arch/x86/kernel/head32.c

Source file repositories/reference/linux-study-clean/arch/x86/kernel/head32.c

File Facts

System
Linux kernel
Corpus path
arch/x86/kernel/head32.c
Extension
.c
Size
4853 bytes
Lines
171
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

#include <linux/start_kernel.h>
#include <linux/mm.h>
#include <linux/memblock.h>

#include <asm/desc.h>
#include <asm/setup.h>
#include <asm/sections.h>
#include <asm/e820/api.h>
#include <asm/page.h>
#include <asm/apic.h>
#include <asm/io_apic.h>
#include <asm/bios_ebda.h>
#include <asm/microcode.h>
#include <asm/tlbflush.h>
#include <asm/bootparam_utils.h>

static void __init i386_default_early_setup(void)
{
	/* Initialize 32bit specific setup functions */
	x86_init.resources.reserve_resources = i386_reserve_resources;
	x86_init.mpparse.setup_ioapic_ids = setup_ioapic_ids_from_mpc;
}

#ifdef CONFIG_MICROCODE_INITRD32
unsigned long __initdata initrd_start_early;
static pte_t __initdata *initrd_pl2p_start, *initrd_pl2p_end;

static void zap_early_initrd_mapping(void)
{
	pte_t *pl2p = initrd_pl2p_start;

	for (; pl2p < initrd_pl2p_end; pl2p++) {
		*pl2p = (pte_t){ .pte = 0 };

		if (!IS_ENABLED(CONFIG_X86_PAE))
			*(pl2p + ((PAGE_OFFSET >> PGDIR_SHIFT))) = (pte_t) {.pte = 0};
	}
}
#else
static inline void zap_early_initrd_mapping(void) { }
#endif

asmlinkage __visible void __init __noreturn i386_start_kernel(void)
{
	/* Make sure IDT is set up before any exception happens */
	idt_setup_early_handler();

	load_ucode_bsp();
	zap_early_initrd_mapping();

	cr4_init_shadow();

	sanitize_boot_params(&boot_params);

	x86_early_init_platform_quirks();

	/* Call the subarch specific early setup function */
	switch (boot_params.hdr.hardware_subarch) {
	case X86_SUBARCH_INTEL_MID:
		x86_intel_mid_early_setup();
		break;
	case X86_SUBARCH_CE4100:
		x86_ce4100_early_setup();
		break;
	default:
		i386_default_early_setup();
		break;
	}

	start_kernel();
}

/*
 * Initialize page tables.  This creates a PDE and a set of page
 * tables, which are located immediately beyond __brk_base.  The variable
 * _brk_end is set up to point to the first "safe" location.
 * Mappings are created both at virtual address 0 (identity mapping)
 * and PAGE_OFFSET for up to _end.
 *
 * In PAE mode initial_page_table is statically defined to contain
 * enough entries to cover the VMSPLIT option (that is the top 1, 2 or 3
 * entries). The identity mapping is handled by pointing two PGD entries
 * to the first kernel PMD. Note the upper half of each PMD or PTE are
 * always zero at this stage.
 */
#ifdef CONFIG_X86_PAE
typedef pmd_t			pl2_t;
#define pl2_base		initial_pg_pmd
#define SET_PL2(val)		{ .pmd = (val), }
#else

Annotation

Implementation Notes