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
18struct boot_params boot_params __attribute__((aligned(16)));
19
20struct port_io_ops pio_ops;
21
22char *HEAP = _end;
23char *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
31static 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 */
66static 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 */
82static 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 */
105static 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
117static 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
136void 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