What are differences, pros and cons of the three referred real time OS framework, extensions or patches? I want to measure a CPU timestamp counter (TSC), time in nanosecond everytime when a data frame or an ack frame of Wifi is sent or received. And I realized that one of three real time technique is required…
Tag: kernel
How to trap memory reads and writes using sigsegv?
How do I trick linux into thinking a memory read/write was successful? I am writing a C++ library such that all reads/writes are redirected and handled transparently to the end user. Anytime a variable is written or read from, the library will need to catch that request and shoot it off to a hardware simulati…
How to limit privileged user access at Linux Kernel level?
I found this answer on learning Linux Kernel Programming and my question is more specific for the security features of the Linux Kernel. I want to know how to limit privileged users or process’s access rights to other processes and files in contrast to full access of root. Until now I found: user and gr…
How does C distinguish between a byte long character and a 2 byte long character?
I have this sample code: First run: Well I think this is all expected as p is 1 byte long character defined in ASCII and I am reading 3 bytes. (2 p’s and Line break) In the terminal, again I see 2 characters. Now let’s try with a character that is 2 bytes long: What I do not understand is,
Bulk message transfer USB Linux
I am at the very beginning to write my own Linux Driver for a dds generator. I want to write 2 bulk messgages to the generator when der Kernel call the probe function. But I dont know how to call the usb_bulk_msg function. I hope you could me. hsync Answer Kernel is kinda self-explanatory project, so usually …
Linux kernel : logging to a specific file
I am trying to edit the linux kernel. I want some information to be written out to a file as a part of the debugging process. I have read about the printk function. But i would like to add text to a particular file (file other from the default files that keep debug logs). To cut it short: I would
Initialization of number of free pages in each order in a memory zone
I am going through the memory initialization code in linux kernel, and I can see the number of free pages for each order and migration type for the each memory zone in a memory node is set to 0. I am not able to figure out how the list is set to the proper state, as in which order has
System calls : difference between sys_exit(), SYS_exit and exit()
What is the difference between SYS_exit, sys_exit() and exit()? What I understand : The linux kernel provides system calls, which are listed in man 2 syscalls. There are wrapper functions of those syscalls provided by glibc which have mostly similar names as the syscalls. My question : In man 2 syscalls, ther…
undefined reference to system call added to kernel
After adding the system call to kernel I tried to compile the kernel. It ran for 2 hours and at the end threw undefined reference to <system call added by me> Any idea what had happened. Kernel 3.9.3 Steps followed are – Get kernel codes from www.kernel.org. wget http://www.kernel.org/pub/linux/ke…
New linux kernels, no lsm using lkms, no kernel hooks now what?
For security reasons, the kernel ceased to export characters necessary for writing security modules in the form of loadable kernel modules (Linux Kernel Module, LKM) starting with version 2.6.24. And you can’t export sys_call_table, again for security reasons. But then, how can I filter filesystem reque…