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Masahiro Yamada 9371f86ecb bpfilter: match bit size of bpfilter_umh to that of the kernel
bpfilter_umh is built for the default machine bit of the compiler,
which may not match to the bit size of the kernel.

This happens in the scenario below:

You can use biarch GCC that defaults to 64-bit for building the 32-bit
kernel. In this case, Kbuild passes -m32 to teach the compiler to
produce 32-bit kernel space objects. However, it is missing when
building bpfilter_umh. It is built as a 64-bit ELF, and then embedded
into the 32-bit kernel.

The 32-bit kernel and 64-bit umh is a bad combination.

In theory, we can have 32-bit umh running on 64-bit kernel, but we do
not have a good reason to support such a usecase.

The best is to match the bit size between them.

Pass -m32 or -m64 to the umh build command if it is found in
$(KBUILD_CFLAGS). Evaluate CC_CAN_LINK against the kernel bit-size.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2020-05-17 18:52:01 +09:00
arch kbuild: remove unused AS assignment 2020-05-12 13:28:33 +09:00
block bdi: use bdi_dev_name() to get device name 2020-05-09 16:07:39 -06:00
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drivers IOMMU Fixes for Linux v5.7-rc4 2020-05-10 11:26:23 -07:00
fs block-5.7-2020-05-09 2020-05-10 11:16:07 -07:00
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init bpfilter: match bit size of bpfilter_umh to that of the kernel 2020-05-17 18:52:01 +09:00
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kernel Stop the ad-hoc games with -Wno-maybe-initialized 2020-05-09 13:57:10 -07:00
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scripts kbuild: warn if always, hostprogs-y, or hostprogs-m is used 2020-05-17 18:51:28 +09:00
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tools A set of fixes for x86: 2020-05-10 11:59:53 -07:00
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README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.