Re: [kvm-unit-tests PATCH v6 19/32] lib/efi: Add support for reading an FDT

[Andrew Jones <andrew.jones@linux.dev>]

On Tue, May 30, 2023 at 05:09:11PM +0100, Nikos Nikoleris wrote:
...
> +static void* efi_get_var(efi_handle_t handle, struct efi_loaded_image_64 *image, efi_char16_t *var)
> +{
> +	efi_status_t status = EFI_SUCCESS;
> +	void *val = NULL;
> +	uint64_t val_size = 100;
> +	efi_guid_t efi_var_guid = EFI_VAR_GUID;
> +
> +	while (efi_grow_buffer(&status, &val, val_size))
> +		status = efi_rs_call(get_variable, var, &efi_var_guid, NULL, &val_size, val);
> +
> +	return val;
> +}

I made the following changes to the above function

    @@ lib/efi.c: static char *efi_convert_cmdline(struct efi_loaded_image_64 *image, i
     +  uint64_t val_size = 100;
     +  efi_guid_t efi_var_guid = EFI_VAR_GUID;
     +
    -+  while (efi_grow_buffer(&status, &val, val_size))
    ++  while (efi_grow_buffer(&status, &val, val_size + 1))
     +          status = efi_rs_call(get_variable, var, &efi_var_guid, NULL, &val_size, val);
     +
    ++  if (val)
    ++          ((efi_char16_t *)val)[val_size / sizeof(efi_char16_t)] = L'\0';
    ++
     +  return val;
     +}
     +

Before ensuring the dtb pathname was nul-terminated efi_load_image()
was reading garbage and unable to find the dtb file.

Thanks,
drew


> +
> +static void *efi_get_fdt(efi_handle_t handle, struct efi_loaded_image_64 *image)
> +{
> +	efi_char16_t var[] = ENV_VARNAME_DTBFILE;
> +	efi_char16_t *val;
> +	void *fdt = NULL;
> +	int fdtsize;
> +
> +	val = efi_get_var(handle, image, var);
> +	if (val)
> +		efi_load_image(handle, image, &fdt, &fdtsize, val);
> +
> +	return fdt;
> +}
> +
>  efi_status_t efi_main(efi_handle_t handle, efi_system_table_t *sys_tab)
>  {
>  	int ret;
> @@ -211,6 +330,7 @@ efi_status_t efi_main(efi_handle_t handle, efi_system_table_t *sys_tab)
>  	}
>  	setup_args(cmdline_ptr);
>  
> +	efi_bootinfo.fdt = efi_get_fdt(handle, image);
>  	/* Set up efi_bootinfo */
>  	efi_bootinfo.mem_map.map = ↦
>  	efi_bootinfo.mem_map.map_size = &map_size;
> -- 
> 2.25.1
>