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