[PATCH v2 27/28] efi_loader: Don't try to add sandbox runtime code

[Heinrich Schuchardt]

On 28.11.24 16:47, Simon Glass wrote:
> This cannot work since the code is not present in the emulated memory.
> In any case, sandbox cannot make use of the runtime code.

For sure an EFI application running on the sandbox can run
ExitBootServices() and then call the ResetSystem() runtime system service.

Have a look at

arch/sandbox/cpu/start.c:472:
void __efi_runtime EFIAPI efi_reset_system().

__efi_runtime implements ResetSystem() after ExitBootServices().

>
> For now, just drop it from sandbox. We can always adjust things to copy
> it into memory, if needed.
>
> Signed-off-by: Simon Glass <sjg at chromium.org>
> ---
>
> (no changes since v1)
>
>   lib/efi_loader/efi_memory.c | 26 ++++++++++++++++----------
>   1 file changed, 16 insertions(+), 10 deletions(-)
>
> diff --git a/lib/efi_loader/efi_memory.c b/lib/efi_loader/efi_memory.c
> index a33c025fa20..796fa99f4fb 100644
> --- a/lib/efi_loader/efi_memory.c
> +++ b/lib/efi_loader/efi_memory.c
> @@ -755,16 +755,22 @@ static void add_u_boot_and_runtime(void)
>   	runtime_mask = SZ_64K - 1;
>   #endif
>
> -	/*
> -	 * Add Runtime Services. We mark surrounding boottime code as runtime as
> -	 * well to fulfill the runtime alignment constraints but avoid padding.
> -	 */
> -	runtime_start = (uintptr_t)__efi_runtime_start & ~runtime_mask;
> -	runtime_end = (uintptr_t)__efi_runtime_stop;
> -	runtime_end = (runtime_end + runtime_mask) & ~runtime_mask;
> -	runtime_pages = (runtime_end - runtime_start) >> EFI_PAGE_SHIFT;
> -	efi_add_memory_map_pg(runtime_start, runtime_pages,
> -			      EFI_RUNTIME_SERVICES_CODE, false);
> +	if (!IS_ENABLED(CONFIG_SANDBOX)) {
> +		/*
> +		 * Add Runtime Services. We mark surrounding boottime code as
> +		 * runtime as well to fulfill the runtime alignment constraints
> +		 * but avoid padding.
> +		 *
> +		 * This is not enabled for sandbox, since we cannot map the
> +		 * sandbox code into emulated SDRAM

The memory map is consumed by an EFI application like shim, GRUB, or the
kernel stub.

The memory map entries must take address values which can be used a
void* without conversion. This is true both on real systems and on the
sandbox.

Isn't __efi_runtime_start a pointer to the start of the efi_runtime code
section on the sandbox?

Best regards

Heinrich
> +		 */
> +		runtime_start = (uintptr_t)__efi_runtime_start & ~runtime_mask;
> +		runtime_end = (uintptr_t)__efi_runtime_stop;
> +		runtime_end = (runtime_end + runtime_mask) & ~runtime_mask;
> +		runtime_pages = (runtime_end - runtime_start) >> EFI_PAGE_SHIFT;
> +		efi_add_memory_map_pg(runtime_start, runtime_pages,
> +				      EFI_RUNTIME_SERVICES_CODE, false);
> +	}
>   }
>
>   int efi_memory_init(void)