1/* SPDX-License-Identifier: GPL-2.0-only */
2/*
3 * AMD Memory Encryption Support
4 *
5 * Copyright (C) 2016 Advanced Micro Devices, Inc.
6 *
7 * Author: Tom Lendacky <thomas.lendacky@amd.com>
8 */
9
10#include <linux/linkage.h>
11#include <asm/pgtable.h>
12#include <asm/page.h>
13#include <asm/processor-flags.h>
14#include <asm/msr-index.h>
15#include <asm/nospec-branch.h>
16
17	.text
18	.code64
19ENTRY(sme_encrypt_execute)
20
21	/*
22	 * Entry parameters:
23	 *   RDI - virtual address for the encrypted mapping
24	 *   RSI - virtual address for the decrypted mapping
25	 *   RDX - length to encrypt
26	 *   RCX - virtual address of the encryption workarea, including:
27	 *     - stack page (PAGE_SIZE)
28	 *     - encryption routine page (PAGE_SIZE)
29	 *     - intermediate copy buffer (PMD_PAGE_SIZE)
30	 *    R8 - physcial address of the pagetables to use for encryption
31	 */
32
33	push	%rbp
34	movq	%rsp, %rbp		/* RBP now has original stack pointer */
35
36	/* Set up a one page stack in the non-encrypted memory area */
37	movq	%rcx, %rax		/* Workarea stack page */
38	leaq	PAGE_SIZE(%rax), %rsp	/* Set new stack pointer */
39	addq	$PAGE_SIZE, %rax	/* Workarea encryption routine */
40
41	push	%r12
42	movq	%rdi, %r10		/* Encrypted area */
43	movq	%rsi, %r11		/* Decrypted area */
44	movq	%rdx, %r12		/* Area length */
45
46	/* Copy encryption routine into the workarea */
47	movq	%rax, %rdi				/* Workarea encryption routine */
48	leaq	__enc_copy(%rip), %rsi			/* Encryption routine */
49	movq	$(.L__enc_copy_end - __enc_copy), %rcx	/* Encryption routine length */
50	rep	movsb
51
52	/* Setup registers for call */
53	movq	%r10, %rdi		/* Encrypted area */
54	movq	%r11, %rsi		/* Decrypted area */
55	movq	%r8, %rdx		/* Pagetables used for encryption */
56	movq	%r12, %rcx		/* Area length */
57	movq	%rax, %r8		/* Workarea encryption routine */
58	addq	$PAGE_SIZE, %r8		/* Workarea intermediate copy buffer */
59
60	ANNOTATE_RETPOLINE_SAFE
61	call	*%rax			/* Call the encryption routine */
62
63	pop	%r12
64
65	movq	%rbp, %rsp		/* Restore original stack pointer */
66	pop	%rbp
67
68	ret
69ENDPROC(sme_encrypt_execute)
70
71ENTRY(__enc_copy)
72/*
73 * Routine used to encrypt memory in place.
74 *   This routine must be run outside of the kernel proper since
75 *   the kernel will be encrypted during the process. So this
76 *   routine is defined here and then copied to an area outside
77 *   of the kernel where it will remain and run decrypted
78 *   during execution.
79 *
80 *   On entry the registers must be:
81 *     RDI - virtual address for the encrypted mapping
82 *     RSI - virtual address for the decrypted mapping
83 *     RDX - address of the pagetables to use for encryption
84 *     RCX - length of area
85 *      R8 - intermediate copy buffer
86 *
87 *     RAX - points to this routine
88 *
89 * The area will be encrypted by copying from the non-encrypted
90 * memory space to an intermediate buffer and then copying from the
91 * intermediate buffer back to the encrypted memory space. The physical
92 * addresses of the two mappings are the same which results in the area
93 * being encrypted "in place".
94 */
95	/* Enable the new page tables */
96	mov	%rdx, %cr3
97
98	/* Flush any global TLBs */
99	mov	%cr4, %rdx
100	andq	$~X86_CR4_PGE, %rdx
101	mov	%rdx, %cr4
102	orq	$X86_CR4_PGE, %rdx
103	mov	%rdx, %cr4
104
105	push	%r15
106	push	%r12
107
108	movq	%rcx, %r9		/* Save area length */
109	movq	%rdi, %r10		/* Save encrypted area address */
110	movq	%rsi, %r11		/* Save decrypted area address */
111
112	/* Set the PAT register PA5 entry to write-protect */
113	movl	$MSR_IA32_CR_PAT, %ecx
114	rdmsr
115	mov	%rdx, %r15		/* Save original PAT value */
116	andl	$0xffff00ff, %edx	/* Clear PA5 */
117	orl	$0x00000500, %edx	/* Set PA5 to WP */
118	wrmsr
119
120	wbinvd				/* Invalidate any cache entries */
121
122	/* Copy/encrypt up to 2MB at a time */
123	movq	$PMD_PAGE_SIZE, %r12
1241:
125	cmpq	%r12, %r9
126	jnb	2f
127	movq	%r9, %r12
128
1292:
130	movq	%r11, %rsi		/* Source - decrypted area */
131	movq	%r8, %rdi		/* Dest   - intermediate copy buffer */
132	movq	%r12, %rcx
133	rep	movsb
134
135	movq	%r8, %rsi		/* Source - intermediate copy buffer */
136	movq	%r10, %rdi		/* Dest   - encrypted area */
137	movq	%r12, %rcx
138	rep	movsb
139
140	addq	%r12, %r11
141	addq	%r12, %r10
142	subq	%r12, %r9		/* Kernel length decrement */
143	jnz	1b			/* Kernel length not zero? */
144
145	/* Restore PAT register */
146	movl	$MSR_IA32_CR_PAT, %ecx
147	rdmsr
148	mov	%r15, %rdx		/* Restore original PAT value */
149	wrmsr
150
151	pop	%r12
152	pop	%r15
153
154	ret
155.L__enc_copy_end:
156ENDPROC(__enc_copy)
157