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/*
* Copyright (c) 2015 Egor Tensin <Egor.Tensin@gmail.com>
* This file is part of the "Windows 7 drivers" project.
* For details, see https://github.com/egor-tensin/windows7-drivers.
* Distributed under the MIT License.
*/
#include <ntddk.h>
static __int64 old_msr_value = 0;
static void *old_ki_fast_call_entry = NULL;
static void __stdcall log_system_call()
{
static LONG count = 0;
static const LONG throttle = 10000;
LONG n = InterlockedIncrement(&count);
if (n % throttle == 0)
DbgPrint("Another %ld of `sysenter`s (eax=)!\n", throttle);
}
static void __declspec(naked) new_ki_fast_call_entry()
{
__asm
{
pushad
pushfd
mov ecx, 0x23
push 0x30
pop fs
mov ds, cx
mov es, cx
call log_system_call
popfd
popad
jmp [old_ki_fast_call_entry]
}
}
#define IA32_SYSENTER_EIP 0x176
static void hook_sysenter()
{
/*
__asm
{
mov ecx, IA32_SYSENTER_EIP
rdmsr
mov old_ki_fast_call_entry, eax
mov eax, new_ki_fast_call_entry
xor edx, edx
wrmsr
}
*/
old_msr_value = __readmsr(IA32_SYSENTER_EIP);
old_ki_fast_call_entry = (void *) old_msr_value;
__writemsr(IA32_SYSENTER_EIP, new_ki_fast_call_entry);
}
static void unhook_sysenter()
{
/*
__asm
{
mov ecx, IA32_SYSENTER_EIP
mov eax, old_ki_fast_call_entry
xor edx, edx
wrmsr
}
*/
__writemsr(IA32_SYSENTER_EIP, old_msr_value);
}
static void on_driver_unload(DRIVER_OBJECT *driver_object)
{
KTIMER timer;
LARGE_INTEGER time_out;
unhook_sysenter();
KeInitializeTimer(&timer);
time_out.QuadPart = -30000000; // 3 sec
KeSetTimer(&timer, time_out, NULL);
KeWaitForSingleObject(&timer, Executive, KernelMode, FALSE, NULL);
}
NTSTATUS DriverEntry(
DRIVER_OBJECT *driver_object,
UNICODE_STRING *registry_path)
{
driver_object->DriverUnload = on_driver_unload;
hook_sysenter();
return STATUS_SUCCESS;
}
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