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, ben(a)skyportsystems.com wrote:
 From: Ben Warren <ben(a)skyportsystems.com&gt;
 
 When resuming from S3, only fw_cfg file keys are known.
 
 Signed-off-by: Ben Warren <ben(a)skyportsystems.com&gt;
 ---
  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