Re: [PATCH v2] hw/core/loader: allow loading larger ROMs

["Daniel P. Berrangé" <berrange@redhat.com>]

On Thu, Jun 27, 2024 at 05:58:17PM -0700, Gregor Haas wrote:
> The read() syscall is not guaranteed to return all data from a file. The
> default ROM loader implementation currently does not take this into account,
> instead failing if all bytes are not read at once. This change loads the ROM
> using load_image_size() instead, which correctly reads all data using
> multiple calls to read().
> 
> Signed-off-by: Gregor Haas <gregorhaas1997@gmail.com>
> ---
>  hw/core/loader.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/core/loader.c b/hw/core/loader.c
> index 2f8105d7de..8216781a75 100644
> --- a/hw/core/loader.c
> +++ b/hw/core/loader.c
> @@ -1115,14 +1115,13 @@ ssize_t rom_add_file(const char *file, const char *fw_dir,
>  
>      rom->datasize = rom->romsize;
>      rom->data     = g_malloc0(rom->datasize);
> -    lseek(fd, 0, SEEK_SET);
> -    rc = read(fd, rom->data, rom->datasize);
> +    close(fd);
> +    rc = load_image_size(rom->path, rom->data, rom->datasize);
>      if (rc != rom->datasize) {
>          fprintf(stderr, "rom: file %-20s: read error: rc=%zd (expected %zd)\n",
>                  rom->name, rc, rom->datasize);
>          goto err;
>      }
> -    close(fd);

This method can be simplified much more.
All of the original 'open', lseek, g_malloc0, read & close, can be
replaced by something approximately like this (untested):

   g_autoptr(GError) gerr = NULL;
   if (!g_file_get_contents(file, &rom->data, &rom->datasize, &gerr)) {
       fprintf(stderr, "unable to load ROM '%s': %s", file, gerr->message);
       goto err;
   }
   

With regards,
Daniel
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