[release-branch.go1.17] runtime: keep //go:cgo_unsafe_args arguments alive to prevent GC

When syscall's DLL.FindProc calls into syscall_getprocaddress with a
byte slice pointer, we need to keep those bytes alive. Otherwise the GC
will collect the allocation, and we wind up calling `GetProcAddress` on
garbage, which showed up as various flakes in the builders. It turns out
that this problem extends to many uses of //go:cgo_unsafe_args
throughout, on all platforms. So this patch fixes the issue by keeping
non-integer pointer arguments alive through their invocation in
//go:cgo_unsafe_args functions.

Fixes #49868.
Updates #49731.

Change-Id: I93e4fbc2e8e210cb3fc53149708758bb33f2f9c7
Reviewed-on: https://go-review.googlesource.com/c/go/+/368355
Trust: Jason A. Donenfeld <[email protected]>
Run-TryBot: Jason A. Donenfeld <[email protected]>
TryBot-Result: Go Bot <[email protected]>
Reviewed-by: Michael Knyszek <[email protected]>

Author: zx2c4

src/runtime/sys_darwin.go

@@ -105,28 +105,38 @@ func syscallNoErr()
 //go:nosplit
 //go:cgo_unsafe_args
 func pthread_attr_init(attr *pthreadattr) int32 {
-	return libcCall(unsafe.Pointer(abi.FuncPCABI0(pthread_attr_init_trampoline)), unsafe.Pointer(&attr))
+	ret := libcCall(unsafe.Pointer(abi.FuncPCABI0(pthread_attr_init_trampoline)), unsafe.Pointer(&attr))
+	KeepAlive(attr)
+	return ret
 }
 func pthread_attr_init_trampoline()
 
 //go:nosplit
 //go:cgo_unsafe_args
 func pthread_attr_getstacksize(attr *pthreadattr, size *uintptr) int32 {
-	return libcCall(unsafe.Pointer(abi.FuncPCABI0(pthread_attr_getstacksize_trampoline)), unsafe.Pointer(&attr))
+	ret := libcCall(unsafe.Pointer(abi.FuncPCABI0(pthread_attr_getstacksize_trampoline)), unsafe.Pointer(&attr))
+	KeepAlive(attr)
+	KeepAlive(size)
+	return ret
 }
 func pthread_attr_getstacksize_trampoline()
 
 //go:nosplit
 //go:cgo_unsafe_args
 func pthread_attr_setdetachstate(attr *pthreadattr, state int) int32 {
-	return libcCall(unsafe.Pointer(abi.FuncPCABI0(pthread_attr_setdetachstate_trampoline)), unsafe.Pointer(&attr))
+	ret := libcCall(unsafe.Pointer(abi.FuncPCABI0(pthread_attr_setdetachstate_trampoline)), unsafe.Pointer(&attr))
+	KeepAlive(attr)
+	return ret
 }
 func pthread_attr_setdetachstate_trampoline()
 
 //go:nosplit
 //go:cgo_unsafe_args
 func pthread_create(attr *pthreadattr, start uintptr, arg unsafe.Pointer) int32 {
-	return libcCall(unsafe.Pointer(abi.FuncPCABI0(pthread_create_trampoline)), unsafe.Pointer(&attr))
+	ret := libcCall(unsafe.Pointer(abi.FuncPCABI0(pthread_create_trampoline)), unsafe.Pointer(&attr))
+	KeepAlive(attr)
+	KeepAlive(arg) // Just for consistency. Arg of course needs to be kept alive for the start function.
+	return ret
 }
 func pthread_create_trampoline()
 
@@ -175,27 +185,32 @@ func mmap_trampoline()
 //go:cgo_unsafe_args
 func munmap(addr unsafe.Pointer, n uintptr) {
 	libcCall(unsafe.Pointer(abi.FuncPCABI0(munmap_trampoline)), unsafe.Pointer(&addr))
+	KeepAlive(addr) // Just for consistency. Hopefully addr is not a Go address.
 }
 func munmap_trampoline()
 
 //go:nosplit
 //go:cgo_unsafe_args
 func madvise(addr unsafe.Pointer, n uintptr, flags int32) {
 	libcCall(unsafe.Pointer(abi.FuncPCABI0(madvise_trampoline)), unsafe.Pointer(&addr))
+	KeepAlive(addr) // Just for consistency. Hopefully addr is not a Go address.
 }
 func madvise_trampoline()
 
 //go:nosplit
 //go:cgo_unsafe_args
 func mlock(addr unsafe.Pointer, n uintptr) {
 	libcCall(unsafe.Pointer(abi.FuncPCABI0(mlock_trampoline)), unsafe.Pointer(&addr))
+	KeepAlive(addr) // Just for consistency. Hopefully addr is not a Go address.
 }
 func mlock_trampoline()
 
 //go:nosplit
 //go:cgo_unsafe_args
 func read(fd int32, p unsafe.Pointer, n int32) int32 {
-	return libcCall(unsafe.Pointer(abi.FuncPCABI0(read_trampoline)), unsafe.Pointer(&fd))
+	ret := libcCall(unsafe.Pointer(abi.FuncPCABI0(read_trampoline)), unsafe.Pointer(&fd))
+	KeepAlive(p)
+	return ret
 }
 func read_trampoline()
 
@@ -239,14 +254,18 @@ func usleep_no_g(usec uint32) {
 //go:nosplit
 //go:cgo_unsafe_args
 func write1(fd uintptr, p unsafe.Pointer, n int32) int32 {
-	return libcCall(unsafe.Pointer(abi.FuncPCABI0(write_trampoline)), unsafe.Pointer(&fd))
+	ret := libcCall(unsafe.Pointer(abi.FuncPCABI0(write_trampoline)), unsafe.Pointer(&fd))
+	KeepAlive(p)
+	return ret
 }
 func write_trampoline()
 
 //go:nosplit
 //go:cgo_unsafe_args
 func open(name *byte, mode, perm int32) (ret int32) {
-	return libcCall(unsafe.Pointer(abi.FuncPCABI0(open_trampoline)), unsafe.Pointer(&name))
+	ret = libcCall(unsafe.Pointer(abi.FuncPCABI0(open_trampoline)), unsafe.Pointer(&name))
+	KeepAlive(name)
+	return
 }
 func open_trampoline()
 
@@ -285,13 +304,17 @@ func walltime_trampoline()
 //go:cgo_unsafe_args
 func sigaction(sig uint32, new *usigactiont, old *usigactiont) {
 	libcCall(unsafe.Pointer(abi.FuncPCABI0(sigaction_trampoline)), unsafe.Pointer(&sig))
+	KeepAlive(new)
+	KeepAlive(old)
 }
 func sigaction_trampoline()
 
 //go:nosplit
 //go:cgo_unsafe_args
 func sigprocmask(how uint32, new *sigset, old *sigset) {
 	libcCall(unsafe.Pointer(abi.FuncPCABI0(sigprocmask_trampoline)), unsafe.Pointer(&how))
+	KeepAlive(new)
+	KeepAlive(old)
 }
 func sigprocmask_trampoline()
 
@@ -306,6 +329,8 @@ func sigaltstack(new *stackt, old *stackt) {
 		new.ss_size = 32768
 	}
 	libcCall(unsafe.Pointer(abi.FuncPCABI0(sigaltstack_trampoline)), unsafe.Pointer(&new))
+	KeepAlive(new)
+	KeepAlive(old)
 }
 func sigaltstack_trampoline()
 
@@ -320,20 +345,32 @@ func raiseproc_trampoline()
 //go:cgo_unsafe_args
 func setitimer(mode int32, new, old *itimerval) {
 	libcCall(unsafe.Pointer(abi.FuncPCABI0(setitimer_trampoline)), unsafe.Pointer(&mode))
+	KeepAlive(new)
+	KeepAlive(old)
 }
 func setitimer_trampoline()
 
 //go:nosplit
 //go:cgo_unsafe_args
 func sysctl(mib *uint32, miblen uint32, oldp *byte, oldlenp *uintptr, newp *byte, newlen uintptr) int32 {
-	return libcCall(unsafe.Pointer(abi.FuncPCABI0(sysctl_trampoline)), unsafe.Pointer(&mib))
+	ret := libcCall(unsafe.Pointer(abi.FuncPCABI0(sysctl_trampoline)), unsafe.Pointer(&mib))
+	KeepAlive(mib)
+	KeepAlive(oldp)
+	KeepAlive(oldlenp)
+	KeepAlive(newp)
+	return ret
 }
 func sysctl_trampoline()
 
 //go:nosplit
 //go:cgo_unsafe_args
 func sysctlbyname(name *byte, oldp *byte, oldlenp *uintptr, newp *byte, newlen uintptr) int32 {
-	return libcCall(unsafe.Pointer(abi.FuncPCABI0(sysctlbyname_trampoline)), unsafe.Pointer(&name))
+	ret := libcCall(unsafe.Pointer(abi.FuncPCABI0(sysctlbyname_trampoline)), unsafe.Pointer(&name))
+	KeepAlive(name)
+	KeepAlive(oldp)
+	KeepAlive(oldlenp)
+	KeepAlive(newp)
+	return ret
 }
 func sysctlbyname_trampoline()
 
@@ -355,56 +392,79 @@ func kqueue_trampoline()
 //go:nosplit
 //go:cgo_unsafe_args
 func kevent(kq int32, ch *keventt, nch int32, ev *keventt, nev int32, ts *timespec) int32 {
-	return libcCall(unsafe.Pointer(abi.FuncPCABI0(kevent_trampoline)), unsafe.Pointer(&kq))
+	ret := libcCall(unsafe.Pointer(abi.FuncPCABI0(kevent_trampoline)), unsafe.Pointer(&kq))
+	KeepAlive(ch)
+	KeepAlive(ev)
+	KeepAlive(ts)
+	return ret
 }
 func kevent_trampoline()
 
 //go:nosplit
 //go:cgo_unsafe_args
 func pthread_mutex_init(m *pthreadmutex, attr *pthreadmutexattr) int32 {
-	return libcCall(unsafe.Pointer(abi.FuncPCABI0(pthread_mutex_init_trampoline)), unsafe.Pointer(&m))
+	ret := libcCall(unsafe.Pointer(abi.FuncPCABI0(pthread_mutex_init_trampoline)), unsafe.Pointer(&m))
+	KeepAlive(m)
+	KeepAlive(attr)
+	return ret
 }
 func pthread_mutex_init_trampoline()
 
 //go:nosplit
 //go:cgo_unsafe_args
 func pthread_mutex_lock(m *pthreadmutex) int32 {
-	return libcCall(unsafe.Pointer(abi.FuncPCABI0(pthread_mutex_lock_trampoline)), unsafe.Pointer(&m))
+	ret := libcCall(unsafe.Pointer(abi.FuncPCABI0(pthread_mutex_lock_trampoline)), unsafe.Pointer(&m))
+	KeepAlive(m)
+	return ret
 }
 func pthread_mutex_lock_trampoline()
 
 //go:nosplit
 //go:cgo_unsafe_args
 func pthread_mutex_unlock(m *pthreadmutex) int32 {
-	return libcCall(unsafe.Pointer(abi.FuncPCABI0(pthread_mutex_unlock_trampoline)), unsafe.Pointer(&m))
+	ret := libcCall(unsafe.Pointer(abi.FuncPCABI0(pthread_mutex_unlock_trampoline)), unsafe.Pointer(&m))
+	KeepAlive(m)
+	return ret
 }
 func pthread_mutex_unlock_trampoline()
 
 //go:nosplit
 //go:cgo_unsafe_args
 func pthread_cond_init(c *pthreadcond, attr *pthreadcondattr) int32 {
-	return libcCall(unsafe.Pointer(abi.FuncPCABI0(pthread_cond_init_trampoline)), unsafe.Pointer(&c))
+	ret := libcCall(unsafe.Pointer(abi.FuncPCABI0(pthread_cond_init_trampoline)), unsafe.Pointer(&c))
+	KeepAlive(c)
+	KeepAlive(attr)
+	return ret
 }
 func pthread_cond_init_trampoline()
 
 //go:nosplit
 //go:cgo_unsafe_args
 func pthread_cond_wait(c *pthreadcond, m *pthreadmutex) int32 {
-	return libcCall(unsafe.Pointer(abi.FuncPCABI0(pthread_cond_wait_trampoline)), unsafe.Pointer(&c))
+	ret := libcCall(unsafe.Pointer(abi.FuncPCABI0(pthread_cond_wait_trampoline)), unsafe.Pointer(&c))
+	KeepAlive(c)
+	KeepAlive(m)
+	return ret
 }
 func pthread_cond_wait_trampoline()
 
 //go:nosplit
 //go:cgo_unsafe_args
 func pthread_cond_timedwait_relative_np(c *pthreadcond, m *pthreadmutex, t *timespec) int32 {
-	return libcCall(unsafe.Pointer(abi.FuncPCABI0(pthread_cond_timedwait_relative_np_trampoline)), unsafe.Pointer(&c))
+	ret := libcCall(unsafe.Pointer(abi.FuncPCABI0(pthread_cond_timedwait_relative_np_trampoline)), unsafe.Pointer(&c))
+	KeepAlive(c)
+	KeepAlive(m)
+	KeepAlive(t)
+	return ret
 }
 func pthread_cond_timedwait_relative_np_trampoline()
 
 //go:nosplit
 //go:cgo_unsafe_args
 func pthread_cond_signal(c *pthreadcond) int32 {
-	return libcCall(unsafe.Pointer(abi.FuncPCABI0(pthread_cond_signal_trampoline)), unsafe.Pointer(&c))
+	ret := libcCall(unsafe.Pointer(abi.FuncPCABI0(pthread_cond_signal_trampoline)), unsafe.Pointer(&c))
+	KeepAlive(c)
+	return ret
 }
 func pthread_cond_signal_trampoline()
 

src/runtime/sys_darwin_arm64.go

@@ -14,7 +14,9 @@ import (
 //go:nosplit
 //go:cgo_unsafe_args
 func g0_pthread_key_create(k *pthreadkey, destructor uintptr) int32 {
-	return asmcgocall(unsafe.Pointer(funcPC(pthread_key_create_trampoline)), unsafe.Pointer(&k))
+	ret := asmcgocall(unsafe.Pointer(funcPC(pthread_key_create_trampoline)), unsafe.Pointer(&k))
+	KeepAlive(k)
+	return ret
 }
 func pthread_key_create_trampoline()
 

src/runtime/sys_openbsd.go

@@ -15,35 +15,47 @@ import "unsafe"
 //go:nosplit
 //go:cgo_unsafe_args
 func pthread_attr_init(attr *pthreadattr) int32 {
-	return libcCall(unsafe.Pointer(funcPC(pthread_attr_init_trampoline)), unsafe.Pointer(&attr))
+	ret := libcCall(unsafe.Pointer(funcPC(pthread_attr_init_trampoline)), unsafe.Pointer(&attr))
+	KeepAlive(attr)
+	return ret
 }
 func pthread_attr_init_trampoline()
 
 //go:nosplit
 //go:cgo_unsafe_args
 func pthread_attr_destroy(attr *pthreadattr) int32 {
-	return libcCall(unsafe.Pointer(funcPC(pthread_attr_destroy_trampoline)), unsafe.Pointer(&attr))
+	ret := libcCall(unsafe.Pointer(funcPC(pthread_attr_destroy_trampoline)), unsafe.Pointer(&attr))
+	KeepAlive(attr)
+	return ret
 }
 func pthread_attr_destroy_trampoline()
 
 //go:nosplit
 //go:cgo_unsafe_args
 func pthread_attr_getstacksize(attr *pthreadattr, size *uintptr) int32 {
-	return libcCall(unsafe.Pointer(funcPC(pthread_attr_getstacksize_trampoline)), unsafe.Pointer(&attr))
+	ret := libcCall(unsafe.Pointer(funcPC(pthread_attr_getstacksize_trampoline)), unsafe.Pointer(&attr))
+	KeepAlive(attr)
+	KeepAlive(size)
+	return ret
 }
 func pthread_attr_getstacksize_trampoline()
 
 //go:nosplit
 //go:cgo_unsafe_args
 func pthread_attr_setdetachstate(attr *pthreadattr, state int) int32 {
-	return libcCall(unsafe.Pointer(funcPC(pthread_attr_setdetachstate_trampoline)), unsafe.Pointer(&attr))
+	ret := libcCall(unsafe.Pointer(funcPC(pthread_attr_setdetachstate_trampoline)), unsafe.Pointer(&attr))
+	KeepAlive(attr)
+	return ret
 }
 func pthread_attr_setdetachstate_trampoline()
 
 //go:nosplit
 //go:cgo_unsafe_args
 func pthread_create(attr *pthreadattr, start uintptr, arg unsafe.Pointer) int32 {
-	return libcCall(unsafe.Pointer(funcPC(pthread_create_trampoline)), unsafe.Pointer(&attr))
+	ret := libcCall(unsafe.Pointer(funcPC(pthread_create_trampoline)), unsafe.Pointer(&attr))
+	KeepAlive(attr)
+	KeepAlive(arg) // Just for consistency. Arg of course needs to be kept alive for the start function.
+	return ret
 }
 func pthread_create_trampoline()
 

src/runtime/sys_openbsd1.go

@@ -12,7 +12,10 @@ import "unsafe"
 //go:nosplit
 //go:cgo_unsafe_args
 func thrsleep(ident uintptr, clock_id int32, tsp *timespec, lock uintptr, abort *uint32) int32 {
-	return libcCall(unsafe.Pointer(funcPC(thrsleep_trampoline)), unsafe.Pointer(&ident))
+	ret := libcCall(unsafe.Pointer(funcPC(thrsleep_trampoline)), unsafe.Pointer(&ident))
+	KeepAlive(tsp)
+	KeepAlive(abort)
+	return ret
 }
 func thrsleep_trampoline()