From 059c65a27af538cba40aa43d2eeb3a544661a9b8 Mon Sep 17 00:00:00 2001
From: Lioncash <mathew1800@gmail.com>
Date: Sun, 28 Dec 2014 06:07:24 -0500
Subject: [PATCH] armemu: Fix underflows in USAD8/USADA8
Initially reported by xdec.
---
src/core/arm/interpreter/armemu.cpp | 8 ++++----
src/core/arm/interpreter/armsupp.cpp | 9 +++++++++
src/core/arm/skyeye_common/armemu.h | 1 +
3 files changed, 14 insertions(+), 4 deletions(-)
diff --git a/src/core/arm/interpreter/armemu.cpp b/src/core/arm/interpreter/armemu.cpp
index 9b680c1e2a..404012b2a8 100644
--- a/src/core/arm/interpreter/armemu.cpp
+++ b/src/core/arm/interpreter/armemu.cpp
@@ -6643,10 +6643,10 @@ L_stm_s_takeabort:
const u32 rm_val = state->Reg[rm_idx];
const u32 rn_val = state->Reg[rn_idx];
- const u8 diff1 = (u8)std::labs((rn_val & 0xFF) - (rm_val & 0xFF));
- const u8 diff2 = (u8)std::labs(((rn_val >> 8) & 0xFF) - ((rm_val >> 8) & 0xFF));
- const u8 diff3 = (u8)std::labs(((rn_val >> 16) & 0xFF) - ((rm_val >> 16) & 0xFF));
- const u8 diff4 = (u8)std::labs(((rn_val >> 24) & 0xFF) - ((rm_val >> 24) & 0xFF));
+ const u8 diff1 = ARMul_UnsignedAbsoluteDifference(rn_val & 0xFF, rm_val & 0xFF);
+ const u8 diff2 = ARMul_UnsignedAbsoluteDifference((rn_val >> 8) & 0xFF, (rm_val >> 8) & 0xFF);
+ const u8 diff3 = ARMul_UnsignedAbsoluteDifference((rn_val >> 16) & 0xFF, (rm_val >> 16) & 0xFF);
+ const u8 diff4 = ARMul_UnsignedAbsoluteDifference((rn_val >> 24) & 0xFF, (rm_val >> 24) & 0xFF);
u32 finalDif = (diff1 + diff2 + diff3 + diff4);
diff --git a/src/core/arm/interpreter/armsupp.cpp b/src/core/arm/interpreter/armsupp.cpp
index 6774f8a74a..61639d1560 100644
--- a/src/core/arm/interpreter/armsupp.cpp
+++ b/src/core/arm/interpreter/armsupp.cpp
@@ -392,6 +392,15 @@ ARMul_NthReg (ARMword instr, unsigned number)
return (bit - 1);
}
+/* Unsigned sum of absolute difference */
+u8 ARMul_UnsignedAbsoluteDifference(u8 left, u8 right)
+{
+ if (left > right)
+ return left - right;
+
+ return right - left;
+}
+
/* Assigns the N and Z flags depending on the value of result. */
void
diff --git a/src/core/arm/skyeye_common/armemu.h b/src/core/arm/skyeye_common/armemu.h
index 3ea14b5a31..04c5d2e1ae 100644
--- a/src/core/arm/skyeye_common/armemu.h
+++ b/src/core/arm/skyeye_common/armemu.h
@@ -600,6 +600,7 @@ extern ARMword ARMul_SwitchMode (ARMul_State *, ARMword, ARMword);
extern ARMword ARMul_Align (ARMul_State *, ARMword, ARMword);
extern ARMword ARMul_SwitchMode (ARMul_State *, ARMword, ARMword);
extern void ARMul_MSRCpsr (ARMul_State *, ARMword, ARMword);
+extern u8 ARMul_UnsignedAbsoluteDifference(u8, u8);
extern void ARMul_SubOverflow (ARMul_State *, ARMword, ARMword, ARMword);
extern void ARMul_AddOverflow (ARMul_State *, ARMword, ARMword, ARMword);
extern void ARMul_AddOverflowQ(ARMul_State*, ARMword, ARMword);