Re: [PATCH] kdump, proc/vmcore: fix building without CONFIG_ARCH_HAS_MEM_ENCRYPT

From: Borislav Petkov <bp@suse.de>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Lianbo Jiang <lijiang@redhat.com>,
	Alexey Dobriyan <adobriyan@gmail.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH] kdump, proc/vmcore: fix building without CONFIG_ARCH_HAS_MEM_ENCRYPT
Date: Wed, 10 Oct 2018 16:40:26 +0200	[thread overview]
Message-ID: <20181010144026.GB5924@zn.tnic> (raw)
In-Reply-To: <20181010143306.2051406-1-arnd@arndb.de>

On Wed, Oct 10, 2018 at 04:32:45PM +0200, Arnd Bergmann wrote:
> We get a link failure when calling copy_oldmem_page_encrypted()
> when the compiler fails to do constant-propagation of the
> sme_active() result into read_from_oldmem:
> 
> fs/proc/vmcore.o: In function `read_from_oldmem.part.0':
> vmcore.c:(.text+0xb7): undefined reference to `copy_oldmem_page_encrypted'
> 
> Adding an IS_ENABLED() check means the compiler will always
> know when it cannot be enabled.
> 
> Fixes: 992b649a3f01 ("kdump, proc/vmcore: Enable kdumping encrypted memory with SME enabled")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> There may be a better way of doing this, not sure what kinds
> of assumptions we want to make here.
> ---
>  fs/proc/vmcore.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
> index d469ce9d8c0c..92e1e520a52d 100644
> --- a/fs/proc/vmcore.c
> +++ b/fs/proc/vmcore.c
> @@ -123,7 +123,9 @@ static ssize_t read_from_oldmem(char *buf, size_t count,
>  		if (pfn_is_ram(pfn) == 0)
>  			memset(buf, 0, nr_bytes);
>  		else {
> -			if (encrypted)
> +			if (IS_ENABLED(CONFIG_X86_64) &&
> +			    IS_ENABLED(CONFIG_ARCH_HAS_MEM_ENCRYPT) &&
> +			    encrypted)
>  				tmp = copy_oldmem_page_encrypted(pfn, buf,
>  								 nr_bytes,
>  								 offset,
> -- 

Doesn't that fix it?

https://git.kernel.org/tip/cf089611f4c446285046fcd426d90c18f37d2905

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)