Commit f88886de authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by Andrii Nakryiko
Browse files

bpf: Add namespace to BPF internal symbols 



Add namespace to BPF internal symbols used by light skeleton
to prevent abuse and document with the code their allowed usage.

Fixes: b1d18a75 ("bpf: Extend sys_bpf commands for bpf_syscall programs.")
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Acked-by: default avatarKumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/bpf/20250425014542.62385-1-alexei.starovoitov@gmail.com
parent 6ae003ad

Documentation/bpf/bpf_devel_QA.rst

+8 −0
Original line number Diff line number Diff line
@@ -382,6 +382,14 @@ In case of new BPF instructions, once the changes have been accepted 
into the Linux kernel, please implement support into LLVM's BPF back

end. See LLVM_ section below for further information.



Q: What "BPF_INTERNAL" symbol namespace is for?

-----------------------------------------------

A: Symbols exported as BPF_INTERNAL can only be used by BPF infrastructure

like preload kernel modules with light skeleton. Most symbols outside

of BPF_INTERNAL are not expected to be used by code outside of BPF either.

Symbols may lack the designation because they predate the namespaces,

or due to an oversight.



Stable submission

=================

kernel/bpf/preload/bpf_preload_kern.c

+1 −0
Original line number Diff line number Diff line
@@ -89,5 +89,6 @@ static void __exit fini(void) 
}

late_initcall(load);

module_exit(fini);

MODULE_IMPORT_NS("BPF_INTERNAL");

MODULE_LICENSE("GPL");

MODULE_DESCRIPTION("Embedded BPF programs for introspection in bpffs");

kernel/bpf/syscall.c

+3 −3
Original line number Diff line number Diff line
@@ -1583,7 +1583,7 @@ struct bpf_map *bpf_map_get(u32 ufd) 


	return map;

}

EXPORT_SYMBOL(bpf_map_get);

EXPORT_SYMBOL_NS(bpf_map_get, "BPF_INTERNAL");



struct bpf_map *bpf_map_get_with_uref(u32 ufd)

{
@@ -3364,7 +3364,7 @@ struct bpf_link *bpf_link_get_from_fd(u32 ufd) 
	bpf_link_inc(link);

	return link;

}

EXPORT_SYMBOL(bpf_link_get_from_fd);

EXPORT_SYMBOL_NS(bpf_link_get_from_fd, "BPF_INTERNAL");



static void bpf_tracing_link_release(struct bpf_link *link)

{
@@ -6020,7 +6020,7 @@ int kern_sys_bpf(int cmd, union bpf_attr *attr, unsigned int size) 
		return ____bpf_sys_bpf(cmd, attr, size);

	}

}

EXPORT_SYMBOL(kern_sys_bpf);

EXPORT_SYMBOL_NS(kern_sys_bpf, "BPF_INTERNAL");



static const struct bpf_func_proto bpf_sys_bpf_proto = {

	.func		= bpf_sys_bpf,