]> git.proxmox.com Git - mirror_edk2.git/blame - OvmfPkg/ResetVector/Ia16/16RealTo32Flat.asm
Fix a security hole in shell binaries:
[mirror_edk2.git] / OvmfPkg / ResetVector / Ia16 / 16RealTo32Flat.asm
CommitLineData
49ba9447 1;------------------------------------------------------------------------------\r
7a55c43b 2; @file\r
3; Transition from 16 bit real mode into 32 bit flat protected mode\r
49ba9447 4;\r
d22d1f53 5; Copyright (c) 2008 - 2010, Intel Corporation\r
49ba9447 6; All rights reserved. This program and the accompanying materials\r
7; are licensed and made available under the terms and conditions of the BSD License\r
8; which accompanies this distribution. The full text of the license may be found at\r
9; http://opensource.org/licenses/bsd-license.php\r
10;\r
11; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,\r
12; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.\r
13;\r
49ba9447 14;------------------------------------------------------------------------------\r
15\r
16%define SEC_DEFAULT_CR0 0x40000023\r
17%define SEC_DEFAULT_CR4 0x640\r
18\r
19BITS 16\r
20\r
7a55c43b 21;\r
22; Modified: EAX, EBX\r
23;\r
24TransitionFromReal16To32BitFlat:\r
49ba9447 25\r
7a55c43b 26 debugShowPostCode POSTCODE_16BIT_MODE\r
49ba9447 27\r
28 cli\r
29\r
30 mov bx, 0xf000\r
31 mov ds, bx\r
32\r
33 mov bx, ADDR16_OF(gdtr)\r
34\r
35o32 lgdt [bx]\r
36\r
37 mov eax, SEC_DEFAULT_CR0\r
38 mov cr0, eax\r
39\r
49ba9447 40 jmp LINEAR_CODE_SEL:dword ADDR_OF(jumpTo32BitAndLandHere)\r
41BITS 32\r
42jumpTo32BitAndLandHere:\r
43\r
44 mov eax, SEC_DEFAULT_CR4\r
45 mov cr4, eax\r
46\r
7a55c43b 47 debugShowPostCode POSTCODE_32BIT_MODE\r
49ba9447 48\r
7a55c43b 49 mov ax, LINEAR_SEL\r
50 mov ds, ax\r
51 mov es, ax\r
52 mov fs, ax\r
53 mov gs, ax\r
54 mov ss, ax\r
49ba9447 55\r
7a55c43b 56 OneTimeCallRet TransitionFromReal16To32BitFlat\r
49ba9447 57\r
58ALIGN 2\r
59\r
60gdtr:\r
61 dw GDT_END - GDT_BASE - 1 ; GDT limit\r
62 dd ADDR_OF(GDT_BASE)\r
63\r
64ALIGN 16\r
65\r
141815f3 66;\r
67; Macros for GDT entries\r
68;\r
69\r
70%define PRESENT_FLAG(p) (p << 7)\r
71%define DPL(dpl) (dpl << 5)\r
72%define SYSTEM_FLAG(s) (s << 4)\r
73%define DESC_TYPE(t) (t)\r
74\r
75; Type: data, expand-up, writable, accessed\r
76%define DATA32_TYPE 3\r
77\r
78; Type: execute, readable, expand-up, accessed\r
79%define CODE32_TYPE 0xb\r
80\r
81; Type: execute, readable, expand-up, accessed\r
82%define CODE64_TYPE 0xb\r
83\r
84%define GRANULARITY_FLAG(g) (g << 7)\r
85%define DEFAULT_SIZE32(d) (d << 6)\r
86%define CODE64_FLAG(l) (l << 5)\r
87%define UPPER_LIMIT(l) (l)\r
88\r
89;\r
90; The Global Descriptor Table (GDT)\r
91;\r
92\r
49ba9447 93GDT_BASE:\r
94; null descriptor\r
95NULL_SEL equ $-GDT_BASE\r
141815f3 96 DW 0 ; limit 15:0\r
97 DW 0 ; base 15:0\r
98 DB 0 ; base 23:16\r
99 DB 0 ; sys flag, dpl, type\r
100 DB 0 ; limit 19:16, flags\r
101 DB 0 ; base 31:24\r
49ba9447 102\r
103; linear data segment descriptor\r
141815f3 104LINEAR_SEL equ $-GDT_BASE\r
105 DW 0xffff ; limit 15:0\r
106 DW 0 ; base 15:0\r
107 DB 0 ; base 23:16\r
108 DB PRESENT_FLAG(1)|DPL(0)|SYSTEM_FLAG(1)|DESC_TYPE(DATA32_TYPE)\r
109 DB GRANULARITY_FLAG(1)|DEFAULT_SIZE32(1)|CODE64_FLAG(0)|UPPER_LIMIT(0xf)\r
110 DB 0 ; base 31:24\r
49ba9447 111\r
112; linear code segment descriptor\r
141815f3 113LINEAR_CODE_SEL equ $-GDT_BASE\r
114 DW 0xffff ; limit 15:0\r
115 DW 0 ; base 15:0\r
116 DB 0 ; base 23:16\r
117 DB PRESENT_FLAG(1)|DPL(0)|SYSTEM_FLAG(1)|DESC_TYPE(CODE32_TYPE)\r
118 DB GRANULARITY_FLAG(1)|DEFAULT_SIZE32(1)|CODE64_FLAG(0)|UPPER_LIMIT(0xf)\r
119 DB 0 ; base 31:24\r
120\r
121%ifdef ARCH_X64\r
122; linear code (64-bit) segment descriptor\r
123LINEAR_CODE64_SEL equ $-GDT_BASE\r
124 DW 0xffff ; limit 15:0\r
125 DW 0 ; base 15:0\r
126 DB 0 ; base 23:16\r
127 DB PRESENT_FLAG(1)|DPL(0)|SYSTEM_FLAG(1)|DESC_TYPE(CODE64_TYPE)\r
128 DB GRANULARITY_FLAG(1)|DEFAULT_SIZE32(0)|CODE64_FLAG(1)|UPPER_LIMIT(0xf)\r
129 DB 0 ; base 31:24\r
130%endif\r
49ba9447 131\r
132GDT_END:\r
133\r