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.
+ 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
