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[NTOS:KE/x64] Improve KiSystemCallHandler code a bit

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- Use an index for the table instead of ugly pointer offset
- Invert the check for GUI calls
- Fail with proper status code on invalid win32k syscall ids
This commit is contained in:
Timo Kreuzer 2024-03-25 22:37:50 +02:00
parent 2ed8541dc8
commit 5442f87080
1 changed files with 19 additions and 15 deletions
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34
ntoskrnl/ke/amd64/traphandler.c
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@ -101,7 +101,7 @@ KiSystemCallHandler(
PKSERVICE_TABLE_DESCRIPTOR DescriptorTable;
PKTHREAD Thread;
PULONG64 KernelParams, UserParams;
ULONG ServiceNumber, Offset, Count;
ULONG ServiceNumber, TableIndex, Count;
ULONG64 UserRsp;
/* Get a pointer to the trap frame */
@ -139,11 +139,11 @@ KiSystemCallHandler(
/* Get the system call number from the trap frame and decode it */
ServiceNumber = (ULONG)TrapFrame->Rax;
Offset = (ServiceNumber >> SERVICE_TABLE_SHIFT) & SERVICE_TABLE_MASK;
TableIndex = (ServiceNumber >> TABLE_OFFSET_BITS) & ((1 << TABLE_NUMBER_BITS) - 1);
ServiceNumber &= SERVICE_NUMBER_MASK;
/* Check for win32k system calls */
if (Offset & SERVICE_TABLE_TEST)
if (TableIndex == WIN32K_SERVICE_INDEX)
{
ULONG GdiBatchCount;
@ -166,25 +166,29 @@ KiSystemCallHandler(
}
/* Get descriptor table */
DescriptorTable = (PVOID)((ULONG_PTR)Thread->ServiceTable + Offset);
DescriptorTable = &((PKSERVICE_TABLE_DESCRIPTOR)Thread->ServiceTable)[TableIndex];
/* Validate the system call number */
if (ServiceNumber >= DescriptorTable->Limit)
{
/* Check if this is a GUI call */
if (!(Offset & SERVICE_TABLE_TEST))
/* Check if this is a GUI call and this is not a GUI thread yet */
if ((TableIndex == WIN32K_SERVICE_INDEX) &&
(Thread->ServiceTable == KeServiceDescriptorTable))
{
/* Fail the call */
TrapFrame->Rax = STATUS_INVALID_SYSTEM_SERVICE;
return (PVOID)NtSyscallFailure;
/* Convert this thread to a GUI thread.
It is invalid to change the stack in the middle of a C function,
therefore we return KiConvertToGuiThread to the system call entry
point, which then calls the asm function KiConvertToGuiThread,
which allocates a new stack, switches to it, calls
PsConvertToGuiThread and resumes in the middle of
KiSystemCallEntry64 to restart the system call handling.
If converting fails, the system call returns a failure code. */
return (PVOID)KiConvertToGuiThread;
}
/* Convert us to a GUI thread
To be entirely correct. we return KiConvertToGuiThread,
which allocates a new stack, switches to it, calls
PsConvertToGuiThread and resumes in the middle of
KiSystemCallEntry64 to restart the system call handling. */
return (PVOID)KiConvertToGuiThread;
/* Fail the call */
TrapFrame->Rax = STATUS_INVALID_SYSTEM_SERVICE;
return (PVOID)NtSyscallFailure;
}
/* Get stack bytes and calculate argument count */