syscall: define RawSyscall in terms of RawSyscall6 on linux

For #51087

Change-Id: I63e07638507328efe33dbf7dd5f8a8b78890e037
Reviewed-on: https://go-review.googlesource.com/c/go/+/388476
Run-TryBot: Michael Pratt <[email protected]>
Reviewed-by: Cherry Mui <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>

Author: prattmic

src/syscall/asm_linux_386.s

@@ -65,28 +65,6 @@ ok6:
 	CALL	runtime·exitsyscall(SB)
 	RET
 
-// func RawSyscall(trap uintptr, a1, a2, a3 uintptr) (r1, r2, err uintptr);
-TEXT ·RawSyscall(SB),NOSPLIT,$0-28
-	MOVL	trap+0(FP), AX	// syscall entry
-	MOVL	a1+4(FP), BX
-	MOVL	a2+8(FP), CX
-	MOVL	a3+12(FP), DX
-	MOVL	$0, SI
-	MOVL	$0, DI
-	INVOKE_SYSCALL
-	CMPL	AX, $0xfffff001
-	JLS	ok1
-	MOVL	$-1, r1+16(FP)
-	MOVL	$0, r2+20(FP)
-	NEGL	AX
-	MOVL	AX, err+24(FP)
-	RET
-ok1:
-	MOVL	AX, r1+16(FP)
-	MOVL	DX, r2+20(FP)
-	MOVL	$0, err+24(FP)
-	RET
-
 // func rawVforkSyscall(trap, a1 uintptr) (r1, err uintptr)
 TEXT ·rawVforkSyscall(SB),NOSPLIT|NOFRAME,$0-16
 	MOVL	trap+0(FP), AX	// syscall entry

src/syscall/asm_linux_amd64.s

@@ -64,26 +64,6 @@ ok6:
 	CALL	runtime·exitsyscall<ABIInternal>(SB)
 	RET
 
-// func RawSyscall(trap, a1, a2, a3 uintptr) (r1, r2, err uintptr)
-TEXT ·RawSyscall(SB),NOSPLIT,$0-56
-	MOVQ	a1+8(FP), DI
-	MOVQ	a2+16(FP), SI
-	MOVQ	a3+24(FP), DX
-	MOVQ	trap+0(FP), AX	// syscall entry
-	SYSCALL
-	CMPQ	AX, $0xfffffffffffff001
-	JLS	ok1
-	MOVQ	$-1, r1+32(FP)
-	MOVQ	$0, r2+40(FP)
-	NEGQ	AX
-	MOVQ	AX, err+48(FP)
-	RET
-ok1:
-	MOVQ	AX, r1+32(FP)
-	MOVQ	DX, r2+40(FP)
-	MOVQ	$0, err+48(FP)
-	RET
-
 // func rawVforkSyscall(trap, a1 uintptr) (r1, err uintptr)
 TEXT ·rawVforkSyscall(SB),NOSPLIT|NOFRAME,$0-32
 	MOVQ	a1+8(FP), DI

src/syscall/asm_linux_arm.s

@@ -102,30 +102,6 @@ okseek:
 	BL	runtime·exitsyscall(SB)
 	RET
 
-// func RawSyscall(trap uintptr, a1, a2, a3 uintptr) (r1, r2, err uintptr);
-TEXT ·RawSyscall(SB),NOSPLIT,$0-28
-	MOVW	trap+0(FP), R7	// syscall entry
-	MOVW	a1+4(FP), R0
-	MOVW	a2+8(FP), R1
-	MOVW	a3+12(FP), R2
-	SWI	$0
-	MOVW	$0xfffff001, R1
-	CMP	R1, R0
-	BLS	ok1
-	MOVW	$-1, R1
-	MOVW	R1, r1+16(FP)
-	MOVW	$0, R2
-	MOVW	R2, r2+20(FP)
-	RSB	$0, R0, R0
-	MOVW	R0, err+24(FP)
-	RET
-ok1:
-	MOVW	R0, r1+16(FP)
-	MOVW	$0, R0
-	MOVW	R0, r2+20(FP)
-	MOVW	R0, err+24(FP)
-	RET
-
 // func rawVforkSyscall(trap, a1 uintptr) (r1, err uintptr)
 TEXT ·rawVforkSyscall(SB),NOSPLIT|NOFRAME,$0-16
 	MOVW	trap+0(FP), R7	// syscall entry

src/syscall/asm_linux_arm64.s

@@ -57,29 +57,6 @@ ok:
 	BL	runtime·exitsyscall<ABIInternal>(SB)
 	RET
 
-TEXT ·RawSyscall(SB),NOSPLIT,$0-56
-	MOVD	a1+8(FP), R0
-	MOVD	a2+16(FP), R1
-	MOVD	a3+24(FP), R2
-	MOVD	$0, R3
-	MOVD	$0, R4
-	MOVD	$0, R5
-	MOVD	trap+0(FP), R8	// syscall entry
-	SVC
-	CMN	$4095, R0
-	BCC	ok
-	MOVD	$-1, R4
-	MOVD	R4, r1+32(FP)	// r1
-	MOVD	ZR, r2+40(FP)	// r2
-	NEG	R0, R0
-	MOVD	R0, err+48(FP)	// errno
-	RET
-ok:
-	MOVD	R0, r1+32(FP)	// r1
-	MOVD	R1, r2+40(FP)	// r2
-	MOVD	ZR, err+48(FP)	// errno
-	RET
-
 // func rawVforkSyscall(trap, a1 uintptr) (r1, err uintptr)
 TEXT ·rawVforkSyscall(SB),NOSPLIT,$0-32
 	MOVD	a1+8(FP), R0

src/syscall/asm_linux_mips64x.s

@@ -59,27 +59,6 @@ ok6:
 	JAL	runtime·exitsyscall(SB)
 	RET
 
-TEXT ·RawSyscall(SB),NOSPLIT,$0-56
-	MOVV	a1+8(FP), R4
-	MOVV	a2+16(FP), R5
-	MOVV	a3+24(FP), R6
-	MOVV	R0, R7
-	MOVV	R0, R8
-	MOVV	R0, R9
-	MOVV	trap+0(FP), R2	// syscall entry
-	SYSCALL
-	BEQ	R7, ok1
-	MOVV	$-1, R1
-	MOVV	R1, r1+32(FP)	// r1
-	MOVV	R0, r2+40(FP)	// r2
-	MOVV	R2, err+48(FP)	// errno
-	RET
-ok1:
-	MOVV	R2, r1+32(FP)	// r1
-	MOVV	R3, r2+40(FP)	// r2
-	MOVV	R0, err+48(FP)	// errno
-	RET
-
 // func rawVforkSyscall(trap, a1 uintptr) (r1, err uintptr)
 TEXT ·rawVforkSyscall(SB),NOSPLIT|NOFRAME,$0-32
 	MOVV	a1+8(FP), R4

src/syscall/asm_linux_mipsx.s

@@ -97,24 +97,6 @@ ok9:
 	JAL	runtime·exitsyscall(SB)
 	RET
 
-TEXT ·RawSyscall(SB),NOSPLIT,$24-28
-	MOVW	a1+4(FP), R4
-	MOVW	a2+8(FP), R5
-	MOVW	a3+12(FP), R6
-	MOVW	trap+0(FP), R2	// syscall entry
-	SYSCALL
-	BEQ	R7, ok1
-	MOVW	$-1, R1
-	MOVW	R1, r1+16(FP)	// r1
-	MOVW	R0, r2+20(FP)	// r2
-	MOVW	R2, err+24(FP)	// errno
-	RET
-ok1:
-	MOVW	R2, r1+16(FP)	// r1
-	MOVW	R3, r2+20(FP)	// r2
-	MOVW	R0, err+24(FP)	// errno
-	RET
-
 // func rawVforkSyscall(trap, a1 uintptr) (r1, err uintptr)
 TEXT ·rawVforkSyscall(SB),NOSPLIT|NOFRAME,$0-16
 	MOVW	a1+4(FP), R4

src/syscall/asm_linux_ppc64x.s

@@ -59,27 +59,6 @@ ok6:
 	BL	runtime·exitsyscall<ABIInternal>(SB)
 	RET
 
-TEXT ·RawSyscall(SB),NOSPLIT,$0-56
-	MOVD	a1+8(FP), R3
-	MOVD	a2+16(FP), R4
-	MOVD	a3+24(FP), R5
-	MOVD	R0, R6
-	MOVD	R0, R7
-	MOVD	R0, R8
-	MOVD	trap+0(FP), R9	// syscall entry
-	SYSCALL R9
-	BVC	ok1
-	MOVD	$-1, R4
-	MOVD	R4, r1+32(FP)	// r1
-	MOVD	R0, r2+40(FP)	// r2
-	MOVD	R3, err+48(FP)	// errno
-	RET
-ok1:
-	MOVD	R3, r1+32(FP)	// r1
-	MOVD	R0, r2+40(FP)	// r2
-	MOVD	R0, err+48(FP)	// errno
-	RET
-
 // func rawVforkSyscall(trap, a1 uintptr) (r1, err uintptr)
 TEXT ·rawVforkSyscall(SB),NOSPLIT|NOFRAME,$0-32
 	MOVD	a1+8(FP), R3

src/syscall/asm_linux_riscv64.s

@@ -59,27 +59,6 @@ err:
 	CALL	runtime·exitsyscall(SB)
 	RET
 
-// func RawSyscall(trap, a1, a2, a3 uintptr) (r1, r2, err uintptr)
-TEXT ·RawSyscall(SB),NOSPLIT,$0-56
-	MOV	a1+8(FP), A0
-	MOV	a2+16(FP), A1
-	MOV	a3+24(FP), A2
-	MOV	trap+0(FP), A7	// syscall entry
-	ECALL
-	MOV	$-4096, T0
-	BLTU	T0, A0, err
-	MOV	A0, r1+32(FP)	// r1
-	MOV	A1, r2+40(FP)	// r2
-	MOV	ZERO, err+48(FP)	// errno
-	RET
-err:
-	MOV	$-1, T0
-	MOV	T0, r1+32(FP)	// r1
-	MOV	ZERO, r2+40(FP)	// r2
-	SUB	A0, ZERO, A0
-	MOV	A0, err+48(FP)	// errno
-	RET
-
 // func rawVforkSyscall(trap, a1 uintptr) (r1, err uintptr)
 TEXT ·rawVforkSyscall(SB),NOSPLIT|NOFRAME,$0-32
 	MOV	a1+8(FP), A0

src/syscall/asm_linux_s390x.s

@@ -60,29 +60,6 @@ ok6:
 	BL	runtime·exitsyscall(SB)
 	RET
 
-// func RawSyscall(trap, a1, a2, a3 uintptr) (r1, r2, err uintptr)
-TEXT ·RawSyscall(SB),NOSPLIT,$0-56
-	MOVD	a1+8(FP), R2
-	MOVD	a2+16(FP), R3
-	MOVD	a3+24(FP), R4
-	MOVD	$0, R5
-	MOVD	$0, R6
-	MOVD	$0, R7
-	MOVD	trap+0(FP), R1	// syscall entry
-	SYSCALL
-	MOVD	$0xfffffffffffff001, R8
-	CMPUBLT	R2, R8, ok1
-	MOVD	$-1, r1+32(FP)
-	MOVD	$0, r2+40(FP)
-	NEG	R2, R2
-	MOVD	R2, err+48(FP)	// errno
-	RET
-ok1:
-	MOVD	R2, r1+32(FP)
-	MOVD	R3, r2+40(FP)
-	MOVD	$0, err+48(FP)	// errno
-	RET
-
 // func rawVforkSyscall(trap, a1 uintptr) (r1, err uintptr)
 TEXT ·rawVforkSyscall(SB),NOSPLIT|NOFRAME,$0-32
 	MOVD	$0, R2

src/syscall/syscall_linux.go

@@ -18,7 +18,6 @@ import (
 
 func Syscall(trap, a1, a2, a3 uintptr) (r1, r2 uintptr, err Errno)
 func Syscall6(trap, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2 uintptr, err Errno)
-func RawSyscall(trap, a1, a2, a3 uintptr) (r1, r2 uintptr, err Errno)
 
 // N.B. RawSyscall6 is provided via linkname by runtime/internal/syscall.
 //
@@ -27,6 +26,27 @@ func RawSyscall(trap, a1, a2, a3 uintptr) (r1, r2 uintptr, err Errno)
 
 func RawSyscall6(trap, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2 uintptr, err Errno)
 
+// N.B. For the Syscall functions below:
+//
+// //go:uintptrkeepalive because the uintptr argument may be converted pointers
+// that need to be kept alive in the caller (this is implied for RawSyscall6
+// since it has no body).
+//
+// //go:nosplit because stack copying does not account for uintptrkeepalive, so
+// the stack must not grow. Stack copying cannot blindly assume that all
+// uintptr arguments are pointers, because some values may look like pointers,
+// but not really be pointers, and adjusting their value would break the call.
+//
+// //go:linkname to ensure ABI wrappers are generated for external callers
+// (notably x/sys/unix assembly).
+
+//go:uintptrkeepalive
+//go:nosplit
+//go:linkname RawSyscall
+func RawSyscall(trap, a1, a2, a3 uintptr) (r1, r2 uintptr, err Errno) {
+	return RawSyscall6(trap, a1, a2, a3, 0, 0, 0)
+}
+
 func rawSyscallNoError(trap, a1, a2, a3 uintptr) (r1, r2 uintptr)
 
 /*