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libbpf: Call memfd_create() syscall directly

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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>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/bpf/20240201172027.604869-2-andrii@kernel.org
This commit is contained in:
Andrii Nakryiko 2024-02-01 09:20:23 -08:00 • committed by Daniel Borkmann
parent 1581e5118e
commit 9fa5e1a180
1 changed files with 10 additions and 1 deletions
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11
tools/lib/bpf/libbpf.c
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@ -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;