Re: [Qemu-devel] [PATCH] fw_cfg: fix the life cycle and the name of "qemu_extra_params_fw"

[Gerd Hoffmann]

On Fri, Jan 18, 2019 at 11:31:52PM +0100, Laszlo Ersek wrote:
> Commit 19bcc4bc3213 ("fw_cfg: Make qemu_extra_params_fw locally",
> 2019-01-04) changed the storage duration of the "qemu_extra_params_fw"
> array from static to automatic. This broke the interface contract on the
> fw_cfg_add_file() function, which is documented as follows, in
> "include/hw/nvram/fw_cfg.h":
> 
> > [...] The data referenced by the starting pointer is only linked, NOT
> > copied, into the data structure of the fw_cfg device. [...]
> 
> As a result, when guest firmware fetches the "etc/boot-menu-wait" fw_cfg
> file, it now sees garbage. Fix the regression by changing the storage
> duration to allocated. (The call is reached at most once, on the realize
> path of the board-specific fw_cfg sysbus device.)
> 
> While at it, clean up the name and the assignment of the object as well.

Reviewed-by: Gerd Hoffmann <address@hidden>

> 
> Cc: Gerd Hoffmann <address@hidden>
> Cc: Markus Armbruster <address@hidden>
> Cc: Philippe Mathieu-Daudé <address@hidden>
> Fixes: 19bcc4bc3213e78c303ad480a7a578f62258252d
> Signed-off-by: Laszlo Ersek <address@hidden>
> ---
>  hw/nvram/fw_cfg.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
> index 53e8e010a8b7..7fdf04adc97f 100644
> --- a/hw/nvram/fw_cfg.c
> +++ b/hw/nvram/fw_cfg.c
> @@ -118,7 +118,6 @@ static void fw_cfg_bootsplash(FWCfgState *s)
>  {
>      const char *boot_splash_filename = NULL;
>      const char *boot_splash_time = NULL;
> -    uint8_t qemu_extra_params_fw[2];
>      char *filename, *file_data;
>      gsize file_size;
>      int file_type;
> @@ -132,6 +131,8 @@ static void fw_cfg_bootsplash(FWCfgState *s)
>      /* insert splash time if user configurated */
>      if (boot_splash_time) {
>          int64_t bst_val = qemu_opt_get_number(opts, "splash-time", -1);
> +        uint16_t bst_le16;
> +
>          /* validate the input */
>          if (bst_val < 0 || bst_val > 0xffff) {
>              error_report("splash-time is invalid,"
> @@ -139,9 +140,9 @@ static void fw_cfg_bootsplash(FWCfgState *s)
>              exit(1);
>          }
>          /* use little endian format */
> -        qemu_extra_params_fw[0] = (uint8_t)(bst_val & 0xff);
> -        qemu_extra_params_fw[1] = (uint8_t)((bst_val >> 8) & 0xff);
> -        fw_cfg_add_file(s, "etc/boot-menu-wait", qemu_extra_params_fw, 2);
> +        bst_le16 = cpu_to_le16(bst_val);
> +        fw_cfg_add_file(s, "etc/boot-menu-wait",
> +                        g_memdup(&bst_le16, sizeof bst_le16), sizeof 
> bst_le16);
>      }
>  
>      /* insert splash file if user configurated */
> -- 
> 2.19.1.3.g30247aa5d201
>