runtime: common auxv parser

Currently several different Linux architectures have separate copies
of the auxv parser. Bring these all together into a single copy of the
parser that calls out to a per-arch handler for each tag/value pair.
This is in preparation for handling common auxv tags in one place.

For #9993.

Change-Id: Iceebc3afad6b4133b70fca7003561ae370445c10
Reviewed-on: https://go-review.googlesource.com/22061
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Michael Hudson-Doyle <michael.hudson@canonical.com>

src/runtime/os_linux.go

@@ -176,6 +176,29 @@ func newosproc0(stacksize uintptr, fn unsafe.Pointer) {
 var failallocatestack = []byte("runtime: failed to allocate stack for the new OS thread\n")
 var failthreadcreate = []byte("runtime: failed to create new OS thread\n")
 
+const (
+	_AT_NULL = 0 // End of vector
+)
+
+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))
+	for i := 0; auxv[i] != _AT_NULL; i += 2 {
+		tag, val := auxv[i], auxv[i+1]
+		archauxv(tag, val)
+	}
+}
+
 func osinit() {
 	ncpu = getproccount()
 }

src/runtime/os_linux_386.go

@@ -4,30 +4,16 @@
 
 package runtime
 
-import (
-	"runtime/internal/sys"
-	"unsafe"
-)
+import "unsafe"
 
 const (
-	_AT_NULL    = 0
 	_AT_RANDOM  = 25
 	_AT_SYSINFO = 32
 )
 
-func sysargs(argc int32, argv **byte) {
-	// skip over argv, envv to get to auxv
-	n := argc + 1
-	for argv_index(argv, n) != nil {
-		n++
-	}
-	n++
-	auxv := (*[1 << 28]uint32)(add(unsafe.Pointer(argv), uintptr(n)*sys.PtrSize))
-
-	for i := 0; auxv[i] != _AT_NULL; i += 2 {
-		switch auxv[i] {
-		case _AT_RANDOM:
-			startupRandomData = (*[16]byte)(unsafe.Pointer(uintptr(auxv[i+1])))[:]
-		}
+func archauxv(tag, val uintptr) {
+	switch tag {
+	case _AT_RANDOM:
+		startupRandomData = (*[16]byte)(unsafe.Pointer(val))[:]
 	}
 }

src/runtime/os_linux_arm.go

@@ -4,13 +4,9 @@
 
 package runtime
 
-import (
-	"runtime/internal/sys"
-	"unsafe"
-)
+import "unsafe"
 
 const (
-	_AT_NULL     = 0
 	_AT_PLATFORM = 15 //  introduced in at least 2.6.11
 	_AT_HWCAP    = 16 // introduced in at least 2.6.11
 	_AT_RANDOM   = 25 // introduced in 2.6.29
@@ -36,33 +32,23 @@ func checkgoarm() {
 	}
 }
 
-func sysargs(argc int32, argv **byte) {
-	// skip over argv, envv to get to auxv
-	n := argc + 1
-	for argv_index(argv, n) != nil {
-		n++
-	}
-	n++
-	auxv := (*[1 << 28]uint32)(add(unsafe.Pointer(argv), uintptr(n)*sys.PtrSize))
-
-	for i := 0; auxv[i] != _AT_NULL; i += 2 {
-		switch auxv[i] {
-		case _AT_RANDOM: // kernel provides a pointer to 16-bytes worth of random data
-			startupRandomData = (*[16]byte)(unsafe.Pointer(uintptr(auxv[i+1])))[:]
-			// the pointer provided may not be word aligned, so we must treat it
-			// as a byte array.
-			randomNumber = uint32(startupRandomData[4]) | uint32(startupRandomData[5])<<8 |
-				uint32(startupRandomData[6])<<16 | uint32(startupRandomData[7])<<24
-
-		case _AT_PLATFORM: // v5l, v6l, v7l
-			t := *(*uint8)(unsafe.Pointer(uintptr(auxv[i+1] + 1)))
-			if '5' <= t && t <= '7' {
-				armArch = t - '0'
-			}
-
-		case _AT_HWCAP: // CPU capability bit flags
-			hwcap = auxv[i+1]
+func archauxv(tag, val uintptr) {
+	switch tag {
+	case _AT_RANDOM: // kernel provides a pointer to 16-bytes worth of random data
+		startupRandomData = (*[16]byte)(unsafe.Pointer(val))[:]
+		// the pointer provided may not be word aligned, so we must treat it
+		// as a byte array.
+		randomNumber = uint32(startupRandomData[4]) | uint32(startupRandomData[5])<<8 |
+			uint32(startupRandomData[6])<<16 | uint32(startupRandomData[7])<<24
+
+	case _AT_PLATFORM: // v5l, v6l, v7l
+		t := *(*uint8)(unsafe.Pointer(val + 1))
+		if '5' <= t && t <= '7' {
+			armArch = t - '0'
 		}
+
+	case _AT_HWCAP: // CPU capability bit flags
+		hwcap = uint32(val)
 	}
 }
 

src/runtime/os_linux_arm64.go

@@ -4,36 +4,22 @@
 
 package runtime
 
-import (
-	"runtime/internal/sys"
-	"unsafe"
-)
+import "unsafe"
 
 const (
-	_AT_NULL   = 0
 	_AT_RANDOM = 25 // introduced in 2.6.29
 )
 
 var randomNumber uint32
 
-func sysargs(argc int32, argv **byte) {
-	// skip over argv, envv to get to auxv
-	n := argc + 1
-	for argv_index(argv, n) != nil {
-		n++
-	}
-	n++
-	auxv := (*[1 << 29]uint64)(add(unsafe.Pointer(argv), uintptr(n)*sys.PtrSize))
-
-	for i := 0; auxv[i] != _AT_NULL; i += 2 {
-		switch auxv[i] {
-		case _AT_RANDOM: // kernel provides a pointer to 16-bytes worth of random data
-			startupRandomData = (*[16]byte)(unsafe.Pointer(uintptr(auxv[i+1])))[:]
-			// the pointer provided may not be word aligned, so we must treat it
-			// as a byte array.
-			randomNumber = uint32(startupRandomData[4]) | uint32(startupRandomData[5])<<8 |
-				uint32(startupRandomData[6])<<16 | uint32(startupRandomData[7])<<24
-		}
+func archauxv(tag, val uintptr) {
+	switch tag {
+	case _AT_RANDOM: // kernel provides a pointer to 16-bytes worth of random data
+		startupRandomData = (*[16]byte)(unsafe.Pointer(val))[:]
+		// the pointer provided may not be word aligned, so we must treat it
+		// as a byte array.
+		randomNumber = uint32(startupRandomData[4]) | uint32(startupRandomData[5])<<8 |
+			uint32(startupRandomData[6])<<16 | uint32(startupRandomData[7])<<24
 	}
 }
 

src/runtime/os_linux_noauxv.go

+// Copyright 2014 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 !386,!amd64,!arm,!arm64
+
+package runtime
+
+func archauxv(tag, val uintptr) {
+}

src/runtime/vdso_linux_amd64.go

@@ -4,10 +4,7 @@
 
 package runtime
 
-import (
-	"runtime/internal/sys"
-	"unsafe"
-)
+import "unsafe"
 
 // Look up symbols in the Linux vDSO.
 
@@ -23,7 +20,6 @@ import (
 const (
 	_AT_RANDOM       = 25
 	_AT_SYSINFO_EHDR = 33
-	_AT_NULL         = 0 /* End of vector */
 
 	_PT_LOAD    = 1 /* Loadable program segment */
 	_PT_DYNAMIC = 2 /* Dynamic linking information */
@@ -294,37 +290,21 @@ func vdso_parse_symbols(info *vdso_info, version int32) {
 	}
 }
 
-func sysargs(argc int32, argv **byte) {
-	n := argc + 1
-
-	// skip envp to get to ELF auxiliary vector.
-	for argv_index(argv, n) != nil {
-		n++
-	}
-
-	// skip NULL separator
-	n++
-
-	// now argv+n is auxv
-	auxv := (*[1 << 32]elf64Auxv)(add(unsafe.Pointer(argv), uintptr(n)*sys.PtrSize))
-
-	for i := 0; auxv[i].a_type != _AT_NULL; i++ {
-		av := &auxv[i]
-		switch av.a_type {
-		case _AT_SYSINFO_EHDR:
-			if av.a_val == 0 {
-				// Something went wrong
-				continue
-			}
-			var info vdso_info
-			// TODO(rsc): I don't understand why the compiler thinks info escapes
-			// when passed to the three functions below.
-			info1 := (*vdso_info)(noescape(unsafe.Pointer(&info)))
-			vdso_init_from_sysinfo_ehdr(info1, (*elf64Ehdr)(unsafe.Pointer(uintptr(av.a_val))))
-			vdso_parse_symbols(info1, vdso_find_version(info1, &linux26))
-
-		case _AT_RANDOM:
-			startupRandomData = (*[16]byte)(unsafe.Pointer(uintptr(av.a_val)))[:]
+func archauxv(tag, val uintptr) {
+	switch tag {
+	case _AT_SYSINFO_EHDR:
+		if val == 0 {
+			// Something went wrong
+			return
 		}
+		var info vdso_info
+		// TODO(rsc): I don't understand why the compiler thinks info escapes
+		// when passed to the three functions below.
+		info1 := (*vdso_info)(noescape(unsafe.Pointer(&info)))
+		vdso_init_from_sysinfo_ehdr(info1, (*elf64Ehdr)(unsafe.Pointer(val)))
+		vdso_parse_symbols(info1, vdso_find_version(info1, &linux26))
+
+	case _AT_RANDOM:
+		startupRandomData = (*[16]byte)(unsafe.Pointer(val))[:]
 	}
 }

src/runtime/vdso_none.go

@@ -2,10 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !linux !amd64
-// +build !linux !386
-// +build !linux !arm
-// +build !linux !arm64
+// +build !linux
 
 package runtime