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Sun, 30 Mar 2025 14:13:58 -0700 (PDT) Date: Sun, 30 Mar 2025 21:13:23 +0000 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.49.0.472.ge94155a9ec-goog Message-ID: <20250330211325.530677-1-cmllamas@google.com> Subject: [PATCH bpf] libbpf: Fix implicit memfd_create() for bionic From: Carlos Llamas To: bpf@vger.kernel.org, Andrii Nakryiko , Eduard Zingerman , Alexei Starovoitov , Daniel Borkmann , Alastair Robertson Cc: linux-kernel@vger.kernel.org, kernel-team@android.com, Carlos Llamas , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa X-Patchwork-Delegate: bpf@iogearbox.net 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"). Cc: Alastair Robertson Cc: Andrii Nakryiko Fixes: 6d5e5e5d7ce1 ("libbpf: Extend linker API to support in-memory ELF files") Signed-off-by: Carlos Llamas --- tools/lib/bpf/libbpf.c | 9 --------- tools/lib/bpf/libbpf_internal.h | 9 +++++++++ tools/lib/bpf/linker.c | 2 +- 3 files changed, 10 insertions(+), 10 deletions(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 194809da5172..1f36e16461e1 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -1719,15 +1719,6 @@ 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); -} - #ifndef MFD_CLOEXEC #define MFD_CLOEXEC 0x0001U #endif diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h index de498e2dd6b0..19770402807f 100644 --- a/tools/lib/bpf/libbpf_internal.h +++ b/tools/lib/bpf/libbpf_internal.h @@ -666,6 +666,15 @@ 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. diff --git a/tools/lib/bpf/linker.c b/tools/lib/bpf/linker.c index b52f71c59616..077af6f8bebb 100644 --- a/tools/lib/bpf/linker.c +++ b/tools/lib/bpf/linker.c @@ -573,7 +573,7 @@ int bpf_linker__add_buf(struct bpf_linker *linker, void *buf, size_t buf_sz, snprintf(filename, sizeof(filename), "mem:%p+%zu", buf, buf_sz); - fd = memfd_create(filename, 0); + fd = sys_memfd_create(filename, 0); if (fd < 0) { ret = -errno; pr_warn("failed to create memfd '%s': %s\n", filename, errstr(ret));