selector.c

//https://github.com/haidragon/newbluepill    主要用于动态解析段描述符
#include "selector.h"

NTSTATUS InitializeSegmentSelector(PSEGMENT_SELECTOR SegmentSelector, USHORT Selector, ULONG64 GdtBase)
{
	PSEGMENT_DESCRIPTOR2 SegDesc;

	if (!SegmentSelector)
	{
		return STATUS_INVALID_PARAMETER;
	}

	//
	// 如果段选择子的T1 = 1表示索引LDT中的项, 这里没有实现这个功能
	//
	if (Selector & 0x4)
	{

		return STATUS_INVALID_PARAMETER;
	}

	//
	// 在GDT中取出原始的段描述符
	//
	SegDesc = (PSEGMENT_DESCRIPTOR2)((PUCHAR)GdtBase + (Selector & ~0x7));

	//
	// 段选择子
	//
	SegmentSelector->sel = Selector;

	//
	// 段基址15-39位 55-63位
	//
	SegmentSelector->base = SegDesc->base0 | SegDesc->base1 << 16 | SegDesc->base2 << 24;

	//
	// 段限长0-15位  47-51位, 看它的取法
	//
	SegmentSelector->limit = SegDesc->limit0 | (SegDesc->limit1attr1 & 0xf) << 16;

	//
	// 段属性39-47 51-55 注意观察取法
	//
	SegmentSelector->attributes.UCHARs = SegDesc->attr0 | (SegDesc->limit1attr1 & 0xf0) << 4;

	//
	// 这里判断属性的DT位, 判断是否是系统段描述符还是代码数据段描述符
	//
	if (!(SegDesc->attr0 & LA_STANDARD))
	{
		ULONG64 tmp;

		//
		// 这里表示是系统段描述符或者门描述符, 感觉这是为64位准备的吧,
		// 32位下面段基址只有32位啊. 难道64位下面有什么区别了?
		//
		tmp = (*(PULONG64)((PUCHAR)SegDesc + 8));

		SegmentSelector->base = (SegmentSelector->base & 0xffffffff) | (tmp << 32);
	}

	//
	// 这是段界限的粒度位, 1为4K. 0为1BYTE
	//
	if (SegmentSelector->attributes.fields.g)
	{
		//
		// 如果粒度位为1, 那么就乘以4K. 左移动12位
		//
		SegmentSelector->limit = (SegmentSelector->limit << 12) + 0xfff;
	}

	return STATUS_SUCCESS;
}




NTSTATUS FillGuestSelectorData(ULONG64 GdtBase, ULONG Segreg, USHORT
	Selector)
{

	SEGMENT_SELECTOR SegmentSelector = { 0 };
	ULONG uAccessRights;

	InitializeSegmentSelector(&SegmentSelector, Selector, GdtBase);
	uAccessRights = ((PUCHAR)&SegmentSelector.attributes)[0] + (((PUCHAR)&
		SegmentSelector.attributes)[1] << 12);

	if (!Selector)
		uAccessRights |= 0x10000;

	__vmx_vmwrite(VMCS_GUSTAREA_ES + Segreg * 2, Selector);
	__vmx_vmwrite(VMCS_GUSTAREA_ES_BASE + Segreg * 2, SegmentSelector.base);
	__vmx_vmwrite(VMCS_GUSTAREA_ES_LIMT + Segreg * 2, SegmentSelector.limit);
	__vmx_vmwrite(VMCS_GUSTAREA_ES_ACCR + Segreg * 2, uAccessRights);
	if ((Segreg == LDTR) || (Segreg == TR))
		// don't setup for FS/GS - their bases are stored in MSR values
		__vmx_vmwrite(VMCS_GUSTAREA_ES_BASE + Segreg * 2, SegmentSelector.base);
	return STATUS_SUCCESS;
}