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From: Jiri Olsa <olsajiri@gmail.com>
To: Yonghong Song <yhs@fb.com>
Cc: bpf@vger.kernel.org, Alexei Starovoitov <ast@kernel.org>,
	Andrii Nakryiko <andrii@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	kernel-team@fb.com
Subject: Re: [PATCH bpf-next v4 3/8] bpf: Update descriptions for helpers bpf_get_func_arg[_cnt]()
Date: Fri, 2 Sep 2022 09:56:41 +0200	[thread overview]
Message-ID: <YxG3OVk72IaSEJd6@krava> (raw)
In-Reply-To: <20220831152657.2078805-1-yhs@fb.com>

On Wed, Aug 31, 2022 at 08:26:57AM -0700, Yonghong Song wrote:
> Now instead of the number of arguments, the number of registers
> holding argument values are stored in trampoline. Update
> the description of bpf_get_func_arg[_cnt]() helpers. Previous
> programs without struct arguments should continue to work
> as usual.
> 
> Signed-off-by: Yonghong Song <yhs@fb.com>
> ---
>  include/uapi/linux/bpf.h       | 9 +++++----
>  tools/include/uapi/linux/bpf.h | 9 +++++----
>  2 files changed, 10 insertions(+), 8 deletions(-)
> 
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 962960a98835..f9f43343ef93 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -5079,12 +5079,12 @@ union bpf_attr {
>   *
>   * long bpf_get_func_arg(void *ctx, u32 n, u64 *value)
>   *	Description
> - *		Get **n**-th argument (zero based) of the traced function (for tracing programs)
> + *		Get **n**-th argument register (zero based) of the traced function (for tracing programs)

I'm bit worried about the confusion between args/regs we create with
this, but I don't any have better idea how to solve this

keeping extra stack values for nr_args and nr_regs and have new helpers
to get reg values.. but then bpf_get_func_arg still does not return the
full argument value.. also given that the struct args should be rare,
I guess it's fine ;-)

jirka

>   *		returned in **value**.
>   *
>   *	Return
>   *		0 on success.
> - *		**-EINVAL** if n >= arguments count of traced function.
> + *		**-EINVAL** if n >= argument register count of traced function.
>   *
>   * long bpf_get_func_ret(void *ctx, u64 *value)
>   *	Description
> @@ -5097,10 +5097,11 @@ union bpf_attr {
>   *
>   * long bpf_get_func_arg_cnt(void *ctx)
>   *	Description
> - *		Get number of arguments of the traced function (for tracing programs).
> + *		Get number of registers of the traced function (for tracing programs) where
> + *		function arguments are stored in these registers.
>   *
>   *	Return
> - *		The number of arguments of the traced function.
> + *		The number of argument registers of the traced function.
>   *
>   * int bpf_get_retval(void)
>   *	Description
> diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
> index f4ba82a1eace..f13fa71822f4 100644
> --- a/tools/include/uapi/linux/bpf.h
> +++ b/tools/include/uapi/linux/bpf.h
> @@ -5079,12 +5079,12 @@ union bpf_attr {
>   *
>   * long bpf_get_func_arg(void *ctx, u32 n, u64 *value)
>   *	Description
> - *		Get **n**-th argument (zero based) of the traced function (for tracing programs)
> + *		Get **n**-th argument register (zero based) of the traced function (for tracing programs)
>   *		returned in **value**.
>   *
>   *	Return
>   *		0 on success.
> - *		**-EINVAL** if n >= arguments count of traced function.
> + *		**-EINVAL** if n >= argument register count of traced function.
>   *
>   * long bpf_get_func_ret(void *ctx, u64 *value)
>   *	Description
> @@ -5097,10 +5097,11 @@ union bpf_attr {
>   *
>   * long bpf_get_func_arg_cnt(void *ctx)
>   *	Description
> - *		Get number of arguments of the traced function (for tracing programs).
> + *		Get number of registers of the traced function (for tracing programs) where
> + *		function arguments are stored in these registers.
>   *
>   *	Return
> - *		The number of arguments of the traced function.
> + *		The number of argument registers of the traced function.
>   *
>   * int bpf_get_retval(void)
>   *	Description
> -- 
> 2.30.2
> 

  reply	other threads:[~2022-09-02  7:57 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-08-31 15:26 [PATCH bpf-next v4 0/8] bpf: Support struct argument for trampoline base progs Yonghong Song
2022-08-31 15:26 ` [PATCH bpf-next v4 1/8] bpf: Allow struct argument in trampoline based programs Yonghong Song
2022-08-31 15:26 ` [PATCH bpf-next v4 2/8] bpf: x86: Support in-register struct arguments in trampoline programs Yonghong Song
2022-09-06 16:40   ` Kui-Feng Lee
2022-09-06 19:30     ` Yonghong Song
2022-09-07  3:00   ` Alexei Starovoitov
2022-09-07 18:04     ` Yonghong Song
2022-08-31 15:26 ` [PATCH bpf-next v4 3/8] bpf: Update descriptions for helpers bpf_get_func_arg[_cnt]() Yonghong Song
2022-09-02  7:56   ` Jiri Olsa [this message]
2022-09-06 16:12     ` Yonghong Song
2022-08-31 15:27 ` [PATCH bpf-next v4 4/8] bpf: arm64: No support of struct argument in trampoline programs Yonghong Song
2022-08-31 15:27 ` [PATCH bpf-next v4 5/8] libbpf: Add new BPF_PROG2 macro Yonghong Song
2022-09-09  0:11   ` Andrii Nakryiko
2022-09-09 16:31     ` Yonghong Song
2022-09-09 18:07       ` Andrii Nakryiko
2022-08-31 15:27 ` [PATCH bpf-next v4 6/8] selftests/bpf: Add struct argument tests with fentry/fexit programs Yonghong Song
2022-08-31 15:27 ` [PATCH bpf-next v4 7/8] selftests/bpf: Use BPF_PROG2 for some fentry programs without struct arguments Yonghong Song
2022-08-31 15:27 ` [PATCH bpf-next v4 8/8] selftests/bpf: Add tracing_struct test in DENYLIST.s390x Yonghong Song
2022-09-07  3:10 ` [PATCH bpf-next v4 0/8] bpf: Support struct argument for trampoline base progs patchwork-bot+netdevbpf

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