arch/x86/boot/pm.c

Source file repositories/reference/linux-study-clean/arch/x86/boot/pm.c

File Facts

System
Linux kernel
Corpus path
arch/x86/boot/pm.c
Extension
.c
Size
3025 bytes
Lines
126
Domain
Architecture Layer
Bucket
arch/x86
Inferred role
Architecture Layer: implementation source
Status
source implementation candidate

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

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(DESC_CODE32, 0, 0xfffff),
		/* DS: data, read/write, 4 GB, base 0 */
		[GDT_ENTRY_BOOT_DS] = GDT_ENTRY(DESC_DATA32, 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(DESC_TSS32, 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));
}

Annotation

Implementation Notes