runtime/internal/syscall: use ABIInternal for Syscall6 on amd64

For #51087.

Change-Id: I25971760b63ec0d23d0f011521dd197d81a38976
Reviewed-on: https://go-review.googlesource.com/c/go/+/401096
Run-TryBot: Michael Pratt <mpratt@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

diff --git a/src/runtime/internal/syscall/asm_linux_amd64.s b/src/runtime/internal/syscall/asm_linux_amd64.s
index 961d9bd64025bb912d37bb13d1b5001568154bff..3740ef1beb570d12194e31ba7db245a7333fda51 100644 (file)
--- a/src/runtime/internal/syscall/asm_linux_amd64.s
+++ b/src/runtime/internal/syscall/asm_linux_amd64.s
@@ -6,28 +6,42 @@
 
 // func Syscall6(num, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2, errno uintptr)
 //
-// Syscall # in AX, args in DI SI DX R10 R8 R9, return in AX DX.
+// We need to convert to the syscall ABI.
+//
+// arg | ABIInternal | Syscall
+// ---------------------------
+// num | AX          | AX
+// a1  | BX          | DI
+// a2  | CX          | SI
+// a3  | DI          | DX
+// a4  | SI          | R10
+// a5  | R8          | R8
+// a6  | R9          | R9
+//
+// r1  | AX          | AX
+// r2  | BX          | DX
+// err | CX          | part of AX
 //
 // Note that this differs from "standard" ABI convention, which would pass 4th
 // arg in CX, not R10.
-TEXT ·Syscall6(SB),NOSPLIT,$0-80
-       MOVQ    num+0(FP), AX   // syscall entry
-       MOVQ    a1+8(FP), DI
-       MOVQ    a2+16(FP), SI
-       MOVQ    a3+24(FP), DX
-       MOVQ    a4+32(FP), R10
-       MOVQ    a5+40(FP), R8
-       MOVQ    a6+48(FP), R9
+TEXT ·Syscall6<ABIInternal>(SB),NOSPLIT,$0
+       // a6 already in R9.
+       // a5 already in R8.
+       MOVQ    SI, R10 // a4
+       MOVQ    DI, DX  // a3
+       MOVQ    CX, SI  // a2
+       MOVQ    BX, DI  // a1
+       // num already in AX.
        SYSCALL
        CMPQ    AX, $0xfffffffffffff001
        JLS     ok
-       MOVQ    $-1, r1+56(FP)
-       MOVQ    $0, r2+64(FP)
        NEGQ    AX
-       MOVQ    AX, errno+72(FP)
+       MOVQ    AX, CX  // errno
+       MOVQ    $-1, AX // r1
+       MOVQ    $0, BX  // r2
        RET
 ok:
-       MOVQ    AX, r1+56(FP)
-       MOVQ    DX, r2+64(FP)
-       MOVQ    $0, errno+72(FP)
+       // r1 already in AX.
+       MOVQ    DX, BX // r2
+       MOVQ    $0, CX // errno
        RET