compiler: add syscalls for 32-bit arm

Author: aykevl

.travis.yml

@@ -15,8 +15,11 @@ addons:
     - llvm-7-dev
     - clang-7
     - libclang-7-dev
+    - gcc-arm-linux-gnueabi
     - binutils-arm-none-eabi
+    - libc6-dev-armel-cross
     - qemu-system-arm
+    - qemu-user
     - gcc-avr
     - avr-libc
 

compiler/syscall.go

@@ -5,6 +5,7 @@ package compiler
 
 import (
 	"go/constant"
+	"strconv"
 
 	"golang.org/x/tools/go/ssa"
 	"tinygo.org/x/go-llvm"
@@ -14,6 +15,7 @@ import (
 // OS/arch.
 func (c *Compiler) emitSyscall(frame *Frame, call *ssa.CallCommon) (llvm.Value, error) {
 	num, _ := constant.Uint64Val(call.Args[0].(*ssa.Const).Value)
+	var syscallResult llvm.Value
 	switch {
 	case c.GOARCH == "amd64" && c.GOOS == "linux":
 		// Sources:
@@ -43,25 +45,60 @@ func (c *Compiler) emitSyscall(frame *Frame, call *ssa.CallCommon) (llvm.Value,
 		constraints += ",~{rcx},~{r11}"
 		fnType := llvm.FunctionType(c.uintptrType, argTypes, false)
 		target := llvm.InlineAsm(fnType, "syscall", constraints, true, false, llvm.InlineAsmDialectIntel)
-		syscallResult := c.builder.CreateCall(target, args, "")
-		// Return values: r1, r1, err uintptr
-		// Pseudocode:
-		//     var err uintptr
-		//     if syscallResult < 0 && syscallResult > -4096 {
-		//         err = -syscallResult
-		//     }
-		//     return syscallResult, 0, err
-		zero := llvm.ConstInt(c.uintptrType, 0, false)
-		inrange1 := c.builder.CreateICmp(llvm.IntSLT, syscallResult, llvm.ConstInt(c.uintptrType, 0, false), "")
-		inrange2 := c.builder.CreateICmp(llvm.IntSGT, syscallResult, llvm.ConstInt(c.uintptrType, 0xfffffffffffff000, true), "") // -4096
-		hasError := c.builder.CreateAnd(inrange1, inrange2, "")
-		errResult := c.builder.CreateSelect(hasError, c.builder.CreateNot(syscallResult, ""), zero, "syscallError")
-		retval := llvm.Undef(llvm.StructType([]llvm.Type{c.uintptrType, c.uintptrType, c.uintptrType}, false))
-		retval = c.builder.CreateInsertValue(retval, syscallResult, 0, "")
-		retval = c.builder.CreateInsertValue(retval, zero, 1, "")
-		retval = c.builder.CreateInsertValue(retval, errResult, 2, "")
-		return retval, nil
+		syscallResult = c.builder.CreateCall(target, args, "")
+	case c.GOARCH == "arm" && c.GOOS == "linux":
+		// Implement the EABI system call convention for Linux.
+		// Source: syscall(2) man page.
+		args := []llvm.Value{}
+		argTypes := []llvm.Type{}
+		// Constraints will look something like:
+		//   ={r0},0,{r1},{r2},{r7},~{r3}
+		constraints := "={r0}"
+		for i, arg := range call.Args[1:] {
+			constraints += "," + [...]string{
+				"0", // tie to output
+				"{r1}",
+				"{r2}",
+				"{r3}",
+				"{r4}",
+				"{r5}",
+				"{r6}",
+			}[i]
+			llvmValue, err := c.parseExpr(frame, arg)
+			if err != nil {
+				return llvm.Value{}, err
+			}
+			args = append(args, llvmValue)
+			argTypes = append(argTypes, llvmValue.Type())
+		}
+		args = append(args, llvm.ConstInt(c.uintptrType, num, false))
+		argTypes = append(argTypes, c.uintptrType)
+		constraints += ",{r7}" // syscall number
+		for i := len(call.Args) - 1; i < 4; i++ {
+			// r0-r3 get clobbered after the syscall returns
+			constraints += ",~{r" + strconv.Itoa(i) + "}"
+		}
+		fnType := llvm.FunctionType(c.uintptrType, argTypes, false)
+		target := llvm.InlineAsm(fnType, "svc #0", constraints, true, false, 0)
+		syscallResult = c.builder.CreateCall(target, args, "")
 	default:
 		return llvm.Value{}, c.makeError(call.Pos(), "unknown GOOS/GOARCH for syscall: "+c.GOOS+"/"+c.GOARCH)
 	}
+	// Return values: r0, r1, err uintptr
+	// Pseudocode:
+	//     var err uintptr
+	//     if syscallResult < 0 && syscallResult > -4096 {
+	//         err = -syscallResult
+	//     }
+	//     return syscallResult, 0, err
+	zero := llvm.ConstInt(c.uintptrType, 0, false)
+	inrange1 := c.builder.CreateICmp(llvm.IntSLT, syscallResult, llvm.ConstInt(c.uintptrType, 0, false), "")
+	inrange2 := c.builder.CreateICmp(llvm.IntSGT, syscallResult, llvm.ConstInt(c.uintptrType, 0xfffffffffffff000, true), "") // -4096
+	hasError := c.builder.CreateAnd(inrange1, inrange2, "")
+	errResult := c.builder.CreateSelect(hasError, c.builder.CreateNot(syscallResult, ""), zero, "syscallError")
+	retval := llvm.Undef(llvm.StructType([]llvm.Type{c.uintptrType, c.uintptrType, c.uintptrType}, false))
+	retval = c.builder.CreateInsertValue(retval, syscallResult, 0, "")
+	retval = c.builder.CreateInsertValue(retval, zero, 1, "")
+	retval = c.builder.CreateInsertValue(retval, errResult, 2, "")
+	return retval, nil
 }

main_test.go

@@ -42,7 +42,7 @@ func TestCompiler(t *testing.T) {
 	}
 	defer os.RemoveAll(tmpdir)
 
-	t.Log("running tests on the host...")
+	t.Log("running tests on host...")
 	for _, path := range matches {
 		t.Run(path, func(t *testing.T) {
 			runTest(path, tmpdir, "", t)
@@ -53,7 +53,17 @@ func TestCompiler(t *testing.T) {
 		return
 	}
 
-	t.Log("running tests on the qemu target...")
+	t.Log("running tests for linux/arm...")
+	for _, path := range matches {
+		if path == "testdata/cgo/" {
+			continue // TODO: improve CGo
+		}
+		t.Run(path, func(t *testing.T) {
+			runTest(path, tmpdir, "arm--linux-gnueabi", t)
+		})
+	}
+
+	t.Log("running tests for emulated cortex-m3...")
 	for _, path := range matches {
 		t.Run(path, func(t *testing.T) {
 			runTest(path, tmpdir, "qemu", t)

target.go

@@ -218,10 +218,11 @@ func defaultTarget(goos, goarch, triple string) (*TargetSpec, error) {
 	}
 	if goarch != runtime.GOARCH {
 		// Some educated guesses as to how to invoke helper programs.
-		if goarch == "arm" {
+		if goarch == "arm" && goos == "linux" {
 			spec.Linker = "arm-linux-gnueabi-gcc"
 			spec.Objcopy = "arm-linux-gnueabi-objcopy"
 			spec.GDB = "arm-linux-gnueabi-gdb"
+			spec.Emulator = []string{"qemu-arm", "-L", "/usr/arm-linux-gnueabi"}
 		}
 		if goarch == "arm64" {
 			spec.Linker = "aarch64-linux-gnu-gcc"