strace test fails with kernel 5.0

[jirislaby]

Starting with kernel 5.0, the following test fails:

FAIL: bpf-obj_get_info_by_fd-prog-v.gen
=======================================

--- exp        2019-03-04 11:00:29.052272477 +0000
+++ log        2019-03-04 11:00:29.052272477 +0000
@@ -1,8 +1,8 @@
 bpf(BPF_MAP_CREATE, {map_type=BPF_MAP_TYPE_ARRAY, key_size=4, value_size=8, max_entries=1, map_flags=0, inner_map_fd=0</dev/null>, map_name="test_map", map_ifindex=0}, 48) = 3<anon_inode:bpf-map>
 bpf(BPF_PROG_LOAD, {prog_type=BPF_PROG_TYPE_SOCKET_FILTER, insn_cnt=9, insns=[{code=BPF_ALU64|BPF_K|BPF_MOV, dst_reg=BPF_REG_1, src_reg=BPF_REG_0, off=0, imm=0}, {code=BPF_STX|BPF_W|BPF_MEM, dst_reg=BPF_REG_10, src_reg=BPF_REG_1, off=-4, imm=0}, {code=BPF_ALU64|BPF_X|BPF_MOV, dst_reg=BPF_REG_2, src_reg=BPF_REG_10, off=0, imm=0}, {code=BPF_ALU64|BPF_K|BPF_ADD, dst_reg=BPF_REG_2, src_reg=BPF_REG_0, off=0, imm=0xfffffffc}, {code=BPF_LD|BPF_DW|BPF_IMM, dst_reg=BPF_REG_1, src_reg=BPF_REG_1, off=0, imm=0x3}, {code=BPF_LD|BPF_W|BPF_IMM, dst_reg=BPF_REG_0, src_reg=BPF_REG_0, off=0, imm=0}, {code=BPF_JMP|BPF_K|BPF_CALL, dst_reg=BPF_REG_0, src_reg=BPF_REG_0, off=0, imm=0x1}, {code=BPF_ALU64|BPF_K|BPF_MOV, dst_reg=BPF_REG_0, src_reg=BPF_REG_0, off=0, imm=0}, {code=BPF_JMP|BPF_K|BPF_EXIT, dst_reg=BPF_REG_0, src_reg=BPF_REG_0, off=0, imm=0}], license="BSD", log_level=42, log_size=4096, log_buf="", kern_version=KERNEL_VERSION(57005, 192, 222), prog_flags=0, prog_name="test_prog", prog_ifindex=0, expected_attach_type=BPF_CGROUP_INET_INGRESS}, 72) = 4<anon_inode:bpf-prog>
 bpf(BPF_OBJ_GET_INFO_BY_FD, {info={bpf_fd=3<anon_inode:bpf-map>, info_len=128 => 80, info={type=BPF_MAP_TYPE_ARRAY, id=14, key_size=4, value_size=8, max_entries=1, map_flags=0, name="test_map", ifindex=0, netns_dev=makedev(0, 0), netns_ino=0}}}, 16) = 0
-bpf(BPF_OBJ_GET_INFO_BY_FD, {info={bpf_fd=4<anon_inode:bpf-prog>, info_len=168, info={type=BPF_PROG_TYPE_SOCKET_FILTER, id=12, tag="\xda\xbf\x02\x07\xd1\x99\x24\x86", jited_prog_len=0, jited_prog_insns=NULL, xlated_prog_len=0, xlated_prog_insns=NULL, load_time=63441545963, created_by_uid=399, nr_map_ids=0 => 1, map_ids=NULL, name="test_prog", ifindex=0, netns_dev=makedev(0, 0), netns_ino=0}}}, 16) = 0
+bpf(BPF_OBJ_GET_INFO_BY_FD, {info={bpf_fd=4<anon_inode:bpf-prog>, info_len=168, info={type=BPF_PROG_TYPE_SOCKET_FILTER, id=12, tag="\xda\xbf\x02\x07\xd1\x99\x24\x86", jited_prog_len=0, jited_prog_insns=NULL, xlated_prog_len=0, xlated_prog_insns=NULL, load_time=63441545963, created_by_uid=399, nr_map_ids=0 => 1, map_ids=NULL, name="test_prog", ifindex=0, netns_dev=makedev(0, 0), netns_ino=0, /* bytes 104..167 */ "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x08\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"}}}, 16) = 0
 bpf(BPF_OBJ_GET_INFO_BY_FD, {info={bpf_fd=4<anon_inode:bpf-prog>, info_len=168, info={type=BPF_PROG_TYPE_SOCKET_FILTER, id=12, tag="\xda\xbf\x02\x07\xd1\x99\x24\x86", jited_prog_len=0, jited_prog_insns=NULL, xlated_prog_len=336, xlated_prog_insns=0x7f4129854000, load_time=63441545963, created_by_uid=399, nr_map_ids=2, map_ids=0x7f412984e000, name="test_prog", ifindex=0, netns_dev=makedev(0, 0), netns_ino=0}}}, 16) = -1 EFAULT (Bad address)
-bpf(BPF_OBJ_GET_INFO_BY_FD, {info={bpf_fd=4<anon_inode:bpf-prog>, info_len=168, info={type=BPF_PROG_TYPE_SOCKET_FILTER, id=12, tag="\xda\xbf\x02\x07\xd1\x99\x24\x86", jited_prog_len=0, jited_prog_insns=NULL, xlated_prog_len=0, xlated_prog_insns=[], load_time=63441545963, created_by_uid=399, nr_map_ids=0 => 1, map_ids=[], name="test_prog", ifindex=0, netns_dev=makedev(0, 0), netns_ino=0}}}, 16) = 0
-bpf(BPF_OBJ_GET_INFO_BY_FD, {info={bpf_fd=4<anon_inode:bpf-prog>, info_len=168, info={type=BPF_PROG_TYPE_SOCKET_FILTER, id=12, tag="\xda\xbf\x02\x07\xd1\x99\x24\x86", jited_prog_len=0, jited_prog_insns=NULL, xlated_prog_len=0, xlated_prog_insns=[], load_time=63441545963, created_by_uid=399, nr_map_ids=2 => 1, map_ids=[14], name="test_prog", ifindex=0, netns_dev=makedev(0, 0), netns_ino=0}}}, 16) = 0
+bpf(BPF_OBJ_GET_INFO_BY_FD, {info={bpf_fd=4<anon_inode:bpf-prog>, info_len=168, info={type=BPF_PROG_TYPE_SOCKET_FILTER, id=12, tag="\xda\xbf\x02\x07\xd1\x99\x24\x86", jited_prog_len=0, jited_prog_insns=NULL, xlated_prog_len=0, xlated_prog_insns=[], load_time=63441545963, created_by_uid=399, nr_map_ids=0 => 1, map_ids=[], name="test_prog", ifindex=0, netns_dev=makedev(0, 0), netns_ino=0, /* bytes 104..167 */ "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x08\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"}}}, 16) = 0
+bpf(BPF_OBJ_GET_INFO_BY_FD, {info={bpf_fd=4<anon_inode:bpf-prog>, info_len=168, info={type=BPF_PROG_TYPE_SOCKET_FILTER, id=12, tag="\xda\xbf\x02\x07\xd1\x99\x24\x86", jited_prog_len=0, jited_prog_insns=NULL, xlated_prog_len=0, xlated_prog_insns=[], load_time=63441545963, created_by_uid=399, nr_map_ids=2 => 1, map_ids=[14], name="test_prog", ifindex=0, netns_dev=makedev(0, 0), netns_ino=0, /* bytes 104..167 */ "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x08\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"}}}, 16) = 0
 +++ exited with 0 +++
bpf-obj_get_info_by_fd-prog-v.gen.test: failed test: ../../strace -a20 -y -v -e trace=bpf ../bpf-obj_get_info_by_fd-prog-v output mismatch
FAIL bpf-obj_get_info_by_fd-prog-v.gen.test (exit status: 1)

As can be seen, strace started putting /* bytes 104..167 */ "\x00\x00... to the output.

I tried also the latest version from git (7cc6eb7) with the same result.

[ldv-alt]

I suppose this is a known issue, strace decoder of BPF_OBJ_GET_INFO_BY_FD
command has to be updated to handle new features added after Linux v4.20:
https://lore.kernel.org/lkml/20190104231358.GC29869@altlinux.org/