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libbpf: fix libbpf_strerror_r() handling unknown errors

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strerror_r(), used from libbpf-specific libbpf_strerror_r() wrapper is
documented to return error in two different ways, depending on glibc
version. Take that into account when handling strerror_r()'s own errors,
which happens when we pass some non-standard (internal) kernel error to
it. Before this patch we'd have "ERROR: strerror_r(524)=22", which is
quite confusing. Now for the same situation we'll see a bit less
visually scary "unknown error (-524)".

At least we won't confuse user with irrelevant EINVAL (22).

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20240507001335.1445325-5-andrii@kernel.org
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
This commit is contained in:
Andrii Nakryiko 2024-05-06 17:13:32 -07:00 committed by Martin KaFai Lau
parent 9d66d60e96
commit 548c2ede0d
1 changed files with 14 additions and 2 deletions
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16
tools/lib/bpf/str_error.c
View file

@ -2,6 +2,7 @@
#undef _GNU_SOURCE
#include <string.h>
#include <stdio.h>
#include <errno.h>
#include "str_error.h"
/* make sure libbpf doesn't use kernel-only integer typedefs */
@ -15,7 +16,18 @@
char *libbpf_strerror_r(int err, char *dst, int len)
{
int ret = strerror_r(err < 0 ? -err : err, dst, len);
if (ret)
snprintf(dst, len, "ERROR: strerror_r(%d)=%d", err, ret);
/* on glibc <2.13, ret == -1 and errno is set, if strerror_r() can't
* handle the error, on glibc >=2.13 *positive* (errno-like) error
* code is returned directly
*/
if (ret == -1)
ret = errno;
if (ret) {
if (ret == EINVAL)
/* strerror_r() doesn't recognize this specific error */
snprintf(dst, len, "unknown error (%d)", err < 0 ? err : -err);
else
snprintf(dst, len, "ERROR: strerror_r(%d)=%d", err, ret);
}
return dst;
}