[PATCH bpf-next v3 1/4] libbpf: introduce errstr() for stringifying errno

[Mykyta Yatsenko <mykyta.yatsenko5@gmail.com>]

From: Mykyta Yatsenko <yatsenko@meta.com>

Add function errstr(int err) that allows converting numeric error codes
into string representations.

Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
---
 tools/lib/bpf/str_error.c | 59 +++++++++++++++++++++++++++++++++++++++
 tools/lib/bpf/str_error.h |  7 +++++
 2 files changed, 66 insertions(+)

diff --git a/tools/lib/bpf/str_error.c b/tools/lib/bpf/str_error.c
index 5e6a1e27ddf9..cf817c0c7ddd 100644
--- a/tools/lib/bpf/str_error.c
+++ b/tools/lib/bpf/str_error.c
@@ -5,6 +5,10 @@
 #include <errno.h>
 #include "str_error.h"
 
+#ifndef ENOTSUPP
+#define ENOTSUPP	524
+#endif
+
 /* make sure libbpf doesn't use kernel-only integer typedefs */
 #pragma GCC poison u8 u16 u32 u64 s8 s16 s32 s64
 
@@ -31,3 +35,58 @@ char *libbpf_strerror_r(int err, char *dst, int len)
 	}
 	return dst;
 }
+
+const char *errstr(int err)
+{
+	static __thread char buf[12];
+
+	if (err > 0)
+		err = -err;
+
+	switch (err) {
+	case -EINVAL: return "-EINVAL";
+	case -EPERM: return "-EPERM";
+	case -ENXIO: return "-ENXIO";
+	case -ENOMEM: return "-ENOMEM";
+	case -ENOENT: return "-ENOENT";
+	case -E2BIG: return "-E2BIG";
+	case -EEXIST: return "-EEXIST";
+	case -EFAULT: return "-EFAULT";
+	case -ENOSPC: return "-ENOSPC";
+	case -EACCES: return "-EACCES";
+	case -EAGAIN: return "-EAGAIN";
+	case -EBADF: return "-EBADF";
+	case -ENAMETOOLONG: return "-ENAMETOOLONG";
+	case -ESRCH: return "-ESRCH";
+	case -EBUSY: return "-EBUSY";
+	case -ENOTSUPP: return "-ENOTSUPP";
+	case -EPROTO: return "-EPROTO";
+	case -ERANGE: return "-ERANGE";
+	case -EMSGSIZE: return "-EMSGSIZE";
+	case -EINTR: return "-EINTR";
+	case -ENODATA: return "-ENODATA";
+	case -ENODEV: return "-ENODEV";
+	case -ENOLINK:return "-ENOLINK";
+	case -EIO: return "-EIO";
+	case -EUCLEAN: return "-EUCLEAN";
+	case -EDOM: return "-EDOM";
+	case -ELOOP: return "-ELOOP";
+	case -EPROTONOSUPPORT: return "-EPROTONOSUPPORT";
+	case -EDEADLK: return "-EDEADLK";
+	case -EOVERFLOW: return "-EOVERFLOW";
+	case -EOPNOTSUPP: return "-EOPNOTSUPP";
+	case -EINPROGRESS: return "-EINPROGRESS";
+	case -EBADFD: return "-EBADFD";
+	case -EADDRINUSE: return "-EADDRINUSE";
+	case -EADDRNOTAVAIL: return "-EADDRNOTAVAIL";
+	case -ECANCELED: return "-ECANCELED";
+	case -EILSEQ: return "-EILSEQ";
+	case -EMFILE: return "-EMFILE";
+	case -ENOTTY: return "-ENOTTY";
+	case -EALREADY: return "-EALREADY";
+	case -ECHILD: return "-ECHILD";
+	default:
+		snprintf(buf, sizeof(buf), "%d", err);
+		return buf;
+	}
+}
diff --git a/tools/lib/bpf/str_error.h b/tools/lib/bpf/str_error.h
index 626d7ffb03d6..66ffebde0684 100644
--- a/tools/lib/bpf/str_error.h
+++ b/tools/lib/bpf/str_error.h
@@ -6,4 +6,11 @@
 
 char *libbpf_strerror_r(int err, char *dst, int len);
 
+/**
+ * @brief **errstr()** returns string corresponding to numeric errno
+ * @param err negative numeric errno
+ * @return pointer to string representation of the errno, that is invalidated
+ * upon the next call.
+ */
+const char *errstr(int err);
 #endif /* __LIBBPF_STR_ERROR_H */
-- 
2.47.0