initial commit

This initial commit added the following files
from bpf-next repository:
  src:
    <files from linux:tools/lib/bpf>
    bpf.c bpf.h btf.c btf.h libbpf.c libbpf.h
    libbpf_errno.c netlink.c nlattr.c nlattr.h
    str_error.c str_error.h
  include:
    <files from linux:tools/include/uapi/linux>
    uapi/linux/{bpf.h, btf.h}

    <files from linux:tools/include/tools>
    tools/libc_compat.h

The following files are also added:
  include/linux/{err.h, kernel.h, list.h, overflow.h, types.h}
These files are customized headers to satisfy compilation.
Their original counterparts are at linux:tools/include/linux
directory.

Signed-off-by: Yonghong Song <yhs@fb.com>

src/str_error.c

@@ -0,0 +1,18 @@
+// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
+#undef _GNU_SOURCE
+#include <string.h>
+#include <stdio.h>
+#include "str_error.h"
+
+/*
+ * Wrapper to allow for building in non-GNU systems such as Alpine Linux's musl
+ * libc, while checking strerror_r() return to avoid having to check this in
+ * all places calling it.
+ */
+char *libbpf_strerror_r(int err, char *dst, int len)
+{
+	int ret = strerror_r(err, dst, len);
+	if (ret)
+		snprintf(dst, len, "ERROR: strerror_r(%d)=%d", err, ret);
+	return dst;
+}