netdev - Re: [PATCH] lib/bpf: Fix btf_load error lead to enable debug log

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Date:   Thu, 29 Jul 2021 12:02:20 +0800
From:   zhoufeng <zhoufeng.zf@...edance.com>
To:     netdev@...r.kernel.org
Cc:     stephen@...workplumber.org, kuznet@....inr.ac.ru,
        duanxiongchun@...edance.com, wangdongdong.6@...edance.com,
        chenzhuowen.simon@...edance.com
Subject: Re: [PATCH] lib/bpf: Fix btf_load error lead to enable debug log



在 2021/7/28 下午5:33, Feng zhou 写道:
> From: Feng Zhou <zhoufeng.zf@...edance.com>
> 
> Use tc with no verbose, when bpf_btf_attach fail,
> the conditions:
> "if (fd < 0 && (errno == ENOSPC || !ctx->log_size))"
> will make ctx->log_size != 0. And then, bpf_prog_attach,
> ctx->log_size != 0. so enable debug log.
> The verifier log sometimes is so chatty on larger programs.
> bpf_prog_attach is failed.
> "Log buffer too small to dump verifier log 16777215 bytes (9 tries)!"
> 
> BTF load failure does not affect prog load. prog still work.
> So when BTF/PROG load fail, enlarge log_size and re-fail with
> having verbose.
> 
> Signed-off-by: Feng Zhou <zhoufeng.zf@...edance.com>
> ---
>   lib/bpf_legacy.c | 8 ++++----
>   1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/lib/bpf_legacy.c b/lib/bpf_legacy.c
> index 8a03b9c2..80c49f08 100644
> --- a/lib/bpf_legacy.c
> +++ b/lib/bpf_legacy.c
> @@ -1525,13 +1525,13 @@ retry:
>   	fd = bpf_prog_load_dev(prog->type, prog->insns, prog->size,
>   			       prog->license, ctx->ifindex,
>   			       ctx->log, ctx->log_size);
> -	if (fd < 0 || ctx->verbose) {
> +	if (fd < 0 && ctx->verbose) {
>   		/* The verifier log is pretty chatty, sometimes so chatty
>   		 * on larger programs, that we could fail to dump everything
>   		 * into our buffer. Still, try to give a debuggable error
>   		 * log for the user, so enlarge it and re-fail.
>   		 */
> -		if (fd < 0 && (errno == ENOSPC || !ctx->log_size)) {
> +		if (errno == ENOSPC) {
>   			if (tries++ < 10 && !bpf_log_realloc(ctx))
>   				goto retry;
>   
> @@ -2068,8 +2068,8 @@ retry:
>   	errno = 0;
>   	fd = bpf_btf_load(ctx->btf_data->d_buf, ctx->btf_data->d_size,
>   			  ctx->log, ctx->log_size);
> -	if (fd < 0 || ctx->verbose) {
> -		if (fd < 0 && (errno == ENOSPC || !ctx->log_size)) {
> +	if (fd < 0 && ctx->verbose) {
> +		if (errno == ENOSPC) {
>   			if (tries++ < 10 && !bpf_log_realloc(ctx))
>   				goto retry;
>   
> 

Sorry, this patch is wrong. please ignore it. I will send a new one.