On Fri, Aug 20, 2021 at 7:59 PM Dave Marchevsky <davemarchevsky@xxxxxx> wrote:
>
> MAX_SNPRINTF_VARARGS and MAX_SEQ_PRINTF_VARARGS are used by bpf helpers
> bpf_snprintf and bpf_seq_printf to limit their varargs. Both call into
> bpf_bprintf_prepare for print formatting logic and have convenience
> macros in libbpf (BPF_SNPRINTF, BPF_SEQ_PRINTF) which use the same
> helper macros to convert varargs to a byte array.
>
> Changing shared functionality to support more varargs for either bpf
> helper would affect the other as well, so let's combine the _VARARGS
> macros to make this more obvious.
>
> Signed-off-by: Dave Marchevsky <davemarchevsky@xxxxxx>
> ---
Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
> include/linux/bpf.h | 2 ++
> kernel/bpf/helpers.c | 4 +---
> kernel/trace/bpf_trace.c | 4 +---
> 3 files changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index f4c16f19f83e..be8d57e6e78a 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -2216,6 +2216,8 @@ int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
> struct btf_id_set;
> bool btf_id_set_contains(const struct btf_id_set *set, u32 id);
>
> +#define MAX_BPRINTF_VARARGS 12
> +
> int bpf_bprintf_prepare(char *fmt, u32 fmt_size, const u64 *raw_args,
> u32 **bin_buf, u32 num_args);
> void bpf_bprintf_cleanup(void);
> diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
> index 4e8540716187..5ce19b376ef7 100644
> --- a/kernel/bpf/helpers.c
> +++ b/kernel/bpf/helpers.c
> @@ -969,15 +969,13 @@ int bpf_bprintf_prepare(char *fmt, u32 fmt_size, const u64 *raw_args,
> return err;
> }
>
> -#define MAX_SNPRINTF_VARARGS 12
> -
> BPF_CALL_5(bpf_snprintf, char *, str, u32, str_size, char *, fmt,
> const void *, data, u32, data_len)
> {
> int err, num_args;
> u32 *bin_args;
>
> - if (data_len % 8 || data_len > MAX_SNPRINTF_VARARGS * 8 ||
> + if (data_len % 8 || data_len > MAX_BPRINTF_VARARGS * 8 ||
> (data_len && !data))
> return -EINVAL;
> num_args = data_len / 8;
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index cbc73c08c4a4..2cf4bfa1ab7b 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -414,15 +414,13 @@ const struct bpf_func_proto *bpf_get_trace_printk_proto(void)
> return &bpf_trace_printk_proto;
> }
>
> -#define MAX_SEQ_PRINTF_VARARGS 12
> -
> BPF_CALL_5(bpf_seq_printf, struct seq_file *, m, char *, fmt, u32, fmt_size,
> const void *, data, u32, data_len)
> {
> int err, num_args;
> u32 *bin_args;
>
> - if (data_len & 7 || data_len > MAX_SEQ_PRINTF_VARARGS * 8 ||
> + if (data_len & 7 || data_len > MAX_BPRINTF_VARARGS * 8 ||
> (data_len && !data))
> return -EINVAL;
> num_args = data_len / 8;
> --
> 2.30.2
>
