Re: [PATCH bpf-next v2 2/5] bpf: factor out helpers to check ctx access for BTF function
From: Martin KaFai Lau <hidden>
Date: 2021-10-20 05:01:33
Also in:
netdev
On Sat, Oct 16, 2021 at 08:48:03PM +0800, Hou Tao wrote:
quoted hunk ↗ jump to hunk
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 <redacted> --- 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);
+}