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