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