commit 6c1b26c55098eae66ce95ab7c3712ab6cbfff2b7
author Guoqi Chen <chenguoqi@loongson.cn> Fri Jun 10 20:06:09 2022 +0800
committer Austin Clements <austin@google.com> Tue Jun 14 16:21:38 2022 +0000
tree 3827241a34ef14417db095fe9856dad56fdf92f5
parent 9f5ed59c137dcb0852024edd2e71af63c2d67707

unix: always zero the higher bits of return value on linux/loong64 syscalls

All loong64 syscalls return values only via R4/A0, and R5/A1 may contain
unrelated content. Always zero the second return value.

Change-Id: Ic889f33158c4e4999bd94bd768d1094e95bc6421
Reviewed-on: https://go-review.googlesource.com/c/sys/+/411634
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: David Chase <drchase@google.com>

unix/asm_linux_loong64.s

diff --git a/unix/asm_linux_loong64.s b/unix/asm_linux_loong64.s
index 6abd48e..5653572 100644
--- a/unix/asm_linux_loong64.s
+++ b/unix/asm_linux_loong64.s
@@ -30,7 +30,7 @@
 	MOVV	trap+0(FP), R11	// syscall entry
 	SYSCALL
 	MOVV	R4, r1+32(FP)
-	MOVV	R5, r2+40(FP)
+	MOVV	R0, r2+40(FP)	// r2 is not used. Always set to 0
 	JAL	runtime·exitsyscall(SB)
 	RET
 
@@ -50,5 +50,5 @@
 	MOVV	trap+0(FP), R11	// syscall entry
 	SYSCALL
 	MOVV	R4, r1+32(FP)
-	MOVV	R5, r2+40(FP)
+	MOVV	R0, r2+40(FP)	// r2 is not used. Always set to 0
 	RET