I'm studying OS development and I use brokenthorn resource but with a little bit different tool, namely, I use CentOS, NASM and Qemu as a test/dev environment. I've been facing some issues while creating bootable img file with secondary loader.
I've got two files:
1. bootloader.bin which is first stage loader.
2. stage2.bin which is secondary loader.
In order to create bootable img file I do the following:
dd if=/dev/zero of=floppy.iso bs=1024 count=1440 -- Creating empty file
mkfs.vfat -F 12 floppy.iso --Creating file system in the file
dd if=../bin/bootloader.bin of=floppy.iso bs=512 count=1 conv=notrunc --Writing first loader to the boot sector
sudo mount -o loop floppy.iso /mnt/floppy/ -- Try to mount file system to write secondary loader using previously create FAT-12 files system.
In the last step I'm getting the following error:
mount: /dev/loop0 is write-protected, mounting read-only
mount: wrong fs type, bad option, bad superblock on /dev/loop0,
missing codepage or helper program, or other error
In some cases useful info is found in syslog - try
dmesg | tail or so.
Can you please help me to understand what I'm doing wrong and what other ways I can use to accomplish creating bootable img with file system on board.
Thanks!
I once stumbled upon the similar problem and this answer may be of help to you.
However I would strongly recommend you switching to bootloader like Grub and spend time and effort developing the actual OS of yours. For that I would reccomend grub resque as it's simple to use and allows to to quickly create ISO that you can either burn or feed to virtual machine. Otherwise, you may just drown in all these minor things like enabling protected mode, loading your stages and so on.
Related
What would be the simplest and most portable way (in the sense of only having to copy a few files to the target machine, like procdump is) to generate a kernel dump that has handle information?
procdump has the -mk option which generates a limited dump file pertaining to the specified process. It is reported in WinDbg as:
Mini Kernel Dump File: Only registers and stack trace are available. Most of the commands I try (!handle, !process 0 0) fail to read the data.
Seems that officially, windbg and kd would generate dumps (which would require kernel debugging).
A weird solution I found is using livekd with -ml: Generate live dump using native support (Windows 8.1 and above only).. livekd still looks for kd.exe, but does not use it :) so I can trick it with an empty file, and does not require kernel debugging. Any idea how that works?
LiveKD uses the undocumented NtSystemDebugControl API to capture the memory dump. While you can easily find information about that API online the easiest thing to do is just use LiveKD.
I feel very stupid asking this question, since originally I thought that I just have to enable a config statement and afterwards it runs smoothly. But I do not find the correct settings.
I have an embedded system and build a rootfs, linux kernel, u-boot, etc. using builtroot.
Now I want to implement remote attestation. Therefore I want the different steps during the boot process to extend the pcrs of my TPM 2.0 with the hash values of the next step.
I can run commands on the TPM using tpm2-tools when the system is booted.
I thought that u-boot, the kernel, etc. all got their tpm driver, so it should not be a problem for them to extend the pcr.
But how do I enable this?
Thank you so much for your answer.
I answer my question by myself in case there is someone with a similar problem.
The problem is solved by creating a U-Boot patch. To boot the operating system, uBoot run several steps. These are extended by my patch.
I copy the rootfs into memory, hash over it and extend a pcr with it. The following commands are needed:
$ tpm2 init // init the tpm
$ tpm2 start TPM2_SU_CLEAR // start the tpm
$ mmc read $loadaddr 0x800 0x80000 //read your rootfs
$ hash sha256 $loadaddr *0x10000000 // hash over it
$ tpm2 pcr_extend 4 0x10000000 // extend a pcr with the hashed value
Hopefully someone find it helpful. In case you find an error pls comment.
EDIT: added missing asterisk
I find if you create a compute engine (CentOS or Debian) machine and using gsutil to download (cp) a tgz file will cause a crcmod error...
$ gsutil cp gs://mybucket/data.tgz .
Copying gs://mybucket/data.tgz...
CommandException:
Downloading this composite object requires integrity checking with CRC32c, but
your crcmod installation isn't using the module's C extension, so the the hash
computation will likely throttle download performance. For help installing the
extension, please see:
$ gsutil help crcmod
To download regardless of crcmod performance or to skip slow integrity checks,
see the "check_hashes" option in your boto config file.
Currently I use "check_hashes = never" to bypass the check...
$ vi /etc/boto.cfg
[GSUtil]
default_project_id = 429100748693
default_api_version = 2
check_hashes = never
...
But, what is the root cause? and is there any good solution to solve the problem?
The object you're trying to download is a composite object, which basically means it was uploaded in parallel chunks. gsutil automatically does this when uploading objects larger than 150M (a configurable threshold), to provide better performance.
Composite objects only have a crc32c checksum (no MD5), so in order to validate data integrity when downloading composite objects, gsutil needs to perform a crc32c checksum. Unfortunately, the libraries distributed with Python don't include a compiled crc32c implementation, so unless you install a compiled crc32c, gsutil will use a non-compiled Python implementation of crc32c that's quite slow. That warning is printed to let you know there's a way to fix that performance problem: Please run:
gsutil help crcmod
and follow the instructions there for installing a compiled crc32c. It's pretty easy to do it, and worth the effort.
One other note: I strongly recommend against setting check_hashes = never in your boto config file. That will disable integrity checking, which means it's possible your download could get corrupted and you wouldn't know it. You want data integrity checking enabled to ensure you're working with correct data.
I am learning to write character device drivers from the Kernel Module Programming Guide, and used mknod to create a node in /dev to talk to my driver.
However, I cannot find any obvious way to remove it, after checking the manpage and observing that rmnod is a non-existent command.
What is the correct way to reverse the effect of mknod, and safely remove the node created in /dev?
The correct command is just rm :)
A device node created by mknod is just a file that contains a device major and minor number. When you access that file the first time, Linux looks for a driver that advertises that major/minor and loads it. Your driver then handles all I/O with that file.
When you delete a device node, the usual Un*x file behavior aplies: Linux will wait until there are no more references to the file and then it will be deleted from disk.
Your driver doesn't really notice anything of this. Linux does not automatically unload modules. Your driver wil simply no longer receive requests to do anything. But it will be ready in case anybody recreates the device node.
You are probably looking for a function rather than a command. unlink() is the answer. unlink() will remove the file/special file if no process has the file open. If any processes have the file open, then the file will remain until the last file descriptor referring to it is closed. Read more here: http://man7.org/linux/man-pages/man2/unlink.2.html
I am trying to make a 'dual core' RaspberryPi for a project I am working on. I had followed this tutorial by Simon Cox. Unfortunately I could not get the two RasPi to talk to each other. (This was using Hydra as the process manager)
After looking more carefully at the MPICH installers guide, which can be found here, I tried to use the -phrase to pass the passphrase I had created. However I could not find it as part of the hydra commands. So I re-installed with smpd and after many compiling attempts. I configured with:
/configure -prefix=/home/pi/mpich-install --with-pm=smpd --with-pmi=smpd
I also had to install libbsl-dev to get the MD5 that smpd requires. I also exported the path that the commands mpiexec and mpicc are in. After setting the passphrase I copied the image to a second SD card and put it in a second RasPi. I then set up the passphrase using ssh-keygen.
I was able to run the cpi program on the master Pi and the slave Pi individually but when I tried to run multiple processes on both at the same time I got the error
Fatal error in MPI_Init: Other MPI error, error stack:
MPIR_Init``_thread(392).................:
MPID_Init(139)........................: channel initialization failed
MPIDI_CH3_Init(38)....................:
MPID_nem_init(196)....................:
MPIDI_CH3I_Seg_commit(366)............:
MPIU_SHMW_Hnd_deserialize(324)........:
MPIU_SHMW_Seg_open(863)...............:
MPIU_SHMW_Seg_create_attach_templ(637): open failed - No such file or directory
Can someone please suggest how I can either fix this problem or get the RaspberryPis to communicate using MPICH?
Thanks
E.Lee
If anyone else has this problem make sure your hosts don't have the same name!
You can change it by following this tutorial http://raspi.tv/2012/how-to-change-the-name-of-your-raspberry-pi-new-hostname