LLVM upstream commit https://reviews.llvm.org/D102712 made some changes
to bpf relocations to make them llvm linker lld friendly. The scope of
existing relocations R_BPF_64_{64,32} is narrowed and new relocations
R_BPF_64_{ABS32,ABS64,NODYLD32} are introduced.
Let us add some documentation about llvm bpf relocations so people can
understand how to resolve them properly in their respective tools.
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20210526152457.335210-1-yhs@fb.com
This patch updates the README.rst to specify the clang requirement
to compile the bpf selftests that call kernel function.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20210330054156.2933804-1-kafai@fb.com
Verify that bpf_core_field_size() is working correctly with floats.
Also document the required clang version.
Suggested-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210309005649.162480-2-iii@linux.ibm.com
The original bcc pull request https://github.com/iovisor/bcc/pull/3270 exposed
a verifier failure with Clang 12/13 while Clang 4 works fine.
Further investigation exposed two issues:
Issue 1: LLVM may generate code which uses less refined value. The issue is
fixed in LLVM patch: https://reviews.llvm.org/D97479
Issue 2: Spills with initial value 0 are marked as precise which makes later
state pruning less effective. This is my rough initial analysis and
further investigation is needed to find how to improve verifier
pruning in such cases.
With the above LLVM patch, for the new loop6.c test, which has smaller loop
bound compared to original test, I got:
$ test_progs -s -n 10/16
...
stack depth 64
processed 390735 insns (limit 1000000) max_states_per_insn 87
total_states 8658 peak_states 964 mark_read 6
#10/16 loop6.o:OK
Use the original loop bound, i.e., commenting out "#define WORKAROUND", I got:
$ test_progs -s -n 10/16
...
BPF program is too large. Processed 1000001 insn
stack depth 64
processed 1000001 insns (limit 1000000) max_states_per_insn 91
total_states 23176 peak_states 5069 mark_read 6
...
#10/16 loop6.o:FAIL
The purpose of this patch is to provide a regression test for the above LLVM fix
and also provide a test case for further analyzing the verifier pruning issue.
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Zhenwei Pi <pizhenwei@bytedance.com>
Link: https://lore.kernel.org/bpf/20210226223810.236472-1-yhs@fb.com
Add a short note to make contributors aware of the existence of the
script. The documentation does not intentionally document all the
options of the script to avoid mentioning it in two places (it's
available in the usage / help message of the script).
Signed-off-by: KP Singh <kpsingh@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210204194544.3383814-3-kpsingh@kernel.org
A couple of places in the readme had invalid rst formatting causing the
rendering to be off. This patch fixes them with minimal edits.
Signed-off-by: Andrei Matei <andreimatei1@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20201122022205.57229-2-andreimatei1@gmail.com
The link was bad because of invalid rst; it was pointing to itself and
was rendering badly.
Signed-off-by: Andrei Matei <andreimatei1@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20201122022205.57229-1-andreimatei1@gmail.com
The main purpose of the profiler test to check different llvm generation
patterns to make sure the verifier can load these large programs.
Note that profiler.inc.h test doesn't follow strict kernel coding style.
The code was formatted in the kernel style, but variable declarations are
kept as-is to preserve original llvm IR pattern.
profiler1.c should pass with older and newer llvm
profiler[23].c may fail on older llvm that don't have:
https://reviews.llvm.org/D85570
because llvm may do speculative code motion optimization that
will generate code like this:
// r9 is a pointer to map_value
// r7 is a scalar
17: bf 96 00 00 00 00 00 00 r6 = r9
18: 0f 76 00 00 00 00 00 00 r6 += r7
19: a5 07 01 00 01 01 00 00 if r7 < 257 goto +1
20: bf 96 00 00 00 00 00 00 r6 = r9
// r6 is used here
The verifier will reject such code with the error:
"math between map_value pointer and register with unbounded min value is not allowed"
At insn 18 the r7 is indeed unbounded. The later insn 19 checks the bounds and
the insn 20 undoes map_value addition. It is currently impossible for the
verifier to understand such speculative pointer arithmetic. Hence llvm D85570
addresses it on the compiler side.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20201009011240.48506-4-alexei.starovoitov@gmail.com
Record which built-ins are optional and needed for some of recent BPF CO-RE
subtests. Document Clang diff that fixed corner-case issue with
__builtin_btf_type_id().
Suggested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20200820061411.1755905-4-andriin@fb.com
Getting a clean BPF selftests run involves ensuring latest trunk LLVM/clang
are used, pahole is recent (>=1.16) and config matches the specified
config file as closely as possible. Add to bpf_devel_QA.rst and point
tools/testing/selftests/bpf/README.rst to it.
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/1590146674-25485-1-git-send-email-alan.maguire@oracle.com
Commit 6879c042e1 ("tools/bpf: selftests: Add bpf_iter selftests")
added self tests for bpf_iter feature. But two subtests
ipv6_route and netlink needs llvm latest 10.x release branch
or trunk due to a bug in llvm BPF backend. This patch added
the file README.rst to document these two failures
so people using llvm 10.0.0 can be aware of them.
Suggested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200513180215.2949237-1-yhs@fb.com
