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From:   Martin Lau <kafai@fb.com>
To:     Heiko Carstens <heiko.carstens@de.ibm.com>
CC:     Eugene Syromyatnikov <evgsyr@gmail.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        Yonghong Song <yhs@fb.com>,
        Alexei Starovoitov <ast@kernel.org>,
        "Dmitry V. Levin" <ldv@altlinux.org>
Subject: Re: "bpf: Improve the info.func_info and info.func_info_rec_size
 behavior" breaks strace self tests
Thread-Topic: "bpf: Improve the info.func_info and info.func_info_rec_size
 behavior" breaks strace self tests
Thread-Index: AQHUo1n4FpegqxaW/0erdMKyg0tF/KWd6bEAgAA6fACAABP7AA==
Date:   Thu, 3 Jan 2019 23:52:51 +0000
Message-ID: <20190103235248.kxvhhwq4brcdxzps@kafai-mbp>
References: <20190103114613.GB3957@osiris>
 <20190103191158.yu4cjkb3wd3zvpqk@kafai-mbp> <20190103224118.GA4491@osiris>
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On Thu, Jan 03, 2019 at 11:41:18PM +0100, Heiko Carstens wrote:
> On Thu, Jan 03, 2019 at 07:12:05PM +0000, Martin Lau wrote:
> > On Thu, Jan 03, 2019 at 12:46:13PM +0100, Heiko Carstens wrote:
> > > Hello,
> > >=20
> > > the kernel commit 7337224fc150 ("bpf: Improve the info.func_info and
> > > info.func_info_rec_size behavior") breaks one of strace's self tests:
> > >=20
> > > FAIL: bpf-obj_get_info_by_fd-prog-v.gen
> > The strace's bpf-obj_get_info_by_fd-prog-v test did fail.  However,
> > I failed to see how 7337224fc150 broke it.  How do you trace down to
> > commit 7337224fc150 and can you share your test output?
> >=20
> > The failure I can reproduce is EFAULT.  It should have been failing
> > as early as "nr_jited_ksyms" is added to "struct bpf_prog_info"
> > in linux/bpf.h.
>=20
> Ah, sorry(!), I forgot to mention an important detail: the test
> failure happens only if executed as normal (non-root) user.
>=20
> With 7337224fc150 ("bpf: Improve the info.func_info and
> info.func_info_rec_size behavior") the failure happens. With commit
> 30da46b5dc3a ("tools: bpftool: add a command to dump the trace pipe")
> it passes; which is one commit earlier.
>=20
> FAIL: bpf-obj_get_info_by_fd-prog-v.gen
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
>=20
> --- exp	2019-01-03 23:31:49.576949303 +0100
> +++ log	2019-01-03 23:31:49.576949303 +0100
> @@ -1,8 +1,8 @@
>  bpf(BPF_MAP_CREATE, {map_type=3DBPF_MAP_TYPE_ARRAY, key_size=3D4, value_=
size=3D8, max_entries=3D1, map_flags=3D0, inner_map_fd=3D0</dev/null>, map_=
name=3D"test_map", map_ifindex=3D0}, 48) =3D 3<anon_inode:bpf-map>
>  bpf(BPF_PROG_LOAD, {prog_type=3DBPF_PROG_TYPE_SOCKET_FILTER, insn_cnt=3D=
9, insns=3D[{code=3DBPF_ALU64|BPF_K|BPF_MOV, dst_reg=3DBPF_REG_1, src_reg=
=3DBPF_REG_0, off=3D0, imm=3D0}, {code=3DBPF_STX|BPF_W|BPF_MEM, dst_reg=3DB=
PF_REG_10, src_reg=3DBPF_REG_1, off=3D-4, imm=3D0}, {code=3DBPF_ALU64|BPF_X=
|BPF_MOV, dst_reg=3DBPF_REG_2, src_reg=3DBPF_REG_10, off=3D0, imm=3D0}, {co=
de=3DBPF_ALU64|BPF_K|BPF_ADD, dst_reg=3DBPF_REG_2, src_reg=3DBPF_REG_0, off=
=3D0, imm=3D0xfffffffc}, {code=3DBPF_LD|BPF_DW|BPF_IMM, dst_reg=3DBPF_REG_1=
, src_reg=3DBPF_REG_1, off=3D0, imm=3D0x3}, {code=3DBPF_LD|BPF_W|BPF_IMM, d=
st_reg=3DBPF_REG_0, src_reg=3DBPF_REG_0, off=3D0, imm=3D0}, {code=3DBPF_JMP=
|BPF_K|BPF_CALL, dst_reg=3DBPF_REG_0, src_reg=3DBPF_REG_0, off=3D0, imm=3D0=
x1}, {code=3DBPF_ALU64|BPF_K|BPF_MOV, dst_reg=3DBPF_REG_0, src_reg=3DBPF_RE=
G_0, off=3D0, imm=3D0}, {code=3DBPF_JMP|BPF_K|BPF_EXIT, dst_reg=3DBPF_REG_0=
, src_reg=3DBPF_REG_0, off=3D0, imm=3D0}], license=3D"BSD", log_level=3D42,=
 log_size=3D4096, log_buf=3D"", kern_version=3DKERNEL_VERSION(57005, 192, 2=
22), prog_flags=3D0, prog_name=3D"test_prog", prog_ifindex=3D0, expected_at=
tach_type=3DBPF_CGROUP_INET_INGRESS}, 72) =3D 4<anon_inode:bpf-prog>
>  bpf(BPF_OBJ_GET_INFO_BY_FD, {info=3D{bpf_fd=3D3<anon_inode:bpf-map>, inf=
o_len=3D128 =3D> 80, info=3D{type=3DBPF_MAP_TYPE_ARRAY, id=3D15, key_size=
=3D4, value_size=3D8, max_entries=3D1, map_flags=3D0, name=3D"test_map", if=
index=3D0, netns_dev=3Dmakedev(0, 0), netns_ino=3D0}}}, 16) =3D 0
> -bpf(BPF_OBJ_GET_INFO_BY_FD, {info=3D{bpf_fd=3D4<anon_inode:bpf-prog>, in=
fo_len=3D168 =3D> 152, info=3D{type=3DBPF_PROG_TYPE_SOCKET_FILTER, id=3D8, =
tag=3D"\xde\x90\x83\x18\xfb\x16\xd8\x9c", jited_prog_len=3D0, jited_prog_in=
sns=3DNULL, xlated_prog_len=3D0, xlated_prog_insns=3DNULL, load_time=3D2828=
1352029, created_by_uid=3D1000, nr_map_ids=3D0 =3D> 1, map_ids=3DNULL, name=
=3D"test_prog", ifindex=3D0, netns_dev=3Dmakedev(0, 0), netns_ino=3D0}}}, 1=
6) =3D 0
> -bpf(BPF_OBJ_GET_INFO_BY_FD, {info=3D{bpf_fd=3D4<anon_inode:bpf-prog>, in=
fo_len=3D152, info=3D{type=3DBPF_PROG_TYPE_SOCKET_FILTER, id=3D8, tag=3D"\x=
de\x90\x83\x18\xfb\x16\xd8\x9c", jited_prog_len=3D0, jited_prog_insns=3DNUL=
L, xlated_prog_len=3D336, xlated_prog_insns=3D0x3ff8d6f7000, load_time=3D28=
281352029, created_by_uid=3D1000, nr_map_ids=3D2, map_ids=3D0x3ff8d6f1000, =
name=3D"test_prog", ifindex=3D0, netns_dev=3Dmakedev(0, 0), netns_ino=3D0}}=
}, 16) =3D -1 EFAULT (Bad address)
> -bpf(BPF_OBJ_GET_INFO_BY_FD, {info=3D{bpf_fd=3D4<anon_inode:bpf-prog>, in=
fo_len=3D152, info=3D{type=3DBPF_PROG_TYPE_SOCKET_FILTER, id=3D8, tag=3D"\x=
de\x90\x83\x18\xfb\x16\xd8\x9c", jited_prog_len=3D0, jited_prog_insns=3DNUL=
L, xlated_prog_len=3D0, xlated_prog_insns=3D[], load_time=3D28281352029, cr=
eated_by_uid=3D1000, nr_map_ids=3D0 =3D> 1, map_ids=3D[], name=3D"test_prog=
", ifindex=3D0, netns_dev=3Dmakedev(0, 0), netns_ino=3D0}}}, 16) =3D 0
> -bpf(BPF_OBJ_GET_INFO_BY_FD, {info=3D{bpf_fd=3D4<anon_inode:bpf-prog>, in=
fo_len=3D152, info=3D{type=3DBPF_PROG_TYPE_SOCKET_FILTER, id=3D8, tag=3D"\x=
de\x90\x83\x18\xfb\x16\xd8\x9c", jited_prog_len=3D0, jited_prog_insns=3DNUL=
L, xlated_prog_len=3D0, xlated_prog_insns=3D[], load_time=3D28281352029, cr=
eated_by_uid=3D1000, nr_map_ids=3D2 =3D> 1, map_ids=3D[15], name=3D"test_pr=
og", ifindex=3D0, netns_dev=3Dmakedev(0, 0), netns_ino=3D0}}}, 16) =3D 0
> +bpf(BPF_OBJ_GET_INFO_BY_FD, {info=3D{bpf_fd=3D4<anon_inode:bpf-prog>, in=
fo_len=3D168 =3D> 152, info=3D{type=3DBPF_PROG_TYPE_SOCKET_FILTER, id=3D8, =
tag=3D"\xde\x90\x83\x18\xfb\x16\xd8\x9c", jited_prog_len=3D0, jited_prog_in=
sns=3DNULL, xlated_prog_len=3D0, xlated_prog_insns=3DNULL, load_time=3D2828=
1352029, created_by_uid=3D1000, nr_map_ids=3D0 =3D> 1, map_ids=3DNULL, name=
=3D"test_prog", ifindex=3D0, netns_dev=3Dmakedev(0, 0), netns_ino=3D0, /* b=
ytes 104..151 */ "\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\x08\x00=
\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"}}}, 16) =3D 0
> +bpf(BPF_OBJ_GET_INFO_BY_FD, {info=3D{bpf_fd=3D4<anon_inode:bpf-prog>, in=
fo_len=3D152, info=3D{type=3DBPF_PROG_TYPE_SOCKET_FILTER, id=3D8, tag=3D"\x=
de\x90\x83\x18\xfb\x16\xd8\x9c", jited_prog_len=3D0, jited_prog_insns=3DNUL=
L, xlated_prog_len=3D336, xlated_prog_insns=3D0x3ff8d6f7000, load_time=3D28=
281352029, created_by_uid=3D1000, nr_map_ids=3D2, map_ids=3D0x3ff8d6f1000, =
name=3D"test_prog", ifindex=3D0, netns_dev=3Dmakedev(0, 0), netns_ino=3D0, =
/* bytes 104..151 */ "\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\x08=
\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"}}}, 16) =
=3D -1 EFAULT (Bad address)
> +bpf(BPF_OBJ_GET_INFO_BY_FD, {info=3D{bpf_fd=3D4<anon_inode:bpf-prog>, in=
fo_len=3D152, info=3D{type=3DBPF_PROG_TYPE_SOCKET_FILTER, id=3D8, tag=3D"\x=
de\x90\x83\x18\xfb\x16\xd8\x9c", jited_prog_len=3D0, jited_prog_insns=3DNUL=
L, xlated_prog_len=3D0, xlated_prog_insns=3D[], load_time=3D28281352029, cr=
eated_by_uid=3D1000, nr_map_ids=3D0 =3D> 1, map_ids=3D[], name=3D"test_prog=
", ifindex=3D0, netns_dev=3Dmakedev(0, 0), netns_ino=3D0, /* bytes 104..151=
 */ "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x=
00\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"}}}, 16) =3D 0
> +bpf(BPF_OBJ_GET_INFO_BY_FD, {info=3D{bpf_fd=3D4<anon_inode:bpf-prog>, in=
fo_len=3D152, info=3D{type=3DBPF_PROG_TYPE_SOCKET_FILTER, id=3D8, tag=3D"\x=
de\x90\x83\x18\xfb\x16\xd8\x9c", jited_prog_len=3D0, jited_prog_insns=3DNUL=
L, xlated_prog_len=3D0, xlated_prog_insns=3D[], load_time=3D28281352029, cr=
eated_by_uid=3D1000, nr_map_ids=3D2 =3D> 1, map_ids=3D[15], name=3D"test_pr=
og", ifindex=3D0, netns_dev=3Dmakedev(0, 0), netns_ino=3D0, /* bytes 104..1=
51 */ "\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\x08\x00\x00\x00\x0=
0\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"}}}, 16) =3D 0
>  +++ exited with 0 +++
> bpf-obj_get_info_by_fd-prog-v.gen.test: failed test: ../../strace -a20 -y=
 -v -e trace=3Dbpf ../bpf-obj_get_info_by_fd-prog-v output mismatch
> FAIL bpf-obj_get_info_by_fd-prog-v.gen.test (exit status: 1)
>
I am running against linux-next.  I don't see how root and non-root affect
thing here.  I guess the test has been running without jit so far?

1) root or not, if jit is enabled,
   without the memset() fix in the bpf-obj_get_info_by_fd.c in my last emai=
l,
   they all failed:
   [root@arch-fb-vm1 tests]# ./bpf-obj_get_info_by_fd-prog-v.gen.test
   BPF_OBJ_GET_INFO_BY_FD prog 2 failed: Bad address
   bpf-obj_get_info_by_fd-prog-v.gen.test: skipped test: ../bpf-obj_get_inf=
o_by_fd-prog-v exited with code 77

   Please fix this first.

2) After having the memset fix:
   Root or not, for jited program, if I run
   ./bpf-obj_get_info_by_fd-prog-v.gen.test, they failed.  If I read the
   init.sh correclty, it fails because there is a diff between the
   ./bpf-obj_get_info_by_fd-prog-v stdout and the "strace -o log".  I think
   "strace -o log" only has the /* bytes 104..151 */ part if some bytes
   are non-zero?

   Regardless, the test program "bpf-obj_get_info_by_fd.c" is telling
   the kernel that the userspace "info" is in size 168 bytes.
   The kernel then tells as much details as possible about
   a bpf prog in "info".  I don't see a ABI breakage here.

   I believe the test just happens to work so far because it has been runni=
ng
   without jit?

   If I run it with jit enabled:
-bpf(BPF_OBJ_GET_INFO_BY_FD, {info=3D{bpf_fd=3D4<anon_inode:bpf-prog>, info=
_len=3D168, info=3D{type=3DBPF_PROG_TYPE_SOCKET_FILTER, id=3D35, tag=3D"\xd=
a\xbf\x02\x07\xd1\x99\x24\x86", jited_prog_len=3D0 =3D> 110, jited_prog_ins=
ns=3DNULL, xlated_prog_len=3D0 =3D> 120, xlated_prog_insns=3D[], load_time=
=3D2476906063975, created_by_uid=3D0, nr_map_ids=3D0 =3D> 1, map_ids=3D[], =
name=3D"test_prog", ifindex=3D0, netns_dev=3Dmakedev(0, 0), netns_ino=3D0}}=
}, 16) =3D 0
-bpf(BPF_OBJ_GET_INFO_BY_FD, {info=3D{bpf_fd=3D4<anon_inode:bpf-prog>, info=
_len=3D168, info=3D{type=3DBPF_PROG_TYPE_SOCKET_FILTER, id=3D35, tag=3D"\xd=
a\xbf\x02\x07\xd1\x99\x24\x86", jited_prog_len=3D0 =3D> 110, jited_prog_ins=
ns=3DNULL, xlated_prog_len=3D0 =3D> 120, xlated_prog_insns=3D[], load_time=
=3D2476906063975, created_by_uid=3D0, nr_map_ids=3D2 =3D> 1, map_ids=3D[36]=
, name=3D"test_prog", ifindex=3D0, netns_dev=3Dmakedev(0, 0), netns_ino=3D0=
}}}, 16) =3D 0
+bpf(BPF_OBJ_GET_INFO_BY_FD, {info=3D{bpf_fd=3D4<anon_inode:bpf-prog>, info=
_len=3D168, info=3D{type=3DBPF_PROG_TYPE_SOCKET_FILTER, id=3D35, tag=3D"\xd=
a\xbf\x02\x07\xd1\x99\x24\x86", jited_prog_len=3D0 =3D> 110, jited_prog_ins=
ns=3DNULL, xlated_prog_len=3D0 =3D> 120, xlated_prog_insns=3D[], load_time=
=3D2476906063975, created_by_uid=3D0, nr_map_ids=3D0 =3D> 1, map_ids=3D[], =
name=3D"test_prog", ifindex=3D0, netns_dev=3Dmakedev(0, 0), netns_ino=3D0, =
/* bytes 104..167 */ "\x01\x00\x00\x00\x01\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\x0=
0\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"}}}, 16) =3D 0
+bpf(BPF_OBJ_GET_INFO_BY_FD, {info=3D{bpf_fd=3D4<anon_inode:bpf-prog>, info=
_len=3D168, info=3D{type=3DBPF_PROG_TYPE_SOCKET_FILTER, id=3D35, tag=3D"\xd=
a\xbf\x02\x07\xd1\x99\x24\x86", jited_prog_len=3D0 =3D> 110, jited_prog_ins=
ns=3DNULL, xlated_prog_len=3D0 =3D> 120, xlated_prog_insns=3D[], load_time=
=3D2476906063975, created_by_uid=3D0, nr_map_ids=3D2 =3D> 1, map_ids=3D[36]=
, name=3D"test_prog", ifindex=3D0, netns_dev=3Dmakedev(0, 0), netns_ino=3D0=
, /* bytes 104..167 */ "\x01\x00\x00\x00\x01\x00\x00\x00\x00\x00\x00\x00\x0=
0\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x08\x00\x00\x=
00\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) =3D 0

  The diff comes in as early as byte 104-th which is the nr_jited_ksyms =3D=
=3D 1.

  Please fix the test program.  A protential fix is in bpf-obj_get_info_by_=
fd.c
  to printf the non-zero "/* bytes 104..1xx */..." the same way as the
  "strace -o log" does.