--- /dev/null
+#include <lwk/init.h>
+#include <lwk/kernel.h>
+#include <lwk/string.h>
+#include <lwk/screen_info.h>
+#include <lwk/params.h>
+#include <lwk/smp.h>
+#include <lwk/cpuinfo.h>
+#include <arch/bootsetup.h>
+#include <arch/sections.h>
+#include <arch/pda.h>
+#include <arch/processor.h>
+#include <arch/desc.h>
+#include <arch/proto.h>
+#include <arch/page.h>
+#include <arch/pgtable.h>
+#include <arch/tlbflush.h>
+
+/**
+ * Data passed to the kernel by the bootloader.
+ *
+ * NOTE: This is marked as __initdata so it goes away after the
+ * kernel bootstrap process is complete.
+ */
+char x86_boot_params[BOOT_PARAM_SIZE] __initdata = {0,};
+
+/**
+ * Interrupt Descriptor Table (IDT) descriptor.
+ *
+ * This descriptor contains the length of the IDT table and a
+ * pointer to the table. The lidt instruction (load IDT) requires
+ * this format.
+ */
+struct desc_ptr idt_descr = { 256 * 16 - 1, (unsigned long) idt_table };
+
+/**
+ * Array of pointers to each CPU's per-processor data area.
+ * The array is indexed by CPU ID.
+ */
+struct x8664_pda *_cpu_pda[NR_CPUS] __read_mostly;
+
+/**
+ * Array of per-processor data area structures, one per CPU.
+ * The array is indexed by CPU ID.
+ */
+struct x8664_pda boot_cpu_pda[NR_CPUS] __cacheline_aligned;
+
+/**
+ * This unmaps virtual addresses [0,512GB) by clearing the first entry in the
+ * PGD/PML4T. After this executes, accesses to virtual addresses [0,512GB) will
+ * cause a page fault.
+ */
+static void __init
+zap_identity_mappings(void)
+{
+ pgd_t *pgd = pgd_offset_k(0UL);
+ pgd_clear(pgd);
+ __flush_tlb();
+}
+
+/**
+ * Determines the address of the kernel boot command line.
+ */
+static char * __init
+find_command_line(void)
+{
+ unsigned long new_data;
+
+ new_data = *(u32 *) (x86_boot_params + NEW_CL_POINTER);
+ if (!new_data) {
+ if (OLD_CL_MAGIC != * (u16 *) OLD_CL_MAGIC_ADDR) {
+ return NULL;
+ }
+ new_data = OLD_CL_BASE_ADDR + * (u16 *) OLD_CL_OFFSET;
+ }
+ return __va(new_data);
+}
+
+/**
+ * This is the initial C entry point to the kernel.
+ * NOTE: The order of operations is usually important. Be careful.
+ */
+void __init
+x86_64_start_kernel(char * real_mode_data)
+{
+ int i;
+
+ /*
+ * Zero the "Block Started by Symbol" section...
+ * you know, the one that holds uninitialized data.
+ */
+ memset(__bss_start, 0,
+ (unsigned long) __bss_stop - (unsigned long) __bss_start);
+
+ /*
+ * Make NULL pointer dereferences segfault.
+ */
+ zap_identity_mappings();
+
+ /*
+ * Setup the initial interrupt descriptor table (IDT).
+ * This will be eventually be populated with the real handlers.
+ */
+ for (i = 0; i < 256; i++)
+ set_intr_gate(i, early_idt_handler);
+ asm volatile("lidt %0" :: "m" (idt_descr));
+
+ /*
+ * Early per-processor data area (PDA) initialization.
+ */
+ for (i = 0; i < NR_CPUS; i++)
+ cpu_pda(i) = &boot_cpu_pda[i];
+ pda_init(0, &bootstrap_task_union.task_info);
+
+ /*
+ * Make a copy data passed by the bootloader.
+ * real_mode_data will get clobbered eventually when the memory
+ * subsystem is initialized.
+ */
+ memcpy(x86_boot_params, __va(real_mode_data), sizeof(x86_boot_params));
+ memcpy(lwk_command_line, find_command_line(), sizeof(lwk_command_line));
+
+ /*
+ * Tell the VGA driver the starting line number... this avoids
+ * overwriting BIOS and bootloader messages.
+ */
+ param_set_by_name_int("vga.row", SCREEN_INFO.orig_y);
+
+ /*
+ * Okay... we've done the bare essentials. Call into the
+ * platform-independent bootstrap function. This will in turn
+ * call back into architecture dependent code to do things like
+ * initialize interrupts and boot CPUs.
+ */
+ start_kernel();
+}
+
