From bfdbf6003a73b9f44d037441d56659cef6717398 Mon Sep 17 00:00:00 2001
From: Guoqi Chen <chenguoqi@loongson.cn>
Date: Fri, 5 May 2023 03:28:42 +0800
Subject: [PATCH] loong64: implement buildJmpDirective function

Signed-off-by: Guoqi Chen <chenguoqi@loongson.cn>
---
 README.md      |  1 +
 jmp_loong64.go | 70 ++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 71 insertions(+)
 create mode 100644 jmp_loong64.go

diff --git a/README.md b/README.md
index b3321ba..a69177e 100644
--- a/README.md
+++ b/README.md
@@ -25,6 +25,7 @@ gomonkey is a library to make monkey patching in unit tests easy, and the core i
   - amd64
   - arm64
   - 386
+  - loong64
 
 - OS
   - Linux
diff --git a/jmp_loong64.go b/jmp_loong64.go
new file mode 100644
index 0000000..1b06254
--- /dev/null
+++ b/jmp_loong64.go
@@ -0,0 +1,70 @@
+package gomonkey
+
+import "unsafe"
+
+const (
+	REG_R0  uint32 = 0
+	REG_R29        = 29
+	REG_R30        = 30
+)
+
+const (
+	OP_ORI    uint32 = 0x00E << 22
+	OP_LU12IW        = 0x00A << 25
+	OP_LU32ID        = 0x00B << 25
+	OP_LU52ID        = 0x00C << 22
+	OP_LDD           = 0x0A3 << 22
+	OP_JIRL          = 0x013 << 26
+)
+
+func buildJmpDirective(double uintptr) []byte {
+	res := make([]byte, 0, 24)
+
+	bit11_0 := (double >> 0) & 0xFFF
+	bit31_12 := (double >> 12) & 0xFFFFF
+	bit51_32 := (double >> 32) & 0xFFFFF
+	bit63_52 := (double >> 52) & 0xFFF
+
+	// lu12i.w r29, bit31_12
+	// ori     r29, r29, bit11_0
+	// lu32i.d r29, bit51_32
+	// lu52i.d r29, bit63_52
+	// ld.d,   r30, r29, 0
+	// jirl    r0,  r30, 0
+	res = append(res, wireup_opc(OP_LU12IW, REG_R29, 0, bit31_12)...)
+	res = append(res, wireup_opc(OP_ORI, REG_R29, REG_R29, bit11_0)...)
+	res = append(res, wireup_opc(OP_LU32ID, REG_R29, 0, bit51_32)...)
+	res = append(res, wireup_opc(OP_LU52ID, REG_R29, REG_R29, bit63_52)...)
+	res = append(res, wireup_opc(OP_LDD, REG_R30, REG_R29, 0)...)
+	res = append(res, wireup_opc(OP_JIRL, REG_R0, REG_R30, 0)...)
+
+	return res
+}
+
+func wireup_opc(opc uint32, rd, rj uint32, val uintptr) []byte {
+	var m uint32 = 0
+
+	switch opc {
+	case OP_ORI, OP_LU52ID, OP_LDD:
+		m |= opc
+		m |= (rd & 0x1F) << 0            // rd
+		m |= (rj & 0x1F) << 5            // rj
+		m |= (uint32(val) & 0xFFF) << 10 // si12
+
+	case OP_LU12IW, OP_LU32ID:
+		m |= opc
+		m |= (rd & 0x1F) << 0             // rd
+		m |= (uint32(val) & 0xFFFFF) << 5 // si20
+
+	case OP_JIRL:
+		m |= opc
+		m |= (rd & 0x1F) << 0             // rd
+		m |= (rj & 0x1F) << 5             // rj
+		m |= (uint32(val) & 0xFFFF) << 10 // si16
+	}
+
+	res := make([]byte, 4)
+	*(*uint32)(unsafe.Pointer(&res[0])) = m
+
+	return res
+}