firmware_handler: extract part responsible for running ext program to lib

As a preparation for upcoming commit, extract part which is responsible
for external program execution to libmodprobe so it can be later
re-used not only for firmware handler but also for dynamic module
options handler within libmodprobe.

RunExternalHandler is moved entirely to separate library with two
changes:
- Setting env needed previously by firmware handler was made generic and
  now external handler can get envs_map containing pairs of env and its
  value which needs to be set.
- "Firmware" was removed from one of the log since now it can be used in
  different context (s/External Firmware Handler/External Handler/)

Bug: 335619610
Test: `atest CtsInitTestCases` passed, especially:
      [105/129] ueventd_parser#ExternalFirmwareHandlers: PASSED (0ms)
      [106/129] ueventd_parser#ExternalFirmwareHandlersDuplicate: PASSED (0ms)

Change-Id: Ie07cee763278f224bd3c0acfbe06c44eb36d0a81
diff --git a/init/firmware_handler.cpp b/init/firmware_handler.cpp
index 01957ef..dcfda52 100644
--- a/init/firmware_handler.cpp
+++ b/init/firmware_handler.cpp
@@ -38,6 +38,8 @@
 #include <android-base/strings.h>
 #include <android-base/unique_fd.h>
 
+#include "exthandler/exthandler.h"
+
 using android::base::ReadFdToString;
 using android::base::Socketpair;
 using android::base::Split;
@@ -136,100 +138,6 @@
     : firmware_directories_(std::move(firmware_directories)),
       external_firmware_handlers_(std::move(external_firmware_handlers)) {}
 
-Result<std::string> FirmwareHandler::RunExternalHandler(const std::string& handler, uid_t uid,
-                                                        gid_t gid, const Uevent& uevent) const {
-    unique_fd child_stdout;
-    unique_fd parent_stdout;
-    if (!Socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0, &child_stdout, &parent_stdout)) {
-        return ErrnoError() << "Socketpair() for stdout failed";
-    }
-
-    unique_fd child_stderr;
-    unique_fd parent_stderr;
-    if (!Socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0, &child_stderr, &parent_stderr)) {
-        return ErrnoError() << "Socketpair() for stderr failed";
-    }
-
-    signal(SIGCHLD, SIG_DFL);
-
-    auto pid = fork();
-    if (pid < 0) {
-        return ErrnoError() << "fork() failed";
-    }
-
-    if (pid == 0) {
-        setenv("FIRMWARE", uevent.firmware.c_str(), 1);
-        setenv("DEVPATH", uevent.path.c_str(), 1);
-        parent_stdout.reset();
-        parent_stderr.reset();
-        close(STDOUT_FILENO);
-        close(STDERR_FILENO);
-        dup2(child_stdout.get(), STDOUT_FILENO);
-        dup2(child_stderr.get(), STDERR_FILENO);
-
-        auto args = Split(handler, " ");
-        std::vector<char*> c_args;
-        for (auto& arg : args) {
-            c_args.emplace_back(arg.data());
-        }
-        c_args.emplace_back(nullptr);
-
-        if (gid != 0) {
-            if (setgid(gid) != 0) {
-                fprintf(stderr, "setgid() failed: %s", strerror(errno));
-                _exit(EXIT_FAILURE);
-            }
-        }
-
-        if (setuid(uid) != 0) {
-            fprintf(stderr, "setuid() failed: %s", strerror(errno));
-            _exit(EXIT_FAILURE);
-        }
-
-        execv(c_args[0], c_args.data());
-        fprintf(stderr, "exec() failed: %s", strerror(errno));
-        _exit(EXIT_FAILURE);
-    }
-
-    child_stdout.reset();
-    child_stderr.reset();
-
-    int status;
-    pid_t waited_pid = TEMP_FAILURE_RETRY(waitpid(pid, &status, 0));
-    if (waited_pid == -1) {
-        return ErrnoError() << "waitpid() failed";
-    }
-
-    std::string stdout_content;
-    if (!ReadFdToString(parent_stdout.get(), &stdout_content)) {
-        return ErrnoError() << "ReadFdToString() for stdout failed";
-    }
-
-    std::string stderr_content;
-    if (ReadFdToString(parent_stderr.get(), &stderr_content)) {
-        auto messages = Split(stderr_content, "\n");
-        for (const auto& message : messages) {
-            if (!message.empty()) {
-                LOG(ERROR) << "External Firmware Handler: " << message;
-            }
-        }
-    } else {
-        LOG(ERROR) << "ReadFdToString() for stderr failed";
-    }
-
-    if (WIFEXITED(status)) {
-        if (WEXITSTATUS(status) == EXIT_SUCCESS) {
-            return Trim(stdout_content);
-        } else {
-            return Error() << "exited with status " << WEXITSTATUS(status);
-        }
-    } else if (WIFSIGNALED(status)) {
-        return Error() << "killed by signal " << WTERMSIG(status);
-    }
-
-    return Error() << "unexpected exit status " << status;
-}
-
 std::string FirmwareHandler::GetFirmwarePath(const Uevent& uevent) const {
     for (const auto& external_handler : external_firmware_handlers_) {
         if (external_handler.match(uevent.path)) {
@@ -237,11 +145,15 @@
                       << "' for devpath: '" << uevent.path << "' firmware: '" << uevent.firmware
                       << "'";
 
+            std::unordered_map<std::string, std::string> envs_map;
+            envs_map["FIRMWARE"] = uevent.firmware;
+            envs_map["DEVPATH"] = uevent.path;
+
             auto result = RunExternalHandler(external_handler.handler_path, external_handler.uid,
-                                             external_handler.gid, uevent);
+                                             external_handler.gid, envs_map);
             if (!result.ok() && NeedsRerunExternalHandler()) {
                 auto res = RunExternalHandler(external_handler.handler_path, external_handler.uid,
-                                              external_handler.gid, uevent);
+                                              external_handler.gid, envs_map);
                 result = std::move(res);
             }
             if (!result.ok()) {
diff --git a/init/firmware_handler.h b/init/firmware_handler.h
index fceb392..e5d3538 100644
--- a/init/firmware_handler.h
+++ b/init/firmware_handler.h
@@ -54,8 +54,6 @@
     friend void FirmwareTestWithExternalHandler(const std::string& test_name,
                                                 bool expect_new_firmware);
 
-    Result<std::string> RunExternalHandler(const std::string& handler, uid_t uid, gid_t gid,
-                                           const Uevent& uevent) const;
     std::string GetFirmwarePath(const Uevent& uevent) const;
     void ProcessFirmwareEvent(const std::string& path, const std::string& firmware) const;
     bool ForEachFirmwareDirectory(std::function<bool(const std::string&)> handler) const;
diff --git a/libmodprobe/Android.bp b/libmodprobe/Android.bp
index 12906cc..78b4c83 100644
--- a/libmodprobe/Android.bp
+++ b/libmodprobe/Android.bp
@@ -13,6 +13,7 @@
     vendor_ramdisk_available: true,
     host_supported: true,
     srcs: [
+        "exthandler.cpp",
         "libmodprobe.cpp",
         "libmodprobe_ext.cpp",
     ],
@@ -30,6 +31,7 @@
     ],
     local_include_dirs: ["include/"],
     srcs: [
+        "exthandler.cpp",
         "libmodprobe_test.cpp",
         "libmodprobe.cpp",
         "libmodprobe_ext_test.cpp",
diff --git a/libmodprobe/exthandler.cpp b/libmodprobe/exthandler.cpp
new file mode 100644
index 0000000..f48c259
--- /dev/null
+++ b/libmodprobe/exthandler.cpp
@@ -0,0 +1,131 @@
+/*
+ * Copyright (C) 2024 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <exthandler/exthandler.h>
+
+#include <android-base/chrono_utils.h>
+#include <android-base/file.h>
+#include <android-base/logging.h>
+#include <android-base/parseint.h>
+#include <android-base/strings.h>
+#include <android-base/unique_fd.h>
+#include <fnmatch.h>
+#include <grp.h>
+#include <pwd.h>
+#include <sys/wait.h>
+
+using android::base::ErrnoError;
+using android::base::Error;
+using android::base::ReadFdToString;
+using android::base::Result;
+using android::base::Split;
+using android::base::Trim;
+using android::base::unique_fd;
+
+Result<std::string> RunExternalHandler(const std::string& handler, uid_t uid, gid_t gid,
+                                       std::unordered_map<std::string, std::string>& envs_map) {
+    unique_fd child_stdout;
+    unique_fd parent_stdout;
+    if (!Socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0, &child_stdout, &parent_stdout)) {
+        return ErrnoError() << "Socketpair() for stdout failed";
+    }
+
+    unique_fd child_stderr;
+    unique_fd parent_stderr;
+    if (!Socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0, &child_stderr, &parent_stderr)) {
+        return ErrnoError() << "Socketpair() for stderr failed";
+    }
+
+    signal(SIGCHLD, SIG_DFL);
+
+    auto pid = fork();
+    if (pid < 0) {
+        return ErrnoError() << "fork() failed";
+    }
+
+    if (pid == 0) {
+        for (auto it = envs_map.begin(); it != envs_map.end(); ++it) {
+            setenv(it->first.c_str(), it->second.c_str(), 1);
+        }
+        parent_stdout.reset();
+        parent_stderr.reset();
+        close(STDOUT_FILENO);
+        close(STDERR_FILENO);
+        dup2(child_stdout.get(), STDOUT_FILENO);
+        dup2(child_stderr.get(), STDERR_FILENO);
+
+        auto args = Split(handler, " ");
+        std::vector<char*> c_args;
+        for (auto& arg : args) {
+            c_args.emplace_back(arg.data());
+        }
+        c_args.emplace_back(nullptr);
+
+        if (gid != 0) {
+            if (setgid(gid) != 0) {
+                fprintf(stderr, "setgid() failed: %s", strerror(errno));
+                _exit(EXIT_FAILURE);
+            }
+        }
+
+        if (setuid(uid) != 0) {
+            fprintf(stderr, "setuid() failed: %s", strerror(errno));
+            _exit(EXIT_FAILURE);
+        }
+
+        execv(c_args[0], c_args.data());
+        fprintf(stderr, "exec() failed: %s", strerror(errno));
+        _exit(EXIT_FAILURE);
+    }
+
+    child_stdout.reset();
+    child_stderr.reset();
+
+    int status;
+    pid_t waited_pid = TEMP_FAILURE_RETRY(waitpid(pid, &status, 0));
+    if (waited_pid == -1) {
+        return ErrnoError() << "waitpid() failed";
+    }
+
+    std::string stdout_content;
+    if (!ReadFdToString(parent_stdout.get(), &stdout_content)) {
+        return ErrnoError() << "ReadFdToString() for stdout failed";
+    }
+
+    std::string stderr_content;
+    if (ReadFdToString(parent_stderr.get(), &stderr_content)) {
+        auto messages = Split(stderr_content, "\n");
+        for (const auto& message : messages) {
+            if (!message.empty()) {
+                LOG(ERROR) << "External Handler: " << message;
+            }
+        }
+    } else {
+        LOG(ERROR) << "ReadFdToString() for stderr failed";
+    }
+
+    if (WIFEXITED(status)) {
+        if (WEXITSTATUS(status) == EXIT_SUCCESS) {
+            return Trim(stdout_content);
+        } else {
+            return Error() << "exited with status " << WEXITSTATUS(status);
+        }
+    } else if (WIFSIGNALED(status)) {
+        return Error() << "killed by signal " << WTERMSIG(status);
+    }
+
+    return Error() << "unexpected exit status " << status;
+}
diff --git a/libmodprobe/include/exthandler/exthandler.h b/libmodprobe/include/exthandler/exthandler.h
new file mode 100644
index 0000000..232aa95
--- /dev/null
+++ b/libmodprobe/include/exthandler/exthandler.h
@@ -0,0 +1,23 @@
+/*
+ * Copyright (C) 2024 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+#include <android-base/result.h>
+#include <string>
+
+android::base::Result<std::string> RunExternalHandler(
+        const std::string& handler, uid_t uid, gid_t gid,
+        std::unordered_map<std::string, std::string>& envs_map);