runtime: update newosproc asm to access m.id directly

darwin/386, freebsd/386, and linux/386 use a setldt system call to
setup each M's thread-local storage area, and they need access to the
M's id for this.  The current code copies m.id into m.tls[0] (and this
logic has been cargo culted to OSes like NetBSD and OpenBSD, which
don't even need m.id to configure TLS), and then the 386 assembly
loads m.tls[0]... but since the assembly code already has a pointer to
the M, it might as well just load m.id directly.

Change-Id: I1a7278f1ec8ebda8d1de3aa3a61993070e3a8cdf
Reviewed-on: https://go-review.googlesource.com/16881
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/runtime/os1_darwin.go

@@ -78,9 +78,8 @@ func goenvs() {
 // May run with m.p==nil, so write barriers are not allowed.
 //go:nowritebarrier
 func newosproc(mp *m, stk unsafe.Pointer) {
-	mp.tls[0] = uintptr(mp.id) // so 386 asm can find it
 	if false {
-		print("newosproc stk=", stk, " m=", mp, " g=", mp.g0, " id=", mp.id, "/", int(mp.tls[0]), " ostk=", &mp, "\n")
+		print("newosproc stk=", stk, " m=", mp, " g=", mp.g0, " id=", mp.id, " ostk=", &mp, "\n")
 	}
 
 	var oset uint32

src/runtime/os1_dragonfly.go

@@ -74,7 +74,7 @@ func lwp_start(uintptr)
 //go:nowritebarrier
 func newosproc(mp *m, stk unsafe.Pointer) {
 	if false {
-		print("newosproc stk=", stk, " m=", mp, " g=", mp.g0, " lwp_start=", funcPC(lwp_start), " id=", mp.id, "/", mp.tls[0], " ostk=", &mp, "\n")
+		print("newosproc stk=", stk, " m=", mp, " g=", mp.g0, " lwp_start=", funcPC(lwp_start), " id=", mp.id, " ostk=", &mp, "\n")
 	}
 
 	var oset sigset
@@ -88,8 +88,6 @@ func newosproc(mp *m, stk unsafe.Pointer) {
 		tid2:       nil,
 	}
 
-	mp.tls[0] = uintptr(mp.id) // XXX so 386 asm can find it
-
 	lwp_create(&params)
 	sigprocmask(_SIG_SETMASK, &oset, nil)
 }

src/runtime/os1_freebsd.go

@@ -73,7 +73,7 @@ func thr_start()
 //go:nowritebarrier
 func newosproc(mp *m, stk unsafe.Pointer) {
 	if false {
-		print("newosproc stk=", stk, " m=", mp, " g=", mp.g0, " thr_start=", funcPC(thr_start), " id=", mp.id, "/", mp.tls[0], " ostk=", &mp, "\n")
+		print("newosproc stk=", stk, " m=", mp, " g=", mp.g0, " thr_start=", funcPC(thr_start), " id=", mp.id, " ostk=", &mp, "\n")
 	}
 
 	// NOTE(rsc): This code is confused. stackbase is the top of the stack
@@ -88,7 +88,6 @@ func newosproc(mp *m, stk unsafe.Pointer) {
 		tls_base:   unsafe.Pointer(&mp.tls[0]),
 		tls_size:   unsafe.Sizeof(mp.tls),
 	}
-	mp.tls[0] = uintptr(mp.id) // so 386 asm can find it
 
 	var oset sigset
 	sigprocmask(_SIG_SETMASK, &sigset_all, &oset)

src/runtime/os1_linux.go

@@ -133,9 +133,8 @@ func newosproc(mp *m, stk unsafe.Pointer) {
 	/*
 	 * note: strace gets confused if we use CLONE_PTRACE here.
 	 */
-	mp.tls[0] = uintptr(mp.id) // so 386 asm can find it
 	if false {
-		print("newosproc stk=", stk, " m=", mp, " g=", mp.g0, " clone=", funcPC(clone), " id=", mp.id, "/", mp.tls[0], " ostk=", &mp, "\n")
+		print("newosproc stk=", stk, " m=", mp, " g=", mp.g0, " clone=", funcPC(clone), " id=", mp.id, " ostk=", &mp, "\n")
 	}
 
 	// Disable signals during clone, so that the new thread starts

src/runtime/os1_netbsd.go

@@ -95,11 +95,9 @@ func semawakeup(mp *m) {
 //go:nowritebarrier
 func newosproc(mp *m, stk unsafe.Pointer) {
 	if false {
-		print("newosproc stk=", stk, " m=", mp, " g=", mp.g0, " id=", mp.id, "/", int32(mp.tls[0]), " ostk=", &mp, "\n")
+		print("newosproc stk=", stk, " m=", mp, " g=", mp.g0, " id=", mp.id, " ostk=", &mp, "\n")
 	}
 
-	mp.tls[0] = uintptr(mp.id) // so 386 asm can find it
-
 	var uc ucontextt
 	getcontext(unsafe.Pointer(&uc))
 

src/runtime/os1_openbsd.go

@@ -105,11 +105,9 @@ func semawakeup(mp *m) {
 //go:nowritebarrier
 func newosproc(mp *m, stk unsafe.Pointer) {
 	if false {
-		print("newosproc stk=", stk, " m=", mp, " g=", mp.g0, " id=", mp.id, "/", int32(mp.tls[0]), " ostk=", &mp, "\n")
+		print("newosproc stk=", stk, " m=", mp, " g=", mp.g0, " id=", mp.id, " ostk=", &mp, "\n")
 	}
 
-	mp.tls[0] = uintptr(mp.id) // so 386 asm can find it
-
 	param := tforkt{
 		tf_tcb:   unsafe.Pointer(&mp.tls[0]),
 		tf_tid:   (*int32)(unsafe.Pointer(&mp.procid)),

src/runtime/sys_darwin_386.s

@@ -361,10 +361,8 @@ TEXT runtime·bsdthread_create(SB),NOSPLIT,$32
 //	SP = stack - C_32_STK_ALIGN
 TEXT runtime·bsdthread_start(SB),NOSPLIT,$0
 	// set up ldt 7+id to point at m->tls.
-	// m->tls is at m+40.  newosproc left
-	// the m->id in tls[0].
 	LEAL	m_tls(DX), BP
-	MOVL	0(BP), DI
+	MOVL	m_id(DX), DI
 	ADDL	$7, DI	// m0 is LDT#7. count up.
 	// setldt(tls#, &tls, sizeof tls)
 	PUSHAL	// save registers

src/runtime/sys_freebsd_386.s

@@ -25,7 +25,7 @@ TEXT runtime·thr_start(SB),NOSPLIT,$0
 	MOVL	mm+0(FP), AX
 	MOVL	m_g0(AX), BX
 	LEAL	m_tls(AX), BP
-	MOVL	0(BP), DI
+	MOVL	m_id(AX), DI
 	ADDL	$7, DI
 	PUSHAL
 	PUSHL	$32

src/runtime/sys_linux_386.s

@@ -334,9 +334,8 @@ TEXT runtime·clone(SB),NOSPLIT,$0
 	MOVL	AX, m_procid(BX)	// save tid as m->procid
 
 	// set up ldt 7+id to point at m->tls.
-	// newosproc left the id in tls[0].
 	LEAL	m_tls(BX), BP
-	MOVL	0(BP), DI
+	MOVL	m_id(BX), DI
 	ADDL	$7, DI	// m0 is LDT#7. count up.
 	// setldt(tls#, &tls, sizeof tls)
 	PUSHAL	// save registers