diff mbox series

[bpf-next,1/5] libbpf: call memfd_create() syscall directly

Message ID 20240130193649.3753476-2-andrii@kernel.org (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series Libbpf API and memfd_create() fixes | expand

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netdev/checkpatch warning WARNING: Prefer 'unsigned int' to bare use of 'unsigned' WARNING: line length of 84 exceeds 80 columns
netdev/build_clang_rust success No Rust files in patch. Skipping build
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Commit Message

Andrii Nakryiko Jan. 30, 2024, 7:36 p.m. UTC 
Some versions of Android do not implement memfd_create() wrapper in
their libc implementation, leading to build failures ([0]). On the other
hand, memfd_create() is available as a syscall on quite old kernels
(3.17+, while bpf() syscall itself is available since 3.18+), so it is
ok to assume that syscall availability and call into it with syscall()
helper to avoid Android-specific workarounds.

Validated in libbpf-bootstrap's CI ([1]).

  [0] https://github.com/libbpf/libbpf-bootstrap/actions/runs/7701003207/job/20986080319#step:5:83
  [1] https://github.com/libbpf/libbpf-bootstrap/actions/runs/7715988887/job/21031767212?pr=253

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
 tools/lib/bpf/libbpf.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

Comments

Yonghong Song Jan. 31, 2024, 5:04 a.m. UTC | #1 
On 1/30/24 11:36 AM, Andrii Nakryiko wrote:
> Some versions of Android do not implement memfd_create() wrapper in
> their libc implementation, leading to build failures ([0]). On the other
> hand, memfd_create() is available as a syscall on quite old kernels
> (3.17+, while bpf() syscall itself is available since 3.18+), so it is
> ok to assume that syscall availability and call into it with syscall()
> helper to avoid Android-specific workarounds.
>
> Validated in libbpf-bootstrap's CI ([1]).
>
>    [0] https://github.com/libbpf/libbpf-bootstrap/actions/runs/7701003207/job/20986080319#step:5:83
>    [1] https://github.com/libbpf/libbpf-bootstrap/actions/runs/7715988887/job/21031767212?pr=253
>
> Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

Acked-by: Yonghong Song <yonghong.song@linux.dev>
diff mbox series

Patch

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index db65ea59a05a..b21fda6b9b85 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -1525,11 +1525,20 @@  static Elf64_Sym *find_elf_var_sym(const struct bpf_object *obj, const char *nam
 	return ERR_PTR(-ENOENT);
 }
 
+/* Some versions of Android don't provide memfd_create() in their libc
+ * implementation, so avoid complications and just go straight to Linux
+ * syscall.
+ */
+static int sys_memfd_create(const char *name, unsigned flags)
+{
+	return syscall(__NR_memfd_create, name, flags);
+}
+
 static int create_placeholder_fd(void)
 {
 	int fd;
 
-	fd = ensure_good_fd(memfd_create("libbpf-placeholder-fd", MFD_CLOEXEC));
+	fd = ensure_good_fd(sys_memfd_create("libbpf-placeholder-fd", MFD_CLOEXEC));
 	if (fd < 0)
 		return -errno;
 	return fd;