commit 8daa0b607043e70cb9a897752e6348fc0d492dab
author Maciej Żenczykowski <maze@google.com> Tue Oct 22 16:16:50 2019 -0700
committer Maciej Żenczykowski <maze@google.com> Wed Oct 23 07:31:24 2019 +0000
tree fccc3dd4973969c5c3367d87822909981d517c85
parent 1a4659c1baa30219c2ed29a8468965868a0fc82a

bpf: change how we detect device bpf support level

Now that we're developing Android R and we know upgrades
will only be supported from Android P & Q, we no longer
need to check for Android pre-P (ie. O) - so we can remove
that check.

We also take the opportunity to slightly refactor the code
to make it more readable.

Note: it's not appropriate to backport this into any 'normal'
Q branch, since it *will* break 4.9-O devices upgrading to Q
userspace without upgrading the kernel to at least 4.9-P.

Test: builds, atest
Bug: 139501958
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: Iacb3c2db489061b3f278d8e971e44dd1a5c4c1e6

libbpf_android/BpfUtils.cpp

diff --git a/libbpf_android/BpfUtils.cpp b/libbpf_android/BpfUtils.cpp
index b3ff108..4a4761b 100644
--- a/libbpf_android/BpfUtils.cpp
+++ b/libbpf_android/BpfUtils.cpp
@@ -265,28 +265,22 @@
     int kernel_version_major;
     int kernel_version_minor;
 
-    uint64_t api_level = GetUintProperty<uint64_t>("ro.product.first_api_level", 0);
-    if (api_level == 0) {
-        ALOGE("Cannot determine initial API level of the device");
-        api_level = GetUintProperty<uint64_t>("ro.build.version.sdk", 0);
-    }
-
-    // Check if the device is shipped originally with android P.
-    if (api_level < MINIMUM_API_REQUIRED) return BpfLevel::NONE;
-
+    // Check the device kernel version
     int ret = uname(&buf);
-    if (ret) {
-        return BpfLevel::NONE;
-    }
+    if (ret) return BpfLevel::NONE;
     char dummy;
     ret = sscanf(buf.release, "%d.%d%c", &kernel_version_major, &kernel_version_minor, &dummy);
-    // Check the device kernel version
     if (ret < 2) return BpfLevel::NONE;
-    if (kernel_version_major > 4 || (kernel_version_major == 4 && kernel_version_minor >= 14))
+    if (kernel_version_major > 4)  // 5.4+ R+
         return BpfLevel::EXTENDED;
-    if (kernel_version_major == 4 && kernel_version_minor >= 9) return BpfLevel::BASIC;
+    if (kernel_version_major == 4 && kernel_version_minor >= 19)  // 4.19 Q+
+        return BpfLevel::EXTENDED;
+    if (kernel_version_major == 4 && kernel_version_minor >= 14)  // 4.14 P+
+        return BpfLevel::EXTENDED;
+    if (kernel_version_major == 4 && kernel_version_minor >= 9)  // 4.9 P+
+        return BpfLevel::BASIC;
 
-    return BpfLevel::NONE;
+    return BpfLevel::NONE;  // 4.4-P
 }
 
 }  // namespace bpf