netdev - [PATCH bpf] libbpf: handle BTF parsing and loading properly

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Date:   Fri, 8 Mar 2019 15:58:20 -0800
From:   Andrii Nakryiko <andriin@...com>
To:     <andrii.nakryiko@...il.com>, <kernel-team@...com>, <ast@...com>,
        <netdev@...r.kernel.org>, <bpf@...r.kernel.org>,
        <daniel@...earbox.net>, <kafai@...com>, <tehnerd@...nerd.com>
CC:     Andrii Nakryiko <andriin@...com>
Subject: [PATCH bpf] libbpf: handle BTF parsing and loading properly

This patch splits and cleans up error handling logic for loading BTF data.
Previously, if BTF data was parsed successfully, but failed to load into
kernel, we'd report nonsensical error code, instead of error returned from
btf__load(). Now btf__new() and btf__load() are handled separately with proper
cleanup and warning reporting.

Fixes: d29d87f7e612 ("btf: separate btf creation and loading")
Reported-by: Martin KaFai Lau <kafai@...com>
Signed-off-by: Andrii Nakryiko <andriin@...com>
---
 tools/lib/bpf/libbpf.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index d5b830d60601..5e977d2688da 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -835,12 +835,19 @@ static int bpf_object__elf_collect(struct bpf_object *obj, int flags)
 			obj->efile.maps_shndx = idx;
 		else if (strcmp(name, BTF_ELF_SEC) == 0) {
 			obj->btf = btf__new(data->d_buf, data->d_size);
-			if (IS_ERR(obj->btf) || btf__load(obj->btf)) {
+			if (IS_ERR(obj->btf)) {
 				pr_warning("Error loading ELF section %s: %ld. Ignored and continue.\n",
 					   BTF_ELF_SEC, PTR_ERR(obj->btf));
-				if (!IS_ERR(obj->btf))
-					btf__free(obj->btf);
 				obj->btf = NULL;
+				continue;
+			}
+			err = btf__load(obj->btf);
+			if (err) {
+				pr_warning("Error loading %s into kernel: %d. Ignored and continue.\n",
+					   BTF_ELF_SEC, err);
+				btf__free(obj->btf);
+				obj->btf = NULL;
+				err = 0;
 			}
 		} else if (strcmp(name, BTF_EXT_ELF_SEC) == 0) {
 			btf_ext_data = data;
-- 
2.17.1