ueventd: scans /apex/*/firmware for firmwares

In addition to "firmware_directories", ueventd scans /apex/*/firmware/
directory as well to find firmware files.

Bug: 167942098
Test: loading firmware from vibrator apex successfully.
      (sunfish)
Change-Id: I90fc8f9ad843a08b1ca98a2be1b5d22c0c5954a3

init/README.ueventd.md

@@ -86,6 +86,8 @@ Ueventd by default serves firmware requests by searching through a list of firmw
 for a file matching the uevent `FIRMWARE`. It then forks a process to serve this firmware to the
 kernel.
 
+`/apex/*/firmware` is also searched after a list of firmware directories.
+
 The list of firmware directories is customized by a `firmware_directories` line in a ueventd.rc
 file. This line takes the format of
 

init/firmware_handler.cpp

@@ -17,6 +17,7 @@
 #include "firmware_handler.h"
 
 #include <fcntl.h>
+#include <glob.h>
 #include <pwd.h>
 #include <signal.h>
 #include <stdlib.h>
@@ -30,6 +31,7 @@
 #include <android-base/chrono_utils.h>
 #include <android-base/file.h>
 #include <android-base/logging.h>
+#include <android-base/scopeguard.h>
 #include <android-base/strings.h>
 #include <android-base/unique_fd.h>
 
@@ -203,25 +205,28 @@ void FirmwareHandler::ProcessFirmwareEvent(const std::string& root,
     }
 
     std::vector<std::string> attempted_paths_and_errors;
-
-    int booting = IsBooting();
-try_loading_again:
-    attempted_paths_and_errors.clear();
-    for (const auto& firmware_directory : firmware_directories_) {
+    auto TryLoadFirmware = [&](const std::string& firmware_directory) {
         std::string file = firmware_directory + firmware;
         unique_fd fw_fd(open(file.c_str(), O_RDONLY | O_CLOEXEC));
         if (fw_fd == -1) {
             attempted_paths_and_errors.emplace_back("firmware: attempted " + file +
                                                     ", open failed: " + strerror(errno));
-            continue;
+            return false;
         }
         struct stat sb;
         if (fstat(fw_fd, &sb) == -1) {
             attempted_paths_and_errors.emplace_back("firmware: attempted " + file +
                                                     ", fstat failed: " + strerror(errno));
-            continue;
+            return false;
         }
         LoadFirmware(firmware, root, fw_fd, sb.st_size, loading_fd, data_fd);
+        return true;
+    };
+
+    int booting = IsBooting();
+try_loading_again:
+    attempted_paths_and_errors.clear();
+    if (ForEachFirmwareDirectory(TryLoadFirmware)) {
         return;
     }
 
@@ -242,6 +247,33 @@ try_loading_again:
     write(loading_fd, "-1", 2);
 }
 
+bool FirmwareHandler::ForEachFirmwareDirectory(
+        std::function<bool(const std::string&)> handler) const {
+    for (const std::string& firmware_directory : firmware_directories_) {
+        if (std::invoke(handler, firmware_directory)) {
+            return true;
+        }
+    }
+
+    glob_t glob_result;
+    glob("/apex/*/firmware/", GLOB_MARK, nullptr, &glob_result);
+    auto free_glob = android::base::make_scope_guard(std::bind(&globfree, &glob_result));
+    for (size_t i = 0; i < glob_result.gl_pathc; i++) {
+        char* apex_firmware_directory = glob_result.gl_pathv[i];
+        // Filter-out /apex/<name>@<ver> paths. The paths are bind-mounted to
+        // /apex/<name> paths, so unless we filter them out, we will look into the
+        // same apex twice.
+        if (strchr(apex_firmware_directory, '@')) {
+            continue;
+        }
+        if (std::invoke(handler, apex_firmware_directory)) {
+            return true;
+        }
+    }
+
+    return false;
+}
+
 void FirmwareHandler::HandleUevent(const Uevent& uevent) {
     if (uevent.subsystem != "firmware" || uevent.action != "add") return;
 

init/firmware_handler.h

@@ -18,6 +18,7 @@
 
 #include <pwd.h>
 
+#include <functional>
 #include <string>
 #include <vector>
 
@@ -52,6 +53,7 @@ class FirmwareHandler : public UeventHandler {
                                            const Uevent& uevent) const;
     std::string GetFirmwarePath(const Uevent& uevent) const;
     void ProcessFirmwareEvent(const std::string& root, const std::string& firmware) const;
+    bool ForEachFirmwareDirectory(std::function<bool(const std::string&)> handler) const;
 
     std::vector<std::string> firmware_directories_;
     std::vector<ExternalFirmwareHandler> external_firmware_handlers_;