linux-kernel - Re: [PATCH bpf-next v6 4/5] selftests/bpf: Add test for dmabuf

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Message-ID: <CAPhsuW4uKxFP=i2KgaKPvezD5sBcVheQRBF1fY5DyYafin_yFQ@mail.gmail.com>
Date: Wed, 14 May 2025 13:52:46 -0700
From: Song Liu <song@...nel.org>
To: "T.J. Mercier" <tjmercier@...gle.com>
Cc: sumit.semwal@...aro.org, christian.koenig@....com, ast@...nel.org, 
	daniel@...earbox.net, andrii@...nel.org, martin.lau@...ux.dev, 
	skhan@...uxfoundation.org, alexei.starovoitov@...il.com, 
	linux-kernel@...r.kernel.org, linux-media@...r.kernel.org, 
	dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org, 
	bpf@...r.kernel.org, linux-kselftest@...r.kernel.org, android-mm@...gle.com, 
	simona@...ll.ch, eddyz87@...il.com, yonghong.song@...ux.dev, 
	john.fastabend@...il.com, kpsingh@...nel.org, sdf@...ichev.me, 
	jolsa@...nel.org, mykolal@...com, shuah@...nel.org
Subject: Re: [PATCH bpf-next v6 4/5] selftests/bpf: Add test for dmabuf_iter

On Tue, May 13, 2025 at 9:36 AM T.J. Mercier <tjmercier@...gle.com> wrote:
>
> This test creates a udmabuf, and a dmabuf from the system dmabuf heap,
> and uses a BPF program that prints dmabuf metadata with the new
> dmabuf_iter to verify they can be found.
>
> Signed-off-by: T.J. Mercier <tjmercier@...gle.com>
> Acked-by: Christian König <christian.koenig@....com>

Acked-by: Song Liu <song@...nel.org>

With one more comment below.

[...]

> diff --git a/tools/testing/selftests/bpf/progs/dmabuf_iter.c b/tools/testing/selftests/bpf/progs/dmabuf_iter.c
> new file mode 100644
> index 000000000000..2a1b5397196d
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/dmabuf_iter.c
> @@ -0,0 +1,53 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2025 Google LLC */
> +#include <vmlinux.h>
> +#include <bpf/bpf_core_read.h>
> +#include <bpf/bpf_helpers.h>
> +
> +/* From uapi/linux/dma-buf.h */
> +#define DMA_BUF_NAME_LEN 32
> +
> +char _license[] SEC("license") = "GPL";
> +
> +/*
> + * Fields output by this iterator are delimited by newlines. Convert any
> + * newlines in user-provided printed strings to spaces.
> + */
> +static void sanitize_string(char *src, size_t size)
> +{
> +       for (char *c = src; *c && (size_t)(c - src) < size; ++c)

We should do the size check first, right? IOW:

for (char *c = src; (size_t)(c - src) < size && *c; ++c)



> +               if (*c == '\n')
> +                       *c = ' ';
> +}
> +
[...]