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+[RFC] CONFIG_FORCE_MINIMALLY_SANE_CONFIG=y (was: Re: [RFC PATCH] x86/kconfig:
+Sanity-check config file during oldconfig)
+
+   [Posted January 20, 2016 by corbet]
+
+   From:   Ingo Molnar <mingo-AT-kernel.org>
+   To:   Borislav Petkov <bp-AT-suse.de>, Linus Torvalds
+   <torvalds-AT-linux-foundation.org>, Greg Kroah-Hartman
+   <gregkh-AT-linuxfoundation.org>, Andrew Morton
+   <akpm-AT-linux-foundation.org>
+   Subject:   [RFC] CONFIG_FORCE_MINIMALLY_SANE_CONFIG=y (was: Re: [RFC
+   PATCH] x86/kconfig: Sanity-check config file during oldconfig)
+   Date:   Tue, 19 Jan 2016 09:20:22 +0100
+   Message-ID:   <20160119082022.GB18237@gmail.com>
+   Cc:   Michal Marek <mmarek-AT-suse.cz>,
+   =?iso-8859-1?Q?M=E5ns_Rullg=E5rd?= <mans-AT-mansr.com>, Markus
+   Trippelsdorf <markus-AT-trippelsdorf.de>, Thomas Voegtle
+   <tv-AT-lio96.de>, linux-kernel-AT-vger.kernel.org, x86-ml
+   <x86-AT-kernel.org>, Peter Zijlstra <a.p.zijlstra-AT-chello.nl>, Thomas
+   Gleixner <tglx-AT-linutronix.de>, Andrew Morton
+   <akpm-AT-linux-foundation.org>, Linus Torvalds
+   <torvalds-AT-linux-foundation.org>, Jiri Olsa <jolsa-AT-redhat.com>,
+   Arnaldo Carvalho de Melo <acme-AT-infradead.org>,
+   =?iso-8859-1?Q?Fr=E9d=E9ric?= Weisbecker <fweisbec-AT-gmail.com>
+   Archive-link:   [19]Article, [20]Thread
+
+
+( I've Cc:-ed Linus, Greg and Andrew, to see whether doing something like what I
+
+  suggest below in the x86 architecture would be acceptable. )
+
+* Borislav Petkov <bp@suse.de> wrote:
+
+> From: Borislav Petkov <bp@suse.de>
+>
+> Thomas Voegtle reported that doing oldconfig with a .config which has
+> CONFIG_MICROCODE enabled but BLK_DEV_INITRD disabled prevents the
+> microcode loading mechanism from being built.
+>
+> Add a short script which hooks into the "make oldconfig" handling and
+> sanity-checks the config file for that discrepancy. It issues a message
+> which should hopefully sensitize the user to that issue and point her
+> into the right direction.
+
+So it would be much better to just do such things automatically, and only allow
+'safe' combination of options - without the user having to do anything.
+
+The guiding principle is: kernel configuration is (still...) our worst barrier o
+f
+entry for new users/developers, and kernel configuration still sucks very much
+from a UI point of view.
+
+In fact our kernel configuration UI and workflow is still so bad that it's an
+effort to stay current even with a standalone and working .config, even for
+experienced kernel developers...
+
+Adding a (somewhat hacky) post processing script and forcing users to read
+something 99% of them does not have a clue about is a step in the wrong directio
+n,
+IMHO.
+
+So can we do something more intelligent instead, such as modifying the Kconfigs
+in
+a way that it's not possible to have CONFIG_MICROCODE enabled while BLK_DEV_INIT
+RD
+is disabled?
+
+I'd be fine with a 'select BLK_DEV_INITRD' for example. If people doing super
+specialized setups disagree because they really need that nonsensical combinatio
+n
+of config options, they can complain and provide a better solution.
+
+In fact on x86 I'd suggest we go farther than that and add a core set of selects
+
+that can be disabled only through a sufficiently scary "I really know I'm doing
+something utmost weird" (and default disabled) config option.
+
+From my own randconfig testing I can give a core list of must-have kernel option
+s,
+without which most distros (Fedora, RHEL, Ubuntu, SuSE) won't boot properly:
+
++config FORCE_MINIMALLY_SANE_CONFIG
++       bool
++       default y
++
++       # so that capset() works (sudo, etc.):
++       select SECURITY
++       select SECURITY_CAPABILITIES
++       select BINFMT_ELF
++
++       select SYSFS
++       select SYSFS_DEPRECATED
++       select PROC_FS
++       select FUTEX
++
++       # newer systemd silently relies on the presence of the epoll system call
+:
++       select EPOLL
++       select ANON_INODES
++
++       # newer systemd silently hangs durig early init without these:
++       select PROC_SYSCTL
++       select SYSCTL
++       select POSIX_MQUEUE
++       select POSIX_MQUEUE_SYSCTL
++
++       # systemd needs this syscall:
++       select FHANDLE
++
++       # systemd needs devtmpfs: "systemd[1]: Failed to mount devtmpfs at /dev:
+ No such device"
++       select DEVTMPFS
++
++       # systemd needs tmpfs: "systemd[1]: Failed to mount tmpfs at /sys/fs/cgr
+oup: No such file or
+directory"
++       select SHMEM
++       select TMPFS
++
++       # systemd needs timerfd syscalls: "[    8.198625] systemd[1]: Failed to
+create timerfd: Function
+not implemented^"
++       select TIMERFD
++
++       # systemd needs signalfd support: "[   45.536725] systemd[1]: Failed to
+allocate manager object:
+Function not implemented"
++       select SIGNALFD
++
++       # systemd hangs during bootup without cgroup support:
++       select CGROUPS
++
++       # systemd fails during bootup without this option, with a nonsensical me
+ssage: "[DEPEND]
+Dependency failed for File System Check on /dev/sda1."
++       select FILE_LOCKING
++
++       # systemd fails during bootup without this option:
++       select FSNOTIFY
++       select INOTIFY_USER
++
++       # won't boot otherwise:
++       select RD_GZIP
++       select BLK_DEV_INITRD
++
++       # old F6 userspace needs vsyscalls:
++       select X86_VSYSCALL_EMULATION if X86_64
++       select IA32_EMULATION if X86_64
+
+And yes, many of these options are members of the 'SystemD debuggability Hall Of
+
+Shame'... It cost me many, many days of painful config-bisection to figure the
+often obscure dependencies out, so we might as well upstream this information.
+
+Many braincells died to bring us this information!
+
+Note that some of these have sub-dependencies (and super-dependencies) so the li
+st
+isn't complete from a Kconfig language POV - but it lists most of the 'must have
+'
+leaf features and would form a good starting point.
+
+The idea is that if you have this option enabled, the rest of kernel config shou
+ld
+be 'fool proof' - or at least failures should be a lot more obvious (such as a
+missing hardware driver or a missing filesystem driver).
+
+I'd keep this option x86-only at least initially, because that's still the space
+
+where most of our newbie testers come from, and because I'd like to see how this
+
+evolves before trying to generalize it to 44 architectures...
+
+Also, I'd not try to be per distro, I'd use a single superset of such config
+options: from a usability POV it's _much_ better to have a few more options
+enabled in a .config of thousands of entries, than to accidentally have the one
+option not enabled that your user-space somehow critically depends on ...
+
+Thoughs?
+
+Thanks,
+
+        Ingo
+
+
+   __________________________________________
+
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