syscall: remove more NxM assumptions on Plan 9

LGTM=0intro, r
R=0intro, r
CC=ality, dave, golang-codereviews, jas, mischief, rsc
https://golang.org/cl/111910043

diff --git a/src/pkg/syscall/asm_plan9_amd64.s b/src/pkg/syscall/asm_plan9_amd64.s
index 2154a87d59322cc0015bb7fc03110fe0b7e1bbcb..220ea680022b80ac399306d6ea2c19f292d5ba82 100644 (file)
--- a/src/pkg/syscall/asm_plan9_amd64.s
+++ b/src/pkg/syscall/asm_plan9_amd64.s
@@ -16,12 +16,8 @@
 //func RawSyscall(trap, a1, a2, a3 uintptr) (r1, r2, err uintptr)
 //func RawSyscall6(trap, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2, err uintptr)
 
-// Trap # in BP, args on stack above caller pc.
-// NxM requires that Plan 9 system calls be
-// marked with $0x8000 in AX.
 TEXT   ·Syscall(SB),NOSPLIT,$0-64
        CALL    runtime·entersyscall(SB)
-       MOVQ    $0x8000, AX     // for NxM
        MOVQ    8(SP), BP       // syscall entry
        // slide args down on top of system call number
        LEAQ    16(SP), SI
@@ -57,7 +53,6 @@ copyresult3:
 
 TEXT   ·Syscall6(SB),NOSPLIT,$0-88
        CALL    runtime·entersyscall(SB)
-       MOVQ    $0x8000, AX     // for NxM
        MOVQ    8(SP), BP       // syscall entry
        // slide args down on top of system call number
        LEAQ            16(SP), SI
@@ -95,7 +90,6 @@ copyresult4:
        RET
 
 TEXT ·RawSyscall(SB),NOSPLIT,$0-56
-       MOVQ    $0x8000, AX     // for NxM
        MOVQ    8(SP), BP       // syscall entry
        // slide args down on top of system call number
        LEAQ            16(SP), SI
@@ -111,7 +105,6 @@ TEXT ·RawSyscall(SB),NOSPLIT,$0-56
        RET
 
 TEXT   ·RawSyscall6(SB),NOSPLIT,$0-80
-       MOVQ    $0x8000, AX     // for NxM
        MOVQ    8(SP), BP       // syscall entry
        // slide args down on top of system call number
        LEAQ            16(SP), SI
@@ -136,7 +129,6 @@ TEXT ·seek(SB),NOSPLIT,$0-56
        LEAQ    newoffset+40(SP), AX
        MOVQ    AX, placeholder+8(SP)
        
-       MOVQ    $0x8000, AX     // for NxM
        MOVQ    $SYS_SEEK, BP   // syscall entry
        SYSCALL