[release-branch.go1.14-cmd] unix: provide linux/riscv64 assembly for syscalls
While the linux/riscv64 port is not yet upstream, most of the syscalls package
already has linux/riscv64 support and this will make testing and development
easier.
Updates golang/go#27532
Change-Id: I6e505be55fdbb2942fb6e4f34c040e7b82809630
Reviewed-on: https://go-review.googlesource.com/c/sys/+/177799
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
(cherry picked from commit 4c3a928424d249a1013e789cf5e458d480bcba16)
Reviewed-on: https://go-review.googlesource.com/c/sys/+/217300
Run-TryBot: Filippo Valsorda <filippo@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
diff --git a/unix/asm_linux_riscv64.s b/unix/asm_linux_riscv64.s
new file mode 100644
index 0000000..6db717d
--- /dev/null
+++ b/unix/asm_linux_riscv64.s
@@ -0,0 +1,54 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build riscv64,!gccgo
+
+#include "textflag.h"
+
+//
+// System calls for linux/riscv64.
+//
+// Where available, just jump to package syscall's implementation of
+// these functions.
+
+TEXT ·Syscall(SB),NOSPLIT,$0-56
+ JMP syscall·Syscall(SB)
+
+TEXT ·Syscall6(SB),NOSPLIT,$0-80
+ JMP syscall·Syscall6(SB)
+
+TEXT ·SyscallNoError(SB),NOSPLIT,$0-48
+ CALL runtime·entersyscall(SB)
+ MOV a1+8(FP), A0
+ MOV a2+16(FP), A1
+ MOV a3+24(FP), A2
+ MOV $0, A3
+ MOV $0, A4
+ MOV $0, A5
+ MOV $0, A6
+ MOV trap+0(FP), A7 // syscall entry
+ ECALL
+ MOV A0, r1+32(FP) // r1
+ MOV A1, r2+40(FP) // r2
+ CALL runtime·exitsyscall(SB)
+ RET
+
+TEXT ·RawSyscall(SB),NOSPLIT,$0-56
+ JMP syscall·RawSyscall(SB)
+
+TEXT ·RawSyscall6(SB),NOSPLIT,$0-80
+ JMP syscall·RawSyscall6(SB)
+
+TEXT ·RawSyscallNoError(SB),NOSPLIT,$0-48
+ MOV a1+8(FP), A0
+ MOV a2+16(FP), A1
+ MOV a3+24(FP), A2
+ MOV ZERO, A3
+ MOV ZERO, A4
+ MOV ZERO, A5
+ MOV trap+0(FP), A7 // syscall entry
+ ECALL
+ MOV A0, r1+32(FP)
+ MOV A1, r2+40(FP)
+ RET
