linux: Read /proc/<pid> files via PtraceConnection

Bug: crashpad:250
Change-Id: I93c8944c48a17bd2c2b34cd9b8d81750cf80229c
Reviewed-on: https://chromium-review.googlesource.com/1200311
Commit-Queue: Joshua Peraza <jperaza@chromium.org>
Reviewed-by: Mark Mentovai <mark@chromium.org>

snapshot/linux/process_reader_linux.cc

@@ -236,7 +236,7 @@ bool ProcessReaderLinux::CPUTimes(timeval* user_time,
 
   for (const Thread& thread : threads_) {
     ProcStatReader stat;
-    if (!stat.Initialize(thread.tid)) {
+    if (!stat.Initialize(connection_, thread.tid)) {
       return false;
     }
 

util/linux/proc_stat_reader.cc

@@ -43,9 +43,12 @@ ProcStatReader::ProcStatReader()
 
 ProcStatReader::~ProcStatReader() {}
 
-bool ProcStatReader::Initialize(pid_t tid) {
+bool ProcStatReader::Initialize(PtraceConnection* connection, pid_t tid) {
   INITIALIZATION_STATE_SET_INITIALIZING(initialized_);
-  if (!ReadFile(tid)) {
+
+  char path[32];
+  snprintf(path, arraysize(path), "/proc/%d/stat", tid);
+  if (!connection->ReadFileContents(base::FilePath(path), &contents_)) {
     return false;
   }
 
@@ -110,15 +113,6 @@ bool ProcStatReader::StartTime(timeval* start_time) const {
   return true;
 }
 
-bool ProcStatReader::ReadFile(pid_t tid) {
-  char path[32];
-  snprintf(path, arraysize(path), "/proc/%d/stat", tid);
-  if (!LoggingReadEntireFile(base::FilePath(path), &contents_)) {
-    return false;
-  }
-  return true;
-}
-
 bool ProcStatReader::FindColumn(int col_index, const char** column) const {
   size_t position = third_column_position_;
   for (int index = 2; index < col_index; ++index) {

util/linux/proc_stat_reader.h

@@ -22,6 +22,7 @@
 #include <string>
 
 #include "base/macros.h"
+#include "util/linux/ptrace_connection.h"
 #include "util/misc/initialization_state_dcheck.h"
 
 namespace crashpad {
@@ -36,8 +37,10 @@ class ProcStatReader {
   //!
   //! This method must be successfully called before calling any other.
   //!
+  //! \param[in] connection A connection to the process to which the target
+  //!     thread belongs.
   //! \param[in] tid The thread ID to read the stat file for.
-  bool Initialize(pid_t tid);
+  bool Initialize(PtraceConnection* connection, pid_t tid);
 
   //! \brief Determines the time the thread has spent executing in user mode.
   //!
@@ -64,7 +67,6 @@ class ProcStatReader {
   bool StartTime(timeval* start_time) const;
 
  private:
-  bool ReadFile(pid_t tid);
   bool FindColumn(int index, const char** column) const;
   bool ReadTimeAtIndex(int index, timeval* time_val) const;
 

util/linux/proc_stat_reader_test.cc

@@ -20,6 +20,7 @@
 
 #include "base/logging.h"
 #include "gtest/gtest.h"
+#include "test/linux/fake_ptrace_connection.h"
 #include "util/thread/thread.h"
 
 namespace crashpad {
@@ -27,8 +28,11 @@ namespace test {
 namespace {
 
 TEST(ProcStatReader, Basic) {
+  FakePtraceConnection connection;
+  ASSERT_TRUE(connection.Initialize(getpid()));
+
   ProcStatReader stat;
-  ASSERT_TRUE(stat.Initialize(getpid()));
+  ASSERT_TRUE(stat.Initialize(&connection, getpid()));
 
   timeval start_time;
   ASSERT_TRUE(stat.StartTime(&start_time));
@@ -53,8 +57,11 @@ pid_t gettid() {
 }
 
 void GetStartTime(timeval* start_time) {
+  FakePtraceConnection connection;
+  ASSERT_TRUE(connection.Initialize(getpid()));
+
   ProcStatReader stat;
-  ASSERT_TRUE(stat.Initialize(gettid()));
+  ASSERT_TRUE(stat.Initialize(&connection, gettid()));
   ASSERT_TRUE(stat.StartTime(start_time));
 }
 

util/posix/process_info.h

@@ -174,6 +174,7 @@ class ProcessInfo {
   // multiple successive calls will always produce the same return value and out
   // parameters. This is necessary for intergration with the Snapshot interface.
   // See https://crashpad.chromium.org/bug/9.
+  PtraceConnection* connection_;
   std::set<gid_t> supplementary_groups_;
   mutable timeval start_time_;
   pid_t pid_;

util/posix/process_info_linux.cc

@@ -20,13 +20,15 @@
 #include "base/logging.h"
 #include "util/file/delimited_file_reader.h"
 #include "util/file/file_reader.h"
+#include "util/file/string_file.h"
 #include "util/linux/proc_stat_reader.h"
 #include "util/misc/lexing.h"
 
 namespace crashpad {
 
 ProcessInfo::ProcessInfo()
-    : supplementary_groups_(),
+    : connection_(),
+      supplementary_groups_(),
       start_time_(),
       pid_(-1),
       ppid_(-1),
@@ -45,16 +47,19 @@ bool ProcessInfo::InitializeWithPtrace(PtraceConnection* connection) {
   INITIALIZATION_STATE_SET_INITIALIZING(initialized_);
   DCHECK(connection);
 
+  connection_ = connection;
   pid_ = connection->GetProcessID();
   is_64_bit_ = connection->Is64Bit();
 
   {
     char path[32];
     snprintf(path, sizeof(path), "/proc/%d/status", pid_);
-    FileReader status_file;
+    std::string contents;
-    if (!status_file.Open(base::FilePath(path))) {
+    if (!connection->ReadFileContents(base::FilePath(path), &contents)) {
       return false;
     }
+    StringFile status_file;
+    status_file.SetString(contents);
 
     DelimitedFileReader status_file_line_reader(&status_file);
 
@@ -230,7 +235,7 @@ bool ProcessInfo::StartTime(timeval* start_time) const {
   if (start_time_initialized_.is_uninitialized()) {
     start_time_initialized_.set_invalid();
     ProcStatReader reader;
-    if (!reader.Initialize(pid_)) {
+    if (!reader.Initialize(connection_, pid_)) {
       return false;
     }
     if (!reader.StartTime(&start_time_)) {
@@ -252,10 +257,12 @@ bool ProcessInfo::Arguments(std::vector<std::string>* argv) const {
 
   char path[32];
   snprintf(path, sizeof(path), "/proc/%d/cmdline", pid_);
-  FileReader cmdline_file;
+  std::string contents;
-  if (!cmdline_file.Open(base::FilePath(path))) {
+  if (!connection_->ReadFileContents(base::FilePath(path), &contents)) {
     return false;
   }
+  StringFile cmdline_file;
+  cmdline_file.SetString(contents);
 
   DelimitedFileReader cmdline_file_field_reader(&cmdline_file);