linux-kernel - Re: [Xen-devel] [PATCH] x86/xen/efi: Fix EFI variable 'name' type conversion

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Date:   Mon, 2 Sep 2019 09:54:20 +0200
From:   Jan Beulich <jbeulich@...e.com>
To:     Adam Zerella <adam.zerella@...il.com>
Cc:     Borislav Petkov <bp@...en8.de>,
        Stefano Stabellini <sstabellini@...nel.org>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        xen-devel@...ts.xenproject.org,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Ingo Molnar <mingo@...hat.com>,
        Juergen Gross <jgross@...e.com>, linux-kernel@...r.kernel.org,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [Xen-devel] [PATCH] x86/xen/efi: Fix EFI variable 'name' type
 conversion

On 01.09.2019 08:58, Adam Zerella wrote:
> This resolves a type conversion from 'char *' to 'unsigned short'.

Could you explain this? There's no ...

> --- a/arch/x86/xen/efi.c
> +++ b/arch/x86/xen/efi.c
> @@ -118,8 +118,8 @@ static enum efi_secureboot_mode xen_efi_get_secureboot(void)
>  	unsigned long size;
>  
>  	size = sizeof(secboot);
> -	status = efi.get_variable(L"SecureBoot", &efi_variable_guid,
> -				  NULL, &size, &secboot);
> +	status = efi.get_variable((efi_char16_t *)L"SecureBoot",
> +				  &efi_variable_guid, NULL, &size, &secboot);

... "char *" resulting as type for L"" type strings, hence there
should be no need for a cast: In fact I consider such casts
dangerous, as they may hide actual problems. To me this looks
more like something that wants fixing in sparse; the compilers,
after all, have no issue with such wide character string literals.

> @@ -158,7 +158,7 @@ static enum efi_secureboot_mode xen_efi_get_secureboot(void)
>  	return efi_secureboot_mode_unknown;
>  }
>  
> -void __init xen_efi_init(struct boot_params *boot_params)
> +static void __init xen_efi_init(struct boot_params *boot_params)
>  {
>  	efi_system_table_t *efi_systab_xen;

If I was a maintainer of this code, I'd request this not be part
of a patch with a title being entirely unrelated to the change.

Jan