[linux-2.6-block.git] / arch / x86 / boot / pm.c

// SPDX-License-Identifier: GPL-2.0-only
/* -*- linux-c -*- ------------------------------------------------------- *
 *
 *   Copyright (C) 1991, 1992 Linus Torvalds
 *   Copyright 2007 rPath, Inc. - All Rights Reserved
 *
 * ----------------------------------------------------------------------- */

/*
 * Prepare the machine for transition to protected mode.
 */

#include "boot.h"
#include <asm/segment.h>

/*
 * Invoke the realmode switch hook if present; otherwise
 * disable all interrupts.
 */
static void realmode_switch_hook(void)
{
	if (boot_params.hdr.realmode_swtch) {
		asm volatile("lcallw *%0"
			     : : "m" (boot_params.hdr.realmode_swtch)
			     : "eax", "ebx", "ecx", "edx");
	} else {
		asm volatile("cli");
		outb(0x80, 0x70); /* Disable NMI */
		io_delay();
	}
}

/*
 * Disable all interrupts at the legacy PIC.
 */
static void mask_all_interrupts(void)
{
	outb(0xff, 0xa1);	/* Mask all interrupts on the secondary PIC */
	io_delay();
	outb(0xfb, 0x21);	/* Mask all but cascade on the primary PIC */
	io_delay();
}

/*
 * Reset IGNNE# if asserted in the FPU.
 */
static void reset_coprocessor(void)
{
	outb(0, 0xf0);
	io_delay();
	outb(0, 0xf1);
	io_delay();
}

/*
 * Set up the GDT
 */

struct gdt_ptr {
	u16 len;
	u32 ptr;
} __attribute__((packed));

static void setup_gdt(void)
{
	/* There are machines which are known to not boot with the GDT
	   being 8-byte unaligned.  Intel recommends 16 byte alignment. */
	static const u64 boot_gdt[] __attribute__((aligned(16))) = {
		/* CS: code, read/execute, 4 GB, base 0 */
		[GDT_ENTRY_BOOT_CS] = GDT_ENTRY(0xc09b, 0, 0xfffff),
		/* DS: data, read/write, 4 GB, base 0 */
		[GDT_ENTRY_BOOT_DS] = GDT_ENTRY(0xc093, 0, 0xfffff),
		/* TSS: 32-bit tss, 104 bytes, base 4096 */
		/* We only have a TSS here to keep Intel VT happy;
		   we don't actually use it for anything. */
		[GDT_ENTRY_BOOT_TSS] = GDT_ENTRY(0x0089, 4096, 103),
	};
	/* Xen HVM incorrectly stores a pointer to the gdt_ptr, instead
	   of the gdt_ptr contents.  Thus, make it static so it will
	   stay in memory, at least long enough that we switch to the
	   proper kernel GDT. */
	static struct gdt_ptr gdt;

	gdt.len = sizeof(boot_gdt)-1;
	gdt.ptr = (u32)&boot_gdt + (ds() << 4);

	asm volatile("lgdtl %0" : : "m" (gdt));
}

/*
 * Set up the IDT
 */
static void setup_idt(void)
{
	static const struct gdt_ptr null_idt = {0, 0};
	asm volatile("lidtl %0" : : "m" (null_idt));
}

/*
 * Actual invocation sequence
 */
void go_to_protected_mode(void)
{
	/* Hook before leaving real mode, also disables interrupts */
	realmode_switch_hook();

	/* Enable the A20 gate */
	if (enable_a20()) {
		puts("A20 gate not responding, unable to boot...\n");
		die();
	}

	/* Reset coprocessor (IGNNE#) */
	reset_coprocessor();

	/* Mask all interrupts in the PIC */
	mask_all_interrupts();

	/* Actual transition to protected mode... */
	setup_idt();
	setup_gdt();
	protected_mode_jump(boot_params.hdr.code32_start,
			    (u32)&boot_params + (ds() << 4));
}
Commit	Line	Data
97873a3d	1	// SPDX-License-Identifier: GPL-2.0-only
7052fdd8 PA	2	/* -- linux-c -- ------------------------------------------------------- *
	3	*
	4	* Copyright (C) 1991, 1992 Linus Torvalds
	5	* Copyright 2007 rPath, Inc. - All Rights Reserved
	6	*
7052fdd8 PA	7	* ----------------------------------------------------------------------- */
	8
	9	/*
7052fdd8 PA	10	* Prepare the machine for transition to protected mode.
	11	*/
	12
	13	#include "boot.h"
	14	#include <asm/segment.h>
	15
	16	/*
	17	* Invoke the realmode switch hook if present; otherwise
	18	* disable all interrupts.
	19	*/
	20	static void realmode_switch_hook(void)
	21	{
	22	if (boot_params.hdr.realmode_swtch) {
	23	asm volatile("lcallw *%0"
	24	: : "m" (boot_params.hdr.realmode_swtch)
	25	: "eax", "ebx", "ecx", "edx");
	26	} else {
	27	asm volatile("cli");
	28	outb(0x80, 0x70); /* Disable NMI */
	29	io_delay();
	30	}
	31	}
	32
7052fdd8 PA	33	/*
	34	* Disable all interrupts at the legacy PIC.
	35	*/
	36	static void mask_all_interrupts(void)
	37	{
8218d029	38	outb(0xff, 0xa1); /* Mask all interrupts on the secondary PIC */
7052fdd8 PA	39	io_delay();
	40	outb(0xfb, 0x21); /* Mask all but cascade on the primary PIC */
	41	io_delay();
	42	}
	43
	44	/*
	45	* Reset IGNNE# if asserted in the FPU.
	46	*/
	47	static void reset_coprocessor(void)
	48	{
	49	outb(0, 0xf0);
	50	io_delay();
	51	outb(0, 0xf1);
	52	io_delay();
	53	}
	54
	55	/*
	56	* Set up the GDT
	57	*/
7052fdd8 PA	58
	59	struct gdt_ptr {
	60	u16 len;
	61	u32 ptr;
	62	} __attribute__((packed));
	63
	64	static void setup_gdt(void)
	65	{
	66	/* There are machines which are known to not boot with the GDT
	67	being 8-byte unaligned. Intel recommends 16 byte alignment. */
	68	static const u64 boot_gdt[] __attribute__((aligned(16))) = {
	69	/* CS: code, read/execute, 4 GB, base 0 */
	70	[GDT_ENTRY_BOOT_CS] = GDT_ENTRY(0xc09b, 0, 0xfffff),
	71	/* DS: data, read/write, 4 GB, base 0 */
	72	[GDT_ENTRY_BOOT_DS] = GDT_ENTRY(0xc093, 0, 0xfffff),
88089519 PA	73	/* TSS: 32-bit tss, 104 bytes, base 4096 */
	74	/* We only have a TSS here to keep Intel VT happy;
	75	we don't actually use it for anything. */
	76	[GDT_ENTRY_BOOT_TSS] = GDT_ENTRY(0x0089, 4096, 103),
7052fdd8	77	};
ce29a1f8 CE	78	/* Xen HVM incorrectly stores a pointer to the gdt_ptr, instead
	79	of the gdt_ptr contents. Thus, make it static so it will
	80	stay in memory, at least long enough that we switch to the
	81	proper kernel GDT. */
	82	static struct gdt_ptr gdt;
7052fdd8 PA	83
	84	gdt.len = sizeof(boot_gdt)-1;
	85	gdt.ptr = (u32)&boot_gdt + (ds() << 4);
	86
	87	asm volatile("lgdtl %0" : : "m" (gdt));
	88	}
	89
	90	/*
	91	* Set up the IDT
	92	*/
	93	static void setup_idt(void)
	94	{
	95	static const struct gdt_ptr null_idt = {0, 0};
	96	asm volatile("lidtl %0" : : "m" (null_idt));
	97	}
	98
	99	/*
	100	* Actual invocation sequence
	101	*/
	102	void go_to_protected_mode(void)
	103	{
	104	/* Hook before leaving real mode, also disables interrupts */
	105	realmode_switch_hook();
	106
7052fdd8 PA	107	/* Enable the A20 gate */
	108	if (enable_a20()) {
	109	puts("A20 gate not responding, unable to boot...\n");
	110	die();
	111	}
	112
	113	/* Reset coprocessor (IGNNE#) */
	114	reset_coprocessor();
	115
	116	/* Mask all interrupts in the PIC */
	117	mask_all_interrupts();
	118
	119	/* Actual transition to protected mode... */
	120	setup_idt();
	121	setup_gdt();
	122	protected_mode_jump(boot_params.hdr.code32_start,
	123	(u32)&boot_params + (ds() << 4));
	124	}