Add a method to get the binderfs transactions for a given process

Get the section in /dev/binderfs/binder_logs/transactions for that PID as a
single string.

Test: adb shell am hang
Bug: 316970771
Change-Id: I951621379032550bd347341c9406da8a06fa7b29

2 files changed, 35 insertions, 0 deletions

diff --git a/libs/binderdebug/BinderDebug.cpp b/libs/binderdebug/BinderDebug.cpp
index a8f2cbfb5b..19f3aad04f 100644
--- a/libs/binderdebug/BinderDebug.cpp
+++ b/libs/binderdebug/BinderDebug.cpp
@@ -199,4 +199,31 @@ status_t getBinderClientPids(BinderDebugContext context, pid_t pid, pid_t servic
     return ret;
 }
 
+status_t getBinderTransactions(pid_t pid, std::string& transactionsOutput) {
+    std::ifstream ifs("/dev/binderfs/binder_logs/transactions");
+    if (!ifs.is_open()) {
+        ifs.open("/d/binder/transactions");
+        if (!ifs.is_open()) {
+            LOG(ERROR) << "Could not open /dev/binderfs/binder_logs/transactions. "
+                       << "Likely a permissions issue. errno: " << errno;
+            return -errno;
+        }
+    }
+
+    std::string line;
+    while (getline(ifs, line)) {
+        // The section for this pid ends with another "proc <pid>" for another
+        // process. There is only one entry per pid so we can stop looking after
+        // we've grabbed the whole section
+        if (base::StartsWith(line, "proc " + std::to_string(pid))) {
+            do {
+                transactionsOutput += line + '\n';
+            } while (getline(ifs, line) && !base::StartsWith(line, "proc "));
+            return OK;
+        }
+    }
+
+    return NAME_NOT_FOUND;
+}
+
 } // namespace  android
diff --git a/libs/binderdebug/include/binderdebug/BinderDebug.h b/libs/binderdebug/include/binderdebug/BinderDebug.h
index 6ce8edfc7c..018393c128 100644
--- a/libs/binderdebug/include/binderdebug/BinderDebug.h
+++ b/libs/binderdebug/include/binderdebug/BinderDebug.h
@@ -44,4 +44,12 @@ status_t getBinderPidInfo(BinderDebugContext context, pid_t pid, BinderPidInfo*
 status_t getBinderClientPids(BinderDebugContext context, pid_t pid, pid_t servicePid,
                              int32_t handle, std::vector<pid_t>* pids);
 
+/**
+ * Get the transactions for a given process from /dev/binderfs/binder_logs/transactions
+ * Return: OK if the file was found and the pid was found in the file.
+ *         -errno if there was an issue opening the file
+ *         NAME_NOT_FOUND if the pid wasn't found in the file
+ */
+status_t getBinderTransactions(pid_t pid, std::string& transactionOutput);
+
 } // namespace  android