The iterator can output almost the same result compared to /proc/net/unix. The header line is aligned, and the Inode column uses "%8lu" because "%5lu" can be easily overflown. # cat /sys/fs/bpf/unix Num RefCount Protocol Flags Type St Inode Path ffff963c06689800: 00000002 00000000 00010000 0001 01 18697 private/defer ffff963c7c979c00: 00000002 00000000 00000000 0001 01 598245 @Hello@World@ # cat /proc/net/unix Num RefCount Protocol Flags Type St Inode Path ffff963c06689800: 00000002 00000000 00010000 0001 01 18697 private/defer ffff963c7c979c00: 00000002 00000000 00000000 0001 01 598245 @Hello@World@ Note that this prog requires the patch ([0]) for LLVM code gen. Thanks to Yonghong Song for analysing and fixing. [0] https://reviews.llvm.org/D107483 Signed-off-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxxxx> Acked-by: Yonghong Song <yhs@xxxxxx> --- tools/testing/selftests/bpf/README.rst | 38 +++++++++ .../selftests/bpf/prog_tests/bpf_iter.c | 16 ++++ tools/testing/selftests/bpf/progs/bpf_iter.h | 8 ++ .../selftests/bpf/progs/bpf_iter_unix.c | 77 +++++++++++++++++++ .../selftests/bpf/progs/bpf_tracing_net.h | 4 + 5 files changed, 143 insertions(+) create mode 100644 tools/testing/selftests/bpf/progs/bpf_iter_unix.c diff --git a/tools/testing/selftests/bpf/README.rst b/tools/testing/selftests/bpf/README.rst index 9b17f2867488..314a63b69399 100644 --- a/tools/testing/selftests/bpf/README.rst +++ b/tools/testing/selftests/bpf/README.rst @@ -228,3 +228,41 @@ To fix this issue, user newer libbpf. .. Links .. _clang reloc patch: https://reviews.llvm.org/D102712 .. _kernel llvm reloc: /Documentation/bpf/llvm_reloc.rst + +bpf_iter_unix.o test failure and LLVM optimisation +================================================== + +The ``bpf_iter/unix`` subtest requires `the fix`__ to prevent the LLVM compiler +from transforming the loop exit condition. + +Without the fix, the compiler generates the following code: + +.. code-block:: c + + ; for (i = 1; i < len; i++) + 110: 07 09 00 00 01 00 00 00 r9 += 1 + 111: 5d 98 09 00 00 00 00 00 if r8 != r9 goto +9 <LBB0_18> + +The loop exit condition, where the upper bound is not a constant, is +changed from ``<`` to ``!=``. Thus, the verifier always evaluates it as true, +misleading to an infinite loop. + +.. code-block:: c + + The sequence of 8193 jumps is too complex. + processed 196506 insns (limit 1000000) max_states_per_insn 4 total_states 1830 peak_states 1830 mark_read 3 + +The fix prevents the optimisation by estimating its cost higher in such a +case: + +.. code-block:: c + + ; for (i = 1; i < len; i++) + 110: 07 09 00 00 01 00 00 00 r9 += 1 + 111: ad 89 09 00 00 00 00 00 if r9 < r8 goto +9 <LBB0_18> + +The patch is available in LLVM 14 trunk and has been `backported`__ to the LLVM +13.x release branch. + +__ https://reviews.llvm.org/D107483 +__ https://bugs.llvm.org/show_bug.cgi?id=51363 diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c index 1f1aade56504..77ac24b191d4 100644 --- a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c +++ b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c @@ -13,6 +13,7 @@ #include "bpf_iter_tcp6.skel.h" #include "bpf_iter_udp4.skel.h" #include "bpf_iter_udp6.skel.h" +#include "bpf_iter_unix.skel.h" #include "bpf_iter_test_kern1.skel.h" #include "bpf_iter_test_kern2.skel.h" #include "bpf_iter_test_kern3.skel.h" @@ -313,6 +314,19 @@ static void test_udp6(void) bpf_iter_udp6__destroy(skel); } +static void test_unix(void) +{ + struct bpf_iter_unix *skel; + + skel = bpf_iter_unix__open_and_load(); + if (!ASSERT_OK_PTR(skel, "bpf_iter_unix__open_and_load")) + return; + + do_dummy_read(skel->progs.dump_unix); + + bpf_iter_unix__destroy(skel); +} + /* The expected string is less than 16 bytes */ static int do_read_with_fd(int iter_fd, const char *expected, bool read_one_char) @@ -1255,6 +1269,8 @@ void test_bpf_iter(void) test_udp4(); if (test__start_subtest("udp6")) test_udp6(); + if (test__start_subtest("unix")) + test_unix(); if (test__start_subtest("anon")) test_anon_iter(false); if (test__start_subtest("anon-read-one-char")) diff --git a/tools/testing/selftests/bpf/progs/bpf_iter.h b/tools/testing/selftests/bpf/progs/bpf_iter.h index 3d83b185c4bc..8cfaeba1ddbf 100644 --- a/tools/testing/selftests/bpf/progs/bpf_iter.h +++ b/tools/testing/selftests/bpf/progs/bpf_iter.h @@ -12,6 +12,7 @@ #define tcp6_sock tcp6_sock___not_used #define bpf_iter__udp bpf_iter__udp___not_used #define udp6_sock udp6_sock___not_used +#define bpf_iter__unix bpf_iter__unix___not_used #define bpf_iter__bpf_map_elem bpf_iter__bpf_map_elem___not_used #define bpf_iter__bpf_sk_storage_map bpf_iter__bpf_sk_storage_map___not_used #define bpf_iter__sockmap bpf_iter__sockmap___not_used @@ -32,6 +33,7 @@ #undef tcp6_sock #undef bpf_iter__udp #undef udp6_sock +#undef bpf_iter__unix #undef bpf_iter__bpf_map_elem #undef bpf_iter__bpf_sk_storage_map #undef bpf_iter__sockmap @@ -103,6 +105,12 @@ struct udp6_sock { struct ipv6_pinfo inet6; } __attribute__((preserve_access_index)); +struct bpf_iter__unix { + struct bpf_iter_meta *meta; + struct unix_sock *unix_sk; + uid_t uid; +} __attribute__((preserve_access_index)); + struct bpf_iter__bpf_map_elem { struct bpf_iter_meta *meta; struct bpf_map *map; diff --git a/tools/testing/selftests/bpf/progs/bpf_iter_unix.c b/tools/testing/selftests/bpf/progs/bpf_iter_unix.c new file mode 100644 index 000000000000..0a50b610f6f3 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/bpf_iter_unix.c @@ -0,0 +1,77 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright Amazon.com Inc. or its affiliates. */ +#include "bpf_iter.h" +#include "bpf_tracing_net.h" +#include <bpf/bpf_helpers.h> +#include <bpf/bpf_endian.h> + +char _license[] SEC("license") = "GPL"; + +static long sock_i_ino(const struct sock *sk) +{ + const struct socket *sk_socket = sk->sk_socket; + const struct inode *inode; + unsigned long ino; + + if (!sk_socket) + return 0; + + inode = &container_of(sk_socket, struct socket_alloc, socket)->vfs_inode; + bpf_probe_read_kernel(&ino, sizeof(ino), &inode->i_ino); + return ino; +} + +SEC("iter/unix") +int dump_unix(struct bpf_iter__unix *ctx) +{ + struct unix_sock *unix_sk = ctx->unix_sk; + struct sock *sk = (struct sock *)unix_sk; + struct seq_file *seq; + __u32 seq_num; + + if (!unix_sk) + return 0; + + seq = ctx->meta->seq; + seq_num = ctx->meta->seq_num; + if (seq_num == 0) + BPF_SEQ_PRINTF(seq, "Num RefCount Protocol Flags Type St Inode Path\n"); + + BPF_SEQ_PRINTF(seq, "%pK: %08X %08X %08X %04X %02X %8lu", + unix_sk, + sk->sk_refcnt.refs.counter, + 0, + sk->sk_state == TCP_LISTEN ? __SO_ACCEPTCON : 0, + sk->sk_type, + sk->sk_socket ? + (sk->sk_state == TCP_ESTABLISHED ? SS_CONNECTED : SS_UNCONNECTED) : + (sk->sk_state == TCP_ESTABLISHED ? SS_CONNECTING : SS_DISCONNECTING), + sock_i_ino(sk)); + + if (unix_sk->addr) { + if (!UNIX_ABSTRACT(unix_sk)) { + BPF_SEQ_PRINTF(seq, " %s", unix_sk->addr->name->sun_path); + } else { + /* The name of the abstract UNIX domain socket starts + * with '\0' and can contain '\0'. The null bytes + * should be escaped as done in unix_seq_show(). + */ + int i, len; + + len = unix_sk->addr->len - sizeof(short); + + BPF_SEQ_PRINTF(seq, " @"); + + /* unix_mkname() tests this upper bound. */ + if (len < sizeof(struct sockaddr_un)) + for (i = 1; i < len; i++) + BPF_SEQ_PRINTF(seq, "%c", + unix_sk->addr->name->sun_path[i] ?: + '@'); + } + } + + BPF_SEQ_PRINTF(seq, "\n"); + + return 0; +} diff --git a/tools/testing/selftests/bpf/progs/bpf_tracing_net.h b/tools/testing/selftests/bpf/progs/bpf_tracing_net.h index 3af0998a0623..eef5646ddb19 100644 --- a/tools/testing/selftests/bpf/progs/bpf_tracing_net.h +++ b/tools/testing/selftests/bpf/progs/bpf_tracing_net.h @@ -5,6 +5,10 @@ #define AF_INET 2 #define AF_INET6 10 +#define __SO_ACCEPTCON (1 << 16) +#define UNIX_HASH_SIZE 256 +#define UNIX_ABSTRACT(unix_sk) (unix_sk->addr->hash < UNIX_HASH_SIZE) + #define SOL_TCP 6 #define TCP_CONGESTION 13 #define TCP_CA_NAME_MAX 16 -- 2.30.2
