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Reading hardware MSR registers (__readmsr / __writemsr) in kernel driver [v2.4 Technical Discussion]

kernel_komrade
Driver Dev
MEMBER
Rep: 145
Datum pridruživanja: Feb 2019
Postovi: 26
Hvala: 45
prije 1 mjeseci · Jul 22, 2026 12:19 AM
#1

Model-Specific Registers (MSRs) control CPU architectural features:

C
#define IA32_LSTAR_MSR 0xC0000082 // Syscall Target Address
#define IA32_GS_BASE_MSR 0xC0000101 // KPCR / Thread Pointer

// Read syscall entry point
ULONG64 lstar = __readmsr(IA32_LSTAR_MSR);
printf("[KERNEL] System Call Target Address: 0x%llX\n", lstar);

Useful for verifying kernel integrity and checking if system call dispatchers have been tampered with.

x64_assembler
Assembly Guru
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Rep: 99
Datum pridruživanja: Sep 2022
Postovi: 14
Hvala: 16
prije 1 mjeseci · Jul 22, 2026 2:57 AM
#2

IA32_GS_BASE holds the pointer to KPCR (Kernel Processor Control Region) which is fundamental to Windows thread scheduling.

stack_smasher
Kernel Explorer
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Rep: 111
Datum pridruživanja: Feb 2019
Postovi: 30
Hvala: 18
prije 1 mjeseci · Jul 22, 2026 2:51 PM
#3

Clean MSR register querying.