Re: [PATCH v5 32/32] x86/mm: Add support to make use of Secure Memory Encryption

Borislav Petkov
2017-05-19T11:30:13Z

On Fri, Apr 21, 2017 at 01:56:13PM -0500, Tom Lendacky wrote:
> On 4/18/2017 4:22 PM, Tom Lendacky wrote:
> > Add support to check if SME has been enabled and if memory encryption
> > should be activated (checking of command line option based on the
> > configuration of the default state). If memory encryption is to be
> > activated, then the encryption mask is set and the kernel is encrypted
> > "in place."
> >
> > Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
> > ---
> > arch/x86/kernel/head_64.S | 1 +
> > arch/x86/mm/mem_encrypt.c | 83 +++++++++++++++++++++++++++++++++++++++++++--
> > 2 files changed, 80 insertions(+), 4 deletions(-)
> >
>
> ...
>
> >
> > -unsigned long __init sme_enable(void)
> > +unsigned long __init sme_enable(struct boot_params *bp)
> > {
> > + const char *cmdline_ptr, *cmdline_arg, *cmdline_on, *cmdline_off;
> > + unsigned int eax, ebx, ecx, edx;
> > + unsigned long me_mask;
> > + bool active_by_default;
> > + char buffer[16];
>
> So it turns out that when KASLR is enabled (CONFIG_RAMDOMIZE_BASE=y)
> the stack-protector support causes issues with this function because

What issues?

> it is called so early. I can get past it by adding:
>
> CFLAGS_mem_encrypt.o := $(nostackp)
>
> in the arch/x86/mm/Makefile, but that obviously eliminates the support
> for the whole file. Would it be better to split out the sme_enable()
> and other boot routines into a separate file or just apply the
> $(nostackp) to the whole file?

Josh might have a better idea here... CCed.

--
Regards/Gruss,
Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.