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  1. 15 11月, 2021 2 次提交
  3. 12 11月, 2021 1 次提交
  5. 07 11月, 2021 1 次提交
  7. 08 9月, 2021 1 次提交
    • M
      kbuild: Only default to -Werror if COMPILE_TEST · b339ec9c
      由 Marco Elver 提交于 
      The cross-product of the kernel's supported toolchains, architectures,
and configuration options is large. So large, that it's generally
accepted to be infeasible to enumerate and build+test them all
(many compile-testers rely on randomly generated configs).

Without the possibility to enumerate all possible combinations of
toolchains, architectures, and configuration options, it is inevitable
that compiler warnings in this space exist.

With -Werror, this means that an innumerable set of kernels are now
broken, yet had been perfectly usable before (confused compilers, code
with warnings unused, or luck).

Distributors will necessarily pick a point in the toolchain X arch X
config space, and if unlucky, will have a broken build. Granted, those
will likely disable CONFIG_WERROR and move on.

The kernel's default configuration is unlikely to be suitable for all
users, but it's inappropriate to force many users to set CONFIG_WERROR=n.

This also holds for CI systems which are focused on runtime testing,
where the odd warning in some subsystem will disrupt testing of the rest
of the kernel. Many of those runtime-focused CI systems run tests or
fuzz the kernel using runtime debugging tools. Runtime testing of
different subsystems can proceed in parallel, and potentially uncover
serious bugs; halting runtime testing of the entire kernel because of
the odd warning (now error) in a subsystem or driver is simply
inappropriate.

Therefore, runtime-focused CI systems will likely choose CONFIG_WERROR=n
as well.

The appropriate usecase for -Werror is therefore compile-test focused
builds (often done by developers or CI systems).

Reflect this in the Kconfig option by making the default value of WERROR
match COMPILE_TEST.
Signed-off-by: NMarco Elver <elver@google.com>
Acked-by: NGuenter Roeck <linux@roeck-us.net>
Acked-by: NRandy Dunlap <rdunlap@infradead.org>
Reviwed-by: NMark Brown <broonie@kernel.org>
Reviewed-by: NNathan Chancellor <nathan@kernel.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      b339ec9c
  9. 06 9月, 2021 1 次提交
    • L
      Enable '-Werror' by default for all kernel builds · 3fe617cc
      由 Linus Torvalds 提交于 
      ... but make it a config option so that broken environments can disable
it when required.

We really should always have a clean build, and will disable specific
over-eager warnings as required, if we can't fix them.  But while I
fairly religiously enforce that in my own tree, it doesn't get enforced
by various build robots that don't necessarily report warnings.

So this just makes '-Werror' a default compiler flag, but allows people
to disable it for their configuration if they have some particular
issues.

Occasionally, new compiler versions end up enabling new warnings, and it
can take a while before we have them fixed (or the warnings disabled if
that is what it takes), so the config option allows for that situation.

Hopefully this will mean that I get fewer pull requests that have new
warnings that were not noticed by various automation we have in place.

Knock wood.
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      3fe617cc
  11. 26 7月, 2021 1 次提交
    • J
      printk: remove NMI tracking · 85e3e7fb
      由 John Ogness 提交于 
      All NMI contexts are handled the same as the safe context: store the
message and defer printing. There is no need to have special NMI
context tracking for this. Using in_nmi() is enough.

There are several parts of the kernel that are manually calling into
the printk NMI context tracking in order to cause general printk
deferred printing:

    arch/arm/kernel/smp.c
    arch/powerpc/kexec/crash.c
    kernel/trace/trace.c

For arm/kernel/smp.c and powerpc/kexec/crash.c, provide a new
function pair printk_deferred_enter/exit that explicitly achieves the
same objective.

For ftrace, remove the printk context manipulation completely. It was
added in commit 03fc7f9c ("printk/nmi: Prevent deadlock when
accessing the main log buffer in NMI"). The purpose was to enforce
storing messages directly into the ring buffer even in NMI context.
It really should have only modified the behavior in NMI context.
There is no need for a special behavior any longer. All messages are
always stored directly now. The console deferring is handled
transparently in vprintk().
Signed-off-by: NJohn Ogness <john.ogness@linutronix.de>
[pmladek@suse.com: Remove special handling in ftrace.c completely.
Signed-off-by: NPetr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210715193359.25946-5-john.ogness@linutronix.de
      85e3e7fb
  13. 19 7月, 2021 1 次提交
    • C
      printk: Userspace format indexing support · 33701557
      由 Chris Down 提交于 
      We have a number of systems industry-wide that have a subset of their
functionality that works as follows:

1. Receive a message from local kmsg, serial console, or netconsole;
2. Apply a set of rules to classify the message;
3. Do something based on this classification (like scheduling a
   remediation for the machine), rinse, and repeat.

As a couple of examples of places we have this implemented just inside
Facebook, although this isn't a Facebook-specific problem, we have this
inside our netconsole processing (for alarm classification), and as part
of our machine health checking. We use these messages to determine
fairly important metrics around production health, and it's important
that we get them right.

While for some kinds of issues we have counters, tracepoints, or metrics
with a stable interface which can reliably indicate the issue, in order
to react to production issues quickly we need to work with the interface
which most kernel developers naturally use when developing: printk.

Most production issues come from unexpected phenomena, and as such
usually the code in question doesn't have easily usable tracepoints or
other counters available for the specific problem being mitigated. We
have a number of lines of monitoring defence against problems in
production (host metrics, process metrics, service metrics, etc), and
where it's not feasible to reliably monitor at another level, this kind
of pragmatic netconsole monitoring is essential.

As one would expect, monitoring using printk is rather brittle for a
number of reasons -- most notably that the message might disappear
entirely in a new version of the kernel, or that the message may change
in some way that the regex or other classification methods start to
silently fail.

One factor that makes this even harder is that, under normal operation,
many of these messages are never expected to be hit. For example, there
may be a rare hardware bug which one wants to detect if it was to ever
happen again, but its recurrence is not likely or anticipated. This
precludes using something like checking whether the printk in question
was printed somewhere fleetwide recently to determine whether the
message in question is still present or not, since we don't anticipate
that it should be printed anywhere, but still need to monitor for its
future presence in the long-term.

This class of issue has happened on a number of occasions, causing
unhealthy machines with hardware issues to remain in production for
longer than ideal. As a recent example, some monitoring around
blk_update_request fell out of date and caused semi-broken machines to
remain in production for longer than would be desirable.

Searching through the codebase to find the message is also extremely
fragile, because many of the messages are further constructed beyond
their callsite (eg. btrfs_printk and other module-specific wrappers,
each with their own functionality). Even if they aren't, guessing the
format and formulation of the underlying message based on the aesthetics
of the message emitted is not a recipe for success at scale, and our
previous issues with fleetwide machine health checking demonstrate as
much.

This provides a solution to the issue of silently changed or deleted
printks: we record pointers to all printk format strings known at
compile time into a new .printk_index section, both in vmlinux and
modules. At runtime, this can then be iterated by looking at
<debugfs>/printk/index/<module>, which emits the following format, both
readable by humans and able to be parsed by machines:

    $ head -1 vmlinux; shuf -n 5 vmlinux
    # <level[,flags]> filename:line function "format"
    <5> block/blk-settings.c:661 disk_stack_limits "%s: Warning: Device %s is misaligned\n"
    <4> kernel/trace/trace.c:8296 trace_create_file "Could not create tracefs '%s' entry\n"
    <6> arch/x86/kernel/hpet.c:144 _hpet_print_config "hpet: %s(%d):\n"
    <6> init/do_mounts.c:605 prepare_namespace "Waiting for root device %s...\n"
    <6> drivers/acpi/osl.c:1410 acpi_no_auto_serialize_setup "ACPI: auto-serialization disabled\n"

This mitigates the majority of cases where we have a highly-specific
printk which we want to match on, as we can now enumerate and check
whether the format changed or the printk callsite disappeared entirely
in userspace. This allows us to catch changes to printks we monitor
earlier and decide what to do about it before it becomes problematic.

There is no additional runtime cost for printk callers or printk itself,
and the assembly generated is exactly the same.
Signed-off-by: NChris Down <chris@chrisdown.name>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Jessica Yu <jeyu@kernel.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kees Cook <keescook@chromium.org>
Reviewed-by: NPetr Mladek <pmladek@suse.com>
Tested-by: NPetr Mladek <pmladek@suse.com>
Reported-by: Nkernel test robot <lkp@intel.com>
Acked-by: NAndy Shevchenko <andy.shevchenko@gmail.com>
Acked-by: Jessica Yu <jeyu@kernel.org> # for module.{c,h}
Signed-off-by: NPetr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/e42070983637ac5e384f17fbdbe86d19c7b212a5.1623775748.git.chris@chrisdown.name
      33701557
  15. 18 7月, 2021 1 次提交
  17. 09 7月, 2021 1 次提交
  19. 23 6月, 2021 1 次提交
  21. 12 5月, 2021 1 次提交
  23. 07 5月, 2021 1 次提交
    • R
      modules: add CONFIG_MODPROBE_PATH · 17652f42
      由 Rasmus Villemoes 提交于 
      Allow the developer to specifiy the initial value of the modprobe_path[]
string.  This can be used to set it to the empty string initially, thus
effectively disabling request_module() during early boot until userspace
writes a new value via the /proc/sys/kernel/modprobe interface.  [1]

When building a custom kernel (often for an embedded target), it's normal
to build everything into the kernel that is needed for booting, and indeed
the initramfs often contains no modules at all, so every such
request_module() done before userspace init has mounted the real rootfs is
a waste of time.

This is particularly useful when combined with the previous patch, which
made the initramfs unpacking asynchronous - for that to work, it had to
make any usermodehelper call wait for the unpacking to finish before
attempting to invoke the userspace helper.  By eliminating all such
(known-to-be-futile) calls of usermodehelper, the initramfs unpacking and
the {device,late}_initcalls can proceed in parallel for much longer.

For a relatively slow ppc board I'm working on, the two patches combined
lead to 0.2s faster boot - but more importantly, the fact that the
initramfs unpacking proceeds completely in the background while devices
get probed means I get to handle the gpio watchdog in time without getting
reset.

[1] __request_module() already has an early -ENOENT return when
modprobe_path is the empty string.

Link: https://lkml.kernel.org/r/20210313212528.2956377-3-linux@rasmusvillemoes.dkSigned-off-by: NRasmus Villemoes <linux@rasmusvillemoes.dk>
Reviewed-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: NJessica Yu <jeyu@kernel.org>
Acked-by: NLuis Chamberlain <mcgrof@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Takashi Iwai <tiwai@suse.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      17652f42
  25. 06 5月, 2021 1 次提交
    • A
      userfaultfd: add minor fault registration mode · 7677f7fd
      由 Axel Rasmussen 提交于 
      Patch series "userfaultfd: add minor fault handling", v9.

Overview
========

This series adds a new userfaultfd feature, UFFD_FEATURE_MINOR_HUGETLBFS.
When enabled (via the UFFDIO_API ioctl), this feature means that any
hugetlbfs VMAs registered with UFFDIO_REGISTER_MODE_MISSING will *also*
get events for "minor" faults.  By "minor" fault, I mean the following
situation:

Let there exist two mappings (i.e., VMAs) to the same page(s) (shared
memory).  One of the mappings is registered with userfaultfd (in minor
mode), and the other is not.  Via the non-UFFD mapping, the underlying
pages have already been allocated & filled with some contents.  The UFFD
mapping has not yet been faulted in; when it is touched for the first
time, this results in what I'm calling a "minor" fault.  As a concrete
example, when working with hugetlbfs, we have huge_pte_none(), but
find_lock_page() finds an existing page.

We also add a new ioctl to resolve such faults: UFFDIO_CONTINUE.  The idea
is, userspace resolves the fault by either a) doing nothing if the
contents are already correct, or b) updating the underlying contents using
the second, non-UFFD mapping (via memcpy/memset or similar, or something
fancier like RDMA, or etc...).  In either case, userspace issues
UFFDIO_CONTINUE to tell the kernel "I have ensured the page contents are
correct, carry on setting up the mapping".

Use Case
========

Consider the use case of VM live migration (e.g. under QEMU/KVM):

1. While a VM is still running, we copy the contents of its memory to a
   target machine. The pages are populated on the target by writing to the
   non-UFFD mapping, using the setup described above. The VM is still running
   (and therefore its memory is likely changing), so this may be repeated
   several times, until we decide the target is "up to date enough".

2. We pause the VM on the source, and start executing on the target machine.
   During this gap, the VM's user(s) will *see* a pause, so it is desirable to
   minimize this window.

3. Between the last time any page was copied from the source to the target, and
   when the VM was paused, the contents of that page may have changed - and
   therefore the copy we have on the target machine is out of date. Although we
   can keep track of which pages are out of date, for VMs with large amounts of
   memory, it is "slow" to transfer this information to the target machine. We
   want to resume execution before such a transfer would complete.

4. So, the guest begins executing on the target machine. The first time it
   touches its memory (via the UFFD-registered mapping), userspace wants to
   intercept this fault. Userspace checks whether or not the page is up to date,
   and if not, copies the updated page from the source machine, via the non-UFFD
   mapping. Finally, whether a copy was performed or not, userspace issues a
   UFFDIO_CONTINUE ioctl to tell the kernel "I have ensured the page contents
   are correct, carry on setting up the mapping".

We don't have to do all of the final updates on-demand. The userfaultfd manager
can, in the background, also copy over updated pages once it receives the map of
which pages are up-to-date or not.

Interaction with Existing APIs
==============================

Because this is a feature, a registered VMA could potentially receive both
missing and minor faults.  I spent some time thinking through how the
existing API interacts with the new feature:

UFFDIO_CONTINUE cannot be used to resolve non-minor faults, as it does not
allocate a new page.  If UFFDIO_CONTINUE is used on a non-minor fault:

- For non-shared memory or shmem, -EINVAL is returned.
- For hugetlb, -EFAULT is returned.

UFFDIO_COPY and UFFDIO_ZEROPAGE cannot be used to resolve minor faults.
Without modifications, the existing codepath assumes a new page needs to
be allocated.  This is okay, since userspace must have a second
non-UFFD-registered mapping anyway, thus there isn't much reason to want
to use these in any case (just memcpy or memset or similar).

- If UFFDIO_COPY is used on a minor fault, -EEXIST is returned.
- If UFFDIO_ZEROPAGE is used on a minor fault, -EEXIST is returned (or -EINVAL
  in the case of hugetlb, as UFFDIO_ZEROPAGE is unsupported in any case).
- UFFDIO_WRITEPROTECT simply doesn't work with shared memory, and returns
  -ENOENT in that case (regardless of the kind of fault).

Future Work
===========

This series only supports hugetlbfs.  I have a second series in flight to
support shmem as well, extending the functionality.  This series is more
mature than the shmem support at this point, and the functionality works
fully on hugetlbfs, so this series can be merged first and then shmem
support will follow.

This patch (of 6):

This feature allows userspace to intercept "minor" faults.  By "minor"
faults, I mean the following situation:

Let there exist two mappings (i.e., VMAs) to the same page(s).  One of the
mappings is registered with userfaultfd (in minor mode), and the other is
not.  Via the non-UFFD mapping, the underlying pages have already been
allocated & filled with some contents.  The UFFD mapping has not yet been
faulted in; when it is touched for the first time, this results in what
I'm calling a "minor" fault.  As a concrete example, when working with
hugetlbfs, we have huge_pte_none(), but find_lock_page() finds an existing
page.

This commit adds the new registration mode, and sets the relevant flag on
the VMAs being registered.  In the hugetlb fault path, if we find that we
have huge_pte_none(), but find_lock_page() does indeed find an existing
page, then we have a "minor" fault, and if the VMA has the userfaultfd
registration flag, we call into userfaultfd to handle it.

This is implemented as a new registration mode, instead of an API feature.
This is because the alternative implementation has significant drawbacks
[1].

However, doing it this was requires we allocate a VM_* flag for the new
registration mode.  On 32-bit systems, there are no unused bits, so this
feature is only supported on architectures with
CONFIG_ARCH_USES_HIGH_VMA_FLAGS.  When attempting to register a VMA in
MINOR mode on 32-bit architectures, we return -EINVAL.

[1] https://lore.kernel.org/patchwork/patch/1380226/

[peterx@redhat.com: fix minor fault page leak]
  Link: https://lkml.kernel.org/r/20210322175132.36659-1-peterx@redhat.com

Link: https://lkml.kernel.org/r/20210301222728.176417-1-axelrasmussen@google.com
Link: https://lkml.kernel.org/r/20210301222728.176417-2-axelrasmussen@google.comSigned-off-by: NAxel Rasmussen <axelrasmussen@google.com>
Reviewed-by: NPeter Xu <peterx@redhat.com>
Reviewed-by: NMike Kravetz <mike.kravetz@oracle.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chinwen Chang <chinwen.chang@mediatek.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Lokesh Gidra <lokeshgidra@google.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: "Michal Koutn" <mkoutny@suse.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Shaohua Li <shli@fb.com>
Cc: Shawn Anastasio <shawn@anastas.io>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Steven Price <steven.price@arm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Adam Ruprecht <ruprecht@google.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Cannon Matthews <cannonmatthews@google.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Oliver Upton <oupton@google.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      7677f7fd
  27. 28 4月, 2021 1 次提交
    • F
      bpf: Implement formatted output helpers with bstr_printf · 48cac3f4
      由 Florent Revest 提交于 
      BPF has three formatted output helpers: bpf_trace_printk, bpf_seq_printf
and bpf_snprintf. Their signatures specify that all arguments are
provided from the BPF world as u64s (in an array or as registers). All
of these helpers are currently implemented by calling functions such as
snprintf() whose signatures take a variable number of arguments, then
placed in a va_list by the compiler to call vsnprintf().

"d9c9e4db bpf: Factorize bpf_trace_printk and bpf_seq_printf" introduced
a bpf_printf_prepare function that fills an array of u64 sanitized
arguments with an array of "modifiers" which indicate what the "real"
size of each argument should be (given by the format specifier). The
BPF_CAST_FMT_ARG macro consumes these arrays and casts each argument to
its real size. However, the C promotion rules implicitely cast them all
back to u64s. Therefore, the arguments given to snprintf are u64s and
the va_list constructed by the compiler will use 64 bits for each
argument. On 64 bit machines, this happens to work well because 32 bit
arguments in va_lists need to occupy 64 bits anyway, but on 32 bit
architectures this breaks the layout of the va_list expected by the
called function and mangles values.

In "88a5c690 bpf: fix bpf_trace_printk on 32 bit archs", this problem
had been solved for bpf_trace_printk only with a "horrid workaround"
that emitted multiple calls to trace_printk where each call had
different argument types and generated different va_list layouts. One of
the call would be dynamically chosen at runtime. This was ok with the 3
arguments that bpf_trace_printk takes but bpf_seq_printf and
bpf_snprintf accept up to 12 arguments. Because this approach scales
code exponentially, it is not a viable option anymore.

Because the promotion rules are part of the language and because the
construction of a va_list is an arch-specific ABI, it's best to just
avoid variadic arguments and va_lists altogether. Thankfully the
kernel's snprintf() has an alternative in the form of bstr_printf() that
accepts arguments in a "binary buffer representation". These binary
buffers are currently created by vbin_printf and used in the tracing
subsystem to split the cost of printing into two parts: a fast one that
only dereferences and remembers values, and a slower one, called later,
that does the pretty-printing.

This patch refactors bpf_printf_prepare to construct binary buffers of
arguments consumable by bstr_printf() instead of arrays of arguments and
modifiers. This gets rid of BPF_CAST_FMT_ARG and greatly simplifies the
bpf_printf_prepare usage but there are a few gotchas that change how
bpf_printf_prepare needs to do things.

Currently, bpf_printf_prepare uses a per cpu temporary buffer as a
generic storage for strings and IP addresses. With this refactoring, the
temporary buffers now holds all the arguments in a structured binary
format.

To comply with the format expected by bstr_printf, certain format
specifiers also need to be pre-formatted: %pB and %pi6/%pi4/%pI4/%pI6.
Because vsnprintf subroutines for these specifiers are hard to expose,
we pre-format these arguments with calls to snprintf().
Reported-by: NRasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: NFlorent Revest <revest@chromium.org>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210427174313.860948-3-revest@chromium.org
      48cac3f4
  29. 25 4月, 2021 4 次提交
    • A
      kbuild: redo fake deps at include/config/*.h · 0e0345b7
      由 Alexey Dobriyan 提交于 
      Make include/config/foo/bar.h fake deps files generation simpler.

* delete .h suffix
	those aren't header files, shorten filenames,

* delete tolower()
	Linux filesystems can deal with both upper and lowercase
	filenames very well,

* put everything in 1 directory
	Presumably 'mkdir -p' split is from dark times when filesystems
	handled huge directories badly, disks were round adding to
	seek times.

	x86_64 allmodconfig lists 12364 files in include/config.

	../obj/include/config/
	├── 104_QUAD_8
	├── 60XX_WDT
	├── 64BIT
		...
	├── ZSWAP_DEFAULT_ON
	├── ZSWAP_ZPOOL_DEFAULT
	└── ZSWAP_ZPOOL_DEFAULT_ZBUD

	0 directories, 12364 files
Signed-off-by: NAlexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
      0e0345b7
    • P
      kbuild: add support for zstd compressed modules · c3d7ef37
      由 Piotr Gorski 提交于 
      kmod 28 supports modules compressed in zstd format so let's add this
possibility to kernel.
Signed-off-by: NPiotr Gorski <lucjan.lucjanov@gmail.com>
Reviewed-by: NOleksandr Natalenko <oleksandr@natalenko.name>
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
      c3d7ef37
    • M
      kbuild: remove CONFIG_MODULE_COMPRESS · d4bbe942
      由 Masahiro Yamada 提交于 
      CONFIG_MODULE_COMPRESS is only used to activate the choice for module
compression algorithm. It will be simpler to make the choice always
visible, and add CONFIG_MODULE_COMPRESS_NONE in the choice.

This is more consistent with the "Kernel compression mode" and "Built-in
initramfs compression mode" choices. CONFIG_KERNEL_UNCOMPRESSED and
CONFIG_INITRAMFS_COMPRESSION_NONE are available to choose no compression.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Reviewed-by: NNick Desaulniers <ndesaulniers@google.com>
      d4bbe942
    • M
      kbuild: check the minimum assembler version in Kconfig · ba64beb1
      由 Masahiro Yamada 提交于 
      Documentation/process/changes.rst defines the minimum assembler version
(binutils version), but we have never checked it in the build time.

Kbuild never invokes 'as' directly because all assembly files in the
kernel tree are *.S, hence must be preprocessed. I do not expect
raw assembly source files (*.s) would be added to the kernel tree.

Therefore, we always use $(CC) as the assembler driver, and commit
aa824e0c ("kbuild: remove AS variable") removed 'AS'. However,
we are still interested in the version of the assembler acting behind.

As usual, the --version option prints the version string.

  $ as --version | head -n 1
  GNU assembler (GNU Binutils for Ubuntu) 2.35.1

But, we do not have $(AS). So, we can add the -Wa prefix so that
$(CC) passes --version down to the backing assembler.

  $ gcc -Wa,--version | head -n 1
  gcc: fatal error: no input files
  compilation terminated.

OK, we need to input something to satisfy gcc.

  $ gcc -Wa,--version -c -x assembler /dev/null -o /dev/null | head -n 1
  GNU assembler (GNU Binutils for Ubuntu) 2.35.1

The combination of Clang and GNU assembler works in the same way:

  $ clang -no-integrated-as -Wa,--version -c -x assembler /dev/null -o /dev/null | head -n 1
  GNU assembler (GNU Binutils for Ubuntu) 2.35.1

Clang with the integrated assembler fails like this:

  $ clang -integrated-as -Wa,--version -c -x assembler /dev/null -o /dev/null | head -n 1
  clang: error: unsupported argument '--version' to option 'Wa,'

For the last case, checking the error message is fragile. If the
proposal for -Wa,--version support [1] is accepted, this may not be
even an error in the future.

One easy way is to check if -integrated-as is present in the passed
arguments. We did not pass -integrated-as to CLANG_FLAGS before, but
we can make it explicit.

Nathan pointed out -integrated-as is the default for all of the
architectures/targets that the kernel cares about, but it goes
along with "explicit is better than implicit" policy. [2]

With all this in my mind, I implemented scripts/as-version.sh to
check the assembler version in Kconfig time.

  $ scripts/as-version.sh gcc
  GNU 23501
  $ scripts/as-version.sh clang -no-integrated-as
  GNU 23501
  $ scripts/as-version.sh clang -integrated-as
  LLVM 0

[1]: https://github.com/ClangBuiltLinux/linux/issues/1320
[2]: https://lore.kernel.org/linux-kbuild/20210307044253.v3h47ucq6ng25iay@archlinux-ax161/Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Reviewed-by: NNathan Chancellor <nathan@kernel.org>
      ba64beb1
  31. 14 4月, 2021 3 次提交
    • M
      kconfig: change "modules" from sub-option to first-level attribute · 6dd85ff1
      由 Masahiro Yamada 提交于 
      Now "modules" is the only member of the "option" property.

Remove "option", and move "modules" to the top level property.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
      6dd85ff1
    • M
      kconfig: do not use allnoconfig_y option · f8f0d064
      由 Masahiro Yamada 提交于 
      allnoconfig_y is an ugly hack that sets a symbol to 'y' by allnoconfig.

allnoconfig does not mean a minimal set of CONFIG options because a
bunch of prompts are hidden by 'if EMBEDDED' or 'if EXPERT', but I do
not like to hack Kconfig this way.

Use the pre-existing feature, KCONFIG_ALLCONFIG, to provide a one
liner config fragment. CONFIG_EMBEDDED=y is still forced when
allnoconfig is invoked as a part of tinyconfig.

No change in the .config file produced by 'make tinyconfig'.

The output of 'make allnoconfig' will be changed; we will get
CONFIG_EMBEDDED=n because allnoconfig literally sets all symbols to n.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
      f8f0d064
    • M
      kconfig: change defconfig_list option to environment variable · b75b0a81
      由 Masahiro Yamada 提交于 
      "defconfig_list" is a weird option that defines a static symbol that
declares the list of base config files in case the .config does not
exist yet.

This is quite different from other normal symbols; we just abused the
"string" type and the "default" properties to list out the input files.
They must be fixed values since these are searched for and loaded in
the parse stage.

It is an ugly hack, and should not exist in the first place. Providing
this feature as an environment variable is a saner approach.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
      b75b0a81
  33. 09 4月, 2021 2 次提交
    • N
      ima: enable signing of modules with build time generated key · 0165f4ca
      由 Nayna Jain 提交于 
      The kernel build process currently only signs kernel modules when
MODULE_SIG is enabled. Also, sign the kernel modules at build time when
IMA_APPRAISE_MODSIG is enabled.
Signed-off-by: NNayna Jain <nayna@linux.ibm.com>
Acked-by: NStefan Berger <stefanb@linux.ibm.com>
Signed-off-by: NMimi Zohar <zohar@linux.ibm.com>
      0165f4ca
    • S
      add support for Clang CFI · cf68fffb
      由 Sami Tolvanen 提交于 
      This change adds support for Clang’s forward-edge Control Flow
Integrity (CFI) checking. With CONFIG_CFI_CLANG, the compiler
injects a runtime check before each indirect function call to ensure
the target is a valid function with the correct static type. This
restricts possible call targets and makes it more difficult for
an attacker to exploit bugs that allow the modification of stored
function pointers. For more details, see:

  https://clang.llvm.org/docs/ControlFlowIntegrity.html

Clang requires CONFIG_LTO_CLANG to be enabled with CFI to gain
visibility to possible call targets. Kernel modules are supported
with Clang’s cross-DSO CFI mode, which allows checking between
independently compiled components.

With CFI enabled, the compiler injects a __cfi_check() function into
the kernel and each module for validating local call targets. For
cross-module calls that cannot be validated locally, the compiler
calls the global __cfi_slowpath_diag() function, which determines
the target module and calls the correct __cfi_check() function. This
patch includes a slowpath implementation that uses __module_address()
to resolve call targets, and with CONFIG_CFI_CLANG_SHADOW enabled, a
shadow map that speeds up module look-ups by ~3x.

Clang implements indirect call checking using jump tables and
offers two methods of generating them. With canonical jump tables,
the compiler renames each address-taken function to <function>.cfi
and points the original symbol to a jump table entry, which passes
__cfi_check() validation. This isn’t compatible with stand-alone
assembly code, which the compiler doesn’t instrument, and would
result in indirect calls to assembly code to fail. Therefore, we
default to using non-canonical jump tables instead, where the compiler
generates a local jump table entry <function>.cfi_jt for each
address-taken function, and replaces all references to the function
with the address of the jump table entry.

Note that because non-canonical jump table addresses are local
to each component, they break cross-module function address
equality. Specifically, the address of a global function will be
different in each module, as it's replaced with the address of a local
jump table entry. If this address is passed to a different module,
it won’t match the address of the same function taken there. This
may break code that relies on comparing addresses passed from other
components.

CFI checking can be disabled in a function with the __nocfi attribute.
Additionally, CFI can be disabled for an entire compilation unit by
filtering out CC_FLAGS_CFI.

By default, CFI failures result in a kernel panic to stop a potential
exploit. CONFIG_CFI_PERMISSIVE enables a permissive mode, where the
kernel prints out a rate-limited warning instead, and allows execution
to continue. This option is helpful for locating type mismatches, but
should only be enabled during development.
Signed-off-by: NSami Tolvanen <samitolvanen@google.com>
Reviewed-by: NKees Cook <keescook@chromium.org>
Tested-by: NNathan Chancellor <nathan@kernel.org>
Signed-off-by: NKees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210408182843.1754385-2-samitolvanen@google.com
      cf68fffb
  35. 05 4月, 2021 1 次提交
    • V
      cgroup: Add misc cgroup controller · a72232ea
      由 Vipin Sharma 提交于 
      The Miscellaneous cgroup provides the resource limiting and tracking
mechanism for the scalar resources which cannot be abstracted like the
other cgroup resources. Controller is enabled by the CONFIG_CGROUP_MISC
config option.

A resource can be added to the controller via enum misc_res_type{} in
the include/linux/misc_cgroup.h file and the corresponding name via
misc_res_name[] in the kernel/cgroup/misc.c file. Provider of the
resource must set its capacity prior to using the resource by calling
misc_cg_set_capacity().

Once a capacity is set then the resource usage can be updated using
charge and uncharge APIs. All of the APIs to interact with misc
controller are in include/linux/misc_cgroup.h.

Miscellaneous controller provides 3 interface files. If two misc
resources (res_a and res_b) are registered then:

misc.capacity
A read-only flat-keyed file shown only in the root cgroup.  It shows
miscellaneous scalar resources available on the platform along with
their quantities::

    $ cat misc.capacity
    res_a 50
    res_b 10

misc.current
A read-only flat-keyed file shown in the non-root cgroups.  It shows
the current usage of the resources in the cgroup and its children::

    $ cat misc.current
    res_a 3
    res_b 0

misc.max
A read-write flat-keyed file shown in the non root cgroups. Allowed
maximum usage of the resources in the cgroup and its children.::

    $ cat misc.max
    res_a max
    res_b 4

Limit can be set by::

    # echo res_a 1 > misc.max

Limit can be set to max by::

    # echo res_a max > misc.max

Limits can be set more than the capacity value in the misc.capacity
file.
Signed-off-by: NVipin Sharma <vipinsh@google.com>
Reviewed-by: NDavid Rientjes <rientjes@google.com>
Signed-off-by: NTejun Heo <tj@kernel.org>
      a72232ea
  37. 14 3月, 2021 1 次提交
    • M
      init/Kconfig: make COMPILE_TEST depend on HAS_IOMEM · ea29b20a
      由 Masahiro Yamada 提交于 
      I read the commit log of the following two:

- bc083a64 ("init/Kconfig: make COMPILE_TEST depend on !UML")
- 334ef6ed ("init/Kconfig: make COMPILE_TEST depend on !S390")

Both are talking about HAS_IOMEM dependency missing in many drivers.

So, 'depends on HAS_IOMEM' seems the direct, sensible solution to me.

This does not change the behavior of UML. UML still cannot enable
COMPILE_TEST because it does not provide HAS_IOMEM.

The current dependency for S390 is too strong. Under the condition of
CONFIG_PCI=y, S390 provides HAS_IOMEM, hence can enable COMPILE_TEST.

I also removed the meaningless 'default n'.

Link: https://lkml.kernel.org/r/20210224140809.1067582-1-masahiroy@kernel.orgSigned-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Arnd Bergmann <arnd@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: KP Singh <kpsingh@google.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Terrell <terrelln@fb.com>
Cc: Quentin Perret <qperret@google.com>
Cc: Valentin Schneider <valentin.schneider@arm.com>
Cc: "Enrico Weigelt, metux IT consult" <lkml@metux.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      ea29b20a
  39. 11 3月, 2021 1 次提交
  41. 28 2月, 2021 1 次提交
  43. 27 2月, 2021 2 次提交
  45. 25 2月, 2021 2 次提交
  47. 24 2月, 2021 1 次提交
    • L
      Kbuild: disable TRIM_UNUSED_KSYMS option · 5cf0fd59
      由 Linus Torvalds 提交于 
      The removal of EXPORT_UNUSED_SYMBOL() in commit 36794822 looks like
(and was sold as) a no-op, but it actually had a rather serious and
subtle side effect: the UNUSED_SYMBOLS option not only enabled the
removed (unused) functionality, it also _disabled_ the TRIM_UNUSED_KSYMS
functionality.

And it turns out that TRIM_UNUSED_KSYMS is a huge time waste, and takes
up a third of the kernel build time for me.  For no actual upside, since
no distro is likely to ever be able to enable it (because they all
support external kernel modules).

Rather than re-enable EXPORT_UNUSED_SYMBOL, this just disables the
TRIM_UNUSED_KSYMS option by marking it broken.  I'm tempted to just
remove the support entirely, but maybe somebody has a use-case and can
fix the behavior of it.

I could have just disabled it for COMPILE_TEST, but it really smells
like the TRIM_UNUSED_KSYMS option is badly done and not really useful,
so this takes the more direct approach - let's see if anybody ever
actually notices or complains.

Cc: Miroslav Benes <mbenes@suse.cz>
Cc: Emil Velikov <emil.l.velikov@gmail.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Jessica Yu <jeyu@kernel.org>
Fixes: 36794822 ("module: remove EXPORT_UNUSED_SYMBOL*")
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      5cf0fd59
  49. 22 2月, 2021 1 次提交
    • M
      kbuild: check the minimum linker version in Kconfig · 02aff859
      由 Masahiro Yamada 提交于 
      Unify the two scripts/ld-version.sh and scripts/lld-version.sh, and
check the minimum linker version like scripts/cc-version.sh did.

I tested this script for some corner cases reported in the past:

 - GNU ld version 2.25-15.fc23
   as reported by commit 8083013f ("ld-version: Fix it on Fedora")

 - GNU ld (GNU Binutils) 2.20.1.20100303
   as reported by commit 0d61ed17 ("ld-version: Drop the 4th and
   5th version components")

This script show an error message if the linker is too old:

  $ make LD=ld.lld-9
    SYNC    include/config/auto.conf
  ***
  *** Linker is too old.
  ***   Your LLD version:    9.0.1
  ***   Minimum LLD version: 10.0.1
  ***
  scripts/Kconfig.include:50: Sorry, this linker is not supported.
  make[2]: *** [scripts/kconfig/Makefile:71: syncconfig] Error 1
  make[1]: *** [Makefile:600: syncconfig] Error 2
  make: *** [Makefile:708: include/config/auto.conf] Error 2

I also moved the check for gold to this script, so gold is still rejected:

  $ make LD=gold
    SYNC    include/config/auto.conf
  gold linker is not supported as it is not capable of linking the kernel proper.
  scripts/Kconfig.include:50: Sorry, this linker is not supported.
  make[2]: *** [scripts/kconfig/Makefile:71: syncconfig] Error 1
  make[1]: *** [Makefile:600: syncconfig] Error 2
  make: *** [Makefile:708: include/config/auto.conf] Error 2

Thanks to David Laight for suggesting shell script improvements.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Acked-by: NNick Desaulniers <ndesaulniers@google.com>
Reviewed-by: NNathan Chancellor <nathan@kernel.org>
Tested-by: NNathan Chancellor <nathan@kernel.org>
      02aff859
  51. 16 2月, 2021 2 次提交
  53. 08 2月, 2021 1 次提交
  55. 06 2月, 2021 1 次提交
  57. 29 1月, 2021 1 次提交
  59. 28 1月, 2021 1 次提交