Re: [PATCH v5] xen/efi: Update error flow for read_file function

["Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>]

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On Sat, Jun 28, 2025 at 07:46:18AM +0100, Frediano Ziglio wrote:
> Use more explicit goto statements to handle common error code
> path instead of a lot of if/else.
> 
> Signed-off-by: Frediano Ziglio <frediano.ziglio@cloud.com>

Reviewed-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>


> ---
> Change since v4:
> - fixed label indentation.
> ---
>  xen/common/efi/boot.c | 80 +++++++++++++++++++++++--------------------
>  1 file changed, 43 insertions(+), 37 deletions(-)
> 
> diff --git a/xen/common/efi/boot.c b/xen/common/efi/boot.c
> index 9306dc8953..1019de6950 100644
> --- a/xen/common/efi/boot.c
> +++ b/xen/common/efi/boot.c
> @@ -792,6 +792,8 @@ static bool __init read_file(EFI_FILE_HANDLE dir_handle, CHAR16 *name,
>  
>      if ( !name )
>          PrintErrMesg(L"No filename", EFI_OUT_OF_RESOURCES);
> +
> +    what = L"Open";
>      if ( dir_handle )
>          ret = dir_handle->Open(dir_handle, &FileHandle, name,
>                                 EFI_FILE_MODE_READ, 0);
> @@ -800,54 +802,58 @@ static bool __init read_file(EFI_FILE_HANDLE dir_handle, CHAR16 *name,
>      if ( file == &cfg && ret == EFI_NOT_FOUND )
>          return false;
>      if ( EFI_ERROR(ret) )
> -        what = L"Open";
> -    else
> -        ret = FileHandle->SetPosition(FileHandle, -1);
> +        goto fail;
> +
> +    what = L"Seek";
> +    ret = FileHandle->SetPosition(FileHandle, -1);
>      if ( EFI_ERROR(ret) )
> -        what = what ?: L"Seek";
> -    else
> -        ret = FileHandle->GetPosition(FileHandle, &size);
> +        goto fail;
> +
> +    what = L"Get size";
> +    ret = FileHandle->GetPosition(FileHandle, &size);
>      if ( EFI_ERROR(ret) )
> -        what = what ?: L"Get size";
> -    else
> -        ret = FileHandle->SetPosition(FileHandle, 0);
> +        goto fail;
> +
> +    what = L"Seek";
> +    ret = FileHandle->SetPosition(FileHandle, 0);
>      if ( EFI_ERROR(ret) )
> -        what = what ?: L"Seek";
> -    else
> -    {
> -        file->addr = min(1UL << (32 + PAGE_SHIFT),
> -                         HYPERVISOR_VIRT_END - DIRECTMAP_VIRT_START);
> -        ret = efi_bs->AllocatePages(AllocateMaxAddress, EfiLoaderData,
> -                                    PFN_UP(size), &file->addr);
> -    }
> +        goto fail;
> +
> +    what = L"Allocation";
> +    file->addr = min(1UL << (32 + PAGE_SHIFT),
> +                     HYPERVISOR_VIRT_END - DIRECTMAP_VIRT_START);
> +    ret = efi_bs->AllocatePages(AllocateMaxAddress, EfiLoaderData,
> +                                PFN_UP(size), &file->addr);
>      if ( EFI_ERROR(ret) )
> -        what = what ?: L"Allocation";
> -    else
> -    {
> -        file->need_to_free = true;
> -        file->size = size;
> -        handle_file_info(name, file, options);
> +        goto fail;
>  
> -        ret = FileHandle->Read(FileHandle, &file->size, file->str);
> -        if ( !EFI_ERROR(ret) && file->size != size )
> -            ret = EFI_ABORTED;
> -        if ( EFI_ERROR(ret) )
> -            what = L"Read";
> -    }
> +    file->need_to_free = true;
> +    file->size = size;
> +    handle_file_info(name, file, options);
>  
> -    if ( FileHandle )
> -        FileHandle->Close(FileHandle);
> +    what = L"Read";
> +    ret = FileHandle->Read(FileHandle, &file->size, file->str);
> +    if ( !EFI_ERROR(ret) && file->size != size )
> +        ret = EFI_ABORTED;
> +    if ( EFI_ERROR(ret) )
> +        goto fail;
>  
> -    if ( what )
> -    {
> -        PrintErr(what);
> -        PrintErr(L" failed for ");
> -        PrintErrMesg(name, ret);
> -    }
> +    FileHandle->Close(FileHandle);
>  
>      efi_arch_flush_dcache_area(file->ptr, file->size);
>  
>      return true;
> +
> + fail:
> +    if ( FileHandle )
> +        FileHandle->Close(FileHandle);
> +
> +    PrintErr(what);
> +    PrintErr(L" failed for ");
> +    PrintErrMesg(name, ret);
> +
> +    /* not reached */
> +    return false;
>  }
>  
>  static bool __init read_section(const EFI_LOADED_IMAGE *image,
> -- 
> 2.43.0
> 

-- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab

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