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Message-ID: <af9a50f7-17ea-a840-6456-b6479e5d7e82@amd.com>
Date: Fri, 23 Jun 2017 12:44:46 -0500
From: Tom Lendacky <thomas.lendacky@....com>
To: Borislav Petkov <bp@...en8.de>
Cc: linux-arch@...r.kernel.org, linux-efi@...r.kernel.org,
kvm@...r.kernel.org, linux-doc@...r.kernel.org, x86@...nel.org,
kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
kasan-dev@...glegroups.com, xen-devel@...ts.xen.org,
linux-mm@...ck.org, iommu@...ts.linux-foundation.org,
Brijesh Singh <brijesh.singh@....com>,
Toshimitsu Kani <toshi.kani@....com>,
Radim Krčmář <rkrcmar@...hat.com>,
Matt Fleming <matt@...eblueprint.co.uk>,
Alexander Potapenko <glider@...gle.com>,
"H. Peter Anvin" <hpa@...or.com>,
Larry Woodman <lwoodman@...hat.com>,
Jonathan Corbet <corbet@....net>,
Joerg Roedel <joro@...tes.org>,
"Michael S. Tsirkin" <mst@...hat.com>,
Ingo Molnar <mingo@...hat.com>,
Andrey Ryabinin <aryabinin@...tuozzo.com>,
Dave Young <dyoung@...hat.com>, Rik van Riel <riel@...hat.com>,
Arnd Bergmann <arnd@...db.de>,
Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
Andy Lutomirski <luto@...nel.org>,
Boris Ostrovsky <boris.ostrovsky@...cle.com>,
Dmitry Vyukov <dvyukov@...gle.com>,
Juergen Gross <jgross@...e.com>,
Thomas Gleixner <tglx@...utronix.de>,
Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [PATCH v7 34/36] x86/mm: Add support to encrypt the kernel
in-place
On 6/23/2017 5:00 AM, Borislav Petkov wrote:
> On Fri, Jun 16, 2017 at 01:56:19PM -0500, Tom Lendacky wrote:
>> Add the support to encrypt the kernel in-place. This is done by creating
>> new page mappings for the kernel - a decrypted write-protected mapping
>> and an encrypted mapping. The kernel is encrypted by copying it through
>> a temporary buffer.
>>
>> Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
>> ---
>> arch/x86/include/asm/mem_encrypt.h | 6 +
>> arch/x86/mm/Makefile | 2
>> arch/x86/mm/mem_encrypt.c | 314 ++++++++++++++++++++++++++++++++++++
>> arch/x86/mm/mem_encrypt_boot.S | 150 +++++++++++++++++
>> 4 files changed, 472 insertions(+)
>> create mode 100644 arch/x86/mm/mem_encrypt_boot.S
>>
>> diff --git a/arch/x86/include/asm/mem_encrypt.h b/arch/x86/include/asm/mem_encrypt.h
>> index af835cf..7da6de3 100644
>> --- a/arch/x86/include/asm/mem_encrypt.h
>> +++ b/arch/x86/include/asm/mem_encrypt.h
>> @@ -21,6 +21,12 @@
>>
>> extern unsigned long sme_me_mask;
>>
>> +void sme_encrypt_execute(unsigned long encrypted_kernel_vaddr,
>> + unsigned long decrypted_kernel_vaddr,
>> + unsigned long kernel_len,
>> + unsigned long encryption_wa,
>> + unsigned long encryption_pgd);
>> +
>> void __init sme_early_encrypt(resource_size_t paddr,
>> unsigned long size);
>> void __init sme_early_decrypt(resource_size_t paddr,
>> diff --git a/arch/x86/mm/Makefile b/arch/x86/mm/Makefile
>> index 9e13841..0633142 100644
>> --- a/arch/x86/mm/Makefile
>> +++ b/arch/x86/mm/Makefile
>> @@ -38,3 +38,5 @@ obj-$(CONFIG_NUMA_EMU) += numa_emulation.o
>> obj-$(CONFIG_X86_INTEL_MPX) += mpx.o
>> obj-$(CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS) += pkeys.o
>> obj-$(CONFIG_RANDOMIZE_MEMORY) += kaslr.o
>> +
>> +obj-$(CONFIG_AMD_MEM_ENCRYPT) += mem_encrypt_boot.o
>> diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
>> index 842c8a6..6e87662 100644
>> --- a/arch/x86/mm/mem_encrypt.c
>> +++ b/arch/x86/mm/mem_encrypt.c
>> @@ -24,6 +24,8 @@
>> #include <asm/setup.h>
>> #include <asm/bootparam.h>
>> #include <asm/set_memory.h>
>> +#include <asm/cacheflush.h>
>> +#include <asm/sections.h>
>>
>> /*
>> * Since SME related variables are set early in the boot process they must
>> @@ -209,8 +211,320 @@ void swiotlb_set_mem_attributes(void *vaddr, unsigned long size)
>> set_memory_decrypted((unsigned long)vaddr, size >> PAGE_SHIFT);
>> }
>>
>> +static void __init sme_clear_pgd(pgd_t *pgd_base, unsigned long start,
>> + unsigned long end)
>> +{
>> + unsigned long pgd_start, pgd_end, pgd_size;
>> + pgd_t *pgd_p;
>> +
>> + pgd_start = start & PGDIR_MASK;
>> + pgd_end = end & PGDIR_MASK;
>> +
>> + pgd_size = (((pgd_end - pgd_start) / PGDIR_SIZE) + 1);
>> + pgd_size *= sizeof(pgd_t);
>> +
>> + pgd_p = pgd_base + pgd_index(start);
>> +
>> + memset(pgd_p, 0, pgd_size);
>> +}
>> +
>> +#ifndef CONFIG_X86_5LEVEL
>> +#define native_make_p4d(_x) (p4d_t) { .pgd = native_make_pgd(_x) }
>> +#endif
>
> Huh, why isn't this in arch/x86/include/asm/pgtable_types.h in the #else
> branch of #if CONFIG_PGTABLE_LEVELS > 4 ?
Normally the __p4d() macro would be used and that would be ok whether
CONFIG_X86_5LEVEL is defined or not. But since __p4d() is part of the
paravirt ops path I have to use native_make_p4d(). I'd be the only user
of the function and thought it would be best to localize it this way.
>
> Also
>
> ERROR: Macros with complex values should be enclosed in parentheses
> #105: FILE: arch/x86/mm/mem_encrypt.c:232:
> +#define native_make_p4d(_x) (p4d_t) { .pgd = native_make_pgd(_x) }
>
> so why isn't it a function?
I can define it as an inline function.
>
>> +
>> +#define PGD_FLAGS _KERNPG_TABLE_NOENC
>> +#define P4D_FLAGS _KERNPG_TABLE_NOENC
>> +#define PUD_FLAGS _KERNPG_TABLE_NOENC
>> +#define PMD_FLAGS (__PAGE_KERNEL_LARGE_EXEC & ~_PAGE_GLOBAL)
>> +
>> +static void __init *sme_populate_pgd(pgd_t *pgd_base, void *pgtable_area,
>> + unsigned long vaddr, pmdval_t pmd_val)
>> +{
>> + pgd_t *pgd_p;
>> + p4d_t *p4d_p;
>> + pud_t *pud_p;
>> + pmd_t *pmd_p;
>> +
>> + pgd_p = pgd_base + pgd_index(vaddr);
>> + if (native_pgd_val(*pgd_p)) {
>> + if (IS_ENABLED(CONFIG_X86_5LEVEL))
>
> Err, I don't understand: so this is a Kconfig symbol and when it is
> enabled at build time, you do a 5level pagetable.
>
> But you can't stick a 5level pagetable to a hardware which doesn't know
> about it.
True, 5-level will only be turned on for specific hardware which is why
I originally had this as only 4-level pagetables. But in a comment from
you back on the v5 version you said it needed to support 5-level. I
guess we should have discussed this more, but I also thought that should
our hardware ever support 5-level paging in the future then this would
be good to go.
>
> Or do you mean that p4d layer folding at runtime to happen? (I admit, I
> haven't looked at that in detail.) But then I'd hope that the generic
> macros/functions would give you the ability to not care whether we have
> a p4d or not and not add a whole bunch of ifdeffery to this code.
The macros work great if you are not running identity mapped. You could
use p*d_offset() to move easily through the tables, but those functions
use __va() to generate table virtual addresses. I've seen where
boot/compressed/pagetable.c #defines __va() to work with identity mapped
pages but that would only work if I create a separate file just for this
function.
Given when this occurs it's very similar to what __startup_64() does in
regards to the IS_ENABLED(CONFIG_X86_5LEVEL) checks.
Thanks,
Tom
>
> Hmmm.
>
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