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mirror_ubuntu-kernels/tools/testing/selftests/bpf
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Yonghong Song 7fb5eefd76 selftests/bpf: Fix test_sysctl_loop{1, 2} failure due to clang change 
Andrii reported that with latest clang, when building selftests, we have
error likes:
  error: progs/test_sysctl_loop1.c:23:16: in function sysctl_tcp_mem i32 (%struct.bpf_sysctl*):
  Looks like the BPF stack limit of 512 bytes is exceeded.
  Please move large on stack variables into BPF per-cpu array map.

The error is triggered by the following LLVM patch:
  https://reviews.llvm.org/D87134

For example, the following code is from test_sysctl_loop1.c:
  static __always_inline int is_tcp_mem(struct bpf_sysctl *ctx)
  {
    volatile char tcp_mem_name[] = "net/ipv4/tcp_mem/very_very_very_very_long_pointless_string";
    ...
  }
Without the above LLVM patch, the compiler did optimization to load the string
(59 bytes long) with 7 64bit loads, 1 8bit load and 1 16bit load,
occupying 64 byte stack size.

With the above LLVM patch, the compiler only uses 8bit loads, but subregister is 32bit.
So stack requirements become 4 * 59 = 236 bytes. Together with other stuff on
the stack, total stack size exceeds 512 bytes, hence compiler complains and quits.

To fix the issue, removing "volatile" key word or changing "volatile" to
"const"/"static const" does not work, the string is put in .rodata.str1.1 section,
which libbpf did not process it and errors out with
  libbpf: elf: skipping unrecognized data section(6) .rodata.str1.1
  libbpf: prog 'sysctl_tcp_mem': bad map relo against '.L__const.is_tcp_mem.tcp_mem_name'
          in section '.rodata.str1.1'

Defining the string const as global variable can fix the issue as it puts the string constant
in '.rodata' section which is recognized by libbpf. In the future, when libbpf can process
'.rodata.str*.*' properly, the global definition can be changed back to local definition.

Defining tcp_mem_name as a global, however, triggered a verifier failure.
   ./test_progs -n 7/21
  libbpf: load bpf program failed: Permission denied
  libbpf: -- BEGIN DUMP LOG ---
  libbpf:
  invalid stack off=0 size=1
  verification time 6975 usec
  stack depth 160+64
  processed 889 insns (limit 1000000) max_states_per_insn 4 total_states
  14 peak_states 14 mark_read 10

  libbpf: -- END LOG --
  libbpf: failed to load program 'sysctl_tcp_mem'
  libbpf: failed to load object 'test_sysctl_loop2.o'
  test_bpf_verif_scale:FAIL:114
  #7/21 test_sysctl_loop2.o:FAIL
This actually exposed a bpf program bug. In test_sysctl_loop{1,2}, we have code
like
  const char tcp_mem_name[] = "<...long string...>";
  ...
  char name[64];
  ...
  for (i = 0; i < sizeof(tcp_mem_name); ++i)
      if (name[i] != tcp_mem_name[i])
          return 0;
In the above code, if sizeof(tcp_mem_name) > 64, name[i] access may be
out of bound. The sizeof(tcp_mem_name) is 59 for test_sysctl_loop1.c and
79 for test_sysctl_loop2.c.

Without promotion-to-global change, old compiler generates code where
the overflowed stack access is actually filled with valid value, so hiding
the bpf program bug. With promotion-to-global change, the code is different,
more specifically, the previous loading constants to stack is gone, and
"name" occupies stack[-64:0] and overflow access triggers a verifier error.
To fix the issue, adjust "name" buffer size properly.

Reported-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200909171542.3673449-1-yhs@fb.com
2020-09-09 11:21:34 -07:00
..
benchs selftests/bpf: Add sleepable tests 2020-08-28 21:20:33 +02:00
gnu
map_tests .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
prog_tests selftests/bpf: Fix check in global_data_init. 2020-09-03 17:33:31 -07:00
progs selftests/bpf: Fix test_sysctl_loop{1, 2} failure due to clang change 2020-09-09 11:21:34 -07:00
verifier selftests/bpf: Add test for map_ptr arithmetic 2020-09-08 18:04:07 -07:00
.gitignore selftests/bpf: Remove test_align leftovers 2020-08-20 14:25:25 -07:00
bench.c selftests/bpf: Add sleepable tests 2020-08-28 21:20:33 +02:00
bench.h selftests/bpf: Add benchmark runner infrastructure 2020-05-13 12:19:38 -07:00
bpf_legacy.h selftests: bpf: Remove unused bpf_map_def_legacy struct 2020-07-08 01:33:14 +02:00
bpf_rand.h
bpf_rlimit.h
bpf_tcp_helpers.h libbpf: Merge selftests' bpf_trace_helpers.h into libbpf's bpf_tracing.h 2020-03-02 16:25:14 -08:00
bpf_util.h selftests: Use consistent include paths for libbpf 2020-01-20 16:37:45 -08:00
cgroup_helpers.c bpf, selftests: Use single cgroup helpers for both test_sockmap/progs 2020-08-01 20:20:59 -07:00
cgroup_helpers.h bpf, selftests: Use single cgroup helpers for both test_sockmap/progs 2020-08-01 20:20:59 -07:00
config selftests/bpf: CONFIG_LIRC required for test_lirc_mode2.sh 2020-05-23 01:12:31 +02:00
flow_dissector_load.c
flow_dissector_load.h selftests/bpf: Don't use deprecated libbpf APIs 2020-09-03 17:14:40 -07:00
get_cgroup_id_user.c bpf, selftests: Use single cgroup helpers for both test_sockmap/progs 2020-08-01 20:20:59 -07:00
Makefile Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next 2020-09-01 13:22:59 -07:00
netcnt_common.h
network_helpers.c bpf: selftests: Add fastopen_connect to network_helpers 2020-08-24 14:35:00 -07:00
network_helpers.h bpf: selftests: Add fastopen_connect to network_helpers 2020-08-24 14:35:00 -07:00
README.rst selftests/bpf: List newest Clang built-ins needed for some CO-RE selftests 2020-08-20 16:45:09 +02:00
settings selftests: bpf: Switch off timeout 2020-08-06 16:57:05 -07:00
tcp_client.py bpf, selftests: use :: 1 for localhost in tcp_server.py 2020-07-29 00:10:35 +02:00
tcp_server.py bpf, selftests: use :: 1 for localhost in tcp_server.py 2020-07-29 00:10:35 +02:00
test_bpftool_build.sh selftests, bpftool: Skip the build test if not in tree 2019-11-24 16:58:45 -08:00
test_bpftool.py selftests/bpf: Add test for "bpftool feature" command 2020-02-26 18:34:34 +01:00
test_bpftool.sh selftests/bpf: Add test for "bpftool feature" command 2020-02-26 18:34:34 +01:00
test_btf.c selftest/bpf: Fix compilation warnings in 32-bit mode 2020-08-13 16:45:41 -07:00
test_btf.h
test_cgroup_storage.c bpf, selftests: Use single cgroup helpers for both test_sockmap/progs 2020-08-01 20:20:59 -07:00
test_cpp.cpp selftests: Use consistent include paths for libbpf 2020-01-20 16:37:45 -08:00
test_current_pid_tgid_new_ns.c selftests/bpf: Fix two minor compilation warnings reported by GCC 4.9 2020-08-20 16:45:09 +02:00
test_dev_cgroup.c bpf, selftests: Use single cgroup helpers for both test_sockmap/progs 2020-08-01 20:20:59 -07:00
test_flow_dissector.c
test_flow_dissector.sh selftests/bpf: Add test based on port range for BPF flow dissector 2020-01-27 11:25:07 +01:00
test_ftrace.sh selftests/bpf: Test function_graph tracer and bpf trampoline together 2019-12-11 15:19:29 -08:00
test_iptunnel_common.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 206 2019-05-30 11:29:53 -07:00
test_kmod.sh selftests: bpf: test_kmod.sh: Fix running out of srctree 2020-07-21 13:26:24 -07:00
test_lirc_mode2_user.c
test_lirc_mode2.sh
test_lpm_map.c bpf: lpm_trie: check left child of last leftmost node for NULL 2019-06-11 13:52:37 +02:00
test_lru_map.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 206 2019-05-30 11:29:53 -07:00
test_lwt_ip_encap.sh selftests/bpf: More compatible nc options in test_lwt_ip_encap 2019-10-08 23:59:22 +02:00
test_lwt_seg6local.sh selftests/bpf: Fix test_lwt_seg6local.sh hangs 2020-07-21 13:26:26 -07:00
test_maps.c selftests: bpf: Fix detach from sockmap tests 2020-07-09 23:41:37 +02:00
test_maps.h
test_netcnt.c bpf, selftests: Use single cgroup helpers for both test_sockmap/progs 2020-08-01 20:20:59 -07:00
test_offload.py selftests/bpf: fix netdevsim trap_flow_action_cookie read 2020-07-30 16:33:07 -07:00
test_progs.c selftests/bpf: test_progs avoid minus shell exit codes 2020-07-09 00:35:33 +02:00
test_progs.h selftest/bpf: Fix compilation warnings in 32-bit mode 2020-08-13 16:45:41 -07:00
test_select_reuseport_common.h
test_skb_cgroup_id_user.c bpf, selftests: Use single cgroup helpers for both test_sockmap/progs 2020-08-01 20:20:59 -07:00
test_skb_cgroup_id.sh
test_sock_addr.c bpf, selftests: Use single cgroup helpers for both test_sockmap/progs 2020-08-01 20:20:59 -07:00
test_sock_addr.sh
test_sock_fields.c bpf, selftests: Use single cgroup helpers for both test_sockmap/progs 2020-08-01 20:20:59 -07:00
test_sock.c bpf, selftests: Use single cgroup helpers for both test_sockmap/progs 2020-08-01 20:20:59 -07:00
test_socket_cookie.c selftests/bpf: Don't use deprecated libbpf APIs 2020-09-03 17:14:40 -07:00
test_sockmap.c bpf, selftests: Use single cgroup helpers for both test_sockmap/progs 2020-08-01 20:20:59 -07:00
test_stub.c selftests/bpf: Integrate verbose verifier log into test_progs 2019-11-24 16:58:45 -08:00
test_sysctl.c bpf, selftests: Use single cgroup helpers for both test_sockmap/progs 2020-08-01 20:20:59 -07:00
test_tag.c
test_tc_edt.sh selftests/bpf: More compatible nc options in test_tc_edt 2019-10-18 22:33:57 +02:00
test_tc_tunnel.sh selftests, bpf: Fix test_tc_tunnel hanging 2019-11-18 21:31:49 +01:00
test_tcp_check_syncookie_user.c selftests/bpf: add test for bpf_tcp_gen_syncookie 2019-07-30 21:03:05 -07:00
test_tcp_check_syncookie.sh selftests/bpf: add test for bpf_tcp_gen_syncookie 2019-07-30 21:03:05 -07:00
test_tcp_hdr_options.h bpf: selftests: Tcp header options 2020-08-24 14:35:00 -07:00
test_tcpbpf_user.c bpf, selftests: Use single cgroup helpers for both test_sockmap/progs 2020-08-01 20:20:59 -07:00
test_tcpbpf.h selftests/bpf: De-flake test_tcpbpf 2019-12-04 18:01:05 -08:00
test_tcpnotify_user.c bpf: Fix compilation warning of selftests 2020-08-06 16:58:42 -07:00
test_tcpnotify.h
test_tunnel.sh selftests/bpf: fail test_tunnel.sh if subtests fail 2019-05-28 11:08:57 +02:00
test_verifier_log.c
test_verifier.c selftests/bpf: Add verifier test for d_path helper 2020-08-25 15:41:15 -07:00
test_xdp_meta.sh
test_xdp_redirect.sh selftests/bpf: Add xdpdrv mode for test_xdp_redirect 2020-07-31 00:43:49 +02:00
test_xdp_veth.sh selftests, bpf: Add test for veth native XDP 2019-06-24 18:18:30 -07:00
test_xdp_vlan_mode_generic.sh selftests/bpf: add wrapper scripts for test_xdp_vlan.sh 2019-08-05 11:17:40 -07:00
test_xdp_vlan_mode_native.sh selftests/bpf: add wrapper scripts for test_xdp_vlan.sh 2019-08-05 11:17:40 -07:00
test_xdp_vlan.sh selftests/bpf: reduce time to execute test_xdp_vlan.sh 2019-08-05 11:17:40 -07:00
test_xdping.sh selftests/bpf: measure RTT from xdp using xdping 2019-05-31 19:53:45 -07:00
testing_helpers.c selftests/bpf: Add link detach tests for cgroup, netns, and xdp bpf_links 2020-08-01 20:38:28 -07:00
testing_helpers.h selftests/bpf: Add link detach tests for cgroup, netns, and xdp bpf_links 2020-08-01 20:38:28 -07:00
trace_helpers.c samples, bpf: Move read_trace_pipe to trace_helpers 2020-03-23 22:27:51 +01:00
trace_helpers.h samples, bpf: Move read_trace_pipe to trace_helpers 2020-03-23 22:27:51 +01:00
urandom_read.c
with_addr.sh
with_tunnels.sh
xdping.c selftests: bpf: correct perror strings 2019-11-28 22:40:30 -08:00
xdping.h selftests/bpf: measure RTT from xdp using xdping 2019-05-31 19:53:45 -07:00

README.rst 

==================
BPF Selftest Notes
==================
General instructions on running selftests can be found in
`Documentation/bpf/bpf_devel_QA.rst`_.

Additional information about selftest failures are
documented here.

bpf_iter test failures with clang/llvm 10.0.0
=============================================

With clang/llvm 10.0.0, the following two bpf_iter tests failed:
  * ``bpf_iter/ipv6_route``
  * ``bpf_iter/netlink``

The symptom for ``bpf_iter/ipv6_route`` looks like

.. code-block:: c

  2: (79) r8 = *(u64 *)(r1 +8)
  ...
  14: (bf) r2 = r8
  15: (0f) r2 += r1
  ; BPF_SEQ_PRINTF(seq, "%pi6 %02x ", &rt->fib6_dst.addr, rt->fib6_dst.plen);
  16: (7b) *(u64 *)(r8 +64) = r2
  only read is supported

The symptom for ``bpf_iter/netlink`` looks like

.. code-block:: c

  ; struct netlink_sock *nlk = ctx->sk;
  2: (79) r7 = *(u64 *)(r1 +8)
  ...
  15: (bf) r2 = r7
  16: (0f) r2 += r1
  ; BPF_SEQ_PRINTF(seq, "%pK %-3d ", s, s->sk_protocol);
  17: (7b) *(u64 *)(r7 +0) = r2
  only read is supported

This is due to a llvm BPF backend bug. The fix 
  https://reviews.llvm.org/D78466
has been pushed to llvm 10.x release branch and will be
available in 10.0.1. The fix is available in llvm 11.0.0 trunk.

BPF CO-RE-based tests and Clang version
=======================================

A set of selftests use BPF target-specific built-ins, which might require
bleeding-edge Clang versions (Clang 12 nightly at this time).

Few sub-tests of core_reloc test suit (part of test_progs test runner) require
the following built-ins, listed with corresponding Clang diffs introducing
them to Clang/LLVM. These sub-tests are going to be skipped if Clang is too
old to support them, they shouldn't cause build failures or runtime test
failures:

  - __builtin_btf_type_id() ([0], [1], [2]);
  - __builtin_preserve_type_info(), __builtin_preserve_enum_value() ([3], [4]).

  [0] https://reviews.llvm.org/D74572
  [1] https://reviews.llvm.org/D74668
  [2] https://reviews.llvm.org/D85174
  [3] https://reviews.llvm.org/D83878
  [4] https://reviews.llvm.org/D83242