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libbpf: Mark BPF subprogs with hidden visibility as static for BPF verifier

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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 <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20210423181348.1801389-5-andrii@kernel.org
This commit is contained in:
Andrii Nakryiko
2021-04-23 11:13:34 -07:00
committed by Andrii Nakryiko
parent 2e430712f5
commit 3319982d34
4 changed files with 58 additions and 6 deletions
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8
src/bpf_helpers.h
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@@ -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