The Linux scheduler (on recent Linux kernels, e.g. 3.0 at least) is scheduling schedulable tasks or simply tasks. A task may be : a single-threaded process (e.g. created by fork without any thread library) any thread inside a multi-threaded process (including its main thread), in particular Posix threads (pthreads) kernel tasks, which are started internally … Read more
The really simplified answer is that the kernel runs in kernel space, and normal programs run in user space. User space is basically a form of sand-boxing — it restricts user programs so they can’t mess with memory (and other resources) owned by other programs or by the OS kernel. This limits (but usually doesn’t … Read more
A trap is an exception in a user process. It’s caused by division by zero or invalid memory access. It’s also the usual way to invoke a kernel routine (a system call) because those run with a higher priority than user code. Handling is synchronous (so the user code is suspended and continues afterwards). In … Read more
The kernel allocates PIDs in the range of (RESERVED_PIDS, PID_MAX_DEFAULT). It does so sequentially in each namespace (tasks in different namespaces can have the same IDs). In case the range is exhausted, pid assignment wraps around. Some relevant code: Inside alloc_pid(…) for (i = ns->level; i >= 0; i–) { nr = alloc_pidmap(tmp); if (nr … Read more
It allows tools like sparse to tell kernel developers that they’re possibly using an untrusted pointer (or a pointer that may be invalid in the current virtual address mapping) improperly.
You have a number of issues with your code. The main ones are discussed individually below. The HLT instruction will halt the current CPU waiting for the next interrupt. You do have interrupts enabled by this point. After the first interrupt (keystroke) the code after HLT will be executed. It will start executing whatever random … Read more
You can not make kernel-mode device drivers in C# as the runtime can’t be safely loaded into ring0 and operate as expected. Additionally, C# doesn’t create binaries suitable for loading as device drivers, particularly regarding entry points that drivers need to expose. The dependency on the runtime to jump in and analyze and JIT the … Read more
From the netfilter FAQ: The answer unfortunately is: No. Now you might think ‘but what about libiptc?’. As has been pointed out numerous times on the mailinglist(s), libiptc was NEVER meant to be used as a public interface. We don’t guarantee a stable interface, and it is planned to remove it in the next incarnation … Read more
When they say map, they mean that each kernel thread is assigned to a certain number of user mode threads. Kernel threads are used to provide privileged services to applications (such as system calls ). They are also used by the kernel to keep track of what all is running on the system, how much … Read more
Another option is to use an ICE or JTAG controller, and GDB. This ‘hardware’ solution is especially used with embedded systems. But for instance QEMU offers similar features: start QEMU with a GDB ‘remote’ stub which listens on ‘localhost:1234’ : qemu -s …, then with GDB, you open the kernel file vmlinux compiled with debug … Read more