From 472b37fbf06e3588ff8ec9496aef44758ebf1bc3 Mon Sep 17 00:00:00 2001
From: Michael Smith <mikesmiffy128@gmail.com>
Date: Sat, 29 Jul 2023 13:24:03 +0100
Subject: Fix another x86 case and add regression tests

---
 compile         |  2 ++
 compile.bat     |  2 ++
 src/x86.c       |  2 +-
 test/x86.test.c | 41 +++++++++++++++++++++++++++++++++++++++++
 4 files changed, 46 insertions(+), 1 deletion(-)
 create mode 100644 test/x86.test.c

diff --git a/compile b/compile
index fc88c10..bf01493 100755
--- a/compile
+++ b/compile
@@ -102,5 +102,7 @@ $HOSTCC -O2 -g3 -include test/test.h -o .build/bitbuf.test test/bitbuf.test.c
 #.build/hook.test
 $HOSTCC -O2 -g3 -include test/test.h -o .build/kv.test test/kv.test.c
 .build/kv.test
+$HOSTCC -O2 -g3 -include test/test.h -o .build/x86.test test/x86.test.c
+.build/x86.test
 
 # vi: sw=4 tw=4 noet tw=80 cc=80
diff --git a/compile.bat b/compile.bat
index 67b35f4..75ac2fe 100644
--- a/compile.bat
+++ b/compile.bat
@@ -121,6 +121,8 @@ del .build\sst.lib
 .build\hook.test.exe || exit /b
 %HOSTCC% -O2 -g -include test/test.h -o .build/kv.test.exe test/kv.test.c || exit /b
 .build\kv.test.exe || exit /b
+%HOSTCC% -O2 -g -include test/test.h -o .build/x86.test.exe test/x86.test.c || exit /b
+.build\x86.test.exe || exit /b
 
 endlocal
 
diff --git a/src/x86.c b/src/x86.c
index dc3610e..7a5d00e 100644
--- a/src/x86.c
+++ b/src/x86.c
@@ -74,7 +74,7 @@ P:		X86_SEG_PREFIXES(CASES)
 		case X86_CRAZY8: operandlen = 1;
 		case X86_CRAZYW:
 			if ((insn[1] & 0x38) >= 0x10) operandlen = 0;
-			return pfxlen + 2 + operandlen + mrmsib(insn + 1, addrlen);
+			return pfxlen + 1 + operandlen + mrmsib(insn + 1, addrlen);
 		case X86_2BYTE: ++insn; goto b2;
 	}
 	return -1;
diff --git a/test/x86.test.c b/test/x86.test.c
new file mode 100644
index 0000000..ab0a679
--- /dev/null
+++ b/test/x86.test.c
@@ -0,0 +1,41 @@
+/* This file is dedicated to the public domain. */
+
+{.desc = "x86 opcode parsing"};
+
+#include "../src/x86.c"
+#include "../src/intdefs.h"
+
+TEST("The \"crazy\" instructions should be given correct lengths\n") {
+	const uchar test8[] = {
+		0xF6, 0x05, 0x12, 0x34, 0x56, 0x78, 0x12
+	};
+	const uchar test16[] = {
+		0x66, 0xF7, 0x05, 0x12, 0x34, 0x56, 0x78, 0x12, 0x34
+	};
+	const uchar test32[] = {
+		0xF7, 0x05, 0x12, 0x34, 0x56, 0x78, 0x12, 0x34, 0x56, 0x78
+	};
+	const uchar not8[] = {
+		0xF6, 0x15, 0x12, 0x34, 0x56, 0x78
+	};
+	const uchar not16[] = {
+		0x66, 0xF7, 0x15, 0x12, 0x34, 0x56, 0x78
+	};
+	const uchar not32[] = {
+		0xF7, 0x15, 0x12, 0x34, 0x56, 0x78
+	};
+	if (x86_len(test8) != 7) return false;
+	if (x86_len(test16) != 9) return false;
+	if (x86_len(test32) != 10) return false;
+	if (x86_len(not8) != 6) return false;
+	if (x86_len(not16) != 7) return false;
+	if (x86_len(not32) != 6) return false;
+	return true;
+}
+
+TEST("SIB bytes should be decoded correctly") {
+	const uchar fstp[] = {0xD9, 0x1C, 0x24}; // old buggy case, for regressions
+	return x86_len(fstp) == 3;
+}
+
+// vi: sw=4 ts=4 noet tw=80 cc=80
-- 
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