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selftests/bpf: Preserve errno in test_progs CHECK macros

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It's follow-up for discussion [1]

CHECK and CHECK_FAIL macros in test_progs.h can affect errno in some
circumstances, e.g. if some code accidentally closes stdout. It makes
checking errno in patterns like this unreliable:

	if (CHECK(!bpf_prog_attach_xattr(...), "tag", "msg"))
		goto err;
	CHECK_FAIL(errno != ENOENT);

, since by CHECK_FAIL time errno could be affected not only by
bpf_prog_attach_xattr but by CHECK as well.

Fix it by saving and restoring errno in the macros. There is no "Fixes"
tag since no problems were discovered yet and it's rather precaution.

test_progs was run with this change and no difference was identified.

[1] https://lore.kernel.org/bpf/20191219210907.GD16266@rdna-mbp.dhcp.thefacebook.com/

Signed-off-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20191220000511.1684853-1-rdna@fb.com
This commit is contained in:
Andrey Ignatov 2019-12-19 16:05:11 -08:00 committed by Alexei Starovoitov
parent ce3cec2793
commit 478bee0df0
1 changed files with 4 additions and 0 deletions
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4
tools/testing/selftests/bpf/test_progs.h
View file

@ -100,6 +100,7 @@ extern struct ipv6_packet pkt_v6;
#define _CHECK(condition, tag, duration, format...) ({ \
int __ret = !!(condition); \
int __save_errno = errno; \
if (__ret) { \
test__fail(); \
printf("%s:FAIL:%s ", __func__, tag); \
@ -108,15 +109,18 @@ extern struct ipv6_packet pkt_v6;
printf("%s:PASS:%s %d nsec\n", \
__func__, tag, duration); \
} \
errno = __save_errno; \
__ret; \
})
#define CHECK_FAIL(condition) ({ \
int __ret = !!(condition); \
int __save_errno = errno; \
if (__ret) { \
test__fail(); \
printf("%s:FAIL:%d\n", __func__, __LINE__); \
} \
errno = __save_errno; \
__ret; \
})