From:   Andrii Nakryiko <redacted>
Date:   Fri, 13 Aug 2021 16:25:53 -0700

On Thu, Aug 12, 2021 at 9:46 AM Kuniyuki Iwashima [off-list ref] wrote:

quoted

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!

quoted

  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 <redacted>
Acked-by: Yonghong Song <redacted>
---

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

quoted

 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

[...]

quoted

+                       /* 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!

quoted

+                       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<---

quoted

+                                       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