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@xxxxxx>
> ---
> 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
>
