From aea28a602fa19fb4fe66374030ab7e2c8ddf643e Mon Sep 17 00:00:00 2001 From: Andrii Nakryiko Date: Fri, 23 Apr 2021 11:13:34 -0700 Subject: libbpf: Mark BPF subprogs with hidden visibility as static for BPF verifier Define __hidden helper macro in bpf_helpers.h, which is a short-hand for __attribute__((visibility("hidden"))). Add libbpf support to mark BPF subprograms marked with __hidden as static in BTF information to enforce BPF verifier's static function validation algorithm, which takes more information (caller's context) into account during a subprogram validation. Signed-off-by: Andrii Nakryiko Signed-off-by: Alexei Starovoitov Acked-by: Yonghong Song Link: https://lore.kernel.org/bpf/20210423181348.1801389-5-andrii@kernel.org --- tools/lib/bpf/bpf_helpers.h | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'tools/lib/bpf/bpf_helpers.h') diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h index 75c7581b304c..9720dc0b4605 100644 --- a/tools/lib/bpf/bpf_helpers.h +++ b/tools/lib/bpf/bpf_helpers.h @@ -47,6 +47,14 @@ #define __weak __attribute__((weak)) #endif +/* + * Use __hidden attribute to mark a non-static BPF subprogram effectively + * static for BPF verifier's verification algorithm purposes, allowing more + * extensive and permissive BPF verification process, taking into account + * subprogram's caller context. + */ +#define __hidden __attribute__((visibility("hidden"))) + /* When utilizing vmlinux.h with BPF CO-RE, user BPF programs can't include * any system-level headers (such as stddef.h, linux/version.h, etc), and * commonly-used macros like NULL and KERNEL_VERSION aren't available through -- cgit v1.2.3