From: Yonghong Song <yhs@xxxxxx> Date: Sun, 15 Aug 2021 11:10:49 -0700 > On 8/13/21 5:21 PM, Kuniyuki Iwashima wrote: > > From: Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx> > > Date: Fri, 13 Aug 2021 16:25:53 -0700 > >> On Thu, Aug 12, 2021 at 9:46 AM Kuniyuki Iwashima <kuniyu@xxxxxxxxxxxx> wrote: > >>> > >>> 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 > >> > >> It's totally my OCD, but why the column name is not aligned with > >> values? I mean the "Inode" column. It's left aligned, but values > >> (numbers) are right-aligned? I'd fix that while applying, but I can't > >> apply due to selftests failures, so please take a look. > > > > Ah, honestly, I've felt something strange about the column... will fix it! > > > > > >> > >> > >>> 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> > >>> --- > >> > >> This selftests breaks test_progs-no_alu32 ([0], the error log is super > >> long and can freeze browser; it looks like an infinite loop and BPF > >> verifier just keeps reporting it until it runs out of 1mln > >> instructions or something). Please check what's going on there, I > >> can't land it as it is right now. > >> > >> [0] https://github.com/kernel-patches/bpf/runs/3326071112?check_suite_focus=true#step:6:124288 > >> > >> > >>> 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 > >>> > >> > >> [...] > >> > >>> + /* 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; > >>> + > >> > >> no_alu32 variant probably isn't happy about using int for this, it > >> probably does << 32, >> 32 dance and loses track of actual value in > >> the loop. You can try using u64 instead. > > > > Sorry, I missed the no_alu32 test. > > Changing int to __u64 fixed the error, thanks! > > Indeed for no_alu32, the index has << 32 and >> 32, which makes > verifier *equivalent* register tracking not effective, see below: > > 96: r1 = r8 > > 97: r1 <<= 32 > > 98: r2 = r1 > > 99: r2 >>= 32 > > 100: if r2 > 109 goto +19 <LBB0_21> > > 101: r1 s>>= 32 > > 102: if r1 s< 2 goto +17 <LBB0_21> > > 103: r9 = 1 > > 104: r8 <<= 32 > > 105: r8 >>= 32 > > Because these shifting, r1/r2/r8 equivalence cannot be > easily established, so verifier ends with conservative > r8 and cannot verify program successfully. > > Using __u64 for 'i' and 'len', the upper bound is directly > tested: > 98: if r8 > 109 goto +16 <LBB0_21> > > 99: if r8 < 2 goto +15 <LBB0_21> > and verifier is very happy with this. Thanks for explanation! I understand that the shift dance is to mimic the overflow of int because actually 64-bit register is allocated to 'i' and 32-bit operations cannot be used in no_alu32 test, so using __64 to remove the dance resolves it. > > > > > > >> > >>> + 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++) > >> > >> if you move above if inside the loop to break out of the loop, does it > >> change how Clang generates code? > >> > >> for (i = 1; i < len i++) { > >> if (i >= sizeof(struct sockaddr_un)) > >> break; > >> BPF_SEQ_PRINTF(...); > >> } > > > > Yes, but there seems little defference. > > Which is preferable? > > > > ---8<--- > > before (for inside if) <- -> after (if inside loop) > > 96: 07 08 00 00 fe ff ff ff r8 += -2 | ; for (i = 1; i < len; i++) { > > ; if (len < sizeof(struct sockaddr_un)) | 97: bf 81 00 00 00 00 00 00 r1 = r8 > > 97: 25 08 10 00 6d 00 00 00 if r8 > 109 goto +16 <LBB0_21> | 98: 07 01 00 00 fc ff ff ff r1 += -4 > > ; for (i = 1; i < len; i++) | 99: 25 01 12 00 6b 00 00 00 if r1 > 107 goto +18 <LBB0_21> > > 98: a5 08 0f 00 02 00 00 00 if r8 < 2 goto +15 <LBB0_21> | 100: 07 08 00 00 fe ff ff ff r8 += -2 > > 99: b7 09 00 00 01 00 00 00 r9 = 1 | 101: b7 09 00 00 01 00 00 00 r9 = 1 > > 100: 05 00 16 00 00 00 00 00 goto +22 <LBB0_18> | 102: b7 06 00 00 02 00 00 00 r6 = 2 > > | 103: 05 00 17 00 00 00 00 00 goto +23 <LBB0_17> > > ... > > 111: 85 00 00 00 7e 00 00 00 call 126 | 113: b4 05 00 00 08 00 00 00 w5 = 8 > > ; for (i = 1; i < len; i++) | 114: 85 00 00 00 7e 00 00 00 call 126 > > 112: 07 09 00 00 01 00 00 00 r9 += 1 | ; for (i = 1; i < len; i++) { > > 113: ad 89 09 00 00 00 00 00 if r9 < r8 goto +9 <LBB0_18> | 115: 25 08 02 00 6d 00 00 00 if r8 > 109 goto +2 <LBB0_21> > > > 116: 07 09 00 00 01 00 00 00 r9 += 1 > > > ; for (i = 1; i < len; i++) { > > > 117: ad 89 09 00 00 00 00 00 if r9 < r8 goto +9 <LBB0_17> > > ---8<--- > > > > > >> > >> > >>> + 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 > >>>
