linux-kernel - [PATCH 5.16 0268/1039] libbpf: Add "bool skipped" to struct bpf

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Message-Id: <20220124184134.312014386@linuxfoundation.org>
Date:   Mon, 24 Jan 2022 19:34:17 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Shuyi Cheng <chengshuyi@...ux.alibaba.com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.16 0268/1039] libbpf: Add "bool skipped" to struct bpf_map

From: Shuyi Cheng <chengshuyi@...ux.alibaba.com>

[ Upstream commit 229fae38d0fc0d6ff58d57cbeb1432da55e58d4f ]

Fix error: "failed to pin map: Bad file descriptor, path:
/sys/fs/bpf/_rodata_str1_1."

In the old kernel, the global data map will not be created, see [0]. So
we should skip the pinning of the global data map to avoid
bpf_object__pin_maps returning error. Therefore, when the map is not
created, we mark “map->skipped" as true and then check during relocation
and during pinning.

Fixes: 16e0c35c6f7a ("libbpf: Load global data maps lazily on legacy kernels")
Signed-off-by: Shuyi Cheng <chengshuyi@...ux.alibaba.com>
Signed-off-by: Andrii Nakryiko <andrii@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 tools/lib/bpf/libbpf.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 4050a0f8dad66..fd25e30e70cc2 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -400,6 +400,7 @@ struct bpf_map {
 	char *pin_path;
 	bool pinned;
 	bool reused;
+	bool skipped;
 	__u64 map_extra;
 };
 
@@ -5003,8 +5004,10 @@ bpf_object__create_maps(struct bpf_object *obj)
 		 * kernels.
 		 */
 		if (bpf_map__is_internal(map) &&
-		    !kernel_supports(obj, FEAT_GLOBAL_DATA))
+		    !kernel_supports(obj, FEAT_GLOBAL_DATA)) {
+			map->skipped = true;
 			continue;
+		}
 
 		retried = false;
 retry:
@@ -5607,8 +5610,7 @@ bpf_object__relocate_data(struct bpf_object *obj, struct bpf_program *prog)
 			} else {
 				const struct bpf_map *map = &obj->maps[relo->map_idx];
 
-				if (bpf_map__is_internal(map) &&
-				    !kernel_supports(obj, FEAT_GLOBAL_DATA)) {
+				if (map->skipped) {
 					pr_warn("prog '%s': relo #%d: kernel doesn't support global data\n",
 						prog->name, i);
 					return -ENOTSUP;
@@ -7733,6 +7735,9 @@ int bpf_object__pin_maps(struct bpf_object *obj, const char *path)
 		char *pin_path = NULL;
 		char buf[PATH_MAX];
 
+		if (map->skipped)
+			continue;
+
 		if (path) {
 			int len;
 
-- 
2.34.1