Print this page
Rearrange multiboot2_entry.S so all data is first, code64 is second, code32 is third. (No more dual code64 sections.)
Use `iretq` method of jumping to 32-bit so VirtualBox (and maybe QEMU/KVM too?)
can cope and not get its `ljmp <mem48>` emulation bug(s) tickled.
| Split |
Close |
| Expand all |
| Collapse all |
--- old/src/arch/x86/image/multiboot2_entry.S
+++ new/src/arch/x86/image/multiboot2_entry.S
1 1 /*
2 2 * Parts copyright Michael Brown <mbrown@fensystems.co.uk>
3 3 *
4 - * Copyright (c) 2019, Joyent, Inc.
4 + * Copyright 2020 Joyent, Inc.
5 5 */
6 6
7 7 FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL )
8 8
9 9 /* CR0: protection enabled */
10 10 #define CR0_PE ( 1 << 0 )
11 11
12 12 /* CR0: paging */
13 13 #define CR0_PG ( 1 << 31 )
14 14
15 15 /* CR4: physical address extensions */
16 16 #define CR4_PSE ( 1 << 4 )
17 17 #define CR4_PAE ( 1 << 5 )
18 18 #define CR4_PGE ( 1 << 7 )
19 19
20 20 /* Extended feature enable MSR (EFER) */
21 21 #define MSR_EFER 0xc0000080
22 22
|
↓ open down ↓ |
8 lines elided |
↑ open up ↑ |
23 23 /* EFER: long mode enable */
24 24 #define EFER_LME ( 1 << 8 )
25 25
26 26 #define GDTSEL_CODE 0x8
27 27 #define GDTSEL_DATA 0x10
28 28
29 29 #if defined(PXE_EFI) && defined(__x86_64__)
30 30
31 31 .section ".text", "ax", @progbits
32 32
33 + .data
34 +
35 +entry_gdt:
36 + /* null entry */
37 + .word 0x0, 0x0
38 + .byte 0x0, 0x0, 0x0, 0x0
39 +
40 + /* 32 bit protected mode code segment */
41 + .word 0xffff, 0x0
42 + .byte 0x0, 0x9f, 0xcf, 0x0
43 +
44 + /* 32 bit protected mode data segment */
45 + .word 0xffff, 0x0
46 + .byte 0x0, 0x93, 0xcf, 0x0
47 +
48 +entry_gdt_end:
49 + .equ entry_gdt_length, entry_gdt_end - entry_gdt
50 +
51 +entry_gdtr:
52 + .word entry_gdt_length - 1
53 +entry_gdt_base:
54 + .quad 0
55 +
33 56 /*
57 + * %rdi -> struct mb2 *
58 + * %rsi -> stack pointer to switch to
59 + * %rdx -> &multiboot2_enter_kernel
60 + */
61 + .code64
62 + .globl multiboot2_bounce
63 +
64 +multiboot2_bounce:
65 + movq %rsi, %rsp
66 + jmp *%rdx
67 +
68 + /*
34 69 * %rdi -> multiboot2 magic
35 70 * %rsi -> multiboot info pointer
36 71 * %rdx -> entry address (32 bits)
37 72 *
38 73 *
39 74 * We need to transition from our 64-bit environment into the one
40 75 * defined by the multiboot2 spec, section 3.3. Namely, drop down to
41 76 * 32-bit protected mode with a basic GDT, paging disabled, interrupts
42 77 * off, and
43 78 *
44 79 * %eax -> multiboot2 magic
45 80 * %ebx -> multiboot info pointer (physical)
46 81 */
47 - .align 16
48 82 .globl multiboot2_entry
49 83
50 84 multiboot2_entry:
51 85 cli
52 86
53 87 movq %rsi, %rbx /* mb2 infop */
54 88 movq %rdx, %rsi /* entry address */
55 89
56 90 /* Load the mb2-mandated code and data segments. */
57 91 leaq entry_gdt_base(%rip), %rcx
58 92 leaq entry_gdt(%rip), %rax
59 93 movq %rax, (%rcx)
60 94
61 95 leaq entry_gdtr(%rip), %rax
62 96 lgdt (%rax)
63 97
64 98 /* Load our new %cs. */
65 - ljmp *newcs_vector
99 + movq %rsp, %rax
100 + pushq $GDTSEL_DATA
101 + pushq %rax
102 + pushf
103 + pushq $GDTSEL_CODE
104 + lea newcs(%rip), %rax
105 + pushq %rax
106 + iretq
66 107
108 +
67 109 .code32
68 110 newcs:
69 111
70 112 movw $GDTSEL_DATA, %ax
71 113 movw %ax, %ds
72 114 movw %ax, %es
73 115 movw %ax, %fs
74 116 movw %ax, %gs
75 117 movw %ax, %ss
76 118
77 119 /* Disable paging */
78 120 movl %cr0, %eax
79 121 andl $~CR0_PG, %eax
80 122 movl %eax, %cr0
81 123
82 124 movl %cr4, %eax
83 125 andb $~(CR4_PAE | CR4_PGE | CR4_PSE), %al
84 126 movl %eax, %cr4
85 127
|
↓ open down ↓ |
9 lines elided |
↑ open up ↑ |
86 128 /* Disable long mode (clobbers %eax, %edx) */
87 129 movl $MSR_EFER, %ecx
88 130 rdmsr
89 131 andw $~EFER_LME, %ax
90 132 wrmsr
91 133
92 134 /* %ebx still has our infop */
93 135 movl %edi, %eax
94 136 jmp *%esi
95 137
96 - /*
97 - * %rdi -> struct mb2 *
98 - * %rsi -> stack pointer to switch to
99 - * %rdx -> &multiboot2_enter_kernel
100 - */
101 - .align 16
102 - .code64
103 - .globl multiboot2_bounce
104 -
105 -multiboot2_bounce:
106 - movq %rsi, %rsp
107 - jmp *%rdx
108 -
109 - .data
110 -
111 -newcs_vector:
112 - .long newcs, GDTSEL_CODE
113 -
114 - .align 16
115 -entry_gdt:
116 - /* null entry */
117 - .word 0x0, 0x0
118 - .byte 0x0, 0x0, 0x0, 0x0
119 -
120 - /* 32 bit protected mode code segment */
121 - .word 0xffff, 0x0
122 - .byte 0x0, 0x9f, 0xcf, 0x0
123 -
124 - /* 32 bit protected mode data segment */
125 - .word 0xffff, 0x0
126 - .byte 0x0, 0x93, 0xcf, 0x0
127 -
128 -entry_gdt_end:
129 - .equ entry_gdt_length, entry_gdt_end - entry_gdt
130 -
131 - .align 16
132 -entry_gdtr:
133 - .word entry_gdt_length - 1
134 -entry_gdt_base:
135 - .quad 0
136 -
137 138 #endif /* PXE_EFI && __x86_64__ */
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX