netdev - [PATCH bpf] selftests/bpf: adjust strobemeta loop to satisfy latest clang

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20190925185205.2857838-1-andriin@fb.com>
Date:   Wed, 25 Sep 2019 11:52:05 -0700
From:   Andrii Nakryiko <andriin@...com>
To:     <bpf@...r.kernel.org>, <netdev@...r.kernel.org>, <ast@...com>,
        <daniel@...earbox.net>
CC:     <andrii.nakryiko@...il.com>, <kernel-team@...com>,
        Andrii Nakryiko <andriin@...com>
Subject: [PATCH bpf] selftests/bpf: adjust strobemeta loop to satisfy latest clang

Some recent changes in latest Clang started causing the following
warning when unrolling strobemeta test case main loop:

  progs/strobemeta.h:416:2: warning: loop not unrolled: the optimizer was
  unable to perform the requested transformation; the transformation might
  be disabled or specified as part of an unsupported transformation
  ordering [-Wpass-failed=transform-warning]

This patch simplifies loop's exit condition to depend only on constant
max iteration number (STROBE_MAX_MAP_ENTRIES), while moving early
termination logic inside the loop body. The changes are equivalent from
program logic standpoint, but fixes the warning. It also appears to
improve generated BPF code, as it fixes previously failing non-unrolled
strobemeta test cases.

Cc: Alexei Starovoitov <ast@...com>
Signed-off-by: Andrii Nakryiko <andriin@...com>
---
 tools/testing/selftests/bpf/progs/strobemeta.h | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/progs/strobemeta.h b/tools/testing/selftests/bpf/progs/strobemeta.h
index 8a399bdfd920..067eb625d01c 100644
--- a/tools/testing/selftests/bpf/progs/strobemeta.h
+++ b/tools/testing/selftests/bpf/progs/strobemeta.h
@@ -413,7 +413,10 @@ static __always_inline void *read_map_var(struct strobemeta_cfg *cfg,
 #else
 #pragma unroll
 #endif
-	for (int i = 0; i < STROBE_MAX_MAP_ENTRIES && i < map.cnt; ++i) {
+	for (int i = 0; i < STROBE_MAX_MAP_ENTRIES; ++i) {
+		if (i >= map.cnt)
+			break;
+
 		descr->key_lens[i] = 0;
 		len = bpf_probe_read_str(payload, STROBE_MAX_STR_LEN,
 					 map.entries[i].key);
-- 
2.17.1