linux.git/Documentation/admin-guide, branch v5.13-rc2

docs: admin-guide: update description for kernel.modprobe sysctl

2021-05-15T02:41:32+00:00

When I added CONFIG_MODPROBE_PATH, I neglected to update Documentation/.
It's still true that this defaults to /sbin/modprobe, but now via a level
of indirection.  So document that the kernel might have been built with
something other than /sbin/modprobe as the initial value.

Link: https://lkml.kernel.org/r/20210420125324.1246826-1-linux@rasmusvillemoes.dk
Fixes: 17652f4240f7a ("modules: add CONFIG_MODPROBE_PATH")
Signed-off-by: Rasmus Villemoes 
Cc: Jonathan Corbet 
Cc: Greg Kroah-Hartman 
Cc: Jessica Yu 
Cc: Luis Chamberlain 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge branch 'master' into next

2021-05-08T11:12:55+00:00

Merge master back into next, this allows us to resolve some conflicts in
arch/powerpc/Kconfig, and also re-sort the symbols under config PPC so
that they are in alphabetical order again.

Merge branch 'akpm' (patches from Andrew)

2021-05-07T07:34:51+00:00

Merge yet more updates from Andrew Morton:
 "This is everything else from -mm for this merge window.

  90 patches.

  Subsystems affected by this patch series: mm (cleanups and slub),
  alpha, procfs, sysctl, misc, core-kernel, bitmap, lib, compat,
  checkpatch, epoll, isofs, nilfs2, hpfs, exit, fork, kexec, gcov,
  panic, delayacct, gdb, resource, selftests, async, initramfs, ipc,
  drivers/char, and spelling"

* emailed patches from Andrew Morton : (90 commits)
  mm: fix typos in comments
  mm: fix typos in comments
  treewide: remove editor modelines and cruft
  ipc/sem.c: spelling fix
  fs: fat: fix spelling typo of values
  kernel/sys.c: fix typo
  kernel/up.c: fix typo
  kernel/user_namespace.c: fix typos
  kernel/umh.c: fix some spelling mistakes
  include/linux/pgtable.h: few spelling fixes
  mm/slab.c: fix spelling mistake "disired" -> "desired"
  scripts/spelling.txt: add "overflw"
  scripts/spelling.txt: Add "diabled" typo
  scripts/spelling.txt: add "overlfow"
  arm: print alloc free paths for address in registers
  mm/vmalloc: remove vwrite()
  mm: remove xlate_dev_kmem_ptr()
  drivers/char: remove /dev/kmem for good
  mm: fix some typos and code style problems
  ipc/sem.c: mundane typo fixes
  ...

drivers/char: remove /dev/kmem for good

2021-05-07T07:26:34+00:00

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 
Acked-by: Michal Hocko 
Acked-by: Kees Cook 
Cc: Linus Torvalds 
Cc: Greg Kroah-Hartman 
Cc: "Alexander A. Klimov" 
Cc: Alexander Viro 
Cc: Alexandre Belloni 
Cc: Andrew Lunn 
Cc: Andrey Zhizhikin 
Cc: Arnd Bergmann 
Cc: Benjamin Herrenschmidt 
Cc: Brian Cain 
Cc: Christian Borntraeger 
Cc: Christophe Leroy 
Cc: Chris Zankel 
Cc: Corentin Labbe 
Cc: "David S. Miller" 
Cc: "Eric W. Biederman" 
Cc: Geert Uytterhoeven 
Cc: Gerald Schaefer 
Cc: Greentime Hu 
Cc: Gregory Clement 
Cc: Heiko Carstens 
Cc: Helge Deller 
Cc: Hillf Danton 
Cc: huang ying 
Cc: Ingo Molnar 
Cc: Ivan Kokshaysky 
Cc: "James E.J. Bottomley" 
Cc: James Troup 
Cc: Jiaxun Yang 
Cc: Jonas Bonn 
Cc: Jonathan Corbet 
Cc: Kairui Song 
Cc: Krzysztof Kozlowski 
Cc: Kuninori Morimoto 
Cc: Liviu Dudau 
Cc: Lorenzo Pieralisi 
Cc: Luc Van Oostenryck 
Cc: Luis Chamberlain 
Cc: Matthew Wilcox 
Cc: Matt Turner 
Cc: Max Filippov 
Cc: Michael Ellerman 
Cc: Mike Rapoport 
Cc: Mikulas Patocka 
Cc: Minchan Kim 
Cc: Niklas Schnelle 
Cc: Oleksiy Avramchenko 
Cc: openrisc@lists.librecores.org
Cc: Palmer Dabbelt 
Cc: Paul Mackerras 
Cc: "Pavel Machek (CIP)" 
Cc: Pavel Machek 
Cc: "Peter Zijlstra (Intel)" 
Cc: Pierre Morel 
Cc: Randy Dunlap 
Cc: Richard Henderson 
Cc: Rich Felker 
Cc: Robert Richter 
Cc: Rob Herring 
Cc: Russell King 
Cc: Sam Ravnborg 
Cc: Sebastian Andrzej Siewior 
Cc: Sebastian Hesselbarth 
Cc: sparclinux@vger.kernel.org
Cc: Stafford Horne 
Cc: Stefan Kristiansson 
Cc: Steven Rostedt 
Cc: Sudeep Holla 
Cc: Theodore Dubois 
Cc: Thomas Bogendoerfer 
Cc: Thomas Gleixner 
Cc: Vasily Gorbik 
Cc: Viresh Kumar 
Cc: William Cohen 
Cc: Xiaoming Ni 
Cc: Yoshinori Sato 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

init/initramfs.c: do unpacking asynchronously

2021-05-07T07:26:33+00:00

Patch series "background initramfs unpacking, and CONFIG_MODPROBE_PATH", v3.

These two patches are independent, but better-together.

The second is a rather trivial patch that simply allows the developer to
change "/sbin/modprobe" to something else - e.g.  the empty string, so
that all request_module() during early boot return -ENOENT early, without
even spawning a usermode helper, needlessly synchronizing with the
initramfs unpacking.

The first patch delegates decompressing the initramfs to a worker thread,
allowing do_initcalls() in main.c to proceed to the device_ and late_
initcalls without waiting for that decompression (and populating of
rootfs) to finish.  Obviously, some of those later calls may rely on the
initramfs being available, so I've added synchronization points in the
firmware loader and usermodehelper paths - there might be other places
that would need this, but so far no one has been able to think of any
places I have missed.

There's not much to win if most of the functionality needed during boot is
only available as modules.  But systems with a custom-made .config and
initramfs can boot faster, partly due to utilizing more than one cpu
earlier, partly by avoiding known-futile modprobe calls (which would still
trigger synchronization with the initramfs unpacking, thus eliminating
most of the first benefit).

This patch (of 2):

Most of the boot process doesn't actually need anything from the
initramfs, until of course PID1 is to be executed.  So instead of doing
the decompressing and populating of the initramfs synchronously in
populate_rootfs() itself, push that off to a worker thread.

This is primarily motivated by an embedded ppc target, where unpacking
even the rather modest sized initramfs takes 0.6 seconds, which is long
enough that the external watchdog becomes unhappy that it doesn't get
attention soon enough.  By doing the initramfs decompression in a worker
thread, we get to do the device_initcalls and hence start petting the
watchdog much sooner.

Normal desktops might benefit as well.  On my mostly stock Ubuntu kernel,
my initramfs is a 26M xz-compressed blob, decompressing to around 126M.
That takes almost two seconds:

[    0.201454] Trying to unpack rootfs image as initramfs...
[    1.976633] Freeing initrd memory: 29416K

Before this patch, these lines occur consecutively in dmesg.  With this
patch, the timestamps on these two lines is roughly the same as above, but
with 172 lines inbetween - so more than one cpu has been kept busy doing
work that would otherwise only happen after the populate_rootfs()
finished.

Should one of the initcalls done after rootfs_initcall time (i.e., device_
and late_ initcalls) need something from the initramfs (say, a kernel
module or a firmware blob), it will simply wait for the initramfs
unpacking to be done before proceeding, which should in theory make this
completely safe.

But if some driver pokes around in the filesystem directly and not via one
of the official kernel interfaces (i.e.  request_firmware*(),
call_usermodehelper*) that theory may not hold - also, I certainly might
have missed a spot when sprinkling wait_for_initramfs().  So there is an
escape hatch in the form of an initramfs_async= command line parameter.

Link: https://lkml.kernel.org/r/20210313212528.2956377-1-linux@rasmusvillemoes.dk
Link: https://lkml.kernel.org/r/20210313212528.2956377-2-linux@rasmusvillemoes.dk
Signed-off-by: Rasmus Villemoes 
Reviewed-by: Luis Chamberlain 
Cc: Jessica Yu 
Cc: Borislav Petkov 
Cc: Jonathan Corbet 
Cc: Greg Kroah-Hartman 
Cc: Nick Desaulniers 
Cc: Takashi Iwai 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge tag 'riscv-for-linus-5.13-mw0' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux

2021-05-06T16:24:18+00:00

Pull RISC-V updates from Palmer Dabbelt:

- Support for the memtest= kernel command-line argument.

- Support for building the kernel with FORTIFY_SOURCE.

- Support for generic clockevent broadcasts.

- Support for the buildtar build target.

- Some build system cleanups to pass more LLVM-friendly arguments.

- Support for kprobes.

- A rearranged kernel memory map, the first part of supporting sv48
systems.

- Improvements to kexec, along with support for kdump and crash
kernels.

- An alternatives-based errata framework, along with support for
handling a pair of errata that manifest on some SiFive designs
(including the HiFive Unmatched).

- Support for XIP.

- A device tree for the Microchip PolarFire ICICLE SoC and associated
dev board.

... along with a bunch of cleanups. There are already a handful of fixes
on the list so there will likely be a part 2.

* tag 'riscv-for-linus-5.13-mw0' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux: (45 commits)
RISC-V: Always define XIP_FIXUP
riscv: Remove 32b kernel mapping from page table dump
riscv: Fix 32b kernel build with CONFIG_DEBUG_VIRTUAL=y
RISC-V: Fix error code returned by riscv_hartid_to_cpuid()
RISC-V: Enable Microchip PolarFire ICICLE SoC
RISC-V: Initial DTS for Microchip ICICLE board
dt-bindings: riscv: microchip: Add YAML documentation for the PolarFire SoC
RISC-V: Add Microchip PolarFire SoC kconfig option
RISC-V: enable XIP
RISC-V: Add crash kernel support
RISC-V: Add kdump support
RISC-V: Improve init_resources()
RISC-V: Add kexec support
RISC-V: Add EM_RISCV to kexec UAPI header
riscv: vdso: fix and clean-up Makefile
riscv/mm: Use BUG_ON instead of if condition followed by BUG.
riscv/kprobe: fix kernel panic when invoking sys_read traced by kprobe
riscv: Set ARCH_HAS_STRICT_MODULE_RWX if MMU
riscv: module: Create module allocations without exec permissions
riscv: bpf: Avoid breaking W^X
...

Merge tag 'docs-5.13-2' of git://git.lwn.net/linux

2021-05-06T15:33:54+00:00

Pull documentation fixes from Jonathan Corbet:
 "A few late-arriving documentation fixes, including some oprofile
  cleanup, a kernel-doc fix, some regression-reporting updates, and the
  usual minor fixes"

* tag 'docs-5.13-2' of git://git.lwn.net/linux:
  Enlisted oprofile version line removed
  oprofiled version output line removed from the list
  Removed the oprofiled version option
  docs: reporting-issues.rst: CC subsystem and maintainers on regressions
  docs: correct URL to bios and kernel developer's guide
  docs/core-api: Consistent code style
  docs/zh_CN: Adjust order and content of zh_CN/index.rst
  Documentation: input: joydev file corrections
  docs: Fix typo in Documentation/x86/x86_64/5level-paging.rst
  kernel-doc: Add support for __deprecated

Merge branch 'akpm' (patches from Andrew)

2021-05-05T20:50:15+00:00

Merge more updates from Andrew Morton:
 "The remainder of the main mm/ queue.

  143 patches.

  Subsystems affected by this patch series (all mm): pagecache, hugetlb,
  userfaultfd, vmscan, compaction, migration, cma, ksm, vmstat, mmap,
  kconfig, util, memory-hotplug, zswap, zsmalloc, highmem, cleanups, and
  kfence"

* emailed patches from Andrew Morton : (143 commits)
  kfence: use power-efficient work queue to run delayed work
  kfence: maximize allocation wait timeout duration
  kfence: await for allocation using wait_event
  kfence: zero guard page after out-of-bounds access
  mm/process_vm_access.c: remove duplicate include
  mm/mempool: minor coding style tweaks
  mm/highmem.c: fix coding style issue
  btrfs: use memzero_page() instead of open coded kmap pattern
  iov_iter: lift memzero_page() to highmem.h
  mm/zsmalloc: use BUG_ON instead of if condition followed by BUG.
  mm/zswap.c: switch from strlcpy to strscpy
  arm64/Kconfig: introduce ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
  x86/Kconfig: introduce ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
  mm,memory_hotplug: add kernel boot option to enable memmap_on_memory
  acpi,memhotplug: enable MHP_MEMMAP_ON_MEMORY when supported
  mm,memory_hotplug: allocate memmap from the added memory range
  mm,memory_hotplug: factor out adjusting present pages into adjust_present_page_count()
  mm,memory_hotplug: relax fully spanned sections check
  drivers/base/memory: introduce memory_block_{online,offline}
  mm/memory_hotplug: remove broken locking of zone PCP structures during hot remove
  ...

Merge tag 'gpio-updates-for-v5.13-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/brgl/linux

2021-05-05T19:39:29+00:00

Pull gpio updates from Bartosz Golaszewski:

 - new driver for the Realtek Otto GPIO controller

 - ACPI support for gpio-mpc8xxx

 - edge event support for gpio-sch (+ Kconfig fixes)

 - Kconfig improvements in gpio-ich

 - fixes to older issues in gpio-mockup

 - ACPI quirk for ignoring EC wakeups on Dell Venue 10 Pro 5055

 - improve the GPIO aggregator code by using more generic interfaces
   instead of reimplementing them in the driver

 - convert the DT bindings for gpio-74x164 to yaml

 - documentation improvements

 - a slew of other minor fixes and improvements to GPIO drivers

* tag 'gpio-updates-for-v5.13-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/brgl/linux: (34 commits)
  dt-bindings: gpio: add YAML description for rockchip,gpio-bank
  gpio: mxs: remove useless function
  dt-bindings: gpio: fairchild,74hc595: Convert to json-schema
  gpio: it87: remove unused code
  gpio: 104-dio-48e: Fix coding style issues
  gpio: mpc8xxx: Add ACPI support
  gpio: ich: Switch to be dependent on LPC_ICH
  gpio: sch: Drop MFD_CORE selection
  gpio: sch: depends on LPC_SCH
  gpiolib: acpi: Add quirk to ignore EC wakeups on Dell Venue 10 Pro 5055
  gpio: sch: Hook into ACPI GPE handler to catch GPIO edge events
  gpio: sch: Add edge event support
  gpio: aggregator: Replace custom get_arg() with a generic next_arg()
  lib/cmdline: Export next_arg() for being used in modules
  gpio: omap: Use device_get_match_data() helper
  gpio: Add Realtek Otto GPIO support
  dt-bindings: gpio: Binding for Realtek Otto GPIO
  docs: kernel-parameters: Add gpio_mockup_named_lines
  docs: kernel-parameters: Move gpio-mockup for alphabetic order
  lib: bitmap: provide devm_bitmap_alloc() and devm_bitmap_zalloc()
  ...

mm,memory_hotplug: add kernel boot option to enable memmap_on_memory

2021-05-05T18:27:27+00:00

Self stored memmap leads to a sparse memory situation which is
unsuitable for workloads that requires large contiguous memory chunks,
so make this an opt-in which needs to be explicitly enabled.

To control this, let memory_hotplug have its own memory space, as
suggested by David, so we can add memory_hotplug.memmap_on_memory
parameter.

Link: https://lkml.kernel.org/r/20210421102701.25051-7-osalvador@suse.de
Signed-off-by: Oscar Salvador 
Reviewed-by: David Hildenbrand 
Acked-by: Michal Hocko 
Cc: Anshuman Khandual 
Cc: Pavel Tatashin 
Cc: Vlastimil Babka 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds