Some patches to GNU/Linux kernel

Here are some patches to GNU/Linux which aims to:

• Fix some bugs in the kernel.
• Make it possible to compile the kernel with many compiler warnings flags, because several compiler warnings are useful but can't be used in vanilla kernel code because of "false-positives". The compiler-flag configuration is in make_allmodconfig.sh script.
• Enable using clang to compile the kernel, which reports different warnings from gcc, by using LLVMLinux patches (http://llvm.linuxfoundation.org/index.php/Main_Page). NB: according to ClangBuiltLinux/linux#219 LLVMLinux seems to be now deprecated. A list of issues of building Linux with clang is available at https://github.com/ClangBuiltLinux/linux/issues.

How to build a kernel with these patches?

Short answer, in a terminal:

./apply_patches.sh && ./make_allmodconfig.sh "-j$(nproc)"

This command line will clone GNU/Linux git repository, apply patches and build a kernel with clang using a parallel build.

In order to explain what each script does, here is a workflow when updating the patches with a more recent version of GNU/Linux:

• ./apply_patches.sh : clone GNU/Linux git repository in linux/ and apply patches from patches/ directory
• cd linux && git fetch origin && git rebase origin/master : update GNU/Linux to latest master branch and rebase the patches on top of it

• JOBS="$(nproc)" ./test_make_gcc_clang.sh : compile the GNU/Linux once with gcc, then with clang, and if both succeed, record the output in a file named make.log_clang_YYY-MM-DD (with the current date).

  • If there were errors during the build, fix them in new patches and build again

  • It is possible to use make_allmodconfig.sh script to make debugging some issues easier. All parameters given to this script are transmitted to the underlying make command:

    # Build files in kernel/ directory using gcc
    HOSTCC=gcc CC=gcc ./make_allmodconfig.sh kernel/
    
    # Build init/main.o using clang (which is the default compiler)
    HOSTCC=clang CC=clang ./make_allmodconfig.sh init/main.o

• ./export_patches.sh : export the patches back to patches/ directory, using reorganize_patches.py to organize them in sub-directories.

How are the patches organized?

All the patches lies in subdirectories inside patches/:

• patches/bug/ patches fix some bugs which make the compiling fail.
• patches/constify/ patches add const keyword in some places.
• patches/frama-c/ patches modify the kernel so that Frama-C can be used.
• patches/llvmlinux/ patches are related to clang compatibility (c.f. http://llvm.linuxfoundation.org/ ).
• patches/maybe_upstreamable/ patches have a very low priority of being sent upstream.
• patches/not_upstreamble/ patches have no chance to go upstream (they do not comply with coding rules, introduce dirty code, etc.).
• patches/plugin/ patches implement some GCC plugins to analyze the code at compile time.
• patches/pragma/ patches introduce #pragma statement, mostly to ignore warnings when it is expected.
• patches/printf/ patches add __printf attribute to printf-like functions so that potential format string vulnerabilities are detected at build time.
• patches/rejected/ patches were rejected (sometimes silently) by kernel developers.
• patches/sent-upstream/ patches have already been sent upstream even though they were not yet applied.
• patches/typo/ patches fix typos which are sprinkled all around in the kernel.

Moreover there are two important files to apply the patches:

• patches/series define the order used to apply the patches
• patches/upstream-commit.hash contains the GNU/Linux commit ID which is used as the base to apply the patches on.

Upstreamed patches

Patches are occasionally sent upstream. Here are some which got successfully applied:

• https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=c680e41b3a2e944185c74bf60531e3d316d3ecc4 "eventpoll: fix uninitialized variable in epoll_ctl"
• https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=ea6edfbcefec1fcfdb826a1d5a054f402dfbfb24 "mac802154: fix typo in header guard"
• https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=d43698e8abb58a6ac47d16e0f47bb55f452e4fc4 "firmware/ihex2fw.c: restore missing default in switch statement"
• https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=5202efe544c279be152f44f2821010ff7b2d7e5b "coredump: use from_kuid/kgid when formatting corename"
• https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=3958b79266b14729edd61daf9dfb84de45f4ec6d "configfs: fix kernel infoleak through user-controlled format string"
• https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=0fd64291031d3587753b8adc53123b277855c777 "drm/amdgpu: increment queue when iterating on this variable."

Other upstreamed patches can be found using for example https://github.com/torvalds/linux/commits/master?author=fishilico