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PatchEngine/GeckoCode: Heuristic stack checks

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Try to make sure the stack is sane before calling into the
codehandler. This is intended to reduce the possibility of random
memory corruption.
This commit is contained in:
EmptyChaos
2016-09-30 15:29:35 +00:00
parent 31cf8432bf
commit b3547870ee
5 changed files with 78 additions and 49 deletions
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29
Source/Core/Core/PatchEngine.cpp
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@ -20,6 +20,7 @@
#include <string>
#include <vector>
#include "Common/Assert.h"
#include "Common/CommonPaths.h"
#include "Common/FileUtil.h"
#include "Common/IniFile.h"
@ -203,6 +204,32 @@ static void ApplyPatches(const std::vector<Patch>& patches)
}
}
// Requires MSR.DR, MSR.IR
// There's no perfect way to do this, it's just a heuristic.
// We require at least 2 stack frames, if the stack is shallower than that then it won't work.
static bool IsStackSane()
{
_dbg_assert_(ACTIONREPLAY, UReg_MSR(MSR).DR && UReg_MSR(MSR).IR);
// Check the stack pointer
u32 SP = GPR(1);
if (!PowerPC::HostIsRAMAddress(SP))
return false;
// Read the frame pointer from the stack (find 2nd frame from top), assert that it makes sense
u32 next_SP = PowerPC::HostRead_U32(SP);
if (next_SP <= SP || !PowerPC::HostIsRAMAddress(next_SP) ||
!PowerPC::HostIsRAMAddress(next_SP + 4))
return false;
// Check the link register makes sense (that it points to a valid IBAT address)
auto insn = PowerPC::TryReadInstruction(PowerPC::HostRead_U32(next_SP + 4));
if (!insn.valid || !insn.hex)
return false;
return true;
}
bool ApplyFramePatches()
{
// Because we're using the VI Interrupt to time this instead of patching the game with a
@ -210,7 +237,7 @@ bool ApplyFramePatches()
// We deal with this by returning false so that SystemTimers will reschedule us in a few cycles
// where we can try again after the CPU hopefully returns back to the normal instruction flow.
UReg_MSR msr = MSR;
if (!msr.DR || !msr.IR)
if (!msr.DR || !msr.IR || !IsStackSane())
{
INFO_LOG(
ACTIONREPLAY,