libbpf: Fix implicit memfd_create() for bionic

Since memfd_create() is not consistently available across different
bionic libc implementations, using memfd_create() directly can break
some Android builds:

  tools/lib/bpf/linker.c:576:7: error: implicit declaration of function 'memfd_create' [-Werror,-Wimplicit-function-declaration]
    576 |         fd = memfd_create(filename, 0);
        |              ^

To fix this, relocate and inline the sys_memfd_create() helper so that
it can be used in "linker.c". Similar issues were previously fixed by
commit 9fa5e1a180aa ("libbpf: Call memfd_create() syscall directly").

Fixes: 6d5e5e5d7ce1 ("libbpf: Extend linker API to support in-memory ELF files")
Signed-off-by: Carlos Llamas <cmllamas@google.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20250330211325.530677-1-cmllamas@google.com

1 files changed, 9 insertions, 0 deletions

diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index 76669c73dcd1..477a3b3389a0 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -667,6 +667,15 @@ static inline int sys_dup3(int oldfd, int newfd, int flags)
 	return syscall(__NR_dup3, oldfd, newfd, flags);
 }
 
+/* Some versions of Android don't provide memfd_create() in their libc
+ * implementation, so avoid complications and just go straight to Linux
+ * syscall.
+ */
+static inline int sys_memfd_create(const char *name, unsigned flags)
+{
+	return syscall(__NR_memfd_create, name, flags);
+}
+
 /* Point *fixed_fd* to the same file that *tmp_fd* points to.
  * Regardless of success, *tmp_fd* is closed.
  * Whatever *fixed_fd* pointed to is closed silently.