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  1. Mar 23, 2022
  3. Mar 11, 2022
  5. Feb 14, 2022
  7. Feb 13, 2022
    • Elliot Berman's avatar
      kbuild: Add environment variables for userprogs flags · f67695c9
      Elliot Berman authored 
      
Allow additional arguments be passed to userprogs compilation.
Reproducible clang builds need to provide a sysroot and gcc path to
ensure the same toolchain is used across hosts. KCFLAGS is not currently
used for any user programs compilation, so add new USERCFLAGS and
USERLDFLAGS which serves similar purpose as HOSTCFLAGS/HOSTLDFLAGS.

Clang might detect GCC installation on hosts which have it installed
to a default location in /. With addition of these environment
variables, you can specify flags such as:

$ make USERCFLAGS=--sysroot=/path/to/sysroot

This can also be used to specify different sysroots such as musl or
bionic which may be installed on the host in paths that the compiler
may not search by default.

Signed-off-by: default avatarElliot Berman <quic_eberman@quicinc.com>
Reviewed-by: default avatarNick Desaulniers <ndesaulniers@google.com>
Reviewed-by: default avatarFangrui Song <maskray@google.com>
Signed-off-by: default avatarMasahiro Yamada <masahiroy@kernel.org>
      f67695c9
  9. Feb 11, 2022
  11. Feb 06, 2022
    • Eric Dumazet's avatar
      net: initialize init_net earlier · 9c1be193
      Eric Dumazet authored 
      While testing a patch that will follow later
("net: add netns refcount tracker to struct nsproxy")
I found that devtmpfs_init() was called before init_net
was initialized.

This is a bug, because devtmpfs_setup() calls
ksys_unshare(CLONE_NEWNS);

This has the effect of increasing init_net refcount,
which will be later overwritten to 1, as part of setup_net(&init_net)

We had too many prior patches [1] trying to work around the root cause.

Really, make sure init_net is in BSS section, and that net_ns_init()
is called earlier at boot time.

Note that another patch ("vfs: add netns refcount tracker
to struct fs_context") also will need net_ns_init() being called
before vfs_caches_init()

As a bonus, this patch saves around 4KB in .data section.

[1]

f8c46cb3 ("netns: do not call pernet ops for not yet set up init_net namespace")
b5082df8 ("net: Initialise init_net.count to 1")
734b6541

 ("net: Statically initialize init_net.dev_base_head")

v2: fixed a build error reported by kernel build bots (CONFIG_NET=n)

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      9c1be193
  13. Feb 02, 2022
  15. Jan 22, 2022
    • Vlastimil Babka's avatar
      lib/stackdepot: allow optional init and stack_table allocation by kvmalloc() · 2dba5eb1
      Vlastimil Babka authored 
      Currently, enabling CONFIG_STACKDEPOT means its stack_table will be
allocated from memblock, even if stack depot ends up not actually used.
The default size of stack_table is 4MB on 32-bit, 8MB on 64-bit.

This is fine for use-cases such as KASAN which is also a config option
and has overhead on its own.  But it's an issue for functionality that
has to be actually enabled on boot (page_owner) or depends on hardware
(GPU drivers) and thus the memory might be wasted.  This was raised as
an issue [1] when attempting to add stackdepot support for SLUB's debug
object tracking functionality.  It's common to build kernels with
CONFIG_SLUB_DEBUG and enable slub_debug on boot only when needed, or
create only specific kmem caches with debugging for testing purposes.

It would thus be more efficient if stackdepot's table was allocated only
when actually going to be used.  This patch thus makes the allocation
(and whole stack_depot_init() ca...
      2dba5eb1
  17. Jan 11, 2022
    • Dmitry Torokhov's avatar
      module: add in-kernel support for decompressing · b1ae6dc4
      Dmitry Torokhov authored 
      Current scheme of having userspace decompress kernel modules before
loading them into the kernel runs afoul of LoadPin security policy, as
it loses link between the source of kernel module on the disk and binary
blob that is being loaded into the kernel. To solve this issue let's
implement decompression in kernel, so that we can pass a file descriptor
of compressed module file into finit_module() which will keep LoadPin
happy.

To let userspace know what compression/decompression scheme kernel
supports it will create /sys/module/compression attribute. kmod can read
this attribute and decide if it can pass compressed file to
finit_module(). New MODULE_INIT_COMPRESSED_DATA flag indicates that the
kernel should attempt to decompress the data read from file descriptor
prior to trying load the module.

To simplify things kernel will only implement single decompression
method matching compression method selected when generating modules.
This patch implements gzip ...
      b1ae6dc4
  19. Jan 08, 2022
    • Masahiro Yamada's avatar
      kbuild: do not quote string values in include/config/auto.conf · 129ab0d2
      Masahiro Yamada authored 
      The previous commit fixed up all shell scripts to not include
include/config/auto.conf.

Now that include/config/auto.conf is only included by Makefiles,
we can change it into a more Make-friendly form.

Previously, Kconfig output string values enclosed with double-quotes
(both in the .config and include/config/auto.conf):

    CONFIG_X="foo bar"

Unlike shell, Make handles double-quotes (and single-quotes as well)
verbatim. We must rip them off when used.

There are some patterns:

  [1] $(patsubst "%",%,$(CONFIG_X))
  [2] $(CONFIG_X:"%"=%)
  [3] $(subst ",,$(CONFIG_X))
  [4] $(shell echo $(CONFIG_X))

These are not only ugly, but also fragile.

[1] and [2] do not work if the value contains spaces, like
   CONFIG_X=" foo bar "

[3] does not work correctly if the value contains double-quotes like
   CONFIG_X="foo\"bar"

[4] seems to work better, but has a cost of forking a process.

Anyway, quoted strings were always PITA for our Makefiles.

T...
      129ab0d2
  21. Jan 05, 2022
  23. Dec 09, 2021
  25. Dec 02, 2021
  27. Nov 24, 2021
  29. Nov 23, 2021
  31. Nov 17, 2021
  33. Nov 14, 2021
  35. Nov 11, 2021
    • Ingo Molnar's avatar
      mm: allow only SLUB on PREEMPT_RT · 252220da
      Ingo Molnar authored 
      Memory allocators may disable interrupts or preemption as part of the
allocation and freeing process.  For PREEMPT_RT it is important that
these sections remain deterministic and short and therefore don't depend
on the size of the memory to allocate/ free or the inner state of the
algorithm.

Until v3.12-RT the SLAB allocator was an option but involved several
changes to meet all the requirements.  The SLUB design fits better with
PREEMPT_RT model and so the SLAB patches were dropped in the 3.12-RT
patchset.  Comparing the two allocator, SLUB outperformed SLAB in both
throughput (time needed to allocate and free memory) and the maximal
latency of the system measured with cyclictest during hackbench.

SLOB was never evaluated since it was unlikely that it preforms better
than SLAB.  During a quick test, the kernel crashed with SLOB enabled
during boot.

Disable SLAB and SLOB on PREEMPT_RT.

[bigeasy@linutronix.de: commit description]

Link: https://lkml.kernel.org/r/202110...
      252220da
    • Valentin Schneider's avatar
      preempt: Restore preemption model selection configs · a8b76910
      Valentin Schneider authored 
      Commit c597bfdd ("sched: Provide Kconfig support for default dynamic
preempt mode") changed the selectable config names for the preemption
model. This means a config file must now select

  CONFIG_PREEMPT_BEHAVIOUR=y

rather than

  CONFIG_PREEMPT=y

to get a preemptible kernel. This means all arch config files would need to
be updated - right now they'll all end up with the default
CONFIG_PREEMPT_NONE_BEHAVIOUR.

Rather than touch a good hundred of config files, restore usage of
CONFIG_PREEMPT{_NONE, _VOLUNTARY}. Make them configure:
o The build-time preemption model when !PREEMPT_DYNAMIC
o The default boot-time preemption model when PREEMPT_DYNAMIC

Add siblings of those configs with the _BUILD suffix to unconditionally
designate the build-time preemption model (PREEMPT_DYNAMIC is built with
the "highest" preemption model it supports, aka PREEMPT). Downstream
configs should by now all be depending / selected by CONFIG_PREEMPTION
rather than CONFIG_...
      a8b76910
  37. Nov 09, 2021
  39. Nov 06, 2021
  41. Oct 18, 2021
  43. Oct 10, 2021
  45. Sep 22, 2021
  47. Sep 19, 2021
    • Leon Romanovsky's avatar
      init: don't panic if mount_nodev_root failed · 40c8ee67
      Leon Romanovsky authored 
      Attempt to mount 9p file system as root gives the following kernel panic:

 9pnet_virtio: no channels available for device root
 Kernel panic - not syncing: VFS: Unable to mount root "root" (9p), err=-2
 CPU: 2 PID: 1 Comm: swapper/0 Not tainted 5.15.0-rc1+ #127
 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
 Call Trace:
  dump_stack_lvl+0x45/0x59
  panic+0x1e2/0x44b
  ? __warn_printk+0xf3/0xf3
  ? free_unref_page+0x2d4/0x4a0
  ? trace_hardirqs_on+0x32/0x120
  ? free_unref_page+0x2d4/0x4a0
  mount_root+0x189/0x1e0
  prepare_namespace+0x136/0x165
  kernel_init_freeable+0x3b8/0x3cb
  ? rest_init+0x2e0/0x2e0
  kernel_init+0x19/0x130
  ret_from_fork+0x1f/0x30
 Kernel Offset: disabled
 ---[ end Kernel panic - not syncing: VFS: Unable to mount root "root" (9p), err=-2 ]---

QEMU command line:
 "qemu-system-x86_64 -append root=/dev/root rw rootfstype=9p rootflags=trans=virtio ..."

This error is because root_device_name is truncated in prepare_namespace() from
being "/dev/root" to be "root" prior to call to mount_nodev_root().

As a solution, don't treat errors in mount_nodev_root() as errors that
require panics and allow failback to the mount flow that existed before
patch citied in Fixes tag.

Fixes: f9259be6

 ("init: allow mounting arbitrary non-blockdevice filesystems as root")
Signed-off-by: default avatarLeon Romanovsky <leonro@nvidia.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      40c8ee67
    • Vivek Goyal's avatar
      init/do_mounts.c: Harden split_fs_names() against buffer overflow · b51593c4
      Vivek Goyal authored 
      
split_fs_names() currently takes comma separate list of filesystems
and converts it into individual filesystem strings. Pleaces these
strings in the input buffer passed by caller and returns number of
strings.

If caller manages to pass input string bigger than buffer, then we
can write beyond the buffer. Or if string just fits buffer, we will
still write beyond the buffer as we append a '\0' byte at the end.

Pass size of input buffer to split_fs_names() and put enough checks
in place so such buffer overrun possibilities do not occur.

This patch does few things.

- Add a parameter "size" to split_fs_names(). This specifies size
  of input buffer.

- Use strlcpy() (instead of strcpy()) so that we can't go beyond
  buffer size. If input string "names" is larger than passed in
  buffer, input string will be truncated to fit in buffer.

- Stop appending extra '\0' character at the end and avoid one
  possibility of going beyond the input buffer size.

- Do not use extra loop to count number of strings.

- Previously if one passed "rootfstype=foo,,bar", split_fs_names()
  will return only 1 string "foo" (and "bar" will be truncated
  due to extra ,). After this patch, now split_fs_names() will
  return 3 strings ("foo", zero-sized-string, and "bar").

  Callers of split_fs_names() have been modified to check for
  zero sized string and skip to next one.

Reported-by: default avatarxu xin <xu.xin16@zte.com.cn>
Signed-off-by: default avatarVivek Goyal <vgoyal@redhat.com>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      b51593c4
  49. Sep 14, 2021
  51. Sep 08, 2021

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