1/* SPDX-License-Identifier: GPL-2.0 */
2
3/*
4 * Copyright C 2016, Oracle and/or its affiliates. All rights reserved.
5 */
6
7	.code32
8	.text
9#define _pa(x)          ((x) - __START_KERNEL_map)
10
11#include <linux/elfnote.h>
12#include <linux/init.h>
13#include <linux/linkage.h>
14#include <asm/segment.h>
15#include <asm/asm.h>
16#include <asm/boot.h>
17#include <asm/processor-flags.h>
18#include <asm/msr.h>
19#include <asm/nospec-branch.h>
20#include <xen/interface/elfnote.h>
21
22	__HEAD
23
24/*
25 * Entry point for PVH guests.
26 *
27 * Xen ABI specifies the following register state when we come here:
28 *
29 * - `ebx`: contains the physical memory address where the loader has placed
30 *          the boot start info structure.
31 * - `cr0`: bit 0 (PE) must be set. All the other writeable bits are cleared.
32 * - `cr4`: all bits are cleared.
33 * - `cs `: must be a 32-bit read/execute code segment with a base of `0`
34 *          and a limit of `0xFFFFFFFF`. The selector value is unspecified.
35 * - `ds`, `es`: must be a 32-bit read/write data segment with a base of
36 *               `0` and a limit of `0xFFFFFFFF`. The selector values are all
37 *               unspecified.
38 * - `tr`: must be a 32-bit TSS (active) with a base of '0' and a limit
39 *         of '0x67'.
40 * - `eflags`: bit 17 (VM) must be cleared. Bit 9 (IF) must be cleared.
41 *             Bit 8 (TF) must be cleared. Other bits are all unspecified.
42 *
43 * All other processor registers and flag bits are unspecified. The OS is in
44 * charge of setting up it's own stack, GDT and IDT.
45 */
46
47#define PVH_GDT_ENTRY_CS	1
48#define PVH_GDT_ENTRY_DS	2
49#define PVH_CS_SEL		(PVH_GDT_ENTRY_CS * 8)
50#define PVH_DS_SEL		(PVH_GDT_ENTRY_DS * 8)
51
52SYM_CODE_START_LOCAL(pvh_start_xen)
53	UNWIND_HINT_END_OF_STACK
54	cld
55
56	lgdt (_pa(gdt))
57
58	mov $PVH_DS_SEL,%eax
59	mov %eax,%ds
60	mov %eax,%es
61	mov %eax,%ss
62
63	/* Stash hvm_start_info. */
64	mov $_pa(pvh_start_info), %edi
65	mov %ebx, %esi
66	mov _pa(pvh_start_info_sz), %ecx
67	shr $2,%ecx
68	rep
69	movsl
70
71	mov $_pa(early_stack_end), %esp
72
73	/* Enable PAE mode. */
74	mov %cr4, %eax
75	orl $X86_CR4_PAE, %eax
76	mov %eax, %cr4
77
78#ifdef CONFIG_X86_64
79	/* Enable Long mode. */
80	mov $MSR_EFER, %ecx
81	rdmsr
82	btsl $_EFER_LME, %eax
83	wrmsr
84
85	/* Enable pre-constructed page tables. */
86	mov $_pa(init_top_pgt), %eax
87	mov %eax, %cr3
88	mov $(X86_CR0_PG | X86_CR0_PE), %eax
89	mov %eax, %cr0
90
91	/* Jump to 64-bit mode. */
92	ljmp $PVH_CS_SEL, $_pa(1f)
93
94	/* 64-bit entry point. */
95	.code64
961:
97	/* Set base address in stack canary descriptor. */
98	mov $MSR_GS_BASE,%ecx
99	mov $_pa(canary), %eax
100	xor %edx, %edx
101	wrmsr
102
103	call xen_prepare_pvh
104
105	/* startup_64 expects boot_params in %rsi. */
106	mov $_pa(pvh_bootparams), %rsi
107	mov $_pa(startup_64), %rax
108	ANNOTATE_RETPOLINE_SAFE
109	jmp *%rax
110
111#else /* CONFIG_X86_64 */
112
113	call mk_early_pgtbl_32
114
115	mov $_pa(initial_page_table), %eax
116	mov %eax, %cr3
117
118	mov %cr0, %eax
119	or $(X86_CR0_PG | X86_CR0_PE), %eax
120	mov %eax, %cr0
121
122	ljmp $PVH_CS_SEL, $1f
1231:
124	call xen_prepare_pvh
125	mov $_pa(pvh_bootparams), %esi
126
127	/* startup_32 doesn't expect paging and PAE to be on. */
128	ljmp $PVH_CS_SEL, $_pa(2f)
1292:
130	mov %cr0, %eax
131	and $~X86_CR0_PG, %eax
132	mov %eax, %cr0
133	mov %cr4, %eax
134	and $~X86_CR4_PAE, %eax
135	mov %eax, %cr4
136
137	ljmp $PVH_CS_SEL, $_pa(startup_32)
138#endif
139SYM_CODE_END(pvh_start_xen)
140
141	.section ".init.data","aw"
142	.balign 8
143SYM_DATA_START_LOCAL(gdt)
144	.word gdt_end - gdt_start
145	.long _pa(gdt_start)
146	.word 0
147SYM_DATA_END(gdt)
148SYM_DATA_START_LOCAL(gdt_start)
149	.quad 0x0000000000000000            /* NULL descriptor */
150#ifdef CONFIG_X86_64
151	.quad GDT_ENTRY(0xa09a, 0, 0xfffff) /* PVH_CS_SEL */
152#else
153	.quad GDT_ENTRY(0xc09a, 0, 0xfffff) /* PVH_CS_SEL */
154#endif
155	.quad GDT_ENTRY(0xc092, 0, 0xfffff) /* PVH_DS_SEL */
156SYM_DATA_END_LABEL(gdt_start, SYM_L_LOCAL, gdt_end)
157
158	.balign 16
159SYM_DATA_LOCAL(canary, .fill 48, 1, 0)
160
161SYM_DATA_START_LOCAL(early_stack)
162	.fill BOOT_STACK_SIZE, 1, 0
163SYM_DATA_END_LABEL(early_stack, SYM_L_LOCAL, early_stack_end)
164
165	ELFNOTE(Xen, XEN_ELFNOTE_PHYS32_ENTRY,
166	             _ASM_PTR (pvh_start_xen - __START_KERNEL_map))
167