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.

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.

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."