libcutils: add android_get_control_file() (c020d3fa) · Commits · e / os / android_system_core

include/cutils/files.h

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			/*
			* Copyright (C) 2016 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.
			*/

			#ifndef __CUTILS_FILES_H
			#define __CUTILS_FILES_H

			#define ANDROID_FILE_ENV_PREFIX "ANDROID_FILE_"

			#ifdef __cplusplus
			extern "C" {
			#endif

			/*
			* android_get_control_file - simple helper function to get the file
			* descriptor of our init-managed file. `path' is the filename path as
			* given in init.rc. Returns -1 on error.
			*/
			int android_get_control_file(const char* path);

			#ifdef __cplusplus
			}
			#endif

			#endif /* __CUTILS_FILES_H */

libcutils/Android.bp

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	@@ -34,6 +34,7 @@ cc_library {
	host_supported: true,		host_supported: true,
	srcs: [		srcs: [
	"config_utils.c",		"config_utils.c",
			"files.cpp",
	"fs_config.c",		"fs_config.c",
	"canned_fs_config.c",		"canned_fs_config.c",
	"hashmap.c",		"hashmap.c",

libcutils/files.cpp

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			/*
			* Copyright (C) 2016 The Android Open Source Project
			* All rights reserved.
			*
			* Redistribution and use in source and binary forms, with or without
			* modification, are permitted provided that the following conditions
			* are met:
			* * Redistributions of source code must retain the above copyright
			* notice, this list of conditions and the following disclaimer.
			* * Redistributions in binary form must reproduce the above copyright
			* notice, this list of conditions and the following disclaimer in
			* the documentation and/or other materials provided with the
			* distribution.
			*
			* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
			* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
			* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
			* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
			* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
			* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
			* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
			* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
			* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
			* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
			* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
			* SUCH DAMAGE.
			*/

			// This file contains files implementation that can be shared between
			// platforms as long as the correct headers are included.
			#define _GNU_SOURCE 1 // for asprintf

			#include <ctype.h>
			#include <errno.h>
			#include <fcntl.h>
			#include <limits.h>
			#include <stdio.h>
			#include <stdlib.h>
			#include <string.h>
			#include <sys/stat.h>
			#include <sys/types.h>
			#include <unistd.h>

			#include <cutils/files.h>

			#ifndef TEMP_FAILURE_RETRY // _WIN32 does not define
			#define TEMP_FAILURE_RETRY(exp) (exp)
			#endif

			int android_get_control_file(const char* path) {
			if (!path) return -1;

			char *key = NULL;
			if (asprintf(&key, ANDROID_FILE_ENV_PREFIX "%s", path) < 0) return -1;
			if (!key) return -1;

			char *cp = key;
			while (*cp) {
			if (!isalnum(cp)) cp = '_';
			++cp;
			}

			const char* val = getenv(key);
			free(key);
			if (!val) return -1;

			errno = 0;
			long fd = strtol(val, NULL, 10);
			if (errno) return -1;

			// validity checking
			if ((fd < 0) \|\| (fd > INT_MAX)) return -1;
			#if defined(_SC_OPEN_MAX)
			if (fd >= sysconf(_SC_OPEN_MAX)) return -1;
			#elif defined(OPEN_MAX)
			if (fd >= OPEN_MAX) return -1;
			#elif defined(_POSIX_OPEN_MAX)
			if (fd >= _POSIX_OPEN_MAX) return -1;
			#endif

			#if defined(F_GETFD)
			if (TEMP_FAILURE_RETRY(fcntl(fd, F_GETFD)) < 0) return -1;
			#elif defined(F_GETFL)
			if (TEMP_FAILURE_RETRY(fcntl(fd, F_GETFL)) < 0) return -1;
			#else
			struct stat s;
			if (TEMP_FAILURE_RETRY(fstat(fd, &s)) < 0) return -1;
			#endif

			#if defined(__linux__)
			char *proc = NULL;
			if (asprintf(&proc, "/proc/self/fd/%ld", fd) < 0) return -1;
			if (!proc) return -1;

			size_t len = strlen(path);
			char buf = static_cast<char >(calloc(1, len + 2));
			if (!buf) {
			free(proc);
			return -1;
			}
			ssize_t ret = TEMP_FAILURE_RETRY(readlink(proc, buf, len + 1));
			free(proc);
			int cmp = (len != static_cast<size_t>(ret)) \|\| strcmp(buf, path);
			free(buf);
			if (ret < 0) return -1;
			if (cmp != 0) return -1;
			#endif

			// It is what we think it is
			return static_cast<int>(fd);
			}

libcutils/tests/Android.bp

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	@@ -14,7 +14,7 @@

	cc_defaults {		cc_defaults {
	name: "libcutils_test_default",		name: "libcutils_test_default",
	srcs: ["sockets_test.cpp"],		srcs: ["sockets_test.cpp", "files_test.cpp"],

	target: {		target: {
	android: {		android: {

libcutils/tests/files_test.cpp

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			/*
			* Copyright (C) 2016 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 <fcntl.h>
			#include <stdio.h>
			#include <stdlib.h>
			#include <sys/types.h>
			#include <time.h>

			#include <cutils/files.h>
			#include <gtest/gtest.h>

			TEST(FilesTest, android_get_control_file) {
			static const char key[] = ANDROID_FILE_ENV_PREFIX "_dev_kmsg";
			static const char name[] = "/dev/kmsg";

			EXPECT_EQ(unsetenv(key), 0);
			EXPECT_EQ(android_get_control_file(name), -1);

			int fd;
			ASSERT_GE(fd = open(name, O_RDONLY \| O_CLOEXEC), 0);
			EXPECT_EQ(android_get_control_file(name), -1);

			char val[32];
			snprintf(val, sizeof(val), "%d", fd);
			EXPECT_EQ(setenv(key, val, true), 0);

			EXPECT_EQ(android_get_control_file(name), fd);
			close(fd);
			EXPECT_EQ(android_get_control_file(name), -1);
			EXPECT_EQ(unsetenv(key), 0);
			EXPECT_EQ(android_get_control_file(name), -1);
			}