runtime: switch openbsd/arm to pthreads

This switches openbsd/arm to thread creation via pthreads, rather than doing
direct system calls.

Update #36435

Change-Id: Ia8749e3723a9967905c33b6d93dfd9be797a486c
Reviewed-on: https://go-review.googlesource.com/c/go/+/315790
Trust: Joel Sing <joel@sing.id.au>
Reviewed-by: Cherry Mui <cherryyz@google.com>

8 files changed, 153 insertions, 94 deletions

diff --git a/src/runtime/asm_arm.s b/src/runtime/asm_arm.s
index e779fc8f84..6d3573d68f 100644
--- a/src/runtime/asm_arm.s
+++ b/src/runtime/asm_arm.s
@@ -142,6 +142,11 @@ TEXT runtime·rt0_go(SB),NOSPLIT|NOFRAME|TOPFRAME,$0
 
 	BL	runtime·emptyfunc(SB)	// fault if stack check is wrong
 
+#ifdef GOOS_openbsd
+	// Save g to TLS so that it is available from signal trampoline.
+	BL	runtime·save_g(SB)
+#endif
+
 	BL	runtime·_initcgo(SB)	// will clobber R0-R3
 
 	// update stackguard after _cgo_init
@@ -633,9 +638,13 @@ TEXT	·cgocallback(SB),NOSPLIT,$12-12
 	NO_LOCAL_POINTERS
 
 	// Load m and g from thread-local storage.
+#ifdef GOOS_openbsd
+	BL	runtime·load_g(SB)
+#else
 	MOVB	runtime·iscgo(SB), R0
 	CMP	$0, R0
 	BL.NE	runtime·load_g(SB)
+#endif
 
 	// If g is nil, Go did not create the current thread.
 	// Call needm to obtain one for temporary use.
@@ -745,6 +754,9 @@ TEXT setg<>(SB),NOSPLIT|NOFRAME,$0-0
 #ifdef GOOS_windows
 	B	runtime·save_g(SB)
 #else
+#ifdef GOOS_openbsd
+	B	runtime·save_g(SB)
+#else
 	MOVB	runtime·iscgo(SB), R0
 	CMP	$0, R0
 	B.EQ	2(PC)
@@ -753,6 +765,7 @@ TEXT setg<>(SB),NOSPLIT|NOFRAME,$0-0
 	MOVW	g, R0
 	RET
 #endif
+#endif
 
 TEXT runtime·emptyfunc(SB),0,$0-0
 	RET
diff --git a/src/runtime/defs_openbsd_arm.go b/src/runtime/defs_openbsd_arm.go
index 170bb3876c..9b84b5a3a3 100644
--- a/src/runtime/defs_openbsd_arm.go
+++ b/src/runtime/defs_openbsd_arm.go
@@ -30,6 +30,8 @@ const (
 	_SA_RESTART = 0x2
 	_SA_ONSTACK = 0x1
 
+	_PTHREAD_CREATE_DETACHED = 0x1
+
 	_SIGHUP    = 0x1
 	_SIGINT    = 0x2
 	_SIGQUIT   = 0x3
@@ -174,3 +176,10 @@ type keventt struct {
 	udata     *byte
 	pad_cgo_1 [4]byte
 }
+
+type pthread uintptr
+type pthreadattr uintptr
+type pthreadcond uintptr
+type pthreadcondattr uintptr
+type pthreadmutex uintptr
+type pthreadmutexattr uintptr
diff --git a/src/runtime/os_openbsd_libc.go b/src/runtime/os_openbsd_libc.go
index cff5a092d7..8150753796 100644
--- a/src/runtime/os_openbsd_libc.go
+++ b/src/runtime/os_openbsd_libc.go
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build (openbsd && 386) || (openbsd && amd64) || (openbsd && arm64)
-// +build openbsd,386 openbsd,amd64 openbsd,arm64
+//go:build (openbsd && 386) || (openbsd && amd64) || (openbsd && arm) || (openbsd && arm64)
+// +build openbsd,386 openbsd,amd64 openbsd,arm openbsd,arm64
 
 package runtime
 
diff --git a/src/runtime/os_openbsd_syscall.go b/src/runtime/os_openbsd_syscall.go
index 5315487961..94e851cde8 100644
--- a/src/runtime/os_openbsd_syscall.go
+++ b/src/runtime/os_openbsd_syscall.go
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build openbsd && !386 && openbsd && !amd64 && openbsd && !arm64
-// +build openbsd,!386,openbsd,!amd64,openbsd,!arm64
+//go:build openbsd && !386 && openbsd && !amd64 && openbsd && !arm && openbsd && !arm64
+// +build openbsd,!386,openbsd,!amd64,openbsd,!arm,openbsd,!arm64
 
 package runtime
 
diff --git a/src/runtime/proc.go b/src/runtime/proc.go
index d9f8c65530..650ab6a1ee 100644
--- a/src/runtime/proc.go
+++ b/src/runtime/proc.go
@@ -1316,7 +1316,7 @@ func mStackIsSystemAllocated() bool {
 		return true
 	case "openbsd":
 		switch GOARCH {
-		case "386", "amd64", "arm64":
+		case "386", "amd64", "arm", "arm64":
 			return true
 		}
 	}
diff --git a/src/runtime/sys_libc.go b/src/runtime/sys_libc.go
index 91195eb3c0..346b1ab285 100644
--- a/src/runtime/sys_libc.go
+++ b/src/runtime/sys_libc.go
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build darwin || (openbsd && 386) || (openbsd && amd64) || (openbsd && arm64)
-// +build darwin openbsd,386 openbsd,amd64 openbsd,arm64
+//go:build darwin || (openbsd && 386) || (openbsd && amd64) || (openbsd && arm) || (openbsd && arm64)
+// +build darwin openbsd,386 openbsd,amd64 openbsd,arm openbsd,arm64
 
 package runtime
 
diff --git a/src/runtime/sys_openbsd.go b/src/runtime/sys_openbsd.go
index f6146c2e1d..89203bf85f 100644
--- a/src/runtime/sys_openbsd.go
+++ b/src/runtime/sys_openbsd.go
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build (openbsd && 386) || (openbsd && amd64) || (openbsd && arm64)
-// +build openbsd,386 openbsd,amd64 openbsd,arm64
+//go:build (openbsd && 386) || (openbsd && amd64) || (openbsd && arm) || (openbsd && arm64)
+// +build openbsd,386 openbsd,amd64 openbsd,arm openbsd,arm64
 
 package runtime
 
diff --git a/src/runtime/sys_openbsd_arm.s b/src/runtime/sys_openbsd_arm.s
index 45d69a312a..65d29415b0 100644
--- a/src/runtime/sys_openbsd_arm.s
+++ b/src/runtime/sys_openbsd_arm.s
@@ -10,7 +10,7 @@
 #include "go_tls.h"
 #include "textflag.h"
 
-#define CLOCK_REALTIME	$0
+#define	CLOCK_REALTIME	$0
 #define	CLOCK_MONOTONIC	$3
 
 // With OpenBSD 6.7 onwards, an armv7 syscall returns two instructions
@@ -25,6 +25,127 @@
 	NOOP;		\
 	NOOP
 
+// mstart_stub is the first function executed on a new thread started by pthread_create.
+// It just does some low-level setup and then calls mstart.
+// Note: called with the C calling convention.
+TEXT runtime·mstart_stub(SB),NOSPLIT,$0
+	// R0 points to the m.
+	// We are already on m's g0 stack.
+
+	// Save callee-save registers.
+	MOVM.DB.W [R4-R11], (R13)
+
+	MOVW	m_g0(R0), g
+	BL	runtime·save_g(SB)
+
+	BL	runtime·mstart(SB)
+
+	// Restore callee-save registers.
+	MOVM.IA.W (R13), [R4-R11]
+
+	// Go is all done with this OS thread.
+	// Tell pthread everything is ok (we never join with this thread, so
+	// the value here doesn't really matter).
+	MOVW	$0, R0
+	RET
+
+TEXT runtime·sigfwd(SB),NOSPLIT,$0-16
+	MOVW	sig+4(FP), R0
+	MOVW	info+8(FP), R1
+	MOVW	ctx+12(FP), R2
+	MOVW	fn+0(FP), R3
+	MOVW	R13, R9
+	SUB	$24, R13
+	BIC	$0x7, R13 // alignment for ELF ABI
+	BL	(R3)
+	MOVW	R9, R13
+	RET
+
+TEXT runtime·sigtramp(SB),NOSPLIT,$0
+	// Reserve space for callee-save registers and arguments.
+	MOVM.DB.W [R4-R11], (R13)
+	SUB	$16, R13
+
+	// If called from an external code context, g will not be set.
+	// Save R0, since runtime·load_g will clobber it.
+	MOVW	R0, 4(R13)		// signum
+	BL	runtime·load_g(SB)
+
+	MOVW	R1, 8(R13)
+	MOVW	R2, 12(R13)
+	BL	runtime·sigtrampgo(SB)
+
+	// Restore callee-save registers.
+	ADD	$16, R13
+	MOVM.IA.W (R13), [R4-R11]
+
+	RET
+
+TEXT ·publicationBarrier(SB),NOSPLIT|NOFRAME,$0-0
+	B	runtime·armPublicationBarrier(SB)
+
+// TODO(jsing): OpenBSD only supports GOARM=7 machines... this
+// should not be needed, however the linker still allows GOARM=5
+// on this platform.
+TEXT runtime·read_tls_fallback(SB),NOSPLIT|NOFRAME,$0
+	MOVM.WP	[R1, R2, R3, R12], (R13)
+	MOVW	$330, R12		// sys___get_tcb
+	INVOKE_SYSCALL
+	MOVM.IAW (R13), [R1, R2, R3, R12]
+	RET
+
+// These trampolines help convert from Go calling convention to C calling convention.
+// They should be called with asmcgocall - note that while asmcgocall does
+// stack alignment, creation of a frame undoes it again.
+// A pointer to the arguments is passed in R0.
+// A single int32 result is returned in R0.
+// (For more results, make an args/results structure.)
+TEXT runtime·pthread_attr_init_trampoline(SB),NOSPLIT,$0
+	MOVW	R13, R9
+	BIC     $0x7, R13		// align for ELF ABI
+	MOVW	0(R0), R0		// arg 1 attr
+	BL	libc_pthread_attr_init(SB)
+	MOVW	R9, R13
+	RET
+
+TEXT runtime·pthread_attr_destroy_trampoline(SB),NOSPLIT,$0
+	MOVW	R13, R9
+	BIC     $0x7, R13		// align for ELF ABI
+	MOVW	0(R0), R0		// arg 1 attr
+	BL	libc_pthread_attr_destroy(SB)
+	MOVW	R9, R13
+	RET
+
+TEXT runtime·pthread_attr_getstacksize_trampoline(SB),NOSPLIT,$0
+	MOVW	R13, R9
+	BIC     $0x7, R13		// align for ELF ABI
+	MOVW	4(R0), R1		// arg 2 size
+	MOVW	0(R0), R0		// arg 1 attr
+	BL	libc_pthread_attr_getstacksize(SB)
+	MOVW	R9, R13
+	RET
+
+TEXT runtime·pthread_attr_setdetachstate_trampoline(SB),NOSPLIT,$0
+	MOVW	R13, R9
+	BIC     $0x7, R13		// align for ELF ABI
+	MOVW	4(R0), R1		// arg 2 state
+	MOVW	0(R0), R0		// arg 1 attr
+	BL	libc_pthread_attr_setdetachstate(SB)
+	MOVW	R9, R13
+	RET
+
+TEXT runtime·pthread_create_trampoline(SB),NOSPLIT,$0
+	MOVW	R13, R9
+	SUB	$16, R13
+	BIC     $0x7, R13		// align for ELF ABI
+	MOVW	0(R0), R1		// arg 2 attr
+	MOVW	4(R0), R2		// arg 3 start
+	MOVW	8(R0), R3		// arg 4 arg
+	MOVW	R13, R0			// arg 1 &threadid (discarded)
+	BL	libc_pthread_create(SB)
+	MOVW	R9, R13
+	RET
+
 // Exit the entire program (like C exit)
 TEXT runtime·exit(SB),NOSPLIT|NOFRAME,$0
 	MOVW	code+0(FP), R0	// arg 1 - status
@@ -247,80 +368,6 @@ TEXT runtime·obsdsigprocmask(SB),NOSPLIT,$0
 	MOVW	R0, ret+8(FP)
 	RET
 
-TEXT runtime·sigfwd(SB),NOSPLIT,$0-16
-	MOVW	sig+4(FP), R0
-	MOVW	info+8(FP), R1
-	MOVW	ctx+12(FP), R2
-	MOVW	fn+0(FP), R11
-	MOVW	R13, R4
-	SUB	$24, R13
-	BIC	$0x7, R13 // alignment for ELF ABI
-	BL	(R11)
-	MOVW	R4, R13
-	RET
-
-TEXT runtime·sigtramp(SB),NOSPLIT,$0
-	// Reserve space for callee-save registers and arguments.
-	MOVM.DB.W [R4-R11], (R13)
-	SUB	$16, R13
-
-	// If called from an external code context, g will not be set.
-	// Save R0, since runtime·load_g will clobber it.
-	MOVW	R0, 4(R13)		// signum
-	MOVB	runtime·iscgo(SB), R0
-	CMP	$0, R0
-	BL.NE	runtime·load_g(SB)
-
-	MOVW	R1, 8(R13)
-	MOVW	R2, 12(R13)
-	BL	runtime·sigtrampgo(SB)
-
-	// Restore callee-save registers.
-	ADD	$16, R13
-	MOVM.IA.W (R13), [R4-R11]
-
-	RET
-
-// int32 tfork(void *param, uintptr psize, M *mp, G *gp, void (*fn)(void));
-TEXT runtime·tfork(SB),NOSPLIT,$0
-
-	// Copy mp, gp and fn off parent stack for use by child.
-	MOVW	mm+8(FP), R4
-	MOVW	gg+12(FP), R5
-	MOVW	fn+16(FP), R6
-
-	MOVW	param+0(FP), R0		// arg 1 - param
-	MOVW	psize+4(FP), R1		// arg 2 - psize
-	MOVW	$8, R12			// sys___tfork
-	INVOKE_SYSCALL
-
-	// Return if syscall failed.
-	B.CC	4(PC)
-	RSB	$0, R0
-	MOVW	R0, ret+20(FP)
-	RET
-
-	// In parent, return.
-	CMP	$0, R0
-	BEQ	3(PC)
-	MOVW	R0, ret+20(FP)
-	RET
-
-	// Initialise m, g.
-	MOVW	R5, g
-	MOVW	R4, g_m(g)
-
-	// Paranoia; check that stack splitting code works.
-	BL	runtime·emptyfunc(SB)
-
-	// Call fn.
-	BL	(R6)
-
-	// fn should never return.
-	MOVW	$2, R8			// crash if reached
-	MOVW	R8, (R8)
-	RET
-
 TEXT runtime·sigaltstack(SB),NOSPLIT,$0
 	MOVW	new+0(FP), R0		// arg 1 - new sigaltstack
 	MOVW	old+4(FP), R1		// arg 2 - old sigaltstack
@@ -423,13 +470,3 @@ TEXT runtime·setNonblock(SB),NOSPLIT,$0-4
 	MOVW	$92, R12
 	INVOKE_SYSCALL
 	RET
-
-TEXT ·publicationBarrier(SB),NOSPLIT|NOFRAME,$0-0
-	B	runtime·armPublicationBarrier(SB)
-
-TEXT runtime·read_tls_fallback(SB),NOSPLIT|NOFRAME,$0
-	MOVM.WP	[R1, R2, R3, R12], (R13)
-	MOVW	$330, R12		// sys___get_tcb
-	INVOKE_SYSCALL
-	MOVM.IAW (R13), [R1, R2, R3, R12]
-	RET