syscall: define Syscall in terms of RawSyscall on linux

For #51087

Change-Id: I9de7e85ccf137ae73662759382334bcbe7208150
Reviewed-on: https://go-review.googlesource.com/c/go/+/388477
Run-TryBot: Michael Pratt <mpratt@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

11 files changed, 23 insertions, 235 deletions

diff --git a/src/runtime/proc.go b/src/runtime/proc.go
index 4535f62053..b281d9f3b8 100644
--- a/src/runtime/proc.go
+++ b/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.
+// This is exported via linkname to assembly in the syscall package and x/sys.
 //
 //go:nosplit
 //go:linkname entersyscall
diff --git a/src/syscall/asm_linux_386.s b/src/syscall/asm_linux_386.s
index 546d27932d..ae0047b6fb 100644
--- a/src/syscall/asm_linux_386.s
+++ b/src/syscall/asm_linux_386.s
@@ -13,32 +13,6 @@
 // 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)
diff --git a/src/syscall/asm_linux_amd64.s b/src/syscall/asm_linux_amd64.s
index bd50b5ebfe..ea939b39f0 100644
--- a/src/syscall/asm_linux_amd64.s
+++ b/src/syscall/asm_linux_amd64.s
@@ -11,33 +11,6 @@
 
 #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)
diff --git a/src/syscall/asm_linux_arm.s b/src/syscall/asm_linux_arm.s
index 12986f801e..6f9a612fa1 100644
--- a/src/syscall/asm_linux_arm.s
+++ b/src/syscall/asm_linux_arm.s
@@ -9,36 +9,6 @@
 // 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
diff --git a/src/syscall/asm_linux_arm64.s b/src/syscall/asm_linux_arm64.s
index fc1466cc80..c9d28d301a 100644
--- a/src/syscall/asm_linux_arm64.s
+++ b/src/syscall/asm_linux_arm64.s
@@ -4,33 +4,6 @@
 
 #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
diff --git a/src/syscall/asm_linux_mips64x.s b/src/syscall/asm_linux_mips64x.s
index b6f293471d..994d7779fb 100644
--- a/src/syscall/asm_linux_mips64x.s
+++ b/src/syscall/asm_linux_mips64x.s
@@ -10,31 +10,6 @@
 // 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
diff --git a/src/syscall/asm_linux_mipsx.s b/src/syscall/asm_linux_mipsx.s
index 041c353e79..8c45861d64 100644
--- a/src/syscall/asm_linux_mipsx.s
+++ b/src/syscall/asm_linux_mipsx.s
@@ -11,29 +11,6 @@
 // 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.
diff --git a/src/syscall/asm_linux_ppc64x.s b/src/syscall/asm_linux_ppc64x.s
index b03d859ca2..d60e472226 100644
--- a/src/syscall/asm_linux_ppc64x.s
+++ b/src/syscall/asm_linux_ppc64x.s
@@ -10,31 +10,6 @@
 // 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
diff --git a/src/syscall/asm_linux_riscv64.s b/src/syscall/asm_linux_riscv64.s
index f6b7d11c08..60b5cdbc1c 100644
--- a/src/syscall/asm_linux_riscv64.s
+++ b/src/syscall/asm_linux_riscv64.s
@@ -8,30 +8,6 @@
 // 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)
diff --git a/src/syscall/asm_linux_s390x.s b/src/syscall/asm_linux_s390x.s
index 0a4913779a..14dabd85c2 100644
--- a/src/syscall/asm_linux_s390x.s
+++ b/src/syscall/asm_linux_s390x.s
@@ -8,32 +8,6 @@
 // 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)
diff --git a/src/syscall/syscall_linux.go b/src/syscall/syscall_linux.go
index a9a8ecbefd..57e4769731 100644
--- a/src/syscall/syscall_linux.go
+++ b/src/syscall/syscall_linux.go
@@ -16,7 +16,6 @@ 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.
@@ -26,6 +25,18 @@ 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
@@ -47,6 +58,16 @@ 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)
 
 /*