On Mon, Oct 28, 2013 at 09:58:58AM +0100, Jan Kiszka wrote: > CC: Rob Landley <rob@xxxxxxxxxxx> > CC: linux-doc@xxxxxxxxxxxxxxx > Signed-off-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx> > --- > Documentation/gdb-kernel-debugging.txt | 159 +++++++++++++++++++++++++++++++++ > 1 file changed, 159 insertions(+) > create mode 100644 Documentation/gdb-kernel-debugging.txt > > diff --git a/Documentation/gdb-kernel-debugging.txt b/Documentation/gdb-kernel-debugging.txt > new file mode 100644 > index 0000000..944f2d2 > --- /dev/null > +++ b/Documentation/gdb-kernel-debugging.txt > @@ -0,0 +1,159 @@ > +Debugging kernel and modules via gdb > +==================================== > + > +The kernel debugger kgdb, hypervisors like QEMU or JTAG-based hardware > +interfaces allow to debug the Linux kernel and its modules during runtime > +using gdb. Gdb comes with a powerful scripting interface for python. The > +kernel provides a collection of helper scripts that can simplify typical > +kernel debugging steps. This is a short tutorial about how to enable and use > +them. It focuses on QEMU/KVM virtual machines as target, but the examples can > +be transferred to the other gdb stubs as well. > + > + > +Requirements > +------------ > + > + o gdb 7.2+ (recommended: 7.4+) with python support enabled (typically true > + for distributions) > + > + > +Setup > +----- > + > + o Create a virtual Linux machine for QEMU/KVM (see www.linux-kvm.org and > + www.qemu.org for more details). For cross-development, > + http://landley.net/aboriginal/bin keeps a pool of machine images and > + toolchains that can be helpful to start from. > + > + o Build the kernel with CONFIG_DEBUG_INFO and CONFIG_KALLSYMS enabled, but > + leave CONFIG_DEBUG_INFO_REDUCED off. > + > + o Install that kernel on the guest. > + > + Alternatively, QEMU allows to boot the kernel directly using -kernel, > + -append, -initrd command line switches. This is generally only useful if > + you do not depend on modules. See QEMU documentation for more details on > + this mode. > + > + o Enable the gdb stub of QEMU/KVM, either > + - at VM startup time by appending "-s" to the QEMU command line > + or > + - during runtime by issuing "gdbserver" from the QEMU monitor > + console > + > + o cd /path/to/linux-build > + > + o Start gdb: gdb vmlinux > + > + Note: Some distros may restrict auto-loading of gdb scripts to known safe > + directories. In case gdb reports to refuse loading vmlinux-gdb.py, add > + > + add-add-auto-load-safe-path /path/to/linux-build Only one "add-" should be enough :) Btw, gdb is nice enough to tell me: $ gdb vmlinux Reading symbols from /w/kernel/linux-2.6/vmlinux...done. warning: File "/w/kernel/linux-2.6/scripts/gdb/vmlinux-gdb.py" auto-loading has been declined by your `auto-load safe-path' set to "$debugdir:$datadir/auto-load". To enable execution of this file add add-auto-load-safe-path /w/kernel/linux-2.6/scripts/gdb/vmlinux-gdb.py line to your configuration file "/home/boris/.gdbinit". To completely disable this security protection add set auto-load safe-path / line to your configuration file "/home/boris/.gdbinit". For more information about this security protection see the "Auto-loading safe path" section in the GDB manual. E.g., run from the shell: info "(gdb)Auto-loading safe path" Other than that, that's a very cool stuff and I'll make sure to be using it the next time. Acked-by: Borislav Petkov <bp@xxxxxxx> -- Regards/Gruss, Boris. Sent from a fat crate under my desk. Formatting is fine. -- -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
