runtime: M-targeted signals for BSDs

For these, we split up the existing runtime.raise assembly
implementation into its constituent "get thread ID" and "signal
thread" parts. This lets us implement signalM and reimplement raise in
pure Go. (NetBSD conveniently already had lwp_self.)

We also change minit to store the procid directly, rather than
depending on newosproc to do so. This is because newosproc isn't
called for the bootstrap M, but we need a procid for every M. This is
also simpler overall.

For golang#10958, golang#24543.

Change-Id: Ie5f1fcada6a33046375066bcbe054d1f784d39c0
Reviewed-on: https://go-review.googlesource.com/c/go/+/201402
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

Author: aclements

src/runtime/defs_freebsd_386.go

@@ -126,6 +126,8 @@ type thrparam struct {
 	spare      [3]uintptr
 }
 
+type thread int32 // long
+
 type sigset struct {
 	__bits [4]uint32
 }

src/runtime/defs_freebsd_amd64.go

@@ -127,6 +127,8 @@ type thrparam struct {
 	spare      [3]uintptr
 }
 
+type thread int64 // long
+
 type sigset struct {
 	__bits [4]uint32
 }

src/runtime/defs_freebsd_arm.go

@@ -126,6 +126,8 @@ type thrparam struct {
 	spare      [3]uintptr
 }
 
+type thread int32 // long
+
 type sigset struct {
 	__bits [4]uint32
 }

src/runtime/defs_freebsd_arm64.go

@@ -127,6 +127,8 @@ type thrparam struct {
 	spare      [3]uintptr
 }
 
+type thread int64 // long
+
 type sigset struct {
 	__bits [4]uint32
 }

src/runtime/os_dragonfly.go

@@ -38,9 +38,11 @@ func setitimer(mode int32, new, old *itimerval)
 //go:noescape
 func sysctl(mib *uint32, miblen uint32, out *byte, size *uintptr, dst *byte, ndst uintptr) int32
 
-func raise(sig uint32)
 func raiseproc(sig uint32)
 
+func lwp_gettid() int32
+func lwp_kill(pid, tid int32, sig int)
+
 //go:noescape
 func sys_umtx_sleep(addr *uint32, val, timeout int32) int32
 
@@ -151,7 +153,7 @@ func newosproc(mp *m) {
 		start_func: funcPC(lwp_start),
 		arg:        unsafe.Pointer(mp),
 		stack:      uintptr(stk),
-		tid1:       unsafe.Pointer(&mp.procid),
+		tid1:       nil, // minit will record tid
 		tid2:       nil,
 	}
 
@@ -191,10 +193,7 @@ func mpreinit(mp *m) {
 // Called to initialize a new m (including the bootstrap m).
 // Called on the new thread, cannot allocate memory.
 func minit() {
-	// m.procid is a uint64, but lwp_start writes an int32. Fix it up.
-	_g_ := getg()
-	_g_.m.procid = uint64(*(*int32)(unsafe.Pointer(&_g_.m.procid)))
-
+	getg().m.procid = uint64(lwp_gettid())
 	minitSignals()
 }
 
@@ -288,3 +287,17 @@ func sysauxv(auxv []uintptr) {
 		}
 	}
 }
+
+// raise sends a signal to the calling thread.
+//
+// It must be nosplit because it is used by the signal handler before
+// it definitely has a Go stack.
+//
+//go:nosplit
+func raise(sig uint32) {
+	lwp_kill(-1, lwp_gettid(), int(sig))
+}
+
+func signalM(mp *m, sig int) {
+	lwp_kill(-1, int32(mp.procid), sig)
+}

src/runtime/os_freebsd.go

@@ -26,9 +26,11 @@ func setitimer(mode int32, new, old *itimerval)
 //go:noescape
 func sysctl(mib *uint32, miblen uint32, out *byte, size *uintptr, dst *byte, ndst uintptr) int32
 
-func raise(sig uint32)
 func raiseproc(sig uint32)
 
+func thr_self() thread
+func thr_kill(tid thread, sig int)
+
 //go:noescape
 func sys_umtx_op(addr *uint32, mode int32, val uint32, uaddr1 uintptr, ut *umtx_time) int32
 
@@ -195,7 +197,7 @@ func newosproc(mp *m) {
 		arg:        unsafe.Pointer(mp),
 		stack_base: mp.g0.stack.lo,
 		stack_size: uintptr(stk) - mp.g0.stack.lo,
-		child_tid:  unsafe.Pointer(&mp.procid),
+		child_tid:  nil, // minit will record tid
 		parent_tid: nil,
 		tls_base:   unsafe.Pointer(&mp.tls[0]),
 		tls_size:   unsafe.Sizeof(mp.tls),
@@ -231,7 +233,7 @@ func newosproc0(stacksize uintptr, fn unsafe.Pointer) {
 		arg:        nil,
 		stack_base: uintptr(stack), //+stacksize?
 		stack_size: stacksize,
-		child_tid:  unsafe.Pointer(&m0.procid),
+		child_tid:  nil, // minit will record tid
 		parent_tid: nil,
 		tls_base:   unsafe.Pointer(&m0.tls[0]),
 		tls_size:   unsafe.Sizeof(m0.tls),
@@ -290,12 +292,7 @@ func mpreinit(mp *m) {
 // Called to initialize a new m (including the bootstrap m).
 // Called on the new thread, cannot allocate memory.
 func minit() {
-	// m.procid is a uint64, but thr_new writes a uint32 on 32-bit systems.
-	// Fix it up. (Only matters on big-endian, but be clean anyway.)
-	if sys.PtrSize == 4 {
-		_g_ := getg()
-		_g_.m.procid = uint64(*(*uint32)(unsafe.Pointer(&_g_.m.procid)))
-	}
+	getg().m.procid = uint64(thr_self())
 
 	// On FreeBSD before about April 2017 there was a bug such
 	// that calling execve from a thread other than the main
@@ -423,3 +420,17 @@ func sysSigaction(sig uint32, new, old *sigactiont) {
 // asmSigaction is implemented in assembly.
 //go:noescape
 func asmSigaction(sig uintptr, new, old *sigactiont) int32
+
+// raise sends a signal to the calling thread.
+//
+// It must be nosplit because it is used by the signal handler before
+// it definitely has a Go stack.
+//
+//go:nosplit
+func raise(sig uint32) {
+	thr_kill(thr_self(), int(sig))
+}
+
+func signalM(mp *m, sig int) {
+	thr_kill(thread(mp.procid), sig)
+}

src/runtime/os_netbsd.go

@@ -47,9 +47,10 @@ func sysctl(mib *uint32, miblen uint32, out *byte, size *uintptr, dst *byte, nds
 
 func lwp_tramp()
 
-func raise(sig uint32)
 func raiseproc(sig uint32)
 
+func lwp_kill(tid int32, sig int)
+
 //go:noescape
 func getcontext(ctxt unsafe.Pointer)
 
@@ -361,3 +362,17 @@ func sysauxv(auxv []uintptr) {
 		}
 	}
 }
+
+// raise sends signal to the calling thread.
+//
+// It must be nosplit because it is used by the signal handler before
+// it definitely has a Go stack.
+//
+//go:nosplit
+func raise(sig uint32) {
+	lwp_kill(lwp_self(), int(sig))
+}
+
+func signalM(mp *m, sig int) {
+	lwp_kill(int32(mp.procid), sig)
+}

src/runtime/os_openbsd.go

@@ -42,9 +42,11 @@ func sigprocmask(how int32, new, old *sigset) {
 //go:noescape
 func sysctl(mib *uint32, miblen uint32, out *byte, size *uintptr, dst *byte, ndst uintptr) int32
 
-func raise(sig uint32)
 func raiseproc(sig uint32)
 
+func getthrid() int32
+func thrkill(tid int32, sig int)
+
 //go:noescape
 func tfork(param *tforkt, psize uintptr, mm *m, gg *g, fn uintptr) int32
 
@@ -190,7 +192,7 @@ func newosproc(mp *m) {
 	// rather than at the top of it.
 	param := tforkt{
 		tf_tcb:   unsafe.Pointer(&mp.tls[0]),
-		tf_tid:   (*int32)(unsafe.Pointer(&mp.procid)),
+		tf_tid:   nil, // minit will record tid
 		tf_stack: uintptr(stk) - sys.PtrSize,
 	}
 
@@ -238,10 +240,7 @@ func mpreinit(mp *m) {
 // Called to initialize a new m (including the bootstrap m).
 // Called on the new thread, can not allocate memory.
 func minit() {
-	// m.procid is a uint64, but tfork writes an int32. Fix it up.
-	_g_ := getg()
-	_g_.m.procid = uint64(*(*int32)(unsafe.Pointer(&_g_.m.procid)))
-
+	getg().m.procid = uint64(getthrid())
 	minitSignals()
 }
 
@@ -337,3 +336,11 @@ func osStackRemap(s *mspan, flags int32) {
 		throw("remapping stack memory failed")
 	}
 }
+
+func raise(sig uint32) {
+	thrkill(getthrid(), int(sig))
+}
+
+func signalM(mp *m, sig int) {
+	thrkill(int32(mp.procid), sig)
+}

src/runtime/sys_dragonfly_amd64.s

@@ -134,12 +134,16 @@ TEXT runtime·write1(SB),NOSPLIT,$-8
 	MOVL	AX, ret+24(FP)
 	RET
 
-TEXT runtime·raise(SB),NOSPLIT,$16
+TEXT runtime·lwp_gettid(SB),NOSPLIT,$0-4
 	MOVL	$496, AX	// lwp_gettid
 	SYSCALL
-	MOVQ	$-1, DI		// arg 1 - pid
-	MOVQ	AX, SI		// arg 2 - tid
-	MOVL	sig+0(FP), DX	// arg 3 - signum
+	MOVL	AX, ret+0(FP)
+	RET
+
+TEXT runtime·lwp_kill(SB),NOSPLIT,$0-16
+	MOVL	pid+0(FP), DI	// arg 1 - pid
+	MOVL	tid+4(FP), SI	// arg 2 - tid
+	MOVQ	sig+8(FP), DX	// arg 3 - signum
 	MOVL	$497, AX	// lwp_kill
 	SYSCALL
 	RET

src/runtime/sys_freebsd_386.s

@@ -131,17 +131,16 @@ TEXT runtime·write1(SB),NOSPLIT,$-4
 	MOVL	AX, ret+12(FP)
 	RET
 
-TEXT runtime·raise(SB),NOSPLIT,$16
-	// thr_self(&8(SP))
-	LEAL	8(SP), AX
+TEXT runtime·thr_self(SB),NOSPLIT,$8-4
+	// thr_self(&0(FP))
+	LEAL	ret+0(FP), AX
 	MOVL	AX, 4(SP)
 	MOVL	$432, AX
 	INT	$0x80
-	// thr_kill(self, SIGPIPE)
-	MOVL	8(SP), AX
-	MOVL	AX, 4(SP)
-	MOVL	sig+0(FP), AX
-	MOVL	AX, 8(SP)
+	RET
+
+TEXT runtime·thr_kill(SB),NOSPLIT,$-4
+	// thr_kill(tid, sig)
 	MOVL	$433, AX
 	INT	$0x80
 	RET