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@xxxxxxxxxx>
---
tools/lib/bpf/str_error.c | 16 ++++++++++++++--
1 file changed, 14 insertions(+), 2 deletions(-)
diff --git a/tools/lib/bpf/str_error.c b/tools/lib/bpf/str_error.c
index 146da01979c7..5e6a1e27ddf9 100644
--- a/tools/lib/bpf/str_error.c
+++ b/tools/lib/bpf/str_error.c
@@ -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;
}
--
2.43.0
