1/*
2 * EFI entry point.
3 *
4 * Copyright (C) 2013, 2014 Red Hat, Inc.
5 * Author: Mark Salter <msalter@redhat.com>
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
10 *
11 */
12#include <linux/linkage.h>
13#include <linux/init.h>
14
15#include <asm/assembler.h>
16
17#define EFI_LOAD_ERROR 0x8000000000000001
18
19	__INIT
20
21	/*
22	 * We arrive here from the EFI boot manager with:
23	 *
24	 *    * CPU in little-endian mode
25	 *    * MMU on with identity-mapped RAM
26	 *    * Icache and Dcache on
27	 *
28	 * We will most likely be running from some place other than where
29	 * we want to be. The kernel image wants to be placed at TEXT_OFFSET
30	 * from start of RAM.
31	 */
32ENTRY(entry)
33	/*
34	 * Create a stack frame to save FP/LR with extra space
35	 * for image_addr variable passed to efi_entry().
36	 */
37	stp	x29, x30, [sp, #-32]!
38	mov	x29, sp
39
40	/*
41	 * Call efi_entry to do the real work.
42	 * x0 and x1 are already set up by firmware. Current runtime
43	 * address of image is calculated and passed via *image_addr.
44	 *
45	 * unsigned long efi_entry(void *handle,
46	 *                         efi_system_table_t *sys_table,
47	 *                         unsigned long *image_addr) ;
48	 */
49	adr_l	x8, _text
50	add	x2, sp, 16
51	str	x8, [x2]
52	bl	efi_entry
53	cmn	x0, #1
54	b.eq	efi_load_fail
55
56	/*
57	 * efi_entry() will have copied the kernel image if necessary and we
58	 * return here with device tree address in x0 and the kernel entry
59	 * point stored at *image_addr. Save those values in registers which
60	 * are callee preserved.
61	 */
62	mov	x20, x0		// DTB address
63	ldr	x0, [sp, #16]	// relocated _text address
64	ldr	w21, =stext_offset
65	add	x21, x0, x21
66
67	/*
68	 * Calculate size of the kernel Image (same for original and copy).
69	 */
70	adr_l	x1, _text
71	adr_l	x2, _edata
72	sub	x1, x2, x1
73
74	/*
75	 * Flush the copied Image to the PoC, and ensure it is not shadowed by
76	 * stale icache entries from before relocation.
77	 */
78	bl	__flush_dcache_area
79	ic	ialluis
80
81	/*
82	 * Ensure that the rest of this function (in the original Image) is
83	 * visible when the caches are disabled. The I-cache can't have stale
84	 * entries for the VA range of the current image, so no maintenance is
85	 * necessary.
86	 */
87	adr	x0, entry
88	adr	x1, entry_end
89	sub	x1, x1, x0
90	bl	__flush_dcache_area
91
92	/* Turn off Dcache and MMU */
93	mrs	x0, CurrentEL
94	cmp	x0, #CurrentEL_EL2
95	b.ne	1f
96	mrs	x0, sctlr_el2
97	bic	x0, x0, #1 << 0	// clear SCTLR.M
98	bic	x0, x0, #1 << 2	// clear SCTLR.C
99	pre_disable_mmu_workaround
100	msr	sctlr_el2, x0
101	isb
102	b	2f
1031:
104	mrs	x0, sctlr_el1
105	bic	x0, x0, #1 << 0	// clear SCTLR.M
106	bic	x0, x0, #1 << 2	// clear SCTLR.C
107	pre_disable_mmu_workaround
108	msr	sctlr_el1, x0
109	isb
1102:
111	/* Jump to kernel entry point */
112	mov	x0, x20
113	mov	x1, xzr
114	mov	x2, xzr
115	mov	x3, xzr
116	br	x21
117
118efi_load_fail:
119	mov	x0, #EFI_LOAD_ERROR
120	ldp	x29, x30, [sp], #32
121	ret
122
123entry_end:
124ENDPROC(entry)
125