Correct. The old CpuDxe(one year ago) has such code to protect IDT entries used by soft debugger.
Now the UefiCpuPkg/CpuDxe has already been updated to support Method to Reserve Interrupt and Exception Vectors (Introduced from PI spec 1.2.1). And removed such code logic. Thanks! Jeff From: Andrew Fish [mailto:af...@apple.com] Sent: Thursday, October 30, 2014 10:25 AM To: edk2-devel@lists.sourceforge.net Subject: Re: [edk2] question about InitInterruptDescriptorTable() function in CpuDxe.c On Oct 29, 2014, at 7:19 PM, tiger...@via-alliance.com<mailto:tiger...@via-alliance.com> wrote: Hi, experts: I am confused by some codes in InitInterruptDescriptorTable() function (in UefiCpuPkg/CpuDxe/CpuDxe.c). …… if ((OldIdtPtr.Base != 0) && ((OldIdtPtr.Limit & 7) == 7)) { // Based on my understanding, because DxeIpl has created IDT when switching from P-Mode to Long-Mode. // So, should execute below code. OldIdt = (IA32_IDT_GATE_DESCRIPTOR*) OldIdtPtr.Base; OldIdtSize = (OldIdtPtr.Limit + 1) / sizeof (IA32_IDT_GATE_DESCRIPTOR); …… } else { OldIdt = NULL; OldIdtSize = 0; } …… // Based on my understanding, When come here, index = OldIdtSize = 32, so CpuRegisterInterruptHandler() could not be run. for (Index = OldIdtSize; Index < 32; Index++) { Status = CpuRegisterInterruptHandler (&gCpu, Index, CommonExceptionHandler); ASSERT_EFI_ERROR (Status); } My question is: Because DxeIpl has created IDT, and OldIdtSize = 32, so CpuRegisterInterruptHandler() could not be run, right? I think there is an assumption that the OldIdtSize represents vectors from the debugger. If the debugger did not grab any, or all, of the possible exception vectors, then this driver hooks in an exception handler. Thanks, Andrew Fish Best wishes, ------------------------------------------------------------------------------ _______________________________________________ edk2-devel mailing list edk2-devel@lists.sourceforge.net<mailto:edk2-devel@lists.sourceforge.net> https://lists.sourceforge.net/lists/listinfo/edk2-devel
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