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[bpf] libbpf: Prevent overriding errno when logging errors

Message ID 20200813142905.160381-1-toke@redhat.com
State New
Headers show
Series [bpf] libbpf: Prevent overriding errno when logging errors | expand

Commit Message

Toke Høiland-Jørgensen Aug. 13, 2020, 2:29 p.m. UTC 
Turns out there were a few more instances where libbpf didn't save the
errno before writing an error message, causing errno to be overridden by
the printf() return and the error disappearing if logging is enabled.

Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
---
 tools/lib/bpf/libbpf.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)
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Patch

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 0a06124f7999..fd256440e233 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -3478,10 +3478,11 @@  bpf_object__probe_global_data(struct bpf_object *obj)
 
 	map = bpf_create_map_xattr(&map_attr);
 	if (map < 0) {
-		cp = libbpf_strerror_r(errno, errmsg, sizeof(errmsg));
+		ret = -errno;
+		cp = libbpf_strerror_r(-ret, errmsg, sizeof(errmsg));
 		pr_warn("Error in %s():%s(%d). Couldn't create simple array map.\n",
-			__func__, cp, errno);
-		return -errno;
+			__func__, cp, -ret);
+		return ret;
 	}
 
 	insns[0].imm = map;
@@ -6012,9 +6013,10 @@  int bpf_program__pin_instance(struct bpf_program *prog, const char *path,
 	}
 
 	if (bpf_obj_pin(prog->instances.fds[instance], path)) {
-		cp = libbpf_strerror_r(errno, errmsg, sizeof(errmsg));
+		err = -errno;
+		cp = libbpf_strerror_r(-err, errmsg, sizeof(errmsg));
 		pr_warn("failed to pin program: %s\n", cp);
-		return -errno;
+		return err;
 	}
 	pr_debug("pinned program '%s'\n", path);