linux-kernel - Re: [PATCH bpf-next v2 4/7] tools headers UAPI: Update tools's copy of bpf.h header

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Message-ID: <CAEf4BzZvQF+QQ=oip4vdz5A=9bd+OmN-CXk5YARYieaipK9s+A@mail.gmail.com>
Date: Mon, 27 Jan 2025 14:08:10 -0800
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: rsworktech@...look.com
Cc: Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>, 
	Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
	Yonghong Song <yonghong.song@...ux.dev>, John Fastabend <john.fastabend@...il.com>, 
	KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, 
	Jiri Olsa <jolsa@...nel.org>, Matt Bobrowski <mattbobrowski@...gle.com>, 
	Steven Rostedt <rostedt@...dmis.org>, Masami Hiramatsu <mhiramat@...nel.org>, 
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, Mykola Lysenko <mykolal@...com>, 
	Shuah Khan <shuah@...nel.org>, bpf@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-trace-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH bpf-next v2 4/7] tools headers UAPI: Update tools's copy
 of bpf.h header

On Sat, Jan 25, 2025 at 12:30 AM Levi Zim via B4 Relay
<devnull+rsworktech.outlook.com@...nel.org> wrote:
>
> From: Levi Zim <rsworktech@...look.com>
>
> This update brings the new bpf_probe_read_{kernel,user} helpers
>
> Signed-off-by: Levi Zim <rsworktech@...look.com>
> ---
>  tools/include/uapi/linux/bpf.h | 49 ++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 49 insertions(+)
>
> diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
> index 2acf9b33637174bd16b1d12ccc6410c5f55a7ea9..f92cf809b50bc393d54eb0e8de2e1ce2a39e95d0 100644
> --- a/tools/include/uapi/linux/bpf.h
> +++ b/tools/include/uapi/linux/bpf.h
> @@ -5805,6 +5805,52 @@ union bpf_attr {
>   *             0 on success.
>   *
>   *             **-ENOENT** if the bpf_local_storage cannot be found.
> + *
> + * long bpf_probe_read_kernel_dynptr(const struct bpf_dynptr *dst, u32 offset, u32 size, const void *unsafe_ptr, u64 flags)
> + *     Description
> + *             Safely attempt to read *size* bytes from kernel space address
> + *             *unsafe_ptr* and store the data in *dst* starting from *offset*.
> + *             *flags* is currently unused.
> + *     Return
> + *             0 on success.
> + *
> + *             **-E2BIG** if *offset* + *len* exceeds the length of *src*'s data
> + *
> + *             **-EINVAL** if *src* is an invalid dynptr or doesn't support this
> + *             support this helper, or if *flags* is not 0.
> + *
> + *             Or other negative errors on failure reading kernel memory.
> + *
> + * long bpf_probe_read_user_dynptr(const struct bpf_dynptr *dst, u32 offset, u32 size, const void *unsafe_ptr, u64 flags)
> + *     Description
> + *             Safely attempt to read *size* bytes from user space address
> + *             *unsafe_ptr* and store the data in *dst* starting from *offset*.
> + *             *flags* is currently unused.
> + *     Return
> + *             0 on success.
> + *
> + *             **-E2BIG** if *offset* + *len* exceeds the length of *src*'s data
> + *
> + *             **-EINVAL** if *src* is an invalid dynptr or doesn't support this
> + *             support this helper, or if *flags* is not 0.
> + *
> + *             Or other negative errors on failure reading user space memory.
> + *
> + * long bpf_copy_from_user_dynptr(const struct bpf_dynptr *dst, u32 offset, u32 size, const void *user_ptr, u64 flags)
> + *     Description
> + *             Read *size* bytes from user space address *user_ptr* and store
> + *             the data in *dst* starting from *offset*.
> + *             This is a wrapper of **copy_from_user**\ ().
> + *             *flags* is currently unused.
> + *     Return
> + *             0 on success.
> + *
> + *             **-E2BIG** if *offset* + *len* exceeds the length of *src*'s data
> + *
> + *             **-EINVAL** if *src* is an invalid dynptr or doesn't support this
> + *             support this helper, or if *flags* is not 0.
> + *
> + *             Or other negative errors on failure reading user space memory.
>   */
>  #define ___BPF_FUNC_MAPPER(FN, ctx...)                 \
>         FN(unspec, 0, ##ctx)                            \
> @@ -6019,6 +6065,9 @@ union bpf_attr {
>         FN(user_ringbuf_drain, 209, ##ctx)              \
>         FN(cgrp_storage_get, 210, ##ctx)                \
>         FN(cgrp_storage_delete, 211, ##ctx)             \

we probably want to add some big and very noticeable comment here
suggesting kfunc route, to save people time next time. Please consider
adding it as a separate patch for v2.

> +       FN(probe_read_kernel_dynptr, 212, ##ctx)                \
> +       FN(probe_read_user_dynptr, 213, ##ctx)          \
> +       FN(copy_from_user_dynptr, 214, ##ctx)           \
>         /* */
>
>  /* backwards-compatibility macros for users of __BPF_FUNC_MAPPER that don't
>
> --
> 2.48.1
>
>