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>

1 files changed, 9 insertions, 23 deletions

diff --git a/src/runtime/os_linux_arm64.go b/src/runtime/os_linux_arm64.go
index 57184b0d3a..aa9d4d9885 100644
--- a/src/runtime/os_linux_arm64.go
+++ b/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
 	}
 }