linux-kernel - Re: [PATCH] EFI loader: remove dead code

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Message-ID: <20161101230950.GD3567@oranje.usa.hp.com>
Date:   Tue, 1 Nov 2016 16:09:50 -0700
From:   Linn Crosetto <linn@....com>
To:     Eugene Korenevsky <ekorenevsky@...il.com>
Cc:     linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org,
        Matt Fleming <matt@...eblueprint.co.uk>
Subject: Re: [PATCH] EFI loader: remove dead code

On Tue, Nov 01, 2016 at 08:38:08PM +0300, Eugene Korenevsky wrote:
> *e820ext is always NULL in 'alloc_e820ext()' (see the code of 'exit_boot()').
> Therefore the 'if' condition is always false and the entire 'if' statement is
> pointless. Remove it.
> 
> ---
>  arch/x86/boot/compressed/eboot.c | 6 ------
>  1 file changed, 6 deletions(-)
> 
> diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c
> index cc69e37..edfd4d6 100644
> --- a/arch/x86/boot/compressed/eboot.c
> +++ b/arch/x86/boot/compressed/eboot.c
> @@ -956,12 +956,6 @@ static efi_status_t alloc_e820ext(u32 nr_desc, struct setup_data **e820ext,
>  	size = sizeof(struct setup_data) +
>  		sizeof(struct e820entry) * nr_desc;
>  
> -	if (*e820ext) {
> -		efi_call_early(free_pool, *e820ext);
> -		*e820ext = NULL;
> -		*e820ext_size = 0;
> -	}
> -

I agree with your reading of the code. On the other hand, alloc_e820ext()
has no knowledge of the 'first' flag used in exit_boot_func() so the call to
free provides some assurance that memory isn't leaked if the calling code is
changed.

If the caller is responsible for freeing the memory in such a case, then
alloc_e820ext() should at least return an error.

--
Linn