summaryrefslogtreecommitdiffstats
path: root/arch/x86/boot/compressed/efi_mixed.S
blob: fb6d60dcd6ed1f06ee42a98bfcf3b613235c066b (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
/* SPDX-License-Identifier: GPL-2.0 */
/*
 * Copyright (C) 2014, 2015 Intel Corporation; author Matt Fleming
 *
 * Early support for invoking 32-bit EFI services from a 64-bit kernel.
 *
 * Because this thunking occurs before ExitBootServices() we have to
 * restore the firmware's 32-bit GDT and IDT before we make EFI service
 * calls.
 *
 * On the plus side, we don't have to worry about mangling 64-bit
 * addresses into 32-bits because we're executing with an identity
 * mapped pagetable and haven't transitioned to 64-bit virtual addresses
 * yet.
 */

#include <linux/linkage.h>
#include <asm/asm-offsets.h>
#include <asm/msr.h>
#include <asm/page_types.h>
#include <asm/processor-flags.h>
#include <asm/segment.h>
#include <asm/setup.h>

	.code64
	.text
/*
 * When booting in 64-bit mode on 32-bit EFI firmware, startup_64_mixed_mode()
 * is the first thing that runs after switching to long mode. Depending on
 * whether the EFI handover protocol or the compat entry point was used to
 * enter the kernel, it will either branch to the common 64-bit EFI stub
 * entrypoint efi_stub_entry() directly, or via the 64-bit EFI PE/COFF
 * entrypoint efi_pe_entry(). In the former case, the bootloader must provide a
 * struct bootparams pointer as the third argument, so the presence of such a
 * pointer is used to disambiguate.
 *
 *                                                             +--------------+
 *  +------------------+     +------------+            +------>| efi_pe_entry |
 *  | efi32_pe_entry   |---->|            |            |       +-----------+--+
 *  +------------------+     |            |     +------+----------------+  |
 *                           | startup_32 |---->| startup_64_mixed_mode |  |
 *  +------------------+     |            |     +------+----------------+  |
 *  | efi32_stub_entry |---->|            |            |                   |
 *  +------------------+     +------------+            |                   |
 *                                                     V                   |
 *                           +------------+     +----------------+         |
 *                           | startup_64 |<----| efi_stub_entry |<--------+
 *                           +------------+     +----------------+
 */
SYM_FUNC_START(startup_64_mixed_mode)
	lea	efi32_boot_args(%rip), %rdx
	mov	0(%rdx), %edi
	mov	4(%rdx), %esi

	/* Switch to the firmware's stack */
	movl	efi32_boot_sp(%rip), %esp
	andl	$~7, %esp

#ifdef CONFIG_EFI_HANDOVER_PROTOCOL
	mov	8(%rdx), %edx		// saved bootparams pointer
	test	%edx, %edx
	jnz	efi_stub_entry
#endif
	/*
	 * efi_pe_entry uses MS calling convention, which requires 32 bytes of
	 * shadow space on the stack even if all arguments are passed in
	 * registers. We also need an additional 8 bytes for the space that
	 * would be occupied by the return address, and this also results in
	 * the correct stack alignment for entry.
	 */
	sub	$40, %rsp
	mov	%rdi, %rcx		// MS calling convention
	mov	%rsi, %rdx
	jmp	efi_pe_entry
SYM_FUNC_END(startup_64_mixed_mode)

SYM_FUNC_START(__efi64_thunk)
	push	%rbp
	push	%rbx

	movl	%ds, %eax
	push	%rax
	movl	%es, %eax
	push	%rax
	movl	%ss, %eax
	push	%rax

	/* Copy args passed on stack */
	movq	0x30(%rsp), %rbp
	movq	0x38(%rsp), %rbx
	movq	0x40(%rsp), %rax

	/*
	 * Convert x86-64 ABI params to i386 ABI
	 */
	subq	$64, %rsp
	movl	%esi, 0x0(%rsp)
	movl	%edx, 0x4(%rsp)
	movl	%ecx, 0x8(%rsp)
	movl	%r8d, 0xc(%rsp)
	movl	%r9d, 0x10(%rsp)
	movl	%ebp, 0x14(%rsp)
	movl	%ebx, 0x18(%rsp)
	movl	%eax, 0x1c(%rsp)

	leaq	0x20(%rsp), %rbx
	sgdt	(%rbx)
	sidt	16(%rbx)

	leaq	1f(%rip), %rbp

	/*
	 * Switch to IDT and GDT with 32-bit segments. These are the firmware
	 * GDT and IDT that were installed when the kernel started executing.
	 * The pointers were saved by the efi32_entry() routine below.
	 *
	 * Pass the saved DS selector to the 32-bit code, and use far return to
	 * restore the saved CS selector.
	 */
	lidt	efi32_boot_idt(%rip)
	lgdt	efi32_boot_gdt(%rip)

	movzwl	efi32_boot_ds(%rip), %edx
	movzwq	efi32_boot_cs(%rip), %rax
	pushq	%rax
	leaq	efi_enter32(%rip), %rax
	pushq	%rax
	lretq

1:	addq	$64, %rsp
	movq	%rdi, %rax

	pop	%rbx
	movl	%ebx, %ss
	pop	%rbx
	movl	%ebx, %es
	pop	%rbx
	movl	%ebx, %ds
	/* Clear out 32-bit selector from FS and GS */
	xorl	%ebx, %ebx
	movl	%ebx, %fs
	movl	%ebx, %gs

	/*
	 * Convert 32-bit status code into 64-bit.
	 */
	roll	$1, %eax
	rorq	$1, %rax

	pop	%rbx
	pop	%rbp
	RET
SYM_FUNC_END(__efi64_thunk)

	.code32
#ifdef CONFIG_EFI_HANDOVER_PROTOCOL
SYM_FUNC_START(efi32_stub_entry)
	call	1f
1:	popl	%ecx
	leal	(efi32_boot_args - 1b)(%ecx), %ebx

	/* Clear BSS */
	xorl	%eax, %eax
	leal	(_bss - 1b)(%ecx), %edi
	leal	(_ebss - 1b)(%ecx), %ecx
	subl	%edi, %ecx
	shrl	$2, %ecx
	cld
	rep	stosl

	add	$0x4, %esp		/* Discard return address */
	popl	%ecx
	popl	%edx
	popl	%esi
	movl	%esi, 8(%ebx)
	jmp	efi32_entry
SYM_FUNC_END(efi32_stub_entry)
#endif

/*
 * EFI service pointer must be in %edi.
 *
 * The stack should represent the 32-bit calling convention.
 */
SYM_FUNC_START_LOCAL(efi_enter32)
	/* Load firmware selector into data and stack segment registers */
	movl	%edx, %ds
	movl	%edx, %es
	movl	%edx, %fs
	movl	%edx, %gs
	movl	%edx, %ss

	/* Reload pgtables */
	movl	%cr3, %eax
	movl	%eax, %cr3

	/* Disable paging */
	movl	%cr0, %eax
	btrl	$X86_CR0_PG_BIT, %eax
	movl	%eax, %cr0

	/* Disable long mode via EFER */
	movl	$MSR_EFER, %ecx
	rdmsr
	btrl	$_EFER_LME, %eax
	wrmsr

	call	*%edi

	/* We must preserve return value */
	movl	%eax, %edi

	/*
	 * Some firmware will return with interrupts enabled. Be sure to
	 * disable them before we switch GDTs and IDTs.
	 */
	cli

	lidtl	16(%ebx)
	lgdtl	(%ebx)

	movl	%cr4, %eax
	btsl	$(X86_CR4_PAE_BIT), %eax
	movl	%eax, %cr4

	movl	%cr3, %eax
	movl	%eax, %cr3

	movl	$MSR_EFER, %ecx
	rdmsr
	btsl	$_EFER_LME, %eax
	wrmsr

	xorl	%eax, %eax
	lldt	%ax

	pushl	$__KERNEL_CS
	pushl	%ebp

	/* Enable paging */
	movl	%cr0, %eax
	btsl	$X86_CR0_PG_BIT, %eax
	movl	%eax, %cr0
	lret
SYM_FUNC_END(efi_enter32)

/*
 * This is the common EFI stub entry point for mixed mode.
 *
 * Arguments:	%ecx	image handle
 * 		%edx	EFI system table pointer
 *
 * Since this is the point of no return for ordinary execution, no registers
 * are considered live except for the function parameters. [Note that the EFI
 * stub may still exit and return to the firmware using the Exit() EFI boot
 * service.]
 */
SYM_FUNC_START_LOCAL(efi32_entry)
	call	1f
1:	pop	%ebx

	/* Save firmware GDTR and code/data selectors */
	sgdtl	(efi32_boot_gdt - 1b)(%ebx)
	movw	%cs, (efi32_boot_cs - 1b)(%ebx)
	movw	%ds, (efi32_boot_ds - 1b)(%ebx)

	/* Store firmware IDT descriptor */
	sidtl	(efi32_boot_idt - 1b)(%ebx)

	/* Store firmware stack pointer */
	movl	%esp, (efi32_boot_sp - 1b)(%ebx)

	/* Store boot arguments */
	leal	(efi32_boot_args - 1b)(%ebx), %ebx
	movl	%ecx, 0(%ebx)
	movl	%edx, 4(%ebx)
	movb	$0x0, 12(%ebx)          // efi_is64

	/*
	 * Allocate some memory for a temporary struct boot_params, which only
	 * needs the minimal pieces that startup_32() relies on.
	 */
	subl	$PARAM_SIZE, %esp
	movl	%esp, %esi
	movl	$PAGE_SIZE, BP_kernel_alignment(%esi)
	movl	$_end - 1b, BP_init_size(%esi)
	subl	$startup_32 - 1b, BP_init_size(%esi)

	/* Disable paging */
	movl	%cr0, %eax
	btrl	$X86_CR0_PG_BIT, %eax
	movl	%eax, %cr0

	jmp	startup_32
SYM_FUNC_END(efi32_entry)

/*
 * efi_status_t efi32_pe_entry(efi_handle_t image_handle,
 *			       efi_system_table_32_t *sys_table)
 */
SYM_FUNC_START(efi32_pe_entry)
	pushl	%ebp
	movl	%esp, %ebp
	pushl	%ebx				// save callee-save registers
	pushl	%edi

	call	verify_cpu			// check for long mode support
	testl	%eax, %eax
	movl	$0x80000003, %eax		// EFI_UNSUPPORTED
	jnz	2f

	movl	8(%ebp), %ecx			// image_handle
	movl	12(%ebp), %edx			// sys_table
	jmp	efi32_entry			// pass %ecx, %edx
						// no other registers remain live

2:	popl	%edi				// restore callee-save registers
	popl	%ebx
	leave
	RET
SYM_FUNC_END(efi32_pe_entry)

#ifdef CONFIG_EFI_HANDOVER_PROTOCOL
	.org	efi32_stub_entry + 0x200
	.code64
SYM_FUNC_START_NOALIGN(efi64_stub_entry)
	jmp	efi_handover_entry
SYM_FUNC_END(efi64_stub_entry)
#endif

	.data
	.balign	8
SYM_DATA_START_LOCAL(efi32_boot_gdt)
	.word	0
	.quad	0
SYM_DATA_END(efi32_boot_gdt)

SYM_DATA_START_LOCAL(efi32_boot_idt)
	.word	0
	.quad	0
SYM_DATA_END(efi32_boot_idt)

SYM_DATA_LOCAL(efi32_boot_cs, .word 0)
SYM_DATA_LOCAL(efi32_boot_ds, .word 0)
SYM_DATA_LOCAL(efi32_boot_sp, .long 0)
SYM_DATA_LOCAL(efi32_boot_args, .long 0, 0, 0)
SYM_DATA(efi_is64, .byte 1)