runtime: parse auxv on freebsd

Decode AT_PAGESZ to determine physPageSize on freebsd/{386,amd64,arm}
and AT_HWCAP for hwcap and hardDiv on freebsd/arm. Also use hwcap to
perform the FP checks in checkgoarm akin to the linux/arm
implementation.

Change-Id: I532810a1581efe66277e4305cb234acdc79ee91e
Reviewed-on: https://go-review.googlesource.com/99780
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/runtime/os_freebsd.go

@@ -207,7 +207,9 @@ func newosproc(mp *m, stk unsafe.Pointer) {
 
 func osinit() {
 	ncpu = getncpu()
-	physPageSize = getPageSize()
+	if physPageSize == 0 {
+		physPageSize = getPageSize()
+	}
 }
 
 var urandom_dev = []byte("/dev/urandom\x00")
@@ -317,3 +319,38 @@ func sigdelset(mask *sigset, i int) {
 
 func (c *sigctxt) fixsigcode(sig uint32) {
 }
+
+func sysargs(argc int32, argv **byte) {
+	n := argc + 1
+
+	// skip over argv, envp to get to auxv
+	for argv_index(argv, n) != nil {
+		n++
+	}
+
+	// skip NULL separator
+	n++
+
+	// now argv+n is auxv
+	auxv := (*[1 << 28]uintptr)(add(unsafe.Pointer(argv), uintptr(n)*sys.PtrSize))
+	sysauxv(auxv[:])
+}
+
+const (
+	_AT_NULL   = 0  // Terminates the vector
+	_AT_PAGESZ = 6  // Page size in bytes
+	_AT_HWCAP  = 16 // CPU feature flags
+)
+
+func sysauxv(auxv []uintptr) {
+	for i := 0; auxv[i] != _AT_NULL; i += 2 {
+		tag, val := auxv[i], auxv[i+1]
+		switch tag {
+		// _AT_NCPUS from auxv shouldn't be used due to golang.org/issue/15206
+		case _AT_PAGESZ:
+			physPageSize = val
+		}
+
+		archauxv(tag, val)
+	}
+}

src/runtime/os_freebsd_arm.go

@@ -4,10 +4,26 @@
 
 package runtime
 
-var hardDiv bool // TODO: set if a hardware divider is available
+const (
+	_HWCAP_VFP   = 1 << 6
+	_HWCAP_VFPv3 = 1 << 13
+	_HWCAP_IDIVA = 1 << 17
+)
+
+var hwcap uint32 // set by archauxv
+var hardDiv bool // set if a hardware divider is available
 
 func checkgoarm() {
-	// TODO(minux): FP checks like in os_linux_arm.go.
+	if goarm > 5 && hwcap&_HWCAP_VFP == 0 {
+		print("runtime: this CPU has no floating point hardware, so it cannot run\n")
+		print("this GOARM=", goarm, " binary. Recompile using GOARM=5.\n")
+		exit(1)
+	}
+	if goarm > 6 && hwcap&_HWCAP_VFPv3 == 0 {
+		print("runtime: this CPU has no VFPv3 floating point hardware, so it cannot run\n")
+		print("this GOARM=", goarm, " binary. Recompile using GOARM=5.\n")
+		exit(1)
+	}
 
 	// osinit not called yet, so ncpu not set: must use getncpu directly.
 	if getncpu() > 1 && goarm < 7 {
@@ -17,6 +33,14 @@ func checkgoarm() {
 	}
 }
 
+func archauxv(tag, val uintptr) {
+	switch tag {
+	case _AT_HWCAP: // CPU capability bit flags
+		hwcap = uint32(val)
+		hardDiv = (hwcap & _HWCAP_IDIVA) != 0
+	}
+}
+
 //go:nosplit
 func cputicks() int64 {
 	// Currently cputicks() is used in blocking profiler and to seed runtime·fastrand().

src/runtime/os_freebsd_noauxv.go

+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build freebsd
+// +build !arm
+
+package runtime
+
+func archauxv(tag, val uintptr) {
+}

src/runtime/vdso_none.go

@@ -4,6 +4,7 @@
 
 // +build !linux
 // +build !darwin
+// +build !freebsd
 
 package runtime