Thread (82 messages) 82 messages, 5 authors, 2016-09-16

Re: [RFC PATCH v2 09/20] x86: Add support for early encryption/decryption of memory

From: Borislav Petkov <hidden>
Date: 2016-09-06 16:13:09
Also in: kvm, linux-efi, linux-iommu, linux-mm, lkml

On Mon, Aug 22, 2016 at 05:37:10PM -0500, Tom Lendacky wrote:
This adds support to be able to either encrypt or decrypt data during
the early stages of booting the kernel. This does not change the memory
encryption attribute - it is used for ensuring that data present in
either an encrypted or un-encrypted memory area is in the proper state
(for example the initrd will have been loaded by the boot loader and
will not be encrypted, but the memory that it resides in is marked as
encrypted).

Signed-off-by: Tom Lendacky <redacted>
---
...
quoted hunk ↗ jump to hunk
diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
index 00eb705..f35a646 100644
--- a/arch/x86/mm/mem_encrypt.c
+++ b/arch/x86/mm/mem_encrypt.c
@@ -14,6 +14,107 @@
 #include <linux/mm.h>
 
 #include <asm/mem_encrypt.h>
+#include <asm/tlbflush.h>
+#include <asm/fixmap.h>
+
+/* Buffer used for early in-place encryption by BSP, no locking needed */
+static char me_early_buffer[PAGE_SIZE] __aligned(PAGE_SIZE);
+
+/*
+ * This routine does not change the underlying encryption setting of the
+ * page(s) that map this memory. It assumes that eventually the memory is
+ * meant to be accessed as encrypted but the contents are currently not
+ * encyrpted.
s/encyrpted/encrypted/

Ditto below.
+ */
+void __init sme_early_mem_enc(resource_size_t paddr, unsigned long size)
+{
+	void *src, *dst;
+	size_t len;
+
+	if (!sme_me_mask)
+		return;
+
+	local_flush_tlb();
+	wbinvd();
+
+	/*
+	 * There are limited number of early mapping slots, so map (at most)
+	 * one page at time.
+	 */
+	while (size) {
+		len = min_t(size_t, sizeof(me_early_buffer), size);
+
+		/* Create a mapping for non-encrypted write-protected memory */
+		src = early_memremap_dec_wp(paddr, len);
+
+		/* Create a mapping for encrypted memory */
+		dst = early_memremap_enc(paddr, len);
+
+		/*
+		 * If a mapping can't be obtained to perform the encryption,
+		 * then encrypted access to that area will end up causing
+		 * a crash.
+		 */
+		BUG_ON(!src || !dst);
+
+		memcpy(me_early_buffer, src, len);
+		memcpy(dst, me_early_buffer, len);
+
+		early_memunmap(dst, len);
+		early_memunmap(src, len);
+
+		paddr += len;
+		size -= len;
+	}
+}
+
+/*
+ * This routine does not change the underlying encryption setting of the
+ * page(s) that map this memory. It assumes that eventually the memory is
+ * meant to be accessed as not encrypted but the contents are currently
+ * encyrpted.
+ */
+void __init sme_early_mem_dec(resource_size_t paddr, unsigned long size)
+{
...

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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