Re: [SeaBIOS] [PATCH v5 4/5] QEMU fw_cfg: Add functions for accessing files by key

[Kevin O'Connor]

On Fri, Feb 17, 2017 at 10:21:58PM -0800, [e-mail] wrote:
> From: Ben Warren <[e-mail]>
>
> When resuming from S3, only fw_cfg file keys are known.
>
> Signed-off-by: Ben Warren <[e-mail]>
> ---
>  src/fw/paravirt.c | 23 +++++++++++++++++++++++
>  src/fw/paravirt.h |  2 ++
>  2 files changed, 25 insertions(+)
>
> diff --git a/src/fw/paravirt.c b/src/fw/paravirt.c
> index 4618647..e513dd5 100644
> --- a/src/fw/paravirt.c
> +++ b/src/fw/paravirt.c
> @@ -352,6 +352,17 @@ qemu_cfg_write_file(void *src, struct romfile_s *file, u32 offset, u32 len)
>      return len;
>  }
>
> +// Bare-bones function for writing a file knowing only its unique
> +// identifying key (select)
> +int
> +qemu_cfg_write_file_simple(void *src, u16 key, u32 offset, u32 len)
> +{
> +    qemu_cfg_select(key);
> +    qemu_cfg_skip(offset);
> +    qemu_cfg_write(src, len);
> +    return len;
> +}
> +
>  static void
>  qemu_romfile_add(char *name, int select, int skip, int size)
>  {
> @@ -370,6 +381,18 @@ qemu_romfile_add(char *name, int select, int skip, int size)
>  }
>
> u16
> +qemu_get_romfile_key(struct romfile_s *file)
> +{
> +    struct qemu_romfile_s *qfile;
> +    qfile = container_of(file, struct qemu_romfile_s, file);
> +    if (!qfile) {
> +        warn_internalerror();
> +        return 0;
> +    }

This should verify that file->copy==qemu_cfg_read_file before calling
container_of.  As Laszlo points out, there's no point in checking
!qfile after container_of.

-Kevin