[RFC PATCH 0/9] Ksplice: Rebootless kernel updates

From: Jeffrey Brian Arnold
Date: Sat Sep 13 2008 - 00:50:29 EST

These RFC patches add support for Ksplice [1], a rebootless update system,
to the kernel. I previously mentioned Ksplice to the LKML a few months
ago [2]. The basic idea is that Ksplice can apply an update to a running
Linux kernel based only on a source code patch and the original kernel
source. The Ksplice technical overview document [3] describes the design
of Ksplice and one of the ways that Ksplice has been evaluated.

[1] http://web.mit.edu/ksplice
[2] http://lkml.org/lkml/2008/4/23/330
[3] http://web.mit.edu/ksplice/doc/ksplice.pdf

The interface between the Ksplice kernel component and the userspace
utilities is documented in patch 6/9 of this series. The current
implementation of the userspace utilities is available from the Ksplice
website and the Ksplice git repository [4]. The Ksplice userspace
utilities transparently support both "integrated" operation (updating a
kernel patched with this patch series) and "standalone" operation
(updating a completely unmodified kernel).

[4] http://web.mit.edu/ksplice/ksplice.git

This series of patches depends upon the -ffunction-sections and
-fdata-sections patches proposed by Denys Vlasenko (for reasons unrelated
to Ksplice) a few weeks ago [5]. Ksplice's 'run-pre matching' process is
much simpler if the original kernel was compiled with -ffunction-sections
and -fdata-sections, and so we require these compiler options for this
patch series. We think that requiring these options in order to build a
kernel with integrated Ksplice support is reasonable, but we welcome

[5] http://lkml.org/lkml/2008/8/24/159

Denys Vlasenko has already submitted patches to the LKML for allowing all
architectures to compile with -ffunction-sections and -fdata-sections [5];
he has said that he will later submit patches making it possible to run a
kernel with these options [6]. In the meantime, we have a patch that
creates a CONFIG_FUNCTION_DATA_SECTIONS option for x86 and ARM [7], but we
have not polished this patch since Denys Vlasenko is already preparing a
similar change.

[6] http://lkml.org/lkml/2008/8/26/288
[7] http://web.mit.edu/ksplice/tmp/function-data-sections.patch

We're open to suggestions and are available to make whatever changes
people would like to see. (Also, I'll be at the Plumbers Conference next
week and would be happy to chat with anyone about Ksplice in person).

Jeff Arnold


Documentation/ksplice.txt | 247 +++++
arch/Kconfig | 14 +
arch/arm/Kconfig | 1 +
arch/arm/kernel/ksplice-arch.c | 79 ++
arch/x86/Kconfig | 1 +
arch/x86/kernel/ksplice-arch.c | 91 ++
arch/x86/mm/init_32.c | 7 +-
arch/x86/mm/init_64.c | 5 +-
include/linux/kallsyms.h | 13 +
include/linux/ksplice.h | 202 ++++
include/linux/module.h | 27 +
kernel/Makefile | 2 +
kernel/kallsyms.c | 19 +
kernel/ksplice.c | 1997 ++++++++++++++++++++++++++++++++++++++++
kernel/module.c | 144 ++-
kernel/sched.c | 1 +
17 files changed, 2810 insertions(+), 50 deletions(-)
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