bpf: Change bpf_kallsyms_lookup_name size type to ARG_CONST_SIZE_OR_ZERO

Andrii mentioned in [0] that switching to ARG_CONST_SIZE_OR_ZERO lets
user avoid having to prove that string size at runtime is not zero and
helps with not having to supress clang optimizations.

  [0]: https://lore.kernel.org/bpf/CAEf4BzZa_vhXB3c8atNcTS6=krQvC25H7K7c3WWZhM=27ro=Wg@mail.gmail.com

Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20211122235733.634914-2-memxor@gmail.com

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 50f96ea..47089d1 100644 (file)
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -4804,7 +4804,7 @@ const struct bpf_func_proto bpf_kallsyms_lookup_name_proto = {
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_MEM,
-       .arg2_type      = ARG_CONST_SIZE,
+       .arg2_type      = ARG_CONST_SIZE_OR_ZERO,
        .arg3_type      = ARG_ANYTHING,
        .arg4_type      = ARG_PTR_TO_LONG,
 };