fcdb024 internal/fakecgo: circumvent Go 1.20's race code (#73) · purego

M example/main.go +11 -1


@@ -6,9 +6,19 @@
6	6		package main
7	7
8	8		import (
	9	+	"os"
	10	+
9	11		_ "github.com/ebitengine/purego"
10	12		)
11	13
12	14		func main() {
13		-	// TODO: Add an implementation. This example exists only for testing so far.
	15	+	// set and unset an environment variable since this calls into fakecgo.
	16	+	err := os.Setenv("TESTING", "SOMETHING")
	17	+	if err != nil {
	18	+	panic(err)
	19	+	}
	20	+	err = os.Unsetenv("TESTING")
	21	+	if err != nil {
	22	+	panic(err)
	23	+	}
14	24		}


@@ -6,9 +6,19 @@
6		package main	6		package main
7			7
8		import (	8		import (
			9	+	"os"
			10	+
9		_ "github.com/ebitengine/purego"	11		_ "github.com/ebitengine/purego"
10		)	12		)
11			13
12		func main() {	14		func main() {
13	-	// TODO: Add an implementation. This example exists only for testing so far.	15	+	// set and unset an environment variable since this calls into fakecgo.
			16	+	err := os.Setenv("TESTING", "SOMETHING")
			17	+	if err != nil {
			18	+	panic(err)
			19	+	}
			20	+	err = os.Unsetenv("TESTING")
			21	+	if err != nil {
			22	+	panic(err)
			23	+	}
14		}	24		}

M internal/fakecgo/callbacks.go +15 -0


@@ -41,3 +41,18 @@ var _cgo_notify_runtime_init_done = &x_cgo_notify_runtime_init_done_trampoline
41	41
42	42		// TODO: decide if we need x_cgo_set_context_function
43	43		// TODO: decide if we need _cgo_yield
	44	+
	45	+	var (
	46	+	// In Go 1.20 the race detector was rewritten to pure Go
	47	+	// on darwin. This means that when CGO_ENABLED=0 is set
	48	+	// fakecgo is built with race detector code. This is not
	49	+	// good since this code is pretending to be C. The
	50	+	// go:norace comments are not enough since the ABI wrappers
	51	+	// still have race code. These variables will circumvent
	52	+	// that issue by calling the function directly.
	53	+	threadentry_call = threadentry
	54	+	x_cgo_init_call = x_cgo_init
	55	+	x_cgo_setenv_call = x_cgo_setenv
	56	+	x_cgo_unsetenv_call = x_cgo_unsetenv
	57	+	x_cgo_thread_start_call = x_cgo_thread_start
	58	+	)


@@ -41,3 +41,18 @@ var _cgo_notify_runtime_init_done = &x_cgo_notify_runtime_init_done_trampoline
41		41
42	// TODO: decide if we need x_cgo_set_context_function	42		// TODO: decide if we need x_cgo_set_context_function
43	// TODO: decide if we need _cgo_yield	43		// TODO: decide if we need _cgo_yield
		44	+
		45	+	var (
		46	+	// In Go 1.20 the race detector was rewritten to pure Go
		47	+	// on darwin. This means that when CGO_ENABLED=0 is set
		48	+	// fakecgo is built with race detector code. This is not
		49	+	// good since this code is pretending to be C. The
		50	+	// go:norace comments are not enough since the ABI wrappers
		51	+	// still have race code. These variables will circumvent
		52	+	// that issue by calling the function directly.
		53	+	threadentry_call = threadentry
		54	+	x_cgo_init_call = x_cgo_init
		55	+	x_cgo_setenv_call = x_cgo_setenv
		56	+	x_cgo_unsetenv_call = x_cgo_unsetenv
		57	+	x_cgo_thread_start_call = x_cgo_thread_start
		58	+	)

M internal/fakecgo/go_darwin_amd64.go +3 -0


@@ -7,6 +7,7 @@ package fakecgo
7	7		import "unsafe"
8	8
9	9		//go:nosplit
	10	+	//go:norace
10	11		func _cgo_sys_thread_start(ts *ThreadStart) {
11	12		var attr pthread_attr_t
12	13		var ign, oset sigset_t

@@ -41,6 +42,7 @@ var x_threadentry_trampoline byte
41	42		var threadentry_trampolineABI0 = &x_threadentry_trampoline
42	43
43	44		//go:nosplit
	45	+	//go:norace
44	46		func threadentry(v unsafe.Pointer) unsafe.Pointer {
45	47		ts := (ThreadStart)(v)
46	48		free(v)

@@ -58,6 +60,7 @@ func threadentry(v unsafe.Pointer) unsafe.Pointer {
58	60		var setg_func uintptr
59	61
60	62		//go:nosplit
	63	+	//go:norace
61	64		func x_cgo_init(g *G, setg uintptr) {
62	65		var size size_t
63	66		var attr pthread_attr_t


@@ -7,6 +7,7 @@ package fakecgo
7	import "unsafe"	7		import "unsafe"
8		8
9	//go:nosplit	9		//go:nosplit
		10	+	//go:norace
10	func _cgo_sys_thread_start(ts *ThreadStart) {	11		func _cgo_sys_thread_start(ts *ThreadStart) {
11	var attr pthread_attr_t	12		var attr pthread_attr_t
12	var ign, oset sigset_t	13		var ign, oset sigset_t

@@ -41,6 +42,7 @@ var x_threadentry_trampoline byte
41	var threadentry_trampolineABI0 = &x_threadentry_trampoline	42		var threadentry_trampolineABI0 = &x_threadentry_trampoline
42		43
43	//go:nosplit	44		//go:nosplit
		45	+	//go:norace
44	func threadentry(v unsafe.Pointer) unsafe.Pointer {	46		func threadentry(v unsafe.Pointer) unsafe.Pointer {
45	ts := (ThreadStart)(v)	47		ts := (ThreadStart)(v)
46	free(v)	48		free(v)

@@ -58,6 +60,7 @@ func threadentry(v unsafe.Pointer) unsafe.Pointer {
58	var setg_func uintptr	60		var setg_func uintptr
59		61
60	//go:nosplit	62		//go:nosplit
		63	+	//go:norace
61	func x_cgo_init(g *G, setg uintptr) {	64		func x_cgo_init(g *G, setg uintptr) {
62	var size size_t	65		var size size_t
63	var attr pthread_attr_t	66		var attr pthread_attr_t

M internal/fakecgo/go_darwin_arm64.go +3 -0


@@ -7,6 +7,7 @@ package fakecgo
7	7		import "unsafe"
8	8
9	9		//go:nosplit
	10	+	//go:norace
10	11		func _cgo_sys_thread_start(ts *ThreadStart) {
11	12		var attr pthread_attr_t
12	13		var ign, oset sigset_t

@@ -41,6 +42,7 @@ var x_threadentry_trampoline byte
41	42		var threadentry_trampolineABI0 = &x_threadentry_trampoline
42	43
43	44		//go:nosplit
	45	+	//go:norace
44	46		func threadentry(v unsafe.Pointer) unsafe.Pointer {
45	47		ts := (ThreadStart)(v)
46	48		free(v)

@@ -67,6 +69,7 @@ var setg_func uintptr
67	69		// This function can't be go:systemstack since go is not in a state where the systemcheck would work.
68	70		//
69	71		//go:nosplit
	72	+	//go:norace
70	73		func x_cgo_init(g *G, setg uintptr) {
71	74		var size size_t
72	75		var attr pthread_attr_t


@@ -7,6 +7,7 @@ package fakecgo
7	import "unsafe"	7		import "unsafe"
8		8
9	//go:nosplit	9		//go:nosplit
		10	+	//go:norace
10	func _cgo_sys_thread_start(ts *ThreadStart) {	11		func _cgo_sys_thread_start(ts *ThreadStart) {
11	var attr pthread_attr_t	12		var attr pthread_attr_t
12	var ign, oset sigset_t	13		var ign, oset sigset_t

@@ -41,6 +42,7 @@ var x_threadentry_trampoline byte
41	var threadentry_trampolineABI0 = &x_threadentry_trampoline	42		var threadentry_trampolineABI0 = &x_threadentry_trampoline
42		43
43	//go:nosplit	44		//go:nosplit
		45	+	//go:norace
44	func threadentry(v unsafe.Pointer) unsafe.Pointer {	46		func threadentry(v unsafe.Pointer) unsafe.Pointer {
45	ts := (ThreadStart)(v)	47		ts := (ThreadStart)(v)
46	free(v)	48		free(v)

@@ -67,6 +69,7 @@ var setg_func uintptr
67	// This function can't be go:systemstack since go is not in a state where the systemcheck would work.	69		// This function can't be go:systemstack since go is not in a state where the systemcheck would work.
68	//	70		//
69	//go:nosplit	71		//go:nosplit
		72	+	//go:norace
70	func x_cgo_init(g *G, setg uintptr) {	73		func x_cgo_init(g *G, setg uintptr) {
71	var size size_t	74		var size size_t
72	var attr pthread_attr_t	75		var attr pthread_attr_t

M internal/fakecgo/go_libinit.go +1 -0


@@ -19,6 +19,7 @@ func x_cgo_notify_runtime_init_done() {
19	19		// EAGAIN.
20	20		//
21	21		//go:nosplit
	22	+	//go:norace
22	23		func _cgo_try_pthread_create(thread pthread_t, attr pthread_attr_t, pfn unsafe.Pointer, arg *ThreadStart) int {
23	24		var ts syscall.Timespec
24	25		// tries needs to be the same type as syscall.Timespec.Nsec


@@ -19,6 +19,7 @@ func x_cgo_notify_runtime_init_done() {
19	// EAGAIN.	19		// EAGAIN.
20	//	20		//
21	//go:nosplit	21		//go:nosplit
		22	+	//go:norace
22	func _cgo_try_pthread_create(thread pthread_t, attr pthread_attr_t, pfn unsafe.Pointer, arg *ThreadStart) int {	23		func _cgo_try_pthread_create(thread pthread_t, attr pthread_attr_t, pfn unsafe.Pointer, arg *ThreadStart) int {
23	var ts syscall.Timespec	24		var ts syscall.Timespec
24	// tries needs to be the same type as syscall.Timespec.Nsec	25		// tries needs to be the same type as syscall.Timespec.Nsec

M internal/fakecgo/go_setenv.go +2 -0


@@ -6,11 +6,13 @@
6	6		package fakecgo
7	7
8	8		//go:nosplit
	9	+	//go:norace
9	10		func x_cgo_setenv(arg [2]byte) {
10	11		setenv(arg[0], arg[1], 1)
11	12		}
12	13
13	14		//go:nosplit
	15	+	//go:norace
14	16		func x_cgo_unsetenv(arg [1]byte) {
15	17		unsetenv(arg[0])
16	18		}


@@ -6,11 +6,13 @@
6	package fakecgo	6		package fakecgo
7		7
8	//go:nosplit	8		//go:nosplit
		9	+	//go:norace
9	func x_cgo_setenv(arg [2]byte) {	10		func x_cgo_setenv(arg [2]byte) {
10	setenv(arg[0], arg[1], 1)	11		setenv(arg[0], arg[1], 1)
11	}	12		}
12		13
13	//go:nosplit	14		//go:nosplit
		15	+	//go:norace
14	func x_cgo_unsetenv(arg [1]byte) {	16		func x_cgo_unsetenv(arg [1]byte) {
15	unsetenv(arg[0])	17		unsetenv(arg[0])
16	}	18		}

M internal/fakecgo/go_util.go +1 -0


@@ -16,6 +16,7 @@ import "unsafe"
16	16		// This function should be go:systemstack instead of go:nosplit (but that requires runtime)
17	17		//
18	18		//go:nosplit
	19	+	//go:norace
19	20		func x_cgo_thread_start(arg *ThreadStart) {
20	21		var ts *ThreadStart
21	22		// Make our own copy that can persist after we return.


@@ -16,6 +16,7 @@ import "unsafe"
16	// This function should be go:systemstack instead of go:nosplit (but that requires runtime)	16		// This function should be go:systemstack instead of go:nosplit (but that requires runtime)
17	//	17		//
18	//go:nosplit	18		//go:nosplit
		19	+	//go:norace
19	func x_cgo_thread_start(arg *ThreadStart) {	20		func x_cgo_thread_start(arg *ThreadStart) {
20	var ts *ThreadStart	21		var ts *ThreadStart
21	// Make our own copy that can persist after we return.	22		// Make our own copy that can persist after we return.

M internal/fakecgo/trampolines_amd64.s +21 -12


@@ -29,24 +29,32 @@ return value will be in AX
29	29		// these trampolines map the gcc ABI to Go ABI and then calls into the Go equivalent functions.
30	30
31	31		TEXT x_cgo_init_trampoline(SB), NOSPLIT, $16
32		-	MOVQ DI, 0(SP)
33		-	MOVQ SI, 8(SP)
34		-	CALL ·x_cgo_init(SB)
	32	+	MOVQ DI, AX
	33	+	MOVQ SI, BX
	34	+	MOVQ ·x_cgo_init_call(SB), DX
	35	+	MOVQ (DX), CX
	36	+	CALL CX
35	37		RET
36	38
37	39		TEXT x_cgo_thread_start_trampoline(SB), NOSPLIT, $8
38		-	MOVQ DI, 0(SP)
39		-	CALL ·x_cgo_thread_start(SB)
	40	+	MOVQ DI, AX
	41	+	MOVQ ·x_cgo_thread_start_call(SB), DX
	42	+	MOVQ (DX), CX
	43	+	CALL CX
40	44		RET
41	45
42	46		TEXT x_cgo_setenv_trampoline(SB), NOSPLIT, $8
43		-	MOVQ DI, 0(SP)
44		-	CALL ·x_cgo_setenv(SB)
	47	+	MOVQ DI, AX
	48	+	MOVQ ·x_cgo_setenv_call(SB), DX
	49	+	MOVQ (DX), CX
	50	+	CALL CX
45	51		RET
46	52
47	53		TEXT x_cgo_unsetenv_trampoline(SB), NOSPLIT, $8
48		-	MOVQ DI, 0(SP)
49		-	CALL ·x_cgo_unsetenv(SB)
	54	+	MOVQ DI, AX
	55	+	MOVQ ·x_cgo_unsetenv_call(SB), DX
	56	+	MOVQ (DX), CX
	57	+	CALL CX
50	58		RET
51	59
52	60		TEXT x_cgo_notify_runtime_init_done_trampoline(SB), NOSPLIT, $0

@@ -61,9 +69,10 @@ TEXT ·setg_trampoline(SB), NOSPLIT, $0-16
61	69		RET
62	70
63	71		TEXT threadentry_trampoline(SB), NOSPLIT, $16
64		-	MOVQ DI, 0(SP)
65		-	CALL ·threadentry(SB)
66		-	MOVQ 8(SP), AX
	72	+	MOVQ DI, AX
	73	+	MOVQ ·threadentry_call(SB), DX
	74	+	MOVQ (DX), CX
	75	+	CALL CX
67	76		RET
68	77
69	78		TEXT ·call5(SB), NOSPLIT, $0-0

 // these trampolines map the gcc ABI to Go ABI and then calls into the Go equivalent functions.
 TEXT x_cgo_init_trampoline(SB), NOSPLIT, $16
-	MOVQ DI, 0(SP)
+	MOVQ DI, AX
-	MOVQ SI, 8(SP)
+	MOVQ SI, BX
-	CALL ·x_cgo_init(SB)
+	MOVQ ·x_cgo_init_call(SB), DX
+	MOVQ (DX), CX
+	CALL CX
 	RET
 TEXT x_cgo_thread_start_trampoline(SB), NOSPLIT, $8
-	MOVQ DI, 0(SP)
+	MOVQ DI, AX
-	CALL ·x_cgo_thread_start(SB)
+	MOVQ ·x_cgo_thread_start_call(SB), DX
+	MOVQ (DX), CX
+	CALL CX
 	RET
 TEXT x_cgo_setenv_trampoline(SB), NOSPLIT, $8
-	MOVQ DI, 0(SP)
+	MOVQ DI, AX
-	CALL ·x_cgo_setenv(SB)
+	MOVQ ·x_cgo_setenv_call(SB), DX
+	MOVQ (DX), CX
+	CALL CX
 	RET
 TEXT x_cgo_unsetenv_trampoline(SB), NOSPLIT, $8
-	MOVQ DI, 0(SP)
+	MOVQ DI, AX
-	CALL ·x_cgo_unsetenv(SB)
+	MOVQ ·x_cgo_unsetenv_call(SB), DX
+	MOVQ (DX), CX
+	CALL CX
 	RET
 TEXT x_cgo_notify_runtime_init_done_trampoline(SB), NOSPLIT, $0
 	RET
 TEXT threadentry_trampoline(SB), NOSPLIT, $16
-	MOVQ DI, 0(SP)
+	MOVQ DI, AX
-	CALL ·threadentry(SB)
+	MOVQ ·threadentry_call(SB), DX
-	MOVQ 8(SP), AX
+	MOVQ (DX), CX
+	CALL CX
 	RET
 TEXT ·call5(SB), NOSPLIT, $0-0

M internal/fakecgo/trampolines_arm64.s +16 -6


@@ -11,22 +11,30 @@
11	11		TEXT x_cgo_init_trampoline(SB), NOSPLIT, $0-0
12	12		MOVD R0, 8(RSP)
13	13		MOVD R1, 16(RSP)
14		-	CALL ·x_cgo_init(SB)
	14	+	MOVD ·x_cgo_init_call(SB), R26
	15	+	MOVD (R26), R2
	16	+	CALL (R2)
15	17		RET
16	18
17	19		TEXT x_cgo_thread_start_trampoline(SB), NOSPLIT, $0-0
18	20		MOVD R0, 8(RSP)
19		-	CALL ·x_cgo_thread_start(SB)
	21	+	MOVD ·x_cgo_thread_start_call(SB), R26
	22	+	MOVD (R26), R2
	23	+	CALL (R2)
20	24		RET
21	25
22	26		TEXT x_cgo_setenv_trampoline(SB), NOSPLIT, $0-0
23	27		MOVD R0, 8(RSP)
24		-	CALL ·x_cgo_setenv(SB)
	28	+	MOVD ·x_cgo_setenv_call(SB), R26
	29	+	MOVD (R26), R2
	30	+	CALL (R2)
25	31		RET
26	32
27	33		TEXT x_cgo_unsetenv_trampoline(SB), NOSPLIT, $0-0
28	34		MOVD R0, 8(RSP)
29		-	CALL ·x_cgo_unsetenv(SB)
	35	+	MOVD ·x_cgo_unsetenv_call(SB), R26
	36	+	MOVD (R26), R2
	37	+	CALL (R2)
30	38		RET
31	39
32	40		TEXT x_cgo_notify_runtime_init_done_trampoline(SB), NOSPLIT, $0-0

@@ -42,8 +50,10 @@ TEXT ·setg_trampoline(SB), NOSPLIT, $0-16
42	50
43	51		TEXT threadentry_trampoline(SB), NOSPLIT, $0-0
44	52		MOVD R0, 8(RSP)
45		-	CALL ·threadentry(SB)
46		-	MOVD $0, R0 // TODO: get the return value from threadentry
	53	+	MOVD ·threadentry_call(SB), R26
	54	+	MOVD (R26), R2
	55	+	CALL (R2)
	56	+	MOVD $0, R0 // TODO: get the return value from threadentry
47	57		RET
48	58
49	59		TEXT ·call5(SB), NOSPLIT, $0-0

 TEXT x_cgo_init_trampoline(SB), NOSPLIT, $0-0
 	MOVD R0, 8(RSP)
 	MOVD R1, 16(RSP)
-	CALL ·x_cgo_init(SB)
+	MOVD ·x_cgo_init_call(SB), R26
+	MOVD (R26), R2
+	CALL (R2)
 	RET
 TEXT x_cgo_thread_start_trampoline(SB), NOSPLIT, $0-0
 	MOVD R0, 8(RSP)
-	CALL ·x_cgo_thread_start(SB)
+	MOVD ·x_cgo_thread_start_call(SB), R26
+	MOVD (R26), R2
+	CALL (R2)
 	RET
 TEXT x_cgo_setenv_trampoline(SB), NOSPLIT, $0-0
 	MOVD R0, 8(RSP)
-	CALL ·x_cgo_setenv(SB)
+	MOVD ·x_cgo_setenv_call(SB), R26
+	MOVD (R26), R2
+	CALL (R2)
 	RET
 TEXT x_cgo_unsetenv_trampoline(SB), NOSPLIT, $0-0
 	MOVD R0, 8(RSP)
-	CALL ·x_cgo_unsetenv(SB)
+	MOVD ·x_cgo_unsetenv_call(SB), R26
+	MOVD (R26), R2
+	CALL (R2)
 	RET
 TEXT x_cgo_notify_runtime_init_done_trampoline(SB), NOSPLIT, $0-0
 TEXT threadentry_trampoline(SB), NOSPLIT, $0-0
 	MOVD R0, 8(RSP)
-	CALL ·threadentry(SB)
+	MOVD ·threadentry_call(SB), R26
-	MOVD $0, R0           // TODO: get the return value from threadentry
+	MOVD (R26), R2
+	CALL (R2)
+	MOVD $0, R0                     // TODO: get the return value from threadentry
 	RET
 TEXT ·call5(SB), NOSPLIT, $0-0