Re: [Qemu-devel] [PATCH 1/2] tests: fw_cfg: add a function to get the fw_cfg file

[Thomas Huth <thuth@redhat.com>]

On 19/03/2019 03.30, Li Qiang wrote:
> This is useful to write qtest about fw_cfg file entry.
> 
> Signed-off-by: Li Qiang <liq3ea@163.com>
> ---
>  tests/libqos/fw_cfg.c | 45 +++++++++++++++++++++++++++++++++++++++++++
>  tests/libqos/fw_cfg.h |  2 ++
>  2 files changed, 47 insertions(+)
> 
> diff --git a/tests/libqos/fw_cfg.c b/tests/libqos/fw_cfg.c
> index d0889d1e22..2df33df859 100644
> --- a/tests/libqos/fw_cfg.c
> +++ b/tests/libqos/fw_cfg.c
> @@ -16,12 +16,57 @@
>  #include "libqos/fw_cfg.h"
>  #include "libqtest.h"
>  #include "qemu/bswap.h"
> +#include "hw/nvram/fw_cfg.h"
>  
>  void qfw_cfg_select(QFWCFG *fw_cfg, uint16_t key)
>  {
>      fw_cfg->select(fw_cfg, key);
>  }
>  
> +/*
> + * The caller need check the return value. When the return value is
> + * nonzero, it means that some bytes have been transferred.
> + *
> + * If the fw_cfg file in question is smaller than the allocated & passed-in
> + * buffer, then the buffer has been populated only in part.
> + *
> + * If the fw_cfg file in question is larger than the passed-in
> + * buffer, then the return value explains how much room would have been
> + * necessary in total. And, while the caller's buffer has been fully
> + * populated, it has received only a starting slice of the fw_cfg file.
> + */
> +size_t qfw_cfg_get_file(QFWCFG *fw_cfg, const char *filename,
> +                      void *data, size_t buflen)
> +{
> +    uint32_t count;
> +    uint32_t i;
> +    unsigned char *filesbuf = NULL;
> +    size_t dsize;
> +    FWCfgFile *pdir_entry;
> +    size_t filesize = 0;
> +
> +    qfw_cfg_get(fw_cfg, FW_CFG_FILE_DIR, &count, sizeof(count));
> +    count = be32_to_cpu(count);
> +    dsize = sizeof(uint32_t) + count * sizeof(struct fw_cfg_file);
> +    filesbuf = g_malloc0(dsize);
> +    qfw_cfg_get(fw_cfg, FW_CFG_FILE_DIR, filesbuf, dsize);

If I get the code right,  qfw_cfg_get() fills the whole buffer here...
in that case, g_malloc() should be sufficient, so you don't need
g_malloc0() here.

 Thomas