# git rev-parse -q --verify 4f30a60aa78410496e5ffe632a371c00f0d83a8d^{commit}
# git fetch -q -n -f git://fs.ozlabs.ibm.com/kernel/linus master
# git rev-parse -q --verify 4f30a60aa78410496e5ffe632a371c00f0d83a8d^{commit}
4f30a60aa78410496e5ffe632a371c00f0d83a8d
# git checkout -q -f -B kisskb 4f30a60aa78410496e5ffe632a371c00f0d83a8d
# git clean -qxdf
# < git log -1
# commit 4f30a60aa78410496e5ffe632a371c00f0d83a8d
# Merge: 74858abbb103 a5161eeef97c
# Author: Linus Torvalds <torvalds@linux-foundation.org>
# Date:   Tue Aug 4 15:12:02 2020 -0700
# 
#     Merge tag 'close-range-v5.9' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux
#     
#     Pull close_range() implementation from Christian Brauner:
#      "This adds the close_range() syscall. It allows to efficiently close a
#       range of file descriptors up to all file descriptors of a calling
#       task.
#     
#       This is coordinated with the FreeBSD folks which have copied our
#       version of this syscall and in the meantime have already merged it in
#       April 2019:
#     
#         https://reviews.freebsd.org/D21627
#         https://svnweb.freebsd.org/base?view=revision&revision=359836
#     
#       The syscall originally came up in a discussion around the new mount
#       API and making new file descriptor types cloexec by default. During
#       this discussion, Al suggested the close_range() syscall.
#     
#       First, it helps to close all file descriptors of an exec()ing task.
#       This can be done safely via (quoting Al's example from [1] verbatim):
#     
#             /* that exec is sensitive */
#             unshare(CLONE_FILES);
#             /* we don't want anything past stderr here */
#             close_range(3, ~0U);
#             execve(....);
#     
#       The code snippet above is one way of working around the problem that
#       file descriptors are not cloexec by default. This is aggravated by the
#       fact that we can't just switch them over without massively regressing
#       userspace. For a whole class of programs having an in-kernel method of
#       closing all file descriptors is very helpful (e.g. demons, service
#       managers, programming language standard libraries, container managers
#       etc.).
#     
#       Second, it allows userspace to avoid implementing closing all file
#       descriptors by parsing through /proc/<pid>/fd/* and calling close() on
#       each file descriptor and other hacks. From looking at various
#       large(ish) userspace code bases this or similar patterns are very
#       common in service managers, container runtimes, and programming
#       language runtimes/standard libraries such as Python or Rust.
#     
#       In addition, the syscall will also work for tasks that do not have
#       procfs mounted and on kernels that do not have procfs support compiled
#       in. In such situations the only way to make sure that all file
#       descriptors are closed is to call close() on each file descriptor up
#       to UINT_MAX or RLIMIT_NOFILE, OPEN_MAX trickery.
#     
#       Based on Linus' suggestion close_range() also comes with a new flag
#       CLOSE_RANGE_UNSHARE to more elegantly handle file descriptor dropping
#       right before exec. This would usually be expressed in the sequence:
#     
#             unshare(CLONE_FILES);
#             close_range(3, ~0U);
#     
#       as pointed out by Linus it might be desirable to have this be a part
#       of close_range() itself under a new flag CLOSE_RANGE_UNSHARE which
#       gets especially handy when we're closing all file descriptors above a
#       certain threshold.
#     
#       Test-suite as always included"
#     
#     * tag 'close-range-v5.9' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux:
#       tests: add CLOSE_RANGE_UNSHARE tests
#       close_range: add CLOSE_RANGE_UNSHARE
#       tests: add close_range() tests
#       arch: wire-up close_range()
#       open: add close_range()
# < /opt/cross/kisskb/korg/gcc-8.1.0-nolibc/aarch64-linux/bin/aarch64-linux-gcc --version
# < /opt/cross/kisskb/korg/gcc-8.1.0-nolibc/aarch64-linux/bin/aarch64-linux-ld --version
# < git log --format=%s --max-count=1 4f30a60aa78410496e5ffe632a371c00f0d83a8d
# < make -s -j 24 ARCH=arm64 O=/kisskb/build/linus-rand_arm64-randconfig_arm64-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/aarch64-linux/bin/aarch64-linux-  randconfig
KCONFIG_SEED=0xB3B4FD45
# Added to kconfig CONFIG_PREVENT_FIRMWARE_BUILD=y
# < make -s -j 24 ARCH=arm64 O=/kisskb/build/linus-rand_arm64-randconfig_arm64-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/aarch64-linux/bin/aarch64-linux-  help
# make -s -j 24 ARCH=arm64 O=/kisskb/build/linus-rand_arm64-randconfig_arm64-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/aarch64-linux/bin/aarch64-linux-  olddefconfig
# make -s -j 24 ARCH=arm64 O=/kisskb/build/linus-rand_arm64-randconfig_arm64-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/aarch64-linux/bin/aarch64-linux-  
/kisskb/src/drivers/gpu/drm/rockchip/cdn-dp-core.c:1123:12: warning: 'cdn_dp_resume' defined but not used [-Wunused-function]
 static int cdn_dp_resume(struct device *dev)
            ^~~~~~~~~~~~~
/kisskb/src/drivers/mailbox/imx-mailbox.c:611:12: warning: 'imx_mu_resume_noirq' defined but not used [-Wunused-function]
 static int imx_mu_resume_noirq(struct device *dev)
            ^~~~~~~~~~~~~~~~~~~
/kisskb/src/drivers/mailbox/imx-mailbox.c:601:12: warning: 'imx_mu_suspend_noirq' defined but not used [-Wunused-function]
 static int imx_mu_suspend_noirq(struct device *dev)
            ^~~~~~~~~~~~~~~~~~~~
Completed OK
# rm -rf /kisskb/build/linus-rand_arm64-randconfig_arm64-gcc8
# Build took: 0:06:20.976653