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Author SHA1 Message Date
David Hildenbrand
bbcd53c960 drivers/char: remove /dev/kmem for good 
Patch series "drivers/char: remove /dev/kmem for good".

Exploring /dev/kmem and /dev/mem in the context of memory hot(un)plug and
memory ballooning, I started questioning the existence of /dev/kmem.

Comparing it with the /proc/kcore implementation, it does not seem to be
able to deal with things like

a) Pages unmapped from the direct mapping (e.g., to be used by secretmem)
  -> kern_addr_valid(). virt_addr_valid() is not sufficient.

b) Special cases like gart aperture memory that is not to be touched
  -> mem_pfn_is_ram()

Unless I am missing something, it's at least broken in some cases and might
fault/crash the machine.

Looks like its existence has been questioned before in 2005 and 2010 [1],
after ~11 additional years, it might make sense to revive the discussion.

CONFIG_DEVKMEM is only enabled in a single defconfig (on purpose or by
mistake?).  All distributions disable it: in Ubuntu it has been disabled
for more than 10 years, in Debian since 2.6.31, in Fedora at least
starting with FC3, in RHEL starting with RHEL4, in SUSE starting from
15sp2, and OpenSUSE has it disabled as well.

1) /dev/kmem was popular for rootkits [2] before it got disabled
   basically everywhere. Ubuntu documents [3] "There is no modern user of
   /dev/kmem any more beyond attackers using it to load kernel rootkits.".
   RHEL documents in a BZ [5] "it served no practical purpose other than to
   serve as a potential security problem or to enable binary module drivers
   to access structures/functions they shouldn't be touching"

2) /proc/kcore is a decent interface to have a controlled way to read
   kernel memory for debugging puposes. (will need some extensions to
   deal with memory offlining/unplug, memory ballooning, and poisoned
   pages, though)

3) It might be useful for corner case debugging [1]. KDB/KGDB might be a
   better fit, especially, to write random memory; harder to shoot
   yourself into the foot.

4) "Kernel Memory Editor" [4] hasn't seen any updates since 2000 and seems
   to be incompatible with 64bit [1]. For educational purposes,
   /proc/kcore might be used to monitor value updates -- or older
   kernels can be used.

5) It's broken on arm64, and therefore, completely disabled there.

Looks like it's essentially unused and has been replaced by better
suited interfaces for individual tasks (/proc/kcore, KDB/KGDB). Let's
just remove it.

[1] https://lwn.net/Articles/147901/
[2] https://www.linuxjournal.com/article/10505
[3] https://wiki.ubuntu.com/Security/Features#A.2Fdev.2Fkmem_disabled
[4] https://sourceforge.net/projects/kme/
[5] https://bugzilla.redhat.com/show_bug.cgi?id=154796

Link: https://lkml.kernel.org/r/20210324102351.6932-1-david@redhat.com
Link: https://lkml.kernel.org/r/20210324102351.6932-2-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Alexander A. Klimov" <grandmaster@al2klimov.de>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Andrew Lunn <andrew@lunn.ch>
Cc: Andrey Zhizhikin <andrey.zhizhikin@leica-geosystems.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Brian Cain <bcain@codeaurora.org>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Chris Zankel <chris@zankel.net>
Cc: Corentin Labbe <clabbe@baylibre.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Greentime Hu <green.hu@gmail.com>
Cc: Gregory Clement <gregory.clement@bootlin.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Hillf Danton <hdanton@sina.com>
Cc: huang ying <huang.ying.caritas@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: James Troup <james.troup@canonical.com>
Cc: Jiaxun Yang <jiaxun.yang@flygoat.com>
Cc: Jonas Bonn <jonas@southpole.se>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kairui Song <kasong@redhat.com>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Cc: Liviu Dudau <liviu.dudau@arm.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Niklas Schnelle <schnelle@linux.ibm.com>
Cc: Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com>
Cc: openrisc@lists.librecores.org
Cc: Palmer Dabbelt <palmerdabbelt@google.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: "Pavel Machek (CIP)" <pavel@denx.de>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Cc: Pierre Morel <pmorel@linux.ibm.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Rich Felker <dalias@libc.org>
Cc: Robert Richter <rric@kernel.org>
Cc: Rob Herring <robh@kernel.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Cc: sparclinux@vger.kernel.org
Cc: Stafford Horne <shorne@gmail.com>
Cc: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Cc: Theodore Dubois <tblodt@icloud.com>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: William Cohen <wcohen@redhat.com>
Cc: Xiaoming Ni <nixiaoming@huawei.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2021-05-07 00:26:34 -07:00
Alexey Brodkin
3337d5cfe5 configs: get rid of obsolete CONFIG_ENABLE_WARN_DEPRECATED 
This Kconfig option was removed during v4.19 development in commit
771c035372 ("deprecate the '__deprecated' attribute warnings entirely
and for good") so there's no point to keep it in defconfigs any longer.

FWIW defconfigs were patched with:
--------------------------->8----------------------
find . -name *_defconfig -exec sed -i '/CONFIG_ENABLE_WARN_DEPRECATED/d' {} \;
--------------------------->8----------------------

Link: http://lkml.kernel.org/r/20190128152434.41969-1-abrodkin@synopsys.com
Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 2019-03-07 18:32:02 -08:00
Krzysztof Kozlowski
bd5f62605f ARM: defconfig: Cleanup from old Kconfig options 
Remove old, dead Kconfig options (in order appearing in this commit):
 - EXPERIMENTAL is gone since v3.9;
 - INET_LRO: commit 7bbf3cae65 ("ipv4: Remove inet_lro library");
 - MTD_CONCAT: commit f53fdebcc3 ("mtd: drop MTD_CONCAT from Kconfig entirely");
 - MTD_PARTITIONS: commit 6a8a98b22b ("mtd: kill CONFIG_MTD_PARTITIONS");
 - MTD_CHAR: commit 660685d9d1 ("mtd: merge mtdchar module with mtdcore");
 - NETDEV_1000 and NETDEV_10000: commit f860b0522f ("drivers/net:
   Kconfig and Makefile cleanup"); NET_ETHERNET should be replaced with
   just ETHERNET but that is separate change;
 - INOTIFY: commit 2dfc1cae4c ("inotify: remove inotify in kernel interface");
 - MISC_DEVICES: commit 7c5763b845 ("drivers: misc: Remove
   MISC_DEVICES config option");
 - HID_SUPPORT: commit 1f41a6a994 ("HID: Fix the generic Kconfig options");
 - BT_L2CAP and BT_SCO: commit f1e91e1640 ("Bluetooth: Always compile
   SCO and L2CAP in Bluetooth Core");
 - DEBUG_ERRORS: commit b025a3f836 ("ARM: 6876/1: Kconfig.debug:
   Remove unused CONFIG_DEBUG_ERRORS");
 - USB_DEVICE_CLASS: commit 007bab9132 ("USB: remove CONFIG_USB_DEVICE_CLASS");
 - RCU_CPU_STALL_DETECTOR: commit a00e0d714f ("rcu: Remove conditional
   compilation for RCU CPU stall warnings");
 - SYSCTL_SYSCALL_CHECK: commit 7c60c48f58 ("sysctl: Improve the
   sysctl sanity checks");
 - IP_NF_QUEUE: commit 3dd6664fac ("netfilter: remove unused "config IP_NF_QUEUE"");
 - IP_NF_TARGET_ULOG: commit d4da843e6f ("netfilter: kill remnants of ulog targets");
 - IP6_NF_QUEUE: commit d16cf20e2f ("netfilter: remove ip_queue support");
 - IP6_NF_TARGET_LOG: commit 6939c33a75 ("netfilter: merge ipt_LOG and
   ip6_LOG into xt_LOG");
 - USB_LED: commit a335aaf312 ("usb: misc: remove outdated USB LED driver");
 - MMC_UNSAFE_RESUME: commit 2501c9179d ("mmc: core: Use
   MMC_UNSAFE_RESUME as default behavior");
 - AUTOFS_FS: commit 561c5cf923 ("staging: Remove autofs3");
 - DISPLAY_SUPPORT: commit 5a6b5e02d6 ("fbdev: remove display subsystem");
 - CFG80211_REG_DEBUG: commit c799ba6eab ("cfg80211: remove
   CFG80211_REG_DEBUG");
 - VIDEO_OUTPUT_CONTROL: commit f167a64e9d ("video / output: Drop
   display output class support");
 - USB_LIBUSUAL: commit f61870ee6f ("usb: remove libusual");
 - CRYPTO_ZLIB: commit 110492183c ("crypto: compress - remove unused
   pcomp interface");
 - BLK_DEV_UB: commit 68a5059ecf ("block: remove the deprecated ub driver");

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
[for vexpress]
Acked-by: Liviu Dudau <liviu.dudau@arm.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
 2017-06-10 19:28:57 +02:00
Vladimir Murzin
58e696d111 ARM: configs: add MPS2 defconfig 
This patch adds a new config for MPS2 platform.

Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
 2016-04-26 12:53:14 +02:00