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Commit8651ec01da("module: add support for symbol namespaces.") broke linking for arm64 defconfig: | lib/crypto/arc4.o: In function `__ksymtab_arc4_setkey': | arc4.c:(___ksymtab+arc4_setkey+0x8): undefined reference to `no symbol' | lib/crypto/arc4.o: In function `__ksymtab_arc4_crypt': | arc4.c:(___ksymtab+arc4_crypt+0x8): undefined reference to `no symbol' This is because the dummy initialisation of the 'namespace_offset' field in 'struct kernel_symbol' when using EXPORT_SYMBOL on architectures with support for PREL32 locations uses an offset from an absolute address (0) in an effort to trick 'offset_to_pointer' into behaving as a NOP, allowing non-namespaced symbols to be treated in the same way as those belonging to a namespace. Unfortunately, place-relative relocations require a symbol reference rather than an absolute value and, although x86 appears to get away with this due to placing the kernel text at the top of the address space, it almost certainly results in a runtime failure if the kernel is relocated dynamically as a result of KASLR. Rework 'namespace_offset' so that a value of 0, which cannot occur for a valid namespaced symbol, indicates that the corresponding symbol does not belong to a namespace. Cc: Matthias Maennich <maennich@google.com> Cc: Jessica Yu <jeyu@kernel.org> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Fixes:8651ec01da("module: add support for symbol namespaces.") Reported-by: kbuild test robot <lkp@intel.com> Tested-by: Matthias Maennich <maennich@google.com> Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Reviewed-by: Matthias Maennich <maennich@google.com> Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Will Deacon <will@kernel.org> Signed-off-by: Jessica Yu <jeyu@kernel.org>
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.