AssembleYasmBin [ FGristFiles mbr.bin ] : mbr.S ;
+
+DataFileToSourceFile [ FGristFiles MBR.h ] : [ FGristFiles mbr.bin ]
+	: kMBR : kMBRSize ;

src/bin/writembr/writembr.cpp

@@ -0,0 +1,125 @@
+/*
+ * Copyright 2012 Aleksas Pantechovskis, <alexp.frl@gmail.com>
+ * All rights reserved. Distributed under the terms of the MIT License.
+ */
+
+#include <fstream>
+#include <iostream>
+#include <sstream>
+#include <string.h>
+#include <string>
+
+#include <DiskDevice.h>
+#include <DiskDeviceRoster.h>
+#include <Path.h>
+#include <Volume.h>
+#include <VolumeRoster.h>
+
+#include "MBR.h"
+
+
+using namespace std;
+
+const char* kUsageMessage = \
+	"Usage: writembr [ device ] \n"
+	"#\tRewrites the MBR for the specified device.\n"
+	"#\tIf no device is specified, the boot device is used.\n"
+	"#\t--help shows this usage message\n";
+
+
+int
+main(int argc, char** argv)
+{
+	status_t result = B_ERROR;
+
+	if ((argc == 2 && strcmp(argv[1], "--help") == 0) || argc > 2) {
+		cerr << kUsageMessage;
+		return result;
+	}
+
+	BPath device;
+
+	if (argc == 2)
+		// user specified device for rewriting
+		device.SetTo(argv[1]);
+
+	else if (argc == 1) {
+		// no parameters specified, rewrite boot device
+		BVolumeRoster volumeRoster;
+		BVolume bootVolume;
+		if (volumeRoster.GetBootVolume(&bootVolume) != B_OK) {
+			cerr << "Can not find boot device" << endl;
+			return result;
+		}
+
+		BDiskDeviceRoster roster;
+		BDiskDevice bootDevice;
+		if(roster.FindPartitionByVolume(bootVolume, &bootDevice, NULL) != B_OK) {
+			cerr << "Can not find boot device" << endl;
+			return result;
+		}
+
+		bootDevice.GetPath(&device);
+	}
+
+
+	if (strcmp(device.Leaf(), "raw") != 0) {
+		cerr << device.Path() << " is not a raw device" << endl;
+		return result;
+	}
+
+	fstream fs;
+	fs.exceptions(ios::failbit | ios::badbit);
+
+	try {
+		
+		fs.open(device.Path(), fstream::in | fstream::out | fstream::binary);
+
+		unsigned char MBR[kMBRSize];
+		fs.read((char*)MBR, kMBRSize);
+		if (fs.gcount() < kMBRSize ) {
+			stringstream error;
+			error << "only " << fs.gcount() << " of " << kMBRSize
+				<< " bytes was read from " << device.Path();
+			throw fstream::failure(error.str());
+		}
+
+		// update only the code area and the MBR signature
+		memcpy(MBR, kMBR, 0x1be);
+		MBR[0x1FE] = kMBR[0x1FE];
+		MBR[0x1FF] = kMBR[0x1FF];
+
+		cerr << "About to overwrite the MBR boot code on " << device.Path()
+			<< "\nThis may disable any partition managers you have installed.\n"
+			<< "Are you sure you want to continue?\nyes/[no]: ";
+
+		string choice;
+		getline(cin, choice, '\n');
+		if (choice == "no" || choice == "" || choice != "yes")
+			throw fstream::failure("users cancel");
+			
+		cerr << "Rewriting MBR for " << device.Path() << endl;
+		
+		fs.seekg(0, ios::beg);
+		fs.write((char*)MBR, kMBRSize);
+		fs.flush();
+		
+		cerr << "MBR was written OK" << endl;
+		result = B_OK;
+
+	} catch (fstream::failure exception) {
+		cerr << "MBR was NOT written" << endl;
+		cerr << "Error: ";
+		if (fs.is_open())
+			cerr << exception.what();
+		else 
+			cerr << "Can't open " << device.Path();
+		cerr << endl;
+	}
+
+	if (fs.is_open())
+		fs.close();
+
+	return result;
+}
+