[U-Boot] [PATCH 2/3] efi_loader: add checking for incorrect use of EFI_ENTRY/EXIT

[Heinrich Schuchardt]

On 07/26/2017 03:55 PM, Rob Clark wrote:
> Missing an EFI_ENTRY() or doubling up EFI_EXIT() leads to non-obvious
> crashes.  Let's add some error checking.
> 
> Signed-off-by: Rob Clark <robdclark at gmail.com>
> ---
>  include/efi_loader.h          |  5 +++++
>  lib/efi_loader/efi_boottime.c | 13 +++++++++++++
>  2 files changed, 18 insertions(+)
> 
> diff --git a/include/efi_loader.h b/include/efi_loader.h
> index 09bab7dbc6..4b49fac84b 100644
> --- a/include/efi_loader.h
> +++ b/include/efi_loader.h
> @@ -15,11 +15,13 @@
>  
>  #include <linux/list.h>
>  
> +int __efi_check_nesting(int delta);
>  /*
>   * Enter the u-boot world from UEFI:
>   */
>  #define EFI_ENTRY(format, ...) do { \
>  	efi_restore_gd(); \
> +	assert(__efi_check_nesting(+1)); \
>  	debug("EFI: Entry %s(" format ")\n", __func__, ##__VA_ARGS__); \
>  	} while(0)
>  
> @@ -28,6 +30,7 @@
>   */
>  #define EFI_EXIT(ret) ({ \
>  	debug("EFI: Exit: %s: %u\n", __func__, (u32)((ret) & ~EFI_ERROR_MASK)); \
> +	assert(__efi_check_nesting(-1)); \
>  	efi_exit_func(ret); \
>  	})
>  
> @@ -36,10 +39,12 @@
>   */
>  #define EFI_CALL(exp) do { \
>  	debug("EFI: Call: %s\n", #exp); \
> +	assert(__efi_check_nesting(-1)); \
>  	efi_exit_func(EFI_SUCCESS); \
>  	exp; \
>  	efi_restore_gd(); \
>  	debug("EFI: Return From: %s\n", #exp); \
> +	assert(__efi_check_nesting(+1)); \
>  	} while(0)
>  
>  extern struct efi_runtime_services efi_runtime_services;
> diff --git a/lib/efi_loader/efi_boottime.c b/lib/efi_loader/efi_boottime.c
> index 76cafffc1d..b21df7bd5d 100644
> --- a/lib/efi_loader/efi_boottime.c
> +++ b/lib/efi_loader/efi_boottime.c
> @@ -57,6 +57,17 @@ void efi_save_gd(void)
>  #endif
>  }
>  
> +/* Check for incorrect use of EFI_ENTRY() / EFI_EXIT() */
> +int __efi_check_nesting(int delta)
> +{
> +	static int entry_count;
> +	/* post-increment, pre-decrement: */
> +	if (delta > 0)
> +		return entry_count++ == 0;
> +	else
> +		return --entry_count == 0;
> +}
> +
>  /* Called on every callback entry */
>  void efi_restore_gd(void)
>  {
> @@ -716,7 +727,9 @@ static efi_status_t EFIAPI efi_start_image(efi_handle_t image_handle,
>  		return EFI_EXIT(info->exit_status);
>  	}
>  
> +	__efi_check_nesting(-1);
>  	entry(image_handle, &systab);
> +	__efi_check_nesting(+1);
>  
>  	/* Should usually never get here */
>  	return EFI_EXIT(EFI_SUCCESS);
> 

Tested-by: Heinrich Schuchardt <xypron.glpk at gmx.de>