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Jesper Dangaard Brouer e3d91b0ca5 tools/libbpf: handle issues with bpf ELF objects containing .eh_frames
V3: More generic skipping of relo-section (suggested by Daniel)

If clang >= 4.0.1 is missing the option '-target bpf', it will cause
llc/llvm to create two ELF sections for "Exception Frames", with
section names '.eh_frame' and '.rel.eh_frame'.

The BPF ELF loader library libbpf fails when loading files with these
sections.  The other in-kernel BPF ELF loader in samples/bpf/bpf_load.c,
handle this gracefully. And iproute2 loader also seems to work with these
"eh" sections.

The issue in libbpf is caused by bpf_object__elf_collect() skipping
some sections, and later when performing relocation it will be
pointing to a skipped section, as these sections cannot be found by
bpf_object__find_prog_by_idx() in bpf_object__collect_reloc().

This is a general issue that also occurs for other sections, like
debug sections which are also skipped and can have relo section.

As suggested by Daniel.  To avoid keeping state about all skipped
sections, instead perform a direct qlookup in the ELF object.  Lookup
the section that the relo-section points to and check if it contains
executable machine instructions (denoted by the sh_flags
SHF_EXECINSTR).  Use this check to also skip irrelevant relo-sections.

Note, for samples/bpf/ the '-target bpf' parameter to clang cannot be used
due to incompatibility with asm embedded headers, that some of the samples
include. This is explained in more details by Yonghong Song in bpf_devel_QA.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-02-09 00:25:12 +01:00
arch Merge branch 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-02-04 11:45:55 -08:00
block for-linus-20180204 2018-02-04 11:16:35 -08:00
certs
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2018-01-31 14:22:45 -08:00
Documentation Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf 2018-02-04 16:46:58 -05:00
drivers nfp: bpf: fix immed relocation for larger offsets 2018-02-08 11:59:50 +01:00
firmware kbuild: remove all dummy assignments to obj- 2017-11-18 11:46:06 +09:00
fs Refactor support for encrypted symlinks to move common code to fscrypt. 2018-02-04 10:43:12 -08:00
include bpf: sockmap, add sock close() hook to remove socks 2018-02-06 11:39:32 +01:00
init init_task out-of-lining 2018-01-29 09:08:34 -08:00
ipc Merge branch 'work.mqueue' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2018-01-30 18:32:21 -08:00
kernel bpf: sockmap, fix leaking maps with attached but not detached progs 2018-02-06 11:39:32 +01:00
lib bpf: fix selftests/bpf test_kmod.sh failure when CONFIG_BPF_JIT_ALWAYS_ON=y 2018-02-05 00:31:57 +01:00
LICENSES LICENSES: Add MPL-1.1 license 2018-01-06 10:59:44 -07:00
mm Currently, hardened usercopy performs dynamic bounds checking on slab 2018-02-03 16:25:42 -08:00
net net: add a UID to use for ULP socket assignment 2018-02-06 11:39:31 +01:00
samples Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf 2018-02-04 16:46:58 -05:00
scripts Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk 2018-02-01 13:36:15 -08:00
security Currently, hardened usercopy performs dynamic bounds checking on slab 2018-02-03 16:25:42 -08:00
sound Driver Core updates for 4.16-rc1 2018-02-01 10:00:28 -08:00
tools tools/libbpf: handle issues with bpf ELF objects containing .eh_frames 2018-02-09 00:25:12 +01:00
usr
virt Currently, hardened usercopy performs dynamic bounds checking on slab 2018-02-03 16:25:42 -08:00
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore scripts/package: snap-pkg target 2017-12-13 00:00:18 +09:00
.mailmap mailmap: update Mark Yao's email address 2018-01-04 16:45:09 -08:00
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS Bug fixes galore, removal of the ntb atom driver, and updates to the ntb 2018-02-04 11:13:49 -08:00
Makefile Kconfig updates for v4.16 2018-02-01 11:45:49 -08:00
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.