linux-kernel - Re: [tip:efi/core] efibc: Add EFI Bootloader Control module

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Message-ID: <20160429194615.GA22691@gmail.com>
Date:	Fri, 29 Apr 2016 21:46:15 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	"Compostella, Jeremy" <jeremy.compostella@...el.com>
Cc:	Matt Fleming <matt@...eblueprint.co.uk>, stefan.stanacar@...el.com,
	peterz@...radead.org, linux-kernel@...r.kernel.org,
	tglx@...utronix.de, hpa@...or.com, bp@...en8.de,
	ard.biesheuvel@...aro.org, linux-tip-commits@...r.kernel.org
Subject: Re: [tip:efi/core] efibc: Add EFI Bootloader Control module


* Compostella, Jeremy <jeremy.compostella@...el.com> wrote:

> -static void efibc_set_variable(const char *name, const char *value)
> +static int efibc_set_variable(const char *name, const char *value)
>  {
>  	int ret;
>  	efi_guid_t guid = LINUX_EFI_LOADER_ENTRY_GUID;
> -	struct efivar_entry entry;
> +	struct efivar_entry *entry;
>  	size_t size = (strlen(value) + 1) * sizeof(efi_char16_t);
>  
> -	if (size > sizeof(entry.var.Data))
> +	if (size > sizeof(entry->var.Data)) {
>  		pr_err("value is too large");
> +		return -1;
> +	}
>  
> -	efibc_str_to_str16(name, entry.var.VariableName);
> -	efibc_str_to_str16(value, (efi_char16_t *)entry.var.Data);
> -	memcpy(&entry.var.VendorGuid, &guid, sizeof(guid));
> +	entry = kmalloc(sizeof(*entry), GFP_KERNEL);
> +	if (!entry) {
> +		pr_err("failed to allocate efivar entry");
> +		return -1;
> +	}
>  
> -	ret = efivar_entry_set(&entry,
> +	efibc_str_to_str16(name, entry->var.VariableName);
> +	efibc_str_to_str16(value, (efi_char16_t *)entry->var.Data);
> +	memcpy(&entry->var.VendorGuid, &guid, sizeof(guid));
> +
> +	ret = efivar_entry_set(entry,
>  			       EFI_VARIABLE_NON_VOLATILE
>  			       | EFI_VARIABLE_BOOTSERVICE_ACCESS
>  			       | EFI_VARIABLE_RUNTIME_ACCESS,
> -			       size, entry.var.Data, NULL);
> +			       size, entry->var.Data, NULL);
>  	if (ret)
>  		pr_err("failed to set %s EFI variable: 0x%x\n",
>  		       name, ret);
> +
> +	kfree(entry);
> +	return ret;
>  }
>  
>  static int efibc_reboot_notifier_call(struct notifier_block *notifier,
>  				      unsigned long event, void *data)
>  {
>  	const char *reason = "shutdown";
> +	int ret;
>  
>  	if (event == SYS_RESTART)
>  		reason = "reboot";
>  
> -	efibc_set_variable("LoaderEntryRebootReason", reason);
> -
> -	if (!data)
> -		return NOTIFY_DONE;
> +	ret = efibc_set_variable("LoaderEntryRebootReason", reason);
> +	if (ret || !data)
> + 		return NOTIFY_DONE;
>  
>  	efibc_set_variable("LoaderEntryOneShot", (char *)data);

Hm, can reboot notifiers do non-atomic allocations?

Why is efivar_entry so huge?

Thanks,

	Ingo