libprocinfo: introduce.

Add a new library for parsing /proc files. Start with helpers for
parsing /proc/<pid>/status and /proc/<pid>/task.

Bug: http://b/30705528
Test: libprocinfo_test32/64 on host/bullhead
Change-Id: I5757514c0aede8a9d75834b55aae42a5cf762b95

libprocinfo/.clang-format

@@ -0,0 +1,14 @@
+BasedOnStyle: Google
+AllowShortBlocksOnASingleLine: false
+AllowShortFunctionsOnASingleLine: false
+
+ColumnLimit: 100
+CommentPragmas: NOLINT:.*
+DerivePointerAlignment: false
+IndentWidth: 2
+PointerAlignment: Left
+TabWidth: 2
+UseTab: Never
+PenaltyExcessCharacter: 32
+
+Cpp11BracedListStyle: false

libprocinfo/Android.bp

@@ -0,0 +1,73 @@
+//
+// Copyright (C) 2015 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.
+//
+
+libprocinfo_cppflags = [
+    "-Wall",
+    "-Wextra",
+    "-Werror",
+]
+
+cc_library {
+    name: "libprocinfo",
+    host_supported: true,
+    srcs: [
+        "process.cpp",
+    ],
+    cppflags: libprocinfo_cppflags,
+
+    local_include_dirs: ["include"],
+    export_include_dirs: ["include"],
+    shared_libs: ["libbase"],
+    target: {
+        darwin: {
+            enabled: false,
+        },
+        windows: {
+            enabled: false,
+        },
+    },
+}
+
+// Tests
+// ------------------------------------------------------------------------------
+cc_test {
+    name: "libprocinfo_test",
+    host_supported: true,
+    srcs: [
+        "process_test.cpp",
+    ],
+    target: {
+        darwin: {
+            enabled: false,
+        },
+        windows: {
+            enabled: false,
+        },
+    },
+
+    cppflags: libprocinfo_cppflags,
+    shared_libs: ["libbase", "libprocinfo"],
+
+    compile_multilib: "both",
+    multilib: {
+        lib32: {
+            suffix: "32",
+        },
+        lib64: {
+            suffix: "64",
+        },
+    },
+}

libprocinfo/include/procinfo/process.h

@@ -0,0 +1,106 @@
+/*
+ * 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.
+ */
+
+#pragma once
+
+#include <dirent.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <memory>
+#include <string>
+#include <type_traits>
+
+#include <android-base/logging.h>
+#include <android-base/parseint.h>
+#include <android-base/unique_fd.h>
+
+namespace android {
+namespace procinfo {
+
+#if defined(__linux__)
+
+struct ProcessInfo {
+  std::string name;
+  pid_t tid;
+  pid_t pid;
+  pid_t ppid;
+  pid_t tracer;
+  uid_t uid;
+  uid_t gid;
+};
+
+// Parse the contents of /proc/<tid>/status into |process_info|.
+bool GetProcessInfo(pid_t tid, ProcessInfo* process_info);
+
+// Parse the contents of <fd>/status into |process_info|.
+// |fd| should be an fd pointing at a /proc/<pid> directory.
+bool GetProcessInfoFromProcPidFd(int fd, ProcessInfo* process_info);
+
+// Fetch the list of threads from a given process's /proc/<pid> directory.
+// |fd| should be an fd pointing at a /proc/<pid> directory.
+template <typename Collection>
+auto GetProcessTidsFromProcPidFd(int fd, Collection* out) ->
+    typename std::enable_if<sizeof(typename Collection::value_type) >= sizeof(pid_t), bool>::type {
+  out->clear();
+
+  int task_fd = openat(fd, "task", O_DIRECTORY | O_RDONLY | O_CLOEXEC);
+  std::unique_ptr<DIR, int (*)(DIR*)> dir(fdopendir(task_fd), closedir);
+  if (!dir) {
+    PLOG(ERROR) << "failed to open task directory";
+    return false;
+  }
+
+  struct dirent* dent;
+  while ((dent = readdir(dir.get()))) {
+    if (strcmp(dent->d_name, ".") != 0 && strcmp(dent->d_name, "..") != 0) {
+      pid_t tid;
+      if (!android::base::ParseInt(dent->d_name, &tid, 1, std::numeric_limits<pid_t>::max())) {
+        LOG(ERROR) << "failed to parse task id: " << dent->d_name;
+        return false;
+      }
+
+      out->insert(out->end(), tid);
+    }
+  }
+
+  return true;
+}
+
+template <typename Collection>
+auto GetProcessTids(pid_t pid, Collection* out) ->
+    typename std::enable_if<sizeof(typename Collection::value_type) >= sizeof(pid_t), bool>::type {
+  char task_path[PATH_MAX];
+  if (snprintf(task_path, PATH_MAX, "/proc/%d", pid) >= PATH_MAX) {
+    LOG(ERROR) << "task path overflow (pid = " << pid << ")";
+    return false;
+  }
+
+  android::base::unique_fd fd(open(task_path, O_DIRECTORY | O_RDONLY | O_CLOEXEC));
+  if (fd == -1) {
+    PLOG(ERROR) << "failed to open " << task_path;
+    return false;
+  }
+
+  return GetProcessTidsFromProcPidFd(fd.get(), out);
+}
+
+#endif
+
+} /* namespace procinfo */
+} /* namespace android */

libprocinfo/process.cpp

@@ -0,0 +1,109 @@
+/*
+ * 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 <procinfo/process.h>
+
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <string>
+
+#include <android-base/unique_fd.h>
+
+using android::base::unique_fd;
+
+namespace android {
+namespace procinfo {
+
+bool GetProcessInfo(pid_t tid, ProcessInfo* process_info) {
+  char path[PATH_MAX];
+  snprintf(path, sizeof(path), "/proc/%d", tid);
+
+  unique_fd dirfd(open(path, O_DIRECTORY | O_RDONLY));
+  if (dirfd == -1) {
+    PLOG(ERROR) << "failed to open " << path;
+    return false;
+  }
+
+  return GetProcessInfoFromProcPidFd(dirfd.get(), process_info);
+}
+
+bool GetProcessInfoFromProcPidFd(int fd, ProcessInfo* process_info) {
+  int status_fd = openat(fd, "status", O_RDONLY | O_CLOEXEC);
+
+  if (status_fd == -1) {
+    PLOG(ERROR) << "failed to open status fd in GetProcessInfoFromProcPidFd";
+    return false;
+  }
+
+  std::unique_ptr<FILE, decltype(&fclose)> fp(fdopen(status_fd, "r"), fclose);
+  if (!fp) {
+    PLOG(ERROR) << "failed to open status file in GetProcessInfoFromProcPidFd";
+    close(status_fd);
+    return false;
+  }
+
+  int field_bitmap = 0;
+  static constexpr int finished_bitmap = 127;
+  char* line = nullptr;
+  size_t len = 0;
+
+  while (getline(&line, &len, fp.get()) != -1 && field_bitmap != finished_bitmap) {
+    char* tab = strchr(line, '\t');
+    if (tab == nullptr) {
+      continue;
+    }
+
+    size_t header_len = tab - line;
+    std::string header = std::string(line, header_len);
+    if (header == "Name:") {
+      std::string name = line + header_len + 1;
+
+      // line includes the trailing newline.
+      name.pop_back();
+      process_info->name = std::move(name);
+
+      field_bitmap |= 1;
+    } else if (header == "Pid:") {
+      process_info->tid = atoi(tab + 1);
+      field_bitmap |= 2;
+    } else if (header == "Tgid:") {
+      process_info->pid = atoi(tab + 1);
+      field_bitmap |= 4;
+    } else if (header == "PPid:") {
+      process_info->ppid = atoi(tab + 1);
+      field_bitmap |= 8;
+    } else if (header == "TracerPid:") {
+      process_info->tracer = atoi(tab + 1);
+      field_bitmap |= 16;
+    } else if (header == "Uid:") {
+      process_info->uid = atoi(tab + 1);
+      field_bitmap |= 32;
+    } else if (header == "Gid:") {
+      process_info->gid = atoi(tab + 1);
+      field_bitmap |= 64;
+    }
+  }
+
+  free(line);
+  return field_bitmap == finished_bitmap;
+}
+
+} /* namespace procinfo */
+} /* namespace android */

libprocinfo/process_test.cpp

@@ -0,0 +1,84 @@
+/*
+ * 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 <procinfo/process.h>
+
+#include <fcntl.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <set>
+#include <thread>
+#include <vector>
+
+#include <gtest/gtest.h>
+
+#include <android-base/stringprintf.h>
+
+#if !defined(__BIONIC__)
+#include <syscall.h>
+static pid_t gettid() {
+  return syscall(__NR_gettid);
+}
+#endif
+
+TEST(process_info, process_info_smoke) {
+  android::procinfo::ProcessInfo self;
+  ASSERT_TRUE(android::procinfo::GetProcessInfo(gettid(), &self));
+  ASSERT_EQ(gettid(), self.tid);
+  ASSERT_EQ(getpid(), self.pid);
+  ASSERT_EQ(getppid(), self.ppid);
+  ASSERT_EQ(getuid(), self.uid);
+  ASSERT_EQ(getgid(), self.gid);
+}
+
+TEST(process_info, process_info_proc_pid_fd_smoke) {
+  android::procinfo::ProcessInfo self;
+  int fd = open(android::base::StringPrintf("/proc/%d", gettid()).c_str(), O_DIRECTORY | O_RDONLY);
+  ASSERT_NE(-1, fd);
+  ASSERT_TRUE(android::procinfo::GetProcessInfoFromProcPidFd(fd, &self));
+
+  // Process name is capped at 15 bytes.
+  ASSERT_EQ("libprocinfo_tes", self.name);
+  ASSERT_EQ(gettid(), self.tid);
+  ASSERT_EQ(getpid(), self.pid);
+  ASSERT_EQ(getppid(), self.ppid);
+  ASSERT_EQ(getuid(), self.uid);
+  ASSERT_EQ(getgid(), self.gid);
+  close(fd);
+}
+
+TEST(process_info, process_tids_smoke) {
+  pid_t main_tid = gettid();
+  std::thread([main_tid]() {
+    pid_t thread_tid = gettid();
+
+    {
+      std::vector<pid_t> vec;
+      ASSERT_TRUE(android::procinfo::GetProcessTids(getpid(), &vec));
+      ASSERT_EQ(1, std::count(vec.begin(), vec.end(), main_tid));
+      ASSERT_EQ(1, std::count(vec.begin(), vec.end(), thread_tid));
+    }
+
+    {
+      std::set<pid_t> set;
+      ASSERT_TRUE(android::procinfo::GetProcessTids(getpid(), &set));
+      ASSERT_EQ(1, std::count(set.begin(), set.end(), main_tid));
+      ASSERT_EQ(1, std::count(set.begin(), set.end(), thread_tid));
+    }
+  }).join();
+}