From 6e6b2096e18888a6ba84416caf03304ccccf61fe Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Maciej=20=C5=BBenczykowski?= <maze@google.com>
Date: Mon, 24 Jun 2024 23:57:41 +0000
Subject: [PATCH] Exempt Wear on Arm from 64-bit userspace requirement check.
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Arm-only because the 32 bit userspace vs 64-bit kernel
issues are worse on x86 because of some extra 4 vs 8 byte
alignment (when included in structs) ABI issues.

Wear is unlikely to ever run on comparatively high
power usage x86 cpus, so this should be fine.

Manually tested by adding:
  if (isWear()) ALOGI("Wear!");
and additionally logging 'bool watch' within isWear()
on 'cf_gwear_x86-trunk_staging-userdebug'.
Resulting output:
  I NetBpfLoad: NetBpfLoad v0.46 (/apex/com.android.tethering/bin/netbpfload) api:35/36 kver:601004b (32-on-x86-64) uid:0 rc:01
  I NetBpfLoad: isWear(ro.cw_build.wear_sdk.version=6[6] ro.build.characteristics='nosdcard,watch'[1]): true
  I NetBpfLoad: Wear!

Bug: 346252668
Test: TreeHugger
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: I9b2a3b88095264245935950bd1a7dfbb5293334b
---
 netbpfload/NetBpfLoad.cpp | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/netbpfload/NetBpfLoad.cpp b/netbpfload/NetBpfLoad.cpp
index e9c6d8a2d4..0d4a5c4f7b 100644
--- a/netbpfload/NetBpfLoad.cpp
+++ b/netbpfload/NetBpfLoad.cpp
@@ -57,6 +57,7 @@ namespace bpf {
 using base::StartsWith;
 using base::EndsWith;
 using std::string;
+using std::vector;
 
 static bool exists(const char* const path) {
     int v = access(path, F_OK);
@@ -248,6 +249,22 @@ static bool isTV() {
     return tv;
 }
 
+static bool isWear() {
+    static string wearSdkStr = base::GetProperty("ro.cw_build.wear_sdk.version", "");
+    static int wearSdkInt = base::GetIntProperty("ro.cw_build.wear_sdk.version", 0);
+    static string buildChars = base::GetProperty("ro.build.characteristics", "");
+    static vector<string> v = base::Tokenize(buildChars, ",");
+    static bool watch = (std::find(v.begin(), v.end(), "watch") != v.end());
+    static bool wear = (wearSdkInt > 0) || watch;
+    static bool logged = false;
+    if (!logged) {
+        logged = true;
+        ALOGI("isWear(ro.cw_build.wear_sdk.version=%d[%s] ro.build.characteristics='%s'): %s",
+              wearSdkInt, wearSdkStr.c_str(), buildChars.c_str(), wear ? "true" : "false");
+    }
+    return wear;
+}
+
 static int doLoad(char** argv, char * const envp[]) {
     const bool runningAsRoot = !getuid();  // true iff U QPR3 or V+
 
@@ -402,7 +419,8 @@ static int doLoad(char** argv, char * const envp[]) {
          * and 32-bit userspace on 64-bit kernel bpf ringbuffer compatibility is broken.
          */
         ALOGE("64-bit userspace required on 6.2+ kernels.");
-        if (!isTV()) return 1;
+        // Stuff won't work reliably, but exempt TVs & Arm Wear devices
+        if (!isTV() && !(isWear() && isArm())) return 1;
     }
 
     // Ensure we can determine the Android build type.