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libbpf: Fix faccessat() usage on Android 

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: 6a4ab8869d ("libbpf: Fix the case of running as non-root with capabilities")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/bpf/20240126220944.2497665-1-andrii@kernel.org
This commit is contained in:
Andrii Nakryiko 2024-01-26 14:09:44 -08:00 committed by Daniel Borkmann
parent 29788f39a4
commit ad57654053
1 changed files with 14 additions and 0 deletions
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14
tools/lib/bpf/libbpf_internal.h
View File

@ -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