From: Paul E. Murphy <murp@ibm.com>
Date: Mon, 14 Feb 2022 23:15:05 +0000 (-0600)
Subject: syscall, runtime/internal/syscall: always return 0 in r2 on ppc64{,le} linux syscalls
X-Git-Tag: go1.19beta1~1175
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=78070ec3d44fdd8e60271abf31f056aeac919cc3;p=gostls13.git

syscall, runtime/internal/syscall: always return 0 in r2 on ppc64{,le} linux syscalls

Both endians perform syscalls similarly. Only CR0S0 and R3 hold
the resultant status of a syscall. A random value may be stored into
the second return value (r2) result in some cases. Always set it to
zero.

Fixes #51192

Change-Id: Ida6a5692578d2cdadf3099af28478b3bc364f623
Reviewed-on: https://go-review.googlesource.com/c/go/+/385796
Run-TryBot: Paul Murphy <murp@ibm.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
Trust: Paul Murphy <murp@ibm.com>
---

diff --git a/src/runtime/internal/syscall/asm_linux_ppc64x.s b/src/runtime/internal/syscall/asm_linux_ppc64x.s
index 8e8463810d..8cf8737df8 100644
--- a/src/runtime/internal/syscall/asm_linux_ppc64x.s
+++ b/src/runtime/internal/syscall/asm_linux_ppc64x.s
@@ -16,14 +16,13 @@ TEXT ·Syscall6(SB),NOSPLIT,$0-80
 	MOVD	a5+40(FP), R7
 	MOVD	a6+48(FP), R8
 	SYSCALL	R9
+	MOVD	R0, r2+64(FP) // r2 is not used. Always set to 0.
 	BVC	ok
 	MOVD	$-1, R4
 	MOVD	R4, r1+56(FP)
-	MOVD	R0, r2+64(FP)
 	MOVD	R3, errno+72(FP)
 	RET
 ok:
 	MOVD	R3, r1+56(FP)
-	MOVD	R4, r2+64(FP)
 	MOVD	R0, errno+72(FP)
 	RET
diff --git a/src/syscall/asm_linux_ppc64x.s b/src/syscall/asm_linux_ppc64x.s
index 044a479c00..1f5cb37ffe 100644
--- a/src/syscall/asm_linux_ppc64x.s
+++ b/src/syscall/asm_linux_ppc64x.s
@@ -30,7 +30,7 @@ TEXT ·Syscall(SB),NOSPLIT,$0-56
 	RET
 ok:
 	MOVD	R3, r1+32(FP)	// r1
-	MOVD	R4, r2+40(FP)	// r2
+	MOVD	R0, r2+40(FP)	// r2
 	MOVD	R0, err+48(FP)	// errno
 	BL	runtime·exitsyscall(SB)
 	RET
@@ -54,7 +54,7 @@ TEXT ·Syscall6(SB),NOSPLIT,$0-80
 	RET
 ok6:
 	MOVD	R3, r1+56(FP)	// r1
-	MOVD	R4, r2+64(FP)	// r2
+	MOVD	R0, r2+64(FP)	// r2
 	MOVD	R0, err+72(FP)	// errno
 	BL	runtime·exitsyscall(SB)
 	RET
@@ -76,7 +76,7 @@ TEXT ·RawSyscall(SB),NOSPLIT,$0-56
 	RET
 ok1:
 	MOVD	R3, r1+32(FP)	// r1
-	MOVD	R4, r2+40(FP)	// r2
+	MOVD	R0, r2+40(FP)	// r2
 	MOVD	R0, err+48(FP)	// errno
 	RET
 
@@ -97,7 +97,7 @@ TEXT ·RawSyscall6(SB),NOSPLIT,$0-80
 	RET
 ok2:
 	MOVD	R3, r1+56(FP)	// r1
-	MOVD	R4, r2+64(FP)	// r2
+	MOVD	R0, r2+64(FP)	// r2
 	MOVD	R0, err+72(FP)	// errno
 	RET
 
@@ -131,5 +131,5 @@ TEXT ·rawSyscallNoError(SB),NOSPLIT,$0-48
 	MOVD	trap+0(FP), R9	// syscall entry
 	SYSCALL R9
 	MOVD	R3, r1+32(FP)
-	MOVD	R4, r2+40(FP)
+	MOVD	R0, r2+40(FP)
 	RET