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Filename Latest commit message Latest commit date
Sandipan Das 4ca59b14e5 include/linux/compiler-clang.h: handle randomizable anonymous structs
The GCC randomize layout plugin can randomize the member offsets of
sensitive kernel data structures.  To use this feature, certain
annotations and members are added to the structures which affect the
member offsets even if this plugin is not used.

All of these structures are completely randomized, except for task_struct
which leaves out some of its members.  All the other members are wrapped
within an anonymous struct with the __randomize_layout attribute.  This is
done using the randomized_struct_fields_start and
randomized_struct_fields_end defines.

When the plugin is disabled, the behaviour of this attribute can vary
based on the GCC version.  For GCC 5.1+, this attribute maps to
__designated_init otherwise it is just an empty define but the anonymous
structure is still present.  For other compilers, both
randomized_struct_fields_start and randomized_struct_fields_end default
to empty defines meaning the anonymous structure is not introduced at
all.

So, if a module compiled with Clang, such as a BPF program, needs to
access task_struct fields such as pid and comm, the offsets of these
members as recognized by Clang are different from those recognized by
modules compiled with GCC.  If GCC 4.6+ is used to build the kernel,
this can be solved by introducing appropriate defines for Clang so that
the anonymous structure is seen when determining the offsets for the
members.

Link: http://lkml.kernel.org/r/20171109064645.25581-1-sandipan@linux.vnet.ibm.com
Signed-off-by: Sandipan Das <sandipan@linux.vnet.ibm.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Kate Stewart <kstewart@linuxfoundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Cc: Alexei Starovoitov <ast@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-11-17 16:10:01 -08:00
arch bug: define the "cut here" string in a single place 2017-11-17 16:10:01 -08:00
block
certs
crypto
Documentation kernel debug: support resetting WARN*_ONCE 2017-11-17 16:10:00 -08:00
drivers lkdtm: include WARN format string 2017-11-17 16:10:01 -08:00
firmware
fs proc: use do-while in name_to_int() 2017-11-17 16:10:00 -08:00
include include/linux/compiler-clang.h: handle randomizable anonymous structs 2017-11-17 16:10:01 -08:00
init Merge branch 'akpm' (patches from Andrew) 2017-11-15 19:42:40 -08:00
ipc
kernel bug: fix "cut here" location for __WARN_TAINT architectures 2017-11-17 16:10:01 -08:00
lib bug: define the "cut here" string in a single place 2017-11-17 16:10:01 -08:00
mm mm, compaction: remove unneeded pageblock_skip_persistent() checks 2017-11-17 16:10:00 -08:00
net Merge branch 'akpm' (patches from Andrew) 2017-11-15 19:42:40 -08:00
samples media updates for v4.15-rc1 2017-11-15 20:30:12 -08:00
scripts parse-maintainers: add ability to specify filenames 2017-11-17 16:10:01 -08:00
security
sound
tools libnvdimm for 4.15 2017-11-17 09:51:57 -08:00
usr
virt First batch of KVM changes for 4.15 2017-11-16 13:00:24 -08:00
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap Add Jason Gunthorpe as co-maintainer of the RDMA stack 2017-11-17 09:36:18 -08:00
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS libnvdimm for 4.15 2017-11-17 09:51:57 -08:00
Makefile
README

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

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

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.