Build glibc Patchs

Summary

This repository provides a method for working around various issues seen in older linux distributions glibc libraries. The glibc libraries are so core to the behaviour of a system that they rarely get updated in older distributions, so we provide ways to patch those libraries.

Issues Currently Patched

• BZ-19329 (bugzilla report) is a significant sporadic issue in all glibc versions up to 2.34.
• BZ-17645 (bugzilla report) is a significant performance issue on all glibc versions up to 2.35.

Caution

Note that all processes on your machine share glibc libraries so these patches will apply to the system as a whole and not just to MathWorks products. Most applications and programs on your computer are likely to use glibc. Care should be taken to ensure you apply the correct version of the patch to your system based on the current version of glibc. Applying the wrong version could make your whole system unusable. Try installing the patch inside a disposable docker container first to test your install procedure – you can find instructions below.

You can find the major version of glibc you are running using, for example:

$ ldd --version ldd

ldd (Ubuntu GLIBC 2.31-0ubuntu9.2) 2.31
Copyright (C) 2020 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
Written by Roland McGrath and Ulrich Drepper.

More specificity on version can be found using:

$ dpkg-query --show libc6:amd64
libc6:amd64     2.31-0ubuntu9.2

Build procedure

To build a specific version of glibc on your own machine you will need a version of docker that supports BUILDKIT (this feature was added in version 18.09). This repository holds patches for all glibc versions on debian derived systems from 2.24 to 2.33 inclusive, as well as a version for RHEL 8 with glibc 2.28. Running the build process takes between 10 and 60 mins based on the compute ability of your system.

Pre-built artefacts

This repository runs a number of github actions to build artefacts for specific Debian, Ubuntu and RHEL versions and it is likely that these are all that is needed to patch your system. You can download the matching packages for your system from the release area.

Building

1. Clone this repository locally and change folder into the repository

    git clone https://github.com/mathworks/build-glibc-bz-19329-patch.git
    cd build-glibc-bz19329-patch

2. Build (using docker build) for the distribution and specific release you want to patch. Select the distribution and specific distribution version by setting the build argument DIST_BASE and DIST_TAG. DIST_BASE:DIST_TAG must be one of

   debian:9	debian:stretch
   debian:10	debian:buster
   debian:11	debian:bullseye
   ubuntu:18.04	ubuntu:bionic
   ubuntu:20.04	ubuntu:focal
   ubuntu:21.04	ubuntu:hirsute
   almalinux:8.4
   almalinux:8.5

Note: You should only patch RHEL 8.4 or 8.5 if you cannot get glibc-2.28-189.1.el8 onto the machine via the normal upgrade procedures.

Here is an example build command (for debian:9):

DOCKER_BUILDKIT=1 docker build --build-arg DIST_BASE=debian --build-arg DIST_TAG=9 --output type=local,dest=. .

The build command will use a local container image of the specific distribution requested, or pull one if none exists. To ensure you are building the most up-to-date versions of the libraries you should docker pull the specific DIST_BASE:DIST_TAG distribution before building. The build progresses and finally will copy the new debian package to a local folder called ./build/. In that folder will be a libc6 debian package that can be installed on the appropriate distribution. For example having built for debian:9, debian:10, debian:11, and ubuntu:20.04 the folder contains:

$ ls -x build/
libc6_2.24-11+deb9u4.custom_amd64.deb
libc6_2.27-3ubuntu1.4.custom_amd64.deb
libc6_2.28-10.custom_amd64.deb
libc6_2.31-13+deb11u2.custom_amd64.deb

When building for Almalinux you must use the Dockerfile.rhel rather than the debian Dockerfile so the build command is

DOCKER_BUILDKIT=1 docker build --build-arg DIST_TAG=8.5 -f Dockerfile.rhel --output type=local,dest=. .

If you have access to a RHEL subscription you should be able to adapt the Dockerfile.rhel trivially to include the correct repos to support building the sources directly in a ubi8 container.

Overriding package version string

The package version extension defaults to .DIST_BASE.DIST_TAG.custom, where ${DIST_TAG} defaults to the VERSION_CODENAME found in /etc/os-release. This version can be overridden by setting the build argument PKG_EXT.

E.g., on Debian 11, the default packages will be named like libc6_2.31-13+deb11u2.debian.bullseye.custom_amd64.deb. If built with --build-arg PKG_EXT=.test, the package would instead be named libc6_2.31-13+deb11u2.test_amd64.deb.

Installing the built packages

Please note the caution above - take care not to install the wrong package version compared to the rest of your system. Consider trying the install in a disposable docker container first.

Installing a specific debian package on a system is as simple as executing

dpkg -i libc6_2.24-11+deb9u4.custom_amd64.deb

For your system replace the debian package with the correct version that matches the glibc you already have (see for example the output from dpkg-query --show libc6:amd64)

Installing the rpms on a UBI / Almalinux system requires you to install several of the packages at once, for example

dnf install -y  glibc-2.28-164.custom.el8.x86_64.rpm  \
                glibc-common-2.28-164.custom.el8.x86_64.rpm \
                glibc-minimal-langpack-2.28-164.custom.el8.x86_64.rpm

Installing in a Docker container

When building a docker container with a specific patch, assuming the patch is in the top level docker context folder you would have a Dockerfile like

FROM debian:9

COPY libc6_2.24-11+deb9u4.custom_amd64.deb /tmp/
RUN dpkg -i /tmp/libc6_2.24-11+deb9u4.custom_amd64.deb