在前面一篇文章中,已经定位到了变量HalpWakeVector,我也说过这是开启OS S3大门的钥匙,那这篇文章就应该是登堂入室了。
1.从HalpWakeVector过度到HalpLowStubPhysicalAddress:
hal模块对HalpWakeVector的引用不多,只有4处:
但是现阶段只用到HalpSetupRealModeResume函数。
.text:00000001C003D320 HalpSetupRealModeResume proc near ; CODE XREF: HaliAcpiSleep+139↑p
.text:00000001C003D320 ; DATA XREF: .pdata:00000001C0054240↓o
.text:00000001C003D320
.text:00000001C003D320 arg_0 = qword ptr 8
.text:00000001C003D320
.text:00000001C003D320 mov [rsp+arg_0], rcx
.text:00000001C003D325 sub rsp, 28h
.text:00000001C003D329 mov rax, cs:HalpWakeVector
.text:00000001C003D330 test rax, rax
.text:00000001C003D333 jnz short loc_1C003D336
.text:00000001C003D335 int 3 ; Trap to Debugger
.text:00000001C003D336
.text:00000001C003D336 loc_1C003D336: ; CODE XREF: HalpSetupRealModeResume+13↑j
.text:00000001C003D336 mov [rax], edx ; store HalpLowStubPhysicalAddress to HalpWakeVector
HalpSetupRealModeResume入口处先获得HalpWakeVector的地址,如果地址非空,则向其中写入HaliAcpiSleep调用HalpSetupRealModeResume时传入的参数edx。跳转到HaliAcpiSleep,将看到如下代码段:
.text:00000001C003C963 mov edx, dword ptr cs:HalpLowStubPhysicalAddress
.text:00000001C003C969 call HalpSetupRealModeResume
.text:00000001C003C96E test al, al
.text:00000001C003C970 jnz loc_1C003CCA2
HaliAcpiSleep传入的值是HalpLowStubPhysicalAddress。
2.Hal对HalpLowStubPhysicalAddress的引用:
查找Hal模块对HalpLowStubPhysicalAddress的引用:
在xrefs窗口会看到一些熟悉的字眼,比如SetupAcpiPhase0。记得Windows启动过程也分Phase0/Phase1两个阶段,所以,我猜想下面的w xrefs(注意是Write引用)是在OS初始化阶段,对HalpLowStubPhysicalAddress进行初始化:
Down w HalpSetupAcpiPhase0+EC mov cs:HalpLowStubPhysicalAddress, rax
跳转到HalpSetupAcpiPhase0+0xEC处果真如此,它调用HalpAllocPhysicalMemory分配物理页面并将返回值写入HalpLowStubPhysicalAddress:
INIT:00000001C0071E1B mov edx, 100000h
INIT:00000001C0071E20 mov rcx, rbx
INIT:00000001C0071E23 call HalpAllocPhysicalMemory
INIT:00000001C0071E28 mov cs:HalpLowStubPhysicalAddress, rax
INIT:00000001C0071E2F test rax, rax
INIT:00000001C0071E32 jz short loc_1C0071E53
由此可见,双机调试时需要在HalpSetupAcpiPhase0函数上下断点,观察HalpLowStubPhysicalAddress的值是否和UEFI S3Resume时访问的Facs->XFirmwareWakingVector相同。下一篇就动手验证一下。