Core/MMU: Add HostTryRead*() functions.

2 files changed, 218 insertions, 11 deletions

diff --git a/Source/Core/Core/PowerPC/MMU.cpp b/Source/Core/Core/PowerPC/MMU.cpp
index 30dbb8105e..ac0cea0cf3 100644
--- a/Source/Core/Core/PowerPC/MMU.cpp
+++ b/Source/Core/Core/PowerPC/MMU.cpp
@@ -3,6 +3,7 @@
 
 #include "Core/PowerPC/MMU.h"
 
+#include <cassert>
 #include <cstddef>
 #include <cstring>
 #include <string>
@@ -427,6 +428,36 @@ u32 HostRead_Instruction(const u32 address)
   return ReadFromHardware<XCheckTLBFlag::OpcodeNoException, u32>(address);
 }
 
+TryReadResult<u32> HostTryReadInstruction(const u32 address, RequestedAddressSpace space)
+{
+  if (!HostIsInstructionRAMAddress(address, space))
+    return TryReadResult<u32>();
+
+  switch (space)
+  {
+  case RequestedAddressSpace::Effective:
+  {
+    const u32 value = ReadFromHardware<XCheckTLBFlag::OpcodeNoException, u32>(address);
+    return TryReadResult<u32>(!!MSR.DR, value);
+  }
+  case RequestedAddressSpace::Physical:
+  {
+    const u32 value = ReadFromHardware<XCheckTLBFlag::OpcodeNoException, u32, true>(address);
+    return TryReadResult<u32>(false, value);
+  }
+  case RequestedAddressSpace::Virtual:
+  {
+    if (!MSR.DR)
+      return TryReadResult<u32>();
+    const u32 value = ReadFromHardware<XCheckTLBFlag::OpcodeNoException, u32>(address);
+    return TryReadResult<u32>(true, value);
+  }
+  }
+
+  assert(0);
+  return TryReadResult<u32>();
+}
+
 static void Memcheck(u32 address, u32 var, bool write, size_t size)
 {
   if (PowerPC::memchecks.HasAny())
@@ -499,6 +530,73 @@ float Read_F32(const u32 address)
   return Common::BitCast<float>(integral);
 }
 
+template <typename T>
+static TryReadResult<T> HostTryReadUX(const u32 address, RequestedAddressSpace space)
+{
+  if (!HostIsRAMAddress(address, space))
+    return TryReadResult<T>();
+
+  switch (space)
+  {
+  case RequestedAddressSpace::Effective:
+  {
+    T value = ReadFromHardware<XCheckTLBFlag::NoException, T>(address);
+    return TryReadResult<T>(!!MSR.DR, std::move(value));
+  }
+  case RequestedAddressSpace::Physical:
+  {
+    T value = ReadFromHardware<XCheckTLBFlag::NoException, T, true>(address);
+    return TryReadResult<T>(false, std::move(value));
+  }
+  case RequestedAddressSpace::Virtual:
+  {
+    if (!MSR.DR)
+      return TryReadResult<T>();
+    T value = ReadFromHardware<XCheckTLBFlag::NoException, T>(address);
+    return TryReadResult<T>(true, std::move(value));
+  }
+  }
+
+  assert(0);
+  return TryReadResult<T>();
+}
+
+TryReadResult<u8> HostTryReadU8(u32 address, RequestedAddressSpace space)
+{
+  return HostTryReadUX<u8>(address, space);
+}
+
+TryReadResult<u16> HostTryReadU16(u32 address, RequestedAddressSpace space)
+{
+  return HostTryReadUX<u16>(address, space);
+}
+
+TryReadResult<u32> HostTryReadU32(u32 address, RequestedAddressSpace space)
+{
+  return HostTryReadUX<u32>(address, space);
+}
+
+TryReadResult<u64> HostTryReadU64(u32 address, RequestedAddressSpace space)
+{
+  return HostTryReadUX<u64>(address, space);
+}
+
+TryReadResult<float> HostTryReadF32(u32 address, RequestedAddressSpace space)
+{
+  const auto result = HostTryReadUX<u32>(address, space);
+  if (!result)
+    return TryReadResult<float>();
+  return TryReadResult<float>(result.translated, Common::BitCast<float>(result.value));
+}
+
+TryReadResult<double> HostTryReadF64(u32 address, RequestedAddressSpace space)
+{
+  const auto result = HostTryReadUX<u64>(address, space);
+  if (!result)
+    return TryReadResult<double>();
+  return TryReadResult<double>(result.translated, Common::BitCast<double>(result.value));
+}
+
 u32 Read_U8_ZX(const u32 address)
 {
   return Read_U8(address);
@@ -639,6 +737,27 @@ std::string HostGetString(u32 address, size_t size)
   return s;
 }
 
+TryReadResult<std::string> HostTryReadString(u32 address, size_t size, RequestedAddressSpace space)
+{
+  auto c = HostTryReadU8(address, space);
+  if (!c)
+    return TryReadResult<std::string>();
+  if (c.value == 0)
+    return TryReadResult<std::string>(c.translated, "");
+
+  std::string s;
+  s += static_cast<char>(c.value);
+  while (size == 0 || s.length() < size)
+  {
+    ++address;
+    const auto res = HostTryReadU8(address, space);
+    if (!res || res.value == 0)
+      break;
+    s += static_cast<char>(res.value);
+  }
+  return TryReadResult<std::string>(c.translated, std::move(s));
+}
+
 bool IsOptimizableRAMAddress(const u32 address)
 {
   if (PowerPC::memchecks.HasAny())
@@ -688,15 +807,44 @@ static bool IsRAMAddress(u32 address, bool translate)
   return false;
 }
 
-bool HostIsRAMAddress(u32 address)
+bool HostIsRAMAddress(u32 address, RequestedAddressSpace space)
 {
-  return IsRAMAddress<XCheckTLBFlag::NoException>(address, MSR.DR);
+  switch (space)
+  {
+  case RequestedAddressSpace::Effective:
+    return IsRAMAddress<XCheckTLBFlag::NoException>(address, MSR.DR);
+  case RequestedAddressSpace::Physical:
+    return IsRAMAddress<XCheckTLBFlag::NoException>(address, false);
+  case RequestedAddressSpace::Virtual:
+    if (!MSR.DR)
+      return false;
+    return IsRAMAddress<XCheckTLBFlag::NoException>(address, true);
+  }
+
+  assert(0);
+  return false;
 }
 
-bool HostIsInstructionRAMAddress(u32 address)
+bool HostIsInstructionRAMAddress(u32 address, RequestedAddressSpace space)
 {
   // Instructions are always 32bit aligned.
-  return !(address & 3) && IsRAMAddress<XCheckTLBFlag::OpcodeNoException>(address, MSR.IR);
+  if (!(address & 3))
+    return false;
+
+  switch (space)
+  {
+  case RequestedAddressSpace::Effective:
+    return IsRAMAddress<XCheckTLBFlag::OpcodeNoException>(address, MSR.IR);
+  case RequestedAddressSpace::Physical:
+    return IsRAMAddress<XCheckTLBFlag::OpcodeNoException>(address, false);
+  case RequestedAddressSpace::Virtual:
+    if (!MSR.IR)
+      return false;
+    return IsRAMAddress<XCheckTLBFlag::OpcodeNoException>(address, true);
+  }
+
+  assert(0);
+  return false;
 }
 
 void DMA_LCToMemory(const u32 mem_address, const u32 cache_address, const u32 num_blocks)
diff --git a/Source/Core/Core/PowerPC/MMU.h b/Source/Core/Core/PowerPC/MMU.h
index 82c4f8e7eb..591aec44fd 100644
--- a/Source/Core/Core/PowerPC/MMU.h
+++ b/Source/Core/Core/PowerPC/MMU.h
@@ -14,7 +14,19 @@ namespace PowerPC
 {
 // Routines for debugger UI, cheats, etc. to access emulated memory from the
 // perspective of the CPU.  Not for use by core emulation routines.
-// Use "Host_" prefix.
+// Use "Host" prefix.
+
+enum class RequestedAddressSpace
+{
+  Effective,  // whatever the current MMU state is
+  Physical,   // as if the MMU was turned off
+  Virtual,    // specifically want MMU turned on, fails if off
+};
+
+// Reads a value from emulated memory using the currently active MMU settings.
+// If the read fails (eg. address does not correspond to a mapped address in the current address
+// space), a PanicAlert will be shown to the user and zero (or an empty string for the string case)
+// will be returned.
 u8 HostRead_U8(u32 address);
 u16 HostRead_U16(u32 address);
 u32 HostRead_U32(u32 address);
@@ -22,6 +34,54 @@ u64 HostRead_U64(u32 address);
 float HostRead_F32(u32 address);
 double HostRead_F64(u32 address);
 u32 HostRead_Instruction(u32 address);
+std::string HostGetString(u32 address, size_t size = 0);
+
+template <typename T>
+struct TryReadResult
+{
+  // whether the read succeeded; if false, the other fields should not be touched
+  bool success;
+
+  // whether the address had to be translated (given address was treated as virtual) or not (given
+  // address was treated as physical)
+  bool translated;
+
+  // the actual value that was read
+  T value;
+
+  TryReadResult() : success(false) {}
+  TryReadResult(bool translated_, T&& value_)
+      : success(true), translated(translated_), value(std::move(value_))
+  {
+  }
+  TryReadResult(bool translated_, const T& value_)
+      : success(true), translated(translated_), value(value_)
+  {
+  }
+  explicit operator bool() const { return success; }
+};
+
+// Try to read a value from emulated memory at the given address in the given memory space.
+// If the read succeeds, the returned TryReadResult contains the read value and information on
+// whether the given address had to be translated or not. Unlike the HostRead functions, this does
+// not raise a user-visible alert on failure.
+TryReadResult<u8> HostTryReadU8(u32 address,
+                                RequestedAddressSpace space = RequestedAddressSpace::Effective);
+TryReadResult<u16> HostTryReadU16(u32 address,
+                                  RequestedAddressSpace space = RequestedAddressSpace::Effective);
+TryReadResult<u32> HostTryReadU32(u32 address,
+                                  RequestedAddressSpace space = RequestedAddressSpace::Effective);
+TryReadResult<u64> HostTryReadU64(u32 address,
+                                  RequestedAddressSpace space = RequestedAddressSpace::Effective);
+TryReadResult<float> HostTryReadF32(u32 address,
+                                    RequestedAddressSpace space = RequestedAddressSpace::Effective);
+TryReadResult<double>
+HostTryReadF64(u32 address, RequestedAddressSpace space = RequestedAddressSpace::Effective);
+TryReadResult<u32>
+HostTryReadInstruction(u32 address, RequestedAddressSpace space = RequestedAddressSpace::Effective);
+TryReadResult<std::string>
+HostTryReadString(u32 address, size_t size = 0,
+                  RequestedAddressSpace space = RequestedAddressSpace::Effective);
 
 void HostWrite_U8(u8 var, u32 address);
 void HostWrite_U16(u16 var, u32 address);
@@ -30,14 +90,13 @@ void HostWrite_U64(u64 var, u32 address);
 void HostWrite_F32(float var, u32 address);
 void HostWrite_F64(double var, u32 address);
 
-std::string HostGetString(u32 address, size_t size = 0);
-
-// Returns whether a read or write to the given address will resolve to a RAM
-// access given the current CPU state.
-bool HostIsRAMAddress(u32 address);
+// Returns whether a read or write to the given address will resolve to a RAM access in the given
+// address space.
+bool HostIsRAMAddress(u32 address, RequestedAddressSpace space = RequestedAddressSpace::Effective);
 
 // Same as HostIsRAMAddress, but uses IBAT instead of DBAT.
-bool HostIsInstructionRAMAddress(u32 address);
+bool HostIsInstructionRAMAddress(u32 address,
+                                 RequestedAddressSpace space = RequestedAddressSpace::Effective);
 
 // Routines for the CPU core to access memory.