From 8ab5f5fb5b07d62aa9941a15cd7c9a71981c80dd Mon Sep 17 00:00:00 2001
From: Sven Steinbauer <sven@unlogic.co.uk>
Date: Fri, 23 Sep 2016 16:26:07 +0100
Subject: [PATCH] Add short jumps to nz (#5832)

---
 libr/asm/p/asm_x86_nz.c | 69 ++++++++++++++++++++++++++++-------------
 1 file changed, 47 insertions(+), 22 deletions(-)

diff --git a/libr/asm/p/asm_x86_nz.c b/libr/asm/p/asm_x86_nz.c
index 06a44d3a1e..6d883b2369 100644
--- a/libr/asm/p/asm_x86_nz.c
+++ b/libr/asm/p/asm_x86_nz.c
@@ -110,6 +110,7 @@ typedef struct Opcode_t {
 	char *mnemonic;
 	ut32 op[3];
 	size_t op_len;
+	bool is_short;
 	ut8 opcode[3];
 	Operand operands[2];
 } Opcode;
@@ -785,6 +786,9 @@ static int opjc(RAsm *a, ut8 *data, const Opcode op) {
 	int l = 0;
 	ut64 instr_offset = a->pc;
 	int immediate = op.operands[0].immediate * op.operands[0].sign;
+	if (op.is_short && (immediate > ST8_MAX || immediate < ST8_MIN)) {
+		return l;
+	}
 	if (!strcmp (op.mnemonic, "jmp")) {
 		if (op.operands[0].type & OT_GPREG) {
 			data[l++] = 0xff;
@@ -807,59 +811,70 @@ static int opjc(RAsm *a, ut8 *data, const Opcode op) {
 		}
 		return l;
 	}
-	immediate -= 6;
-	data[l++] = 0x0f;
+	if (op.is_short) {
+		immediate -= 2;
+	} else {
+		immediate -= 6;
+	}
+	if (!op.is_short) {data[l++] = 0x0f;}
 	if (!strcmp (op.mnemonic, "ja") ||
 		!strcmp (op.mnemonic, "jnbe")) {
 		data[l++] = 0x87;
 	} else if (!strcmp (op.mnemonic, "jae") ||
-			   !strcmp (op.mnemonic, "jnb") ||
-			   !strcmp (op.mnemonic, "jnc")) {
+				!strcmp (op.mnemonic, "jnb") ||
+				!strcmp (op.mnemonic, "jnc")) {
 		data[l++] = 0x83;
 	} else if (!strcmp (op.mnemonic, "jz") ||
-			   !strcmp (op.mnemonic, "je")) {
+				!strcmp (op.mnemonic, "je")) {
 		data[l++] = 0x84;
 	} else if (!strcmp (op.mnemonic, "jb") ||
-			   !strcmp (op.mnemonic, "jnae") ||
-			   !strcmp (op.mnemonic, "jc")) {
+				!strcmp (op.mnemonic, "jnae") ||
+				!strcmp (op.mnemonic, "jc")) {
 		data[l++] = 0x82;
 	} else if (!strcmp (op.mnemonic, "jbe") ||
-			   !strcmp (op.mnemonic, "jna")) {
+				!strcmp (op.mnemonic, "jna")) {
 		data[l++] = 0x86;
-	} else if (!strcmp (op.mnemonic, "jg")) {
+	} else if (!strcmp (op.mnemonic, "jg") ||
+				!strcmp (op.mnemonic, "jnle")) {
 		data[l++] = 0x8f;
 	} else if (!strcmp (op.mnemonic, "jge") ||
-			   !strcmp (op.mnemonic, "jnl")) {
+				!strcmp (op.mnemonic, "jnl")) {
 		data[l++] = 0x8d;
 	} else if (!strcmp (op.mnemonic, "jl") ||
-			   !strcmp (op.mnemonic, "jnge")) {
+				!strcmp (op.mnemonic, "jnge")) {
 		data[l++] = 0x8c;
 	} else if (!strcmp (op.mnemonic, "jle") ||
-			   !strcmp (op.mnemonic, "jng")) {
+				!strcmp (op.mnemonic, "jng")) {
 		data[l++] = 0x8e;
 	} else if (!strcmp (op.mnemonic, "jne") ||
-			   !strcmp (op.mnemonic, "jnz")) {
+				!strcmp (op.mnemonic, "jnz")) {
 		data[l++] = 0x85;
 	} else if (!strcmp (op.mnemonic, "jno")) {
 		data[l++] = 0x81;
-	} else if (!strcmp (op.mnemonic, "jnp")) {
+	} else if (!strcmp (op.mnemonic, "jnp") ||
+				!strcmp (op.mnemonic, "jpo")) {
 		data[l++] = 0x8b;
 	} else if (!strcmp (op.mnemonic, "jns")) {
 		data[l++] = 0x89;
 	} else if (!strcmp (op.mnemonic, "jo")) {
 		data[l++] = 0x80;
 	} else if (!strcmp (op.mnemonic, "jp") ||
-			!strcmp(op.mnemonic, "jpe")) {
+				!strcmp(op.mnemonic, "jpe")) {
 		data[l++] = 0x8a;
 	} else if (!strcmp (op.mnemonic, "js") ||
-			   !strcmp (op.mnemonic, "jz") ||
-			   !strcmp (op.mnemonic, "jpo")) {
+				!strcmp (op.mnemonic, "jz")) {
 		data[l++] = 0x88;
 	}
+	if (op.is_short) {
+		data[l-1] -= 0x10;
+	}
+
 	data[l++] = immediate;
-	data[l++] = immediate >> 8;
-	data[l++] = immediate >> 16;
-	data[l++] = immediate >> 24;
+	if (!op.is_short) {
+		data[l++] = immediate >> 8;
+		data[l++] = immediate >> 16;
+		data[l++] = immediate >> 24;
+	}
 	return l;
 }
 
@@ -1525,6 +1540,7 @@ LookupTable oplookup[] = {
 	{"jae", &opjc, 0},
 	{"jb", &opjc, 0},
 	{"jbe", &opjc, 0},
+	{"jc", &opjc, 0},
 	{"je", &opjc, 0},
 	{"jg", &opjc, 0},
 	{"jge", &opjc, 0},
@@ -1533,11 +1549,14 @@ LookupTable oplookup[] = {
 	{"jmp", &opjc, 0},
 	{"jna", &opjc, 0},
 	{"jnae", &opjc, 0},
+	{"jnb", &opjc, 0},
 	{"jnbe", &opjc, 0},
+	{"jnc", &opjc, 0},
 	{"jne", &opjc, 0},
 	{"jng", &opjc, 0},
 	{"jnge", &opjc, 0},
 	{"jnl", &opjc, 0},
+	{"jnle", &opjc, 0},
 	{"jno", &opjc, 0},
 	{"jnp", &opjc, 0},
 	{"jns", &opjc, 0},
@@ -1986,12 +2005,18 @@ static int parseOpcode(RAsm *a, const char *op, Opcode *out) {
 	out->operands[0].immediate = out->operands[1].immediate = 0;
 	out->operands[0].sign = out->operands[1].sign = 1;
 	out->operands[0].is_good_flag = out->operands[1].is_good_flag = true;
-
+	out->is_short = false;
 	if (args) {
 		args++;
 	} else {
 		return 1;
 	}
+
+	if (!strncasecmp (args, "short", 5)) {
+		out->is_short = true;
+		args += 5;
+	}
+
 	parseOperand (a, args, &(out->operands[0]));
 	args = strchr (args, ',');
 	if (args) {
@@ -2057,7 +2082,7 @@ static int assemble(RAsm *a, RAsmOp *ao, const char *str) {
 				}
 				break;
 			}
-		} 
+		}
 	}
 	//eprintf ("Error: Unknown instruction (%s)\n", instr.mnemonic);
 	return -1;