Revert "syscall: define Syscall in terms of RawSyscall on linux"

This reverts CL 388477, which breaks cmd/go
TestScript/cover_pkgall_runtime.

For #51087.
For #52472.

Change-Id: Id58af419a889281f15df2471c58fece011fcffbc
Reviewed-on: https://go-review.googlesource.com/c/go/+/401636
Run-TryBot: Michael Pratt <mpratt@google.com>
Auto-Submit: Michael Pratt <mpratt@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

src/runtime/proc.go

@@ -3658,7 +3658,7 @@ func reentersyscall(pc, sp uintptr) {
 
 // Standard syscall entry used by the go syscall library and normal cgo calls.
 //
-// This is exported via linkname to assembly in the syscall package and x/sys.
+// This is exported via linkname to assembly in the syscall package.
 //
 //go:nosplit
 //go:linkname entersyscall

src/syscall/asm_linux_386.s

@@ -13,6 +13,32 @@
 // instead of the glibc-specific "CALL 0x10(GS)".
 #define INVOKE_SYSCALL	INT	$0x80
 
+// func Syscall(trap uintptr, a1, a2, a3 uintptr) (r1, r2, err uintptr);
+// Trap # in AX, args in BX CX DX SI DI, return in AX
+TEXT ·Syscall(SB),NOSPLIT,$0-28
+	CALL	runtime·entersyscall(SB)
+	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	ok
+	MOVL	$-1, r1+16(FP)
+	MOVL	$0, r2+20(FP)
+	NEGL	AX
+	MOVL	AX, err+24(FP)
+	CALL	runtime·exitsyscall(SB)
+	RET
+ok:
+	MOVL	AX, r1+16(FP)
+	MOVL	DX, r2+20(FP)
+	MOVL	$0, err+24(FP)
+	CALL	runtime·exitsyscall(SB)
+	RET
+
 // func Syscall6(trap uintptr, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2, err uintptr);
 TEXT ·Syscall6(SB),NOSPLIT,$0-40
 	CALL	runtime·entersyscall(SB)

src/syscall/asm_linux_amd64.s

@@ -11,6 +11,33 @@
 
 #define SYS_gettimeofday 96
 
+// func Syscall(trap int64, a1, a2, a3 uintptr) (r1, r2, err uintptr);
+// Trap # in AX, args in DI SI DX R10 R8 R9, return in AX DX
+// Note that this differs from "standard" ABI convention, which
+// would pass 4th arg in CX, not R10.
+
+TEXT ·Syscall(SB),NOSPLIT,$0-56
+	CALL	runtime·entersyscall<ABIInternal>(SB)
+	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	ok
+	MOVQ	$-1, r1+32(FP)
+	MOVQ	$0, r2+40(FP)
+	NEGQ	AX
+	MOVQ	AX, err+48(FP)
+	CALL	runtime·exitsyscall<ABIInternal>(SB)
+	RET
+ok:
+	MOVQ	AX, r1+32(FP)
+	MOVQ	DX, r2+40(FP)
+	MOVQ	$0, err+48(FP)
+	CALL	runtime·exitsyscall<ABIInternal>(SB)
+	RET
+
 // func Syscall6(trap, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2, err uintptr)
 TEXT ·Syscall6(SB),NOSPLIT,$0-80
 	CALL	runtime·entersyscall<ABIInternal>(SB)

src/syscall/asm_linux_arm.s

@@ -9,6 +9,36 @@
 // System calls for arm, Linux
 //
 
+// func Syscall(syscall uintptr, a1, a2, a3 uintptr) (r1, r2, err uintptr);
+TEXT ·Syscall(SB),NOSPLIT,$0-28
+	BL	runtime·entersyscall(SB)
+	MOVW	trap+0(FP), R7
+	MOVW	a1+4(FP), R0
+	MOVW	a2+8(FP), R1
+	MOVW	a3+12(FP), R2
+	MOVW	$0, R3
+	MOVW	$0, R4
+	MOVW	$0, R5
+	SWI	$0
+	MOVW	$0xfffff001, R1
+	CMP	R1, R0
+	BLS	ok
+	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)
+	BL	runtime·exitsyscall(SB)
+	RET
+ok:
+	MOVW	R0, r1+16(FP)
+	MOVW	$0, R0
+	MOVW	R0, r2+20(FP)
+	MOVW	R0, err+24(FP)
+	BL	runtime·exitsyscall(SB)
+	RET
+
 // func Syscall6(trap uintptr, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2, err uintptr);
 // Actually Syscall5 but the rest of the code expects it to be named Syscall6.
 TEXT ·Syscall6(SB),NOSPLIT,$0-40

src/syscall/asm_linux_arm64.s

@@ -4,6 +4,33 @@
 
 #include "textflag.h"
 
+// func Syscall(trap int64, a1, a2, a3 int64) (r1, r2, err int64);
+TEXT ·Syscall(SB),NOSPLIT,$0-56
+	BL	runtime·entersyscall<ABIInternal>(SB)
+	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
+	BL	runtime·exitsyscall<ABIInternal>(SB)
+	RET
+ok:
+	MOVD	R0, r1+32(FP)	// r1
+	MOVD	R1, r2+40(FP)	// r2
+	MOVD	ZR, err+48(FP)	// errno
+	BL	runtime·exitsyscall<ABIInternal>(SB)
+	RET
+
 TEXT ·Syscall6(SB),NOSPLIT,$0-80
 	BL	runtime·entersyscall<ABIInternal>(SB)
 	MOVD	a1+8(FP), R0

src/syscall/asm_linux_mips64x.s

@@ -10,6 +10,31 @@
 // System calls for mips64, Linux
 //
 
+// func Syscall(trap int64, a1, a2, a3 int64) (r1, r2, err int64);
+TEXT ·Syscall(SB),NOSPLIT,$0-56
+	JAL	runtime·entersyscall(SB)
+	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, ok
+	MOVV	$-1, R1
+	MOVV	R1, r1+32(FP)	// r1
+	MOVV	R0, r2+40(FP)	// r2
+	MOVV	R2, err+48(FP)	// errno
+	JAL	runtime·exitsyscall(SB)
+	RET
+ok:
+	MOVV	R2, r1+32(FP)	// r1
+	MOVV	R3, r2+40(FP)	// r2
+	MOVV	R0, err+48(FP)	// errno
+	JAL	runtime·exitsyscall(SB)
+	RET
+
 TEXT ·Syscall6(SB),NOSPLIT,$0-80
 	JAL	runtime·entersyscall(SB)
 	MOVV	a1+8(FP), R4

src/syscall/asm_linux_mipsx.s

@@ -11,6 +11,29 @@
 // System calls for mips, Linux
 //
 
+// func Syscall(trap uintptr, a1, a2, a3 uintptr) (r1, r2, err uintptr);
+TEXT ·Syscall(SB),NOSPLIT,$0-28
+	JAL	runtime·entersyscall(SB)
+	MOVW	a1+4(FP), R4
+	MOVW	a2+8(FP), R5
+	MOVW	a3+12(FP), R6
+	MOVW	R0, R7
+	MOVW	trap+0(FP), R2	// syscall entry
+	SYSCALL
+	BEQ	R7, ok
+	MOVW	$-1, R1
+	MOVW	R1, r1+16(FP)	// r1
+	MOVW	R0, r2+20(FP)	// r2
+	MOVW	R2, err+24(FP)	// errno
+	JAL	runtime·exitsyscall(SB)
+	RET
+ok:
+	MOVW	R2, r1+16(FP)	// r1
+	MOVW	R3, r2+20(FP)	// r2
+	MOVW	R0, err+24(FP)	// errno
+	JAL	runtime·exitsyscall(SB)
+	RET
+
 // func Syscall6(trap trap, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2, err uintptr);
 // 5th and 6th arg go at sp+16, sp+20.
 // Note that frame size of 20 means that 24 bytes gets reserved on stack.

src/syscall/asm_linux_ppc64x.s

@@ -10,6 +10,31 @@
 // System calls for ppc64, Linux
 //
 
+// func Syscall(trap int64, a1, a2, a3 int64) (r1, r2, err int64);
+TEXT ·Syscall(SB),NOSPLIT,$0-56
+	BL	runtime·entersyscall<ABIInternal>(SB)
+	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	ok
+	MOVD	$-1, R4
+	MOVD	R4, r1+32(FP)	// r1
+	MOVD	R0, r2+40(FP)	// r2
+	MOVD	R3, err+48(FP)	// errno
+	BL	runtime·exitsyscall<ABIInternal>(SB)
+	RET
+ok:
+	MOVD	R3, r1+32(FP)	// r1
+	MOVD	R0, r2+40(FP)	// r2
+	MOVD	R0, err+48(FP)	// errno
+	BL	runtime·exitsyscall<ABIInternal>(SB)
+	RET
+
 TEXT ·Syscall6(SB),NOSPLIT,$0-80
 	BL	runtime·entersyscall<ABIInternal>(SB)
 	MOVD	a1+8(FP), R3

src/syscall/asm_linux_riscv64.s

@@ -8,6 +8,30 @@
 // System calls for riscv64, Linux
 //
 
+// func Syscall(trap int64, a1, a2, a3 int64) (r1, r2, err int64)
+TEXT ·Syscall(SB),NOSPLIT,$0-56
+	CALL	runtime·entersyscall(SB)
+	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
+	CALL	runtime·exitsyscall(SB)
+	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
+	CALL	runtime·exitsyscall(SB)
+	RET
+
 // func Syscall6(trap, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2, err uintptr)
 TEXT ·Syscall6(SB),NOSPLIT,$0-80
 	CALL	runtime·entersyscall(SB)

src/syscall/asm_linux_s390x.s

@@ -8,6 +8,32 @@
 // System calls for s390x, Linux
 //
 
+// func Syscall(trap int64, a1, a2, a3 int64) (r1, r2, err int64)
+TEXT ·Syscall(SB),NOSPLIT,$0-56
+	BL	runtime·entersyscall(SB)
+	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, ok
+	MOVD	$-1, r1+32(FP)
+	MOVD	$0, r2+40(FP)
+	NEG	R2, R2
+	MOVD	R2, err+48(FP)	// errno
+	BL	runtime·exitsyscall(SB)
+	RET
+ok:
+	MOVD	R2, r1+32(FP)
+	MOVD	R3, r2+40(FP)
+	MOVD	$0, err+48(FP)	// errno
+	BL	runtime·exitsyscall(SB)
+	RET
+
 // func Syscall6(trap, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2, err uintptr)
 TEXT ·Syscall6(SB),NOSPLIT,$0-80
 	BL	runtime·entersyscall(SB)

src/syscall/syscall_linux.go

@@ -16,6 +16,7 @@ import (
 	"unsafe"
 )
 
+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)
 
 // N.B. RawSyscall6 is provided via linkname by runtime/internal/syscall.
@@ -25,18 +26,6 @@ func Syscall6(trap, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2 uintptr, err Errno)
 
 func RawSyscall6(trap, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2 uintptr, err Errno)
 
-// Pull in entersyscall/exitsyscall for Syscall/Syscall6.
-//
-// Note that this can't be a push linkname because the runtime already has a
-// nameless linkname to export to assembly here and in x/sys. Additionally,
-// entersyscall fetches the caller PC and SP and thus can't have a wrapper
-// inbetween.
-
-//go:linkname runtime_entersyscall runtime.entersyscall
-func runtime_entersyscall()
-//go:linkname runtime_exitsyscall runtime.exitsyscall
-func runtime_exitsyscall()
-
 // N.B. For the Syscall functions below:
 //
 // //go:uintptrkeepalive because the uintptr argument may be converted pointers
@@ -58,16 +47,6 @@ func RawSyscall(trap, a1, a2, a3 uintptr) (r1, r2 uintptr, err Errno) {
 	return RawSyscall6(trap, a1, a2, a3, 0, 0, 0)
 }
 
-//go:uintptrkeepalive
-//go:nosplit
-//go:linkname Syscall
-func Syscall(trap, a1, a2, a3 uintptr) (r1, r2 uintptr, err Errno) {
-	runtime_entersyscall()
-	r1, r2, err = RawSyscall(trap, a1, a2, a3)
-	runtime_exitsyscall()
-	return
-}
-
 func rawSyscallNoError(trap, a1, a2, a3 uintptr) (r1, r2 uintptr)
 
 /*