linux-kernel - Re: [PATCH] kdump, proc/vmcore: fix building without CONFIG_ARCH_HAS_MEM

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Date:   Wed, 10 Oct 2018 16:45:24 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Borislav Petkov <bp@...e.de>
Cc:     Lianbo Jiang <lijiang@...hat.com>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] kdump, proc/vmcore: fix building without CONFIG_ARCH_HAS_MEM_ENCRYPT

On 10/10/18, Borislav Petkov <bp@...e.de> wrote:
> 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@...db.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

Sorry, my mistake. I noticed this patch was still in my queue and not marked
as 'submitted'. I forgot we had already discussed it.

      Arnd