What is KGDB in Linux?
KGDB is a debugger for the Linux kernel and the kernels of NetBSD and FreeBSD. It requires two machines that are connected via a serial connection. The target machine (the one being debugged) runs the patched kernel and the other (host) machine runs gdb. The GDB remote protocol is used between the two machines.
How do I enable KGDB?
To enable CONFIG_KGDB you should look under Kernel hacking ‣ Kernel debugging and select KGDB: kernel debugger.
What is kernel debugging in Linux?
A kernel debugger is a debugger present in some operating system kernels to ease debugging and kernel development by the kernel developers. Linux kernel; No kernel debugger was included in the mainline Linux tree prior to version 2.6. 26-rc1 because Linus Torvalds didn’t want a kernel debugger in the kernel.
How do I debug a Linux kernel module?
Setup
- Build the kernel with CONFIG_GDB_SCRIPTS enabled, but leave CONFIG_DEBUG_INFO_REDUCED off.
- Install that kernel on the guest, turn off KASLR if necessary by adding “nokaslr” to the kernel command line.
- Enable the gdb stub of QEMU/KVM, either.
- cd /path/to/linux-build.
- Start gdb: gdb vmlinux.
- Attach to the booted guest:
How do I open a kernel debugger?
Debugger host setup
- Open WinDbg Preview.
- Select File > Start debugging > Attach to kernel > Net.
- Provide the same port number and key as in bcdedit. Press OK.
- Press Break (or use Ctrl + Break ) to enter a debugging session.
How does the Linux kernel work?
The Linux kernel mainly acts as a resource manager acting as an abstract layer for the applications. The applications have a connection with the kernel which in turn interacts with the hardware and services the applications. Linux is a multitasking system allowing multiple processes to execute concurrently.
What type of kernel does Linux use?
monolithic kernel
Different Types of Kernels Linux is a monolithic kernel while OS X (XNU) and Windows 7 use hybrid kernels. Let’s take a quick tour of the three categories so we can go into more detail later. A microkernel takes the approach of only managing what it has to: CPU, memory, and IPC.
How is KGDB used in the Linux kernel?
Kgdb is intended to be used as a source level debugger for the Linux kernel. It is used along with gdb to debug a Linux kernel.
Do you need KGDB for early boot debugging?
Early boot debugging requires a KGDB I/O driver that supports early debugging and the driver must be built into the kernel directly. Kgdb I/O driver configuration takes place via kernel or module parameters which you can learn more about in the in the section that describes the parameter kgdboc.
How to unregister kernel Hook points in KGDB?
If you unconfigure a kgdb I/O driver, kgdb will unregister all the kernel hook points. All kgdb I/O drivers can be reconfigured at run time, if CONFIG_SYSFSand CONFIG_MODULESare enabled, by echo’ing a new config string to /sys/module/ /parameter/ . The driver can be unconfigured by passing an empty string.
Is there a source level debugger for kdb?
Kdb is not a source level debugger, although you can set breakpoints and execute some basic kernel run control. Kdb is mainly aimed at doing some analysis to aid in development or diagnosing kernel problems. You can access some symbols by name in kernel built-ins or in kernel modules if the code was built with CONFIG_KALLSYMS.
