From eb13daf905d2a49f02a71629947f604834a0e08c Mon Sep 17 00:00:00 2001
From: Patrick Rohr <prohr@google.com>
Date: Thu, 18 May 2023 14:36:02 -0700
Subject: [PATCH] NetlinkEvent: use isKernel64Bit in KernelUtils.h

Now that the code has moved, delete the local implementation in favor of
the common one.

Test: builds
Change-Id: Ic29d7c9bcd3d623204f3e4de3a3434483021cbac
---
 libsysutils/Android.bp           |  4 +++
 libsysutils/src/NetlinkEvent.cpp | 56 ++------------------------------
 2 files changed, 6 insertions(+), 54 deletions(-)

diff --git a/libsysutils/Android.bp b/libsysutils/Android.bp
index 5f472b2ab..1b41a6b17 100644
--- a/libsysutils/Android.bp
+++ b/libsysutils/Android.bp
@@ -29,6 +29,10 @@ cc_library {
         "liblog",
     ],
 
+    header_libs: [
+        "bpf_headers",
+    ],
+
     export_include_dirs: ["include"],
 
     tidy: true,
diff --git a/libsysutils/src/NetlinkEvent.cpp b/libsysutils/src/NetlinkEvent.cpp
index 515cc1047..cd9db54fa 100644
--- a/libsysutils/src/NetlinkEvent.cpp
+++ b/libsysutils/src/NetlinkEvent.cpp
@@ -37,10 +37,12 @@
 #include <sys/utsname.h>
 
 #include <android-base/parseint.h>
+#include <bpf/KernelUtils.h>
 #include <log/log.h>
 #include <sysutils/NetlinkEvent.h>
 
 using android::base::ParseInt;
+using android::bpf::isKernel64Bit;
 
 /* From kernel's net/netfilter/xt_quota2.c */
 const int LOCAL_QLOG_NL_EVENT = 112;
@@ -138,60 +140,6 @@ static_assert(sizeof(ulog_packet_msg_t) == sizeof(ulog_packet_msg32_t) ||
 static_assert(sizeof(ulog_packet_msg32_t) == 168);
 static_assert(sizeof(ulog_packet_msg64_t) == 192);
 
-// Figure out the bitness of userspace.
-// Trivial and known at compile time.
-static bool isUserspace64bit(void) {
-    return sizeof(long) == 8;
-}
-
-// Figure out the bitness of the kernel.
-static bool isKernel64Bit(void) {
-    // a 64-bit userspace requires a 64-bit kernel
-    if (isUserspace64bit()) return true;
-
-    static bool init = false;
-    static bool cache = false;
-    if (init) return cache;
-
-    // Retrieve current personality - on Linux this system call *cannot* fail.
-    int p = personality(0xffffffff);
-    // But if it does just assume kernel and userspace (which is 32-bit) match...
-    if (p == -1) return false;
-
-    // This will effectively mask out the bottom 8 bits, and switch to 'native'
-    // personality, and then return the previous personality of this thread
-    // (likely PER_LINUX or PER_LINUX32) with any extra options unmodified.
-    int q = personality((p & ~PER_MASK) | PER_LINUX);
-    // Per man page this theoretically could error out with EINVAL,
-    // but kernel code analysis suggests setting PER_LINUX cannot fail.
-    // Either way, assume kernel and userspace (which is 32-bit) match...
-    if (q != p) return false;
-
-    struct utsname u;
-    (void)uname(&u);  // only possible failure is EFAULT, but u is on stack.
-
-    // Switch back to previous personality.
-    // Theoretically could fail with EINVAL on arm64 with no 32-bit support,
-    // but then we wouldn't have fetched 'p' from the kernel in the first place.
-    // Either way there's nothing meaningul we can do in case of error.
-    // Since PER_LINUX32 vs PER_LINUX only affects uname.machine it doesn't
-    // really hurt us either.  We're really just switching back to be 'clean'.
-    (void)personality(p);
-
-    // Possible values of utsname.machine observed on x86_64 desktop (arm via qemu):
-    //   x86_64 i686 aarch64 armv7l
-    // additionally observed on arm device:
-    //   armv8l
-    // presumably also might just be possible:
-    //   i386 i486 i586
-    // and there might be other weird arm32 cases.
-    // We note that the 64 is present in both 64-bit archs,
-    // and in general is likely to be present in only 64-bit archs.
-    cache = !!strstr(u.machine, "64");
-    init = true;
-    return cache;
-}
-
 /******************************************************************************/
 
 NetlinkEvent::NetlinkEvent() {