From: Andrii Nakryiko <andrii@kernel.org>
To: bpf@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net,
martin.lau@kernel.org
Cc: andrii@kernel.org, kernel-team@meta.com
Subject: [PATCH bpf-next] libbpf: fix faccessat() usage on Android
Date: Fri, 26 Jan 2024 14:09:44 -0800 [thread overview]
Message-ID: <20240126220944.2497665-1-andrii@kernel.org> (raw)
Android implementation of libc errors out with -EINVAL in faccessat() if
passed AT_EACCESS ([0]), this leads to ridiculous issue with libbpf
refusing to load /sys/kernel/btf/vmlinux on Androids ([1]). Fix by
detecting Android and redefining AT_EACCESS to 0, it's equivalent on
Android.
[0] https://android.googlesource.com/platform/bionic/+/refs/heads/android13-release/libc/bionic/faccessat.cpp#50
[1] https://github.com/libbpf/libbpf-bootstrap/issues/250#issuecomment-1911324250
Fixes: 6a4ab8869d0b ("libbpf: Fix the case of running as non-root with capabilities")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
tools/lib/bpf/libbpf_internal.h | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index 930cc9616527..5b30f3b67a02 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -19,6 +19,20 @@
#include <libelf.h>
#include "relo_core.h"
+/* Android's libc doesn't support AT_EACCESS in faccessat() implementation
+ * ([0]), and just returns -EINVAL even if file exists and is accessible.
+ * See [1] for issues caused by this.
+ *
+ * So just redefine it to 0 on Android.
+ *
+ * [0] https://android.googlesource.com/platform/bionic/+/refs/heads/android13-release/libc/bionic/faccessat.cpp#50
+ * [1] https://github.com/libbpf/libbpf-bootstrap/issues/250#issuecomment-1911324250
+ */
+#ifdef __ANDROID__
+#undef AT_EACCESS
+#define AT_EACCESS 0
+#endif
+
/* make sure libbpf doesn't use kernel-only integer typedefs */
#pragma GCC poison u8 u16 u32 u64 s8 s16 s32 s64
--
2.34.1
next reply other threads:[~2024-01-26 22:09 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-26 22:09 Andrii Nakryiko [this message]
2024-01-28 18:56 ` [PATCH bpf-next] libbpf: fix faccessat() usage on Android Jiri Olsa
2024-01-29 15:30 ` patchwork-bot+netdevbpf
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