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, 16 insertions, 30 deletions

diff --git a/src/runtime/os_linux_arm.go b/src/runtime/os_linux_arm.go
index 8fdfb585ba..a61be916b6 100644
--- a/src/runtime/os_linux_arm.go
+++ b/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
+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(uintptr(auxv[i+1] + 1)))
-			if '5' <= t && t <= '7' {
-				armArch = t - '0'
-			}
-
-		case _AT_HWCAP: // CPU capability bit flags
-			hwcap = auxv[i+1]
+	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)
 	}
 }