I've written an application for an embedded linux project, and I want my application to display a particular menu when the user inserts a USB drive. I'm programming the application in C++ with Qt.
My system doesn't have d-bus but it is using udev. It seems to me that udev is the "proper" way to do this detection, but seems complicated.
Can anyone point me in the right direction to get started with this? Is there a way to do it without udev, and if not, is there a good "getting started" guide for udev I could use? I really don't need much functionality, just a way for my application to be notified when a drive is inserted (and enough info for my app to mount the drive).
Thanks
Marlon
The section "libudev - Monitoring Interface" of this document http://www.signal11.us/oss/udev/
should get you started.
Instead of a while(1) loop and a sleep, just make a function with that stuff and then set up a periodic Qt timer to call it every half second or whatever.
Related
What is the simplest way to export data from a bare-bones OS?
I’m developing some assignments for my Computer Architecture course that require students to time different segments of code as accurately as possible. My idea is to insert the code to be timed right into the "Bare Bones"/"Hello World" tutorial from the OSDev wiki (http://wiki.osdev.org/Bare_Bones), which will effectively run the code under test right inside a minimal OS kernel.
This technique works rather well; but, at the moment, my only output option is the VGA text mode. I would like to be able to save the experiment results so the students can analyze/graph the data.
I’m currently installing the “mini-OS” onto a USB flash drive and booting from the flash drive. My original idea was to use BIOS to dump the experiment data back onto the USB drive; but, it looks like calling BIOS routines from protected mode is non-trivial (i.e., requires switching to real or V86 mode).
All I need to do is dump raw binary data somewhere that another machine can read it. I don't need a file system or anything fancy like that. Is there a relatively simple way to access the USB flash drive (or some other external device), or will I need to find/write a complete USB driver or network driver stack? Or, is there a simpler solution?
This post (Real mode BIOS routine and Protected Mode) mentions PwnOS; but the link to the code is broken.
USB drivers are very hard. However, as you mentioned network drivers, you might want to look into serial ports. They are much easier to program than USB.
The osdev wiki should have enough information about this topic.
I have ARM-based device with linux on-board. Its very difficult to flash custom kernel for some reasons (uBoot cant load kernel via tftp or something else)
I need to test my custom kernel.
So, idea is - replace kernel in memory. How do you think, is it possible?
Tell me any suggestions please.
Take a look at this link
It's for a project called Ksplice that allows one to patch a running kernel.
At one point this code was open, but Oracle bought it... So they may have closed it up and made it cost money. If that's the case, look around and see if you can find the formerly open code in the wild...
So, I know Linux kernel is quite "heavy" when considering lower scale embedded systems, but currently but we're a 2 man team trying to see how to create our own embedded system.
I'm the one in charge of all software (the other guy is a HW guy), and thus I would like to re-use existing libraries and frameworks as much as possible, and I would like to bounce off some ideas with gurus around here.
I am fairly comfortable in Linux, but the booting and initialization process is new to me, and I need to dive in to that soon enough. Any book recommendations are welcome as well!
I haven't designed any embedded systems before.. Only own some ARM dev boards (beagleboard and raspberry pi).
Current I have prototype of the software running on beagleboard already, and now we're thinking how to minimize the cost, and to create something our own..
It's a system connected to the internet, and I need to run a tiny web server with some scripting support. Performance wise I don't think it needs to be too powerful.
I would like to minimize all bootloader etc work, since I'm a one man SW team, and just concentrate on the application itself.
Of course I understand that I need to configure our kernel for this, but this is indeed why I thought selecting some SoC would be good, since they usually have some linux and bootloaders ready..
First I thought that Cirrus EP9301 would be perfect, since it seems to be a good package, and not very expensive.. But it seems that it's already in end-of-life, and also support for this is very bad (people on the cirrus forums constantly complain about it).
Are there some good choices for this kind of project, which would enable us "easily" to get linux kernel up and running, with still maintaining some kind of decent BOM (hopefully 20USD or so) ?
Your hardware guy should already know this, but go with an existing reference design. Take the raspberry pi, the beagleboard/bone, open-rd, or any number of other existing systems and clone the part you need. As a result the linux porting will be a matter of removing what you are not using from the reference design instead of adding new stuff and hoping it works. If you go with flat pack parts you can do the work in your garage, if you go with bgas you need the equipment for that or pay someone to do it. (can you tell yet that I hate bgas?).
Is linux a requirement, if not that opens the door to a lot more devices using freertos or chibios or a number of other solutions. the stm32f4 discovery board for example is $20, uses what can barely be called a microcontroller for all the features it has (cortex-m4). Supposedly possible to run uclinux on a cortex-m, but definitely possible to run any number of rtoses and have an ip stack, etc. stellaris (ti.com) has a number of eval boards, one/some with ethernet already (use as a reference design). You can also take the wiznet approach (or a spi ethernet) and use any microcontroller (puts you into the avr/msp430 level and price range). Bang for buck the cortex-m's are good, arm based so comfortable to work with, etc.
Using linux if you are already not an experienced at porting to an embedded platform, and dont want to learn that on this go around, I would definitely go with a clone of an existing design, leverage as much as you can from a project with folks that are experienced at porting linux to a platform. If need be take an existing board (beagle/raspi/openrd) and go through the motions of porting to the platform with the cheat sheet of having access to an existing port, see if you cant get uboot ported and linux booting, etc. (dont really need uboot at all, that is possibly an unnecessary complication, just get dram up and pass the atags, etc to linux and just branch to it, pretty easy to launch linux from bare metal).
You could probably do worse than taking the Broadcom BCM2835 - used on the Raspberry Pi - as your starting point - especially if you want to avoid kernel and boot-loader work and a source of reference schematics. If this proves too expensive, check out other devices in the Broadcom range.
A few bits of advice
You probably want some flash rather than a MMC card interface for production use. eMMC is an option. NAND flash is a nightmare due to rapid component obsolescence and the need to get own and dirty with the MTD drivers.
USB Ethernet will be easier to integrate than a controller hanging off a general purpose bus, but won't perform as well. SmSC seems to be popular source for either
You could also have a look at the work that Olimex is doing with their linux boards. Perhaps even order a som and then combine it with other external components.
I haven't used Visual C++ before, however I'm starting a project that will require me to use it.
I want to get raw data from the USB. Almost every website tells me that I need to write a device driver for it first... Well I know that!
But I want to start simple - with my wireless mouse receiver, which obviously has a driver installed, which works. How can I access the contents which that receiver provides to the computer, using Visual C++?
This is a great project - a ton of fun too. Perhaps you can find some resources from this related post. I go into a lot more detail there. But I'll answer a little bit here too.
First off, you definitely don't want to write a driver. The time of writing drivers is mostly behind us. :) At least for what you are trying to do in particular. As I detail in the aforementioned post, we now mostly use HID descriptors to communicate with HID (usb) devices instead of writing drivers. This is awesome because it seriously simplifies the task.
I will highly recommend you or anyone in the same position use the libusbx library. It makes things very simple and straightforward in terms of communicating directly with HID devices. Again, see the post for a much more involved answer, but this should do it. Good luck!
I've spent a lot of time developing an operating system and working on my low level boot loader. But now I want to take some time off my operating system while not leaving the low-level environment and doing something involving security.
So I chose to build my own standard password utility following the pre-boot authentication scheme. Since I want the software to be at least a little portable I want it to use as little external support as is possible. I figured that I'd be best if I somehow managed to 'hook' into the bios somewhere between the self checks and the int 19 bootstrap from within a running real mode OS.
However finding information on how to modify the bios code proved to be impossible. I've found nothing on how to achieve the before mentioned. I have only found pages describing how to flash your bios.
Does anyone know how I can read/write bios code? Or can someone provide links to pages that describe this?
I know that it's not only possible to brick my device but it is also likely, I'm aware of the risk and willing to take it.
Pinczakko's articles on BIOS reverse engineering are a great place to start looking at this. There was also a book published by the same author but it is now out of print.
I'm not sure if this approach is the best approach towards a secure boot, but the articles on this site are very detailed and should point you towards a method for modifying your BIOS firmware.
I'm not really sure what you are trying to achieve, but:
The BIOS is completely hardware specific - each manufacturer will have their own mechanism for updating / flashing BIOS and so trying to come up with a portable mechanism for updating a BIOS is destined for failure. For example when using Bochs you "update" the BIOS by specifying a different BIOS ROM image.
If you want to modifty / write your own BIOS then its going to be completely specific to that hardware. Your best bet would be to start with something like Bochs as its open source - as you can take a look at the source code for the BIOS (and easily test / debug it) you stand a reasonable chance of understanding the BIOS code and modifying it into something that works, however I suspect this isn't what you are trying to do.
Why not just perform this authentication as your OS boots? If you want to protect the data then you should encrypt it and require that the user supply log in / supply the decryption key on startup.
If you were thinking of working with "legacy" PC BIOS, I would dissuade you from trying for many of the reasons Justin mentioned: 1) legacy BIOS is PC vendor-specific; 2) it is closed source and proprietary; 3) there are no industry standards defining legacy BIOS interfaces for extending the system as you are trying to do.
On the other hand, if you have access to a UEFI-based BIOS PC, you may be able to write your own PEI/DXE driver(s) to implement such a feature. This will at least point you in the right direction:
http://sourceforge.net/apps/mediawiki/tianocore/index.php?title=Welcome
Intel Press book on the topic: Beyond BIOS
Regarding the practicality of read/writing the BIOS, you'll need to identify the SPI part containg the BIOS and get a ROM burner. The SPI part may or may not be socketed; if it is not socketed, you'll need a soldering iron and be able to create a socket/header for the part. You obviously do not want to embark on this project with your primary computer system. Perhaps you could find an older system or a reference board.