mirror of
https://github.com/dynup/kpatch
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af17774865
Allowing the user to build without needing to be root. If the needed packages aren't installed, the error messages will tell the user what to install.
115 lines
3.7 KiB
Plaintext
115 lines
3.7 KiB
Plaintext
====================
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README for kpatch
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====================
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OVERVIEW
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kpatch is a tool for the generation and application of kernel
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modules that patch a running Linux kernel while in operation,
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without requiring a reboot. This is very valuable in cases
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where critical workloads, which do not have high availability via
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scale-out, run on a single machine and are very downtime
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sensitive or require a heavyweight approval process and
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notification of workload users in the event of downtime.
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INSTALLATION
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The default install prefix is in /usr/local.
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make
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sudo make install
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QUICK START
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NOTE: While kpatch is designed to work with any recent Linux
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kernel on any distribution, the "kpatch build" command currently
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only works on Fedora.
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First, use diff to make a source patch against the kernel tree, e.g. foo.patch.
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Then:
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kpatch build foo.patch
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sudo insmod kpatch.ko kpatch-foo.ko
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Voila, your kernel is patched.
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LICENSE
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kpatch is under the GPLv2 license.
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License
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as published by the Free Software Foundation; either version 2
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of the License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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STATUS
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kpatch is currently is early development. For now, it should _not_ be used
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in production environments until significantly more testing on various
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patches and environments is conducted.
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DEPENDENCIES
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kpatch-build tools require libelf library and development headers to be installed.
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See GOTCHAS below.
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GOTCHAS
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The version of elfutils (namely libelf) that ship with most distros as of
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the time of this writing, have a bug in libelf that is exposed by kpatch.
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elfutils-0.158 or higher contains the fix.
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The specific commit is 88ad5ddb71bd1fa8ed043a840157ebf23c0057b3.
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git://git.fedorahosted.org/git/elfutils.git
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HOWTO
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An example script for automating the patch module generation is
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kpatch-build/kpatch-build. The script is written for Fedora but should
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be adaptable to other distributions with limited changes.
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The primary steps in the patch module generation process are:
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- Building the unstripped vmlinux for the kernel
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- Patching the source tree
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- Rebuilding vmlinux and monitoring which objects are building rebuilt.
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These are the "changed objects".
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- Recompile each changed object with -ffunction-sections -fdata-sections
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resulting in the changed patched objects
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- Unpatch the source tree
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- Recompile each changed object with -ffunction-sections -fdata-sections
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resulting in the changed original objects
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- Use create-diff-object to analyze each original/patched object pair
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for patchability and generate an output object containing modified
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sections
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- Link all the output objects in a into a cumulative object
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- Use add-patches-section to add the .patches section that the
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core kpatch module uses to determine the list of functions that need
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to be redirected using ftrace
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- Generate the patch kernel module
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- Use link-vmlinux-syms to hardcode non-exported kernel symbols
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into the symbol table of the patch kernel module
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DEMONSTRATION
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A demonstration of kpatch is available on Youtube:
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http://www.youtube.com/watch?v=WeSmG-XirC4
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This demonstration completes each step in the HOWTO section in a manual
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fashion. However, from a end-user perspective, most of these steps will
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be hidden away in scripts (eventually).
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