Commit 9fa5e1a1 authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Daniel Borkmann
Browse files

libbpf: Call memfd_create() syscall directly 

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: default avatarAndrii Nakryiko <andrii@kernel.org>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarEduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/bpf/20240201172027.604869-2-andrii@kernel.org
parent 1581e511

tools/lib/bpf/libbpf.c

+10 −1
Original line number Diff line number Diff line
@@ -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;