runtime: common handling of _AT_RANDOM auxv

The Linux kernel provides 16 bytes of random data via the auxv vector
at startup. Currently we consume this separately on 386, amd64, arm,
and arm64. Now that we have a common auxv parser, handle _AT_RANDOM in
the common path.

Change-Id: Ib69549a1d37e2d07a351cf0f44007bcd24f0d20d
Reviewed-on: https://go-review.googlesource.com/22062
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

diff --git a/src/runtime/os_linux.go b/src/runtime/os_linux.go
index eeb30c7dd93c51728e1be6f938797bfa298af9eb..4645f1c33d741bd418261c4fe23cd0de0a9cadd1 100644 (file)
--- a/src/runtime/os_linux.go
+++ b/src/runtime/os_linux.go
@@ -177,7 +177,8 @@ var failallocatestack = []byte("runtime: failed to allocate stack for the new OS
 var failthreadcreate = []byte("runtime: failed to create new OS thread\n")
 
 const (
-       _AT_NULL = 0 // End of vector
+       _AT_NULL   = 0  // End of vector
+       _AT_RANDOM = 25 // introduced in 2.6.29
 )
 
 func sysargs(argc int32, argv **byte) {
@@ -195,6 +196,12 @@ func sysargs(argc int32, argv **byte) {
        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]
+               switch tag {
+               case _AT_RANDOM:
+                       // The kernel provides a pointer to 16-bytes
+                       // worth of random data.
+                       startupRandomData = (*[16]byte)(unsafe.Pointer(val))[:]
+               }
                archauxv(tag, val)
        }
 }

diff --git a/src/runtime/os_linux_386.go b/src/runtime/os_linux_386.go
index 2383d962b2971c943bf233ecc5b80e810b5ab671..cf031afe45cd492dcf035a473d1c29caea104b64 100644 (file)
--- a/src/runtime/os_linux_386.go
+++ b/src/runtime/os_linux_386.go
@@ -4,16 +4,9 @@
 
 package runtime
 
-import "unsafe"
-
 const (
-       _AT_RANDOM  = 25
        _AT_SYSINFO = 32
 )
 
 func archauxv(tag, val uintptr) {
-       switch tag {
-       case _AT_RANDOM:
-               startupRandomData = (*[16]byte)(unsafe.Pointer(val))[:]
-       }
 }

diff --git a/src/runtime/os_linux_arm.go b/src/runtime/os_linux_arm.go
index a61be916b6ded9a3327d44f6cde32908228ff613..8e2765a4133ec7c189bea28fb17ac734f7089ced 100644 (file)
--- a/src/runtime/os_linux_arm.go
+++ b/src/runtime/os_linux_arm.go
@@ -9,7 +9,6 @@ import "unsafe"
 const (
        _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
 
        _HWCAP_VFP   = 1 << 6  // introduced in at least 2.6.11
        _HWCAP_VFPv3 = 1 << 13 // introduced in 2.6.30
@@ -34,10 +33,10 @@ func checkgoarm() {
 
 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.
+       case _AT_RANDOM:
+               // sysargs filled in startupRandomData, but that
+               // pointer 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
 

diff --git a/src/runtime/os_linux_arm64.go b/src/runtime/os_linux_arm64.go
index aa9d4d9885b13aa129cc2c2207672c577afe72e5..43262aea1435132d064120fcb72698b21660d961 100644 (file)
--- a/src/runtime/os_linux_arm64.go
+++ b/src/runtime/os_linux_arm64.go
@@ -4,20 +4,14 @@
 
 package runtime
 
-import "unsafe"
-
-const (
-       _AT_RANDOM = 25 // introduced in 2.6.29
-)
-
 var randomNumber uint32
 
 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.
+       case _AT_RANDOM:
+               // sysargs filled in startupRandomData, but that
+               // pointer 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
        }

diff --git a/src/runtime/vdso_linux_amd64.go b/src/runtime/vdso_linux_amd64.go
index 1aae9b65703f4fe7756b10e07374da5a8838fb76..8a970dfbe6d631f2101af112b2b473cd9213f593 100644 (file)
--- a/src/runtime/vdso_linux_amd64.go
+++ b/src/runtime/vdso_linux_amd64.go
@@ -18,7 +18,6 @@ import "unsafe"
 // http://refspecs.linuxfoundation.org/LSB_3.2.0/LSB-Core-generic/LSB-Core-generic/symversion.html
 
 const (
-       _AT_RANDOM       = 25
        _AT_SYSINFO_EHDR = 33
 
        _PT_LOAD    = 1 /* Loadable program segment */
@@ -303,8 +302,5 @@ func archauxv(tag, val uintptr) {
                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))[:]
        }
 }