linux-kernel - Re: [PATCH v2] kcov: fix struct layout for kcov_remote

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Message-ID: <CANpmjNMVW_=8Mg3gERZFKd7NyJS3AS2e7nO33B0PczAsXm7xqg@mail.gmail.com>
Date:   Fri, 6 Dec 2019 14:45:37 +0100
From:   Marco Elver <elver@...gle.com>
To:     Andrey Konovalov <andreyknvl@...gle.com>
Cc:     linux-usb@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alan Stern <stern@...land.harvard.edu>,
        Felipe Balbi <balbi@...nel.org>,
        Chunfeng Yun <chunfeng.yun@...iatek.com>,
        "Jacky . Cao @ sony . com" <Jacky.Cao@...y.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Alexander Potapenko <glider@...gle.com>
Subject: Re: [PATCH v2] kcov: fix struct layout for kcov_remote_arg

On Fri, 6 Dec 2019 at 14:31, Andrey Konovalov <andreyknvl@...gle.com> wrote:
>
> Make the layout of kcov_remote_arg the same for 32-bit and 64-bit code.
> This makes it more convenient to write userspace apps that can be compiled
> into 32-bit or 64-bit binaries and still work with the same 64-bit kernel.
> Also use proper __u32 types in uapi headers instead of unsigned ints.
>
> Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>

Acked-by: Marco Elver <elver@...gle.com>

Thanks!

> ---
>
> Changes v1->v2:
> - Use __aligned_u64 instead of adding a __u32 reserved field.
>
>  Documentation/dev-tools/kcov.rst | 10 +++++-----
>  include/uapi/linux/kcov.h        | 10 +++++-----
>  2 files changed, 10 insertions(+), 10 deletions(-)
>
> diff --git a/Documentation/dev-tools/kcov.rst b/Documentation/dev-tools/kcov.rst
> index 36890b026e77..1c4e1825d769 100644
> --- a/Documentation/dev-tools/kcov.rst
> +++ b/Documentation/dev-tools/kcov.rst
> @@ -251,11 +251,11 @@ selectively from different subsystems.
>  .. code-block:: c
>
>      struct kcov_remote_arg {
> -       unsigned        trace_mode;
> -       unsigned        area_size;
> -       unsigned        num_handles;
> -       uint64_t        common_handle;
> -       uint64_t        handles[0];
> +       __u32           trace_mode;
> +       __u32           area_size;
> +       __u32           num_handles;
> +       __aligned_u64   common_handle;
> +       __aligned_u64   handles[0];
>      };
>
>      #define KCOV_INIT_TRACE                    _IOR('c', 1, unsigned long)
> diff --git a/include/uapi/linux/kcov.h b/include/uapi/linux/kcov.h
> index 409d3ad1e6e2..1d0350e44ae3 100644
> --- a/include/uapi/linux/kcov.h
> +++ b/include/uapi/linux/kcov.h
> @@ -9,11 +9,11 @@
>   * and the comment before kcov_remote_start() for usage details.
>   */
>  struct kcov_remote_arg {
> -       unsigned int    trace_mode;     /* KCOV_TRACE_PC or KCOV_TRACE_CMP */
> -       unsigned int    area_size;      /* Length of coverage buffer in words */
> -       unsigned int    num_handles;    /* Size of handles array */
> -       __u64           common_handle;
> -       __u64           handles[0];
> +       __u32           trace_mode;     /* KCOV_TRACE_PC or KCOV_TRACE_CMP */
> +       __u32           area_size;      /* Length of coverage buffer in words */
> +       __u32           num_handles;    /* Size of handles array */
> +       __aligned_u64   common_handle;
> +       __aligned_u64   handles[0];
>  };
>
>  #define KCOV_REMOTE_MAX_HANDLES                0x100
> --
> 2.24.0.393.g34dc348eaf-goog
>