Dirty Stack?
Posted: Wed Jan 30, 2019 8:39 am
Hi guys! It's me again 
I discovered a weired issue in my VMM-Mapping-Methods.
The following code works:
But without the "const" it doesn't. I've debugged it and it seems like after the first function call (GetAddress), the second parameter gets overwritten and is 0x0 instead of 0x200000 what it should have been. Bitmap seems to stay the same. Could that mean a dirty stack? Or is it maybe something C++-Related?
Thanks for your help!
EDIT: Well i've somehow fixed it... I changed my Check-Methode and now it works without the const in the parameter list... The question is why?
This is the original Check-Methode:
And this is the edited Check-Methode:
Which is obviously more bug-proof
I discovered a weired issue in my VMM-Mapping-Methods.
The following code works:
Code: Select all
void KernelTable::Map2M(void *VirtAddress, const void *PhysAddress, uint64_t Bitmap)
{
uint16_t PML4I = (((uint64_t)VirtAddress) >> 39) & 0x1FF;
uint16_t PDPTI = (((uint64_t)VirtAddress) >> 30) & 0x1FF;
uint16_t PDI = (((uint64_t)VirtAddress) >> 21) & 0x1FF;
uint64_t *PML4E = GetAddress(511, 511, 511, PML4I);
Check(PML4E, Bitmap);
uint64_t *PDPTE = GetAddress(511, 511, PML4I, PDPTI);
Check(PDPTE, Bitmap);
uint64_t *PDE = GetAddress(511, PML4I, PDPTI, PDI);
CheckPage(PDE, PhysAddress, (Bitmap | PG_BIG));
}Thanks for your help!
EDIT: Well i've somehow fixed it... I changed my Check-Methode and now it works without the const in the parameter list... The question is why?
This is the original Check-Methode:
Code: Select all
void KernelTable::Check(uint64_t *Entry, uint64_t Bitmap)
{
if ((*Entry == 0) || (((*Entry) & 0x1) == 0))
{
*Entry = (uint64_t)PMM::Alloc4K.Alloc() | Bitmap;
}
}Code: Select all
void KernelTable::Check(uint64_t *Entry, uint64_t Bitmap)
{
if ((*Entry == 0) || (((*Entry) & 0x1) == 0))
{
*Entry = (uint64_t)PMM::Alloc4K.Alloc() | Bitmap;
void *NextEntry = (uint64_t)Entry << 9;
memset(NextEntry, 0, 4096);
}
}