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bpf: add support for fixed-size memory pointer returns for kfuncs

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Support direct fixed-size (and for now, read-only) memory access when
kfunc's return type is a pointer to non-struct type. Calculate type size
and let BPF program access that many bytes directly. This is crucial for
numbers iterator.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20230302235015.2044271-13-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Andrii Nakryiko 2023-03-02 15:50:10 -08:00 • committed by Alexei Starovoitov
parent a461f5adf1
commit f4b4eee616
1 changed files with 8 additions and 0 deletions
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8
kernel/bpf/verifier.c
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@ -10336,6 +10336,14 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
return -EFAULT;
}
} else if (!__btf_type_is_struct(ptr_type)) {
if (!meta.r0_size) {
__u32 sz;
if (!IS_ERR(btf_resolve_size(desc_btf, ptr_type, &sz))) {
meta.r0_size = sz;
meta.r0_rdonly = true;
}
}
if (!meta.r0_size) {
ptr_type_name = btf_name_by_offset(desc_btf,
ptr_type->name_off);