1 // SPDX-License-Identifier: GPL-2.0-only
2 /* -*- linux-c -*- ------------------------------------------------------- *
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 * Copyright 2007 rPath, Inc. - All Rights Reserved
6 * Copyright 2009 Intel Corporation; author H. Peter Anvin
7 *
8 * ----------------------------------------------------------------------- */
9
10 /*
11 * Main module for the real-mode kernel code
12 */
13 #include <linux/build_bug.h>
14
15 #include "boot.h"
16 #include "string.h"
17
18 struct boot_params boot_params __attribute__((aligned(16)));
19
20 struct port_io_ops pio_ops;
21
22 char *HEAP = _end;
23 char *heap_end = _end; /* Default end of heap = no heap */
24
25 /*
26 * Copy the header into the boot parameter block. Since this
27 * screws up the old-style command line protocol, adjust by
28 * filling in the new-style command line pointer instead.
29 */
30
copy_boot_params(void)31 static void copy_boot_params(void)
32 {
33 struct old_cmdline {
34 u16 cl_magic;
35 u16 cl_offset;
36 };
37 const struct old_cmdline * const oldcmd =
38 absolute_pointer(OLD_CL_ADDRESS);
39
40 BUILD_BUG_ON(sizeof(boot_params) != 4096);
41 memcpy(&boot_params.hdr, &hdr, sizeof(hdr));
42
43 if (!boot_params.hdr.cmd_line_ptr &&
44 oldcmd->cl_magic == OLD_CL_MAGIC) {
45 /* Old-style command line protocol. */
46 u16 cmdline_seg;
47
48 /* Figure out if the command line falls in the region
49 of memory that an old kernel would have copied up
50 to 0x90000... */
51 if (oldcmd->cl_offset < boot_params.hdr.setup_move_size)
52 cmdline_seg = ds();
53 else
54 cmdline_seg = 0x9000;
55
56 boot_params.hdr.cmd_line_ptr =
57 (cmdline_seg << 4) + oldcmd->cl_offset;
58 }
59 }
60
61 /*
62 * Query the keyboard lock status as given by the BIOS, and
63 * set the keyboard repeat rate to maximum. Unclear why the latter
64 * is done here; this might be possible to kill off as stale code.
65 */
keyboard_init(void)66 static void keyboard_init(void)
67 {
68 struct biosregs ireg, oreg;
69 initregs(&ireg);
70
71 ireg.ah = 0x02; /* Get keyboard status */
72 intcall(0x16, &ireg, &oreg);
73 boot_params.kbd_status = oreg.al;
74
75 ireg.ax = 0x0305; /* Set keyboard repeat rate */
76 intcall(0x16, &ireg, NULL);
77 }
78
79 /*
80 * Get Intel SpeedStep (IST) information.
81 */
query_ist(void)82 static void query_ist(void)
83 {
84 struct biosregs ireg, oreg;
85
86 /* Some older BIOSes apparently crash on this call, so filter
87 it from machines too old to have SpeedStep at all. */
88 if (cpu.level < 6)
89 return;
90
91 initregs(&ireg);
92 ireg.ax = 0xe980; /* IST Support */
93 ireg.edx = 0x47534943; /* Request value */
94 intcall(0x15, &ireg, &oreg);
95
96 boot_params.ist_info.signature = oreg.eax;
97 boot_params.ist_info.command = oreg.ebx;
98 boot_params.ist_info.event = oreg.ecx;
99 boot_params.ist_info.perf_level = oreg.edx;
100 }
101
102 /*
103 * Tell the BIOS what CPU mode we intend to run in.
104 */
set_bios_mode(void)105 static void set_bios_mode(void)
106 {
107 #ifdef CONFIG_X86_64
108 struct biosregs ireg;
109
110 initregs(&ireg);
111 ireg.ax = 0xec00;
112 ireg.bx = 2;
113 intcall(0x15, &ireg, NULL);
114 #endif
115 }
116
init_heap(void)117 static void init_heap(void)
118 {
119 char *stack_end;
120
121 if (boot_params.hdr.loadflags & CAN_USE_HEAP) {
122 asm("leal %P1(%%esp),%0"
123 : "=r" (stack_end) : "i" (-STACK_SIZE));
124
125 heap_end = (char *)
126 ((size_t)boot_params.hdr.heap_end_ptr + 0x200);
127 if (heap_end > stack_end)
128 heap_end = stack_end;
129 } else {
130 /* Boot protocol 2.00 only, no heap available */
131 puts("WARNING: Ancient bootloader, some functionality "
132 "may be limited!\n");
133 }
134 }
135
main(void)136 void main(void)
137 {
138 init_default_io_ops();
139
140 /* First, copy the boot header into the "zeropage" */
141 copy_boot_params();
142
143 /* Initialize the early-boot console */
144 console_init();
145 if (cmdline_find_option_bool("debug"))
146 puts("early console in setup code\n");
147
148 /* End of heap check */
149 init_heap();
150
151 /* Make sure we have all the proper CPU support */
152 if (validate_cpu()) {
153 puts("Unable to boot - please use a kernel appropriate "
154 "for your CPU.\n");
155 die();
156 }
157
158 /* Tell the BIOS what CPU mode we intend to run in. */
159 set_bios_mode();
160
161 /* Detect memory layout */
162 detect_memory();
163
164 /* Set keyboard repeat rate (why?) and query the lock flags */
165 keyboard_init();
166
167 /* Query Intel SpeedStep (IST) information */
168 query_ist();
169
170 /* Query APM information */
171 #if defined(CONFIG_APM) || defined(CONFIG_APM_MODULE)
172 query_apm_bios();
173 #endif
174
175 /* Query EDD information */
176 #if defined(CONFIG_EDD) || defined(CONFIG_EDD_MODULE)
177 query_edd();
178 #endif
179
180 /* Set the video mode */
181 set_video();
182
183 /* Do the last things and invoke protected mode */
184 go_to_protected_mode();
185 }
186
