exception.c

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/*++
 
Module Name:
 
    exception.c
 
Purpose:
 
    This translation unit contains the implementation of exception checking & handling in MatanelOS (_try _except macros)
 
Author:
 
    slep (Matanel) 2025.
 
Revision History:
 
--*/
 
#include "../../includes/exception.h"
#include "../../includes/ps.h"
 
bool
ExpIsExceptionHandlerPresent(
    IN PETHREAD Thread
)
 
/*++
 
    Routine description:
 
        Checks if an exception handler is present in the current thread context.
 
    Arguments:
 
        [IN] PETHREAD Thread - The thread to check on.
 
    Return Values:
 
        True if present, false otherwise.
 
--*/
 
{
    if (Thread) {
        if (Thread->ExceptionRegistration.Handler != NULL) {
            return true;
        }
        else {
            return false;
        }
    }
    return false;
}
 
void
ExpDispatchException(
    IN PTRAP_FRAME TrapFrame,
    IN PCONTEXT ContextRecord,
    IN PEXCEPTION_RECORD ExceptionRecord
)
 
/*++
 
    Routine description:
        (UNUSED)
        Changes the trap frame to point to the _except handler of the thread.
 
    Arguments:
 
        [IN] PTRAP_FRAME trap - Pointer to Trap frame of the thread.
        [IN] PCONTEXT ContextRecord - Pointer to Context record of the thread (saved in _try by thread)
        [IN] PEXCEPTION_RECORD ExceptionRecord - Pointer to Exception record of the thread
 
    Return Values:
 
        None.
 
--*/
 
{
    UNREFERENCED_PARAMETER(ExceptionRecord);
    if (ExpIsExceptionHandlerPresent(PsGetCurrentThread())) {
        // Change trap frame to context record set by thread. (except RIP)
        TrapFrame->rsp = ContextRecord->Rsp;
        TrapFrame->rflags = ContextRecord->RFlags;
 
        // General-purpose registers from the context frame
        TrapFrame->r15 = ContextRecord->R15;
        TrapFrame->r14 = ContextRecord->R14;
        TrapFrame->r13 = ContextRecord->R13;
        TrapFrame->r12 = ContextRecord->R12;
 
        TrapFrame->r11 = ContextRecord->R11;
        TrapFrame->r10 = ContextRecord->R10;
        TrapFrame->r9 = ContextRecord->R9;
        TrapFrame->r8 = ContextRecord->R8;
 
        TrapFrame->rbp = ContextRecord->Rbp;
        TrapFrame->rdi = ContextRecord->Rdi;
        TrapFrame->rsi = ContextRecord->Rsi;
 
        TrapFrame->rcx = ContextRecord->Rcx;
        TrapFrame->rbx = ContextRecord->Rbx;
        TrapFrame->rdx = ContextRecord->Rdx;
        TrapFrame->rax = ContextRecord->Rax;
 
        // Enumerate all handlers, if one returned FIXME TODO (Decide between return value approach or completely different approach, i scrapped the exception handling idea for now, too complicated and messy, id rather work on memory
    }
 
 
}
 
uint64_t
ExpFindKernelModeExceptionHandler(
    uint64_t Rip
)
 
/*++
 
    Routine description:
        
        Enumerates the section provided by the linker script to find a suitable exception handler for the kernel RIP given.
 
    Arguments:
 
        [IN] uint64_t Rip - Address that caused the page fault in kernel mode.
 
    Return Values:
 
        Address of exception handler if found, else 0.
 
--*/
 
{
    PEXCEPTION_RANGE Entry = __start_ex_table;
 
    // We could do a binary search since this is address given, but WHO cares. 
    while (Entry < __stop_ex_table) {
        // Check if the faulting RIP is within the range.
        if (Rip >= Entry->start_addr && Rip < Entry->end_addr) {
            // Found a handler!
            return Entry->handler_addr;
        }
 
        // Increment entry.
        Entry++;
    }
 
    // No exception handler found..
    return 0;
}