On Sat, Oct 16, 2021 at 08:48:03PM +0800, Hou Tao wrote:
> Factor out two helpers to check the read access of ctx for BTF
> function. bpf_check_btf_func_arg_access() is used to check the
> read access to argument is valid, and bpf_check_btf_func_ctx_access()
> also checks whether the btf type of argument is valid besides
> the checking of arguments read. bpf_check_btf_func_ctx_access()
> will be used by the following patch.
>
> Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx>
> ---
> include/linux/bpf.h | 27 +++++++++++++++++++++++++++
> kernel/trace/bpf_trace.c | 16 ++--------------
> net/ipv4/bpf_tcp_ca.c | 9 +--------
> 3 files changed, 30 insertions(+), 22 deletions(-)
>
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index b7c1e2bc93f7..b503306da2ab 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -1648,6 +1648,33 @@ bool bpf_prog_test_check_kfunc_call(u32 kfunc_id, struct module *owner);
> bool btf_ctx_access(int off, int size, enum bpf_access_type type,
> const struct bpf_prog *prog,
> struct bpf_insn_access_aux *info);
> +
> +/*
> + * The maximum number of BTF function arguments is MAX_BPF_FUNC_ARGS.
> + * And only aligned read is allowed.
> + */
> +static inline bool bpf_check_btf_func_arg_access(int off, int size,
> + enum bpf_access_type type)
Refactoring makes sense but naming could be hard to figure out here.
"_btf_func_arg" part is confusing with other btf_check_func_arg
functions in btf.c. e.g. it is checking an arg of a bpf subprog or
checking a bpf_prog's ctx here? The name sounds former but it is actually
the latter here (i.e. checking ctx). It is a ctx with an array
of __u64 for tracing. How about bpf_tracing_ctx_access()?
> +{
> + if (off < 0 || off >= sizeof(__u64) * MAX_BPF_FUNC_ARGS)
> + return false;
> + if (type != BPF_READ)
> + return false;
> + if (off % size != 0)
> + return false;
> + return true;
> +}
> +
> +static inline bool bpf_check_btf_func_ctx_access(int off, int size,
> + enum bpf_access_type type,
> + const struct bpf_prog *prog,
> + struct bpf_insn_access_aux *info)
and may be bpf_tracing_btf_ctx_access() here?
> +{
> + if (!bpf_check_btf_func_arg_access(off, size, type))
> + return false;
> + return btf_ctx_access(off, size, type, prog, info);
> +}
