Linux: Guess the thread id for crashing renderers in a different PID namespace.

BUG=48997
TEST=Google Chrome gets valid crash reports for about:crash most of the time.
Review URL: http://codereview.chromium.org/2961008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@52723 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 53 insertions, 0 deletions

diff --git a/base/linux_util.cc b/base/linux_util.cc
index d9fd065..dda6333 100644
--- a/base/linux_util.cc
+++ b/base/linux_util.cc
@@ -6,19 +6,24 @@
 
 #include <dirent.h>
 #include <errno.h>
+#include <fcntl.h>
 #include <glib.h>
 #include <stdlib.h>
 #include <sys/stat.h>
+#include <sys/stat.h>
+#include <sys/types.h>
 #include <unistd.h>
 
 #include <vector>
 
 #include "base/command_line.h"
 #include "base/env_var.h"
+#include "base/file_util.h"
 #include "base/lock.h"
 #include "base/path_service.h"
 #include "base/process_util.h"
 #include "base/singleton.h"
+#include "base/scoped_ptr.h"
 #include "base/string_util.h"
 
 namespace {
@@ -241,4 +246,46 @@ bool FindProcessHoldingSocket(pid_t* pid_out, ino_t socket_inode) {
   return already_found;
 }
 
+pid_t FindThreadIDWithSyscall(pid_t pid, const std::string& expected_data) {
+  char buf[256];
+  snprintf(buf, sizeof(buf), "/proc/%d/task", pid);
+  DIR* task = opendir(buf);
+  if (!task) {
+    LOG(WARNING) << "Cannot open " << buf;
+    return -1;
+  }
+
+  std::vector<pid_t> tids;
+  struct dirent* dent;
+  while ((dent = readdir(task))) {
+    char *endptr;
+    const unsigned long int tid_ul = strtoul(dent->d_name, &endptr, 10);
+    if (tid_ul == ULONG_MAX || *endptr)
+      continue;
+    tids.push_back(tid_ul);
+  }
+  closedir(task);
+
+  scoped_array<char> syscall_data(new char[expected_data.length()]);
+  for (std::vector<pid_t>::const_iterator
+       i = tids.begin(); i != tids.end(); ++i) {
+    const pid_t current_tid = *i;
+    snprintf(buf, sizeof(buf), "/proc/%d/task/%d/syscall", pid, current_tid);
+    int fd = open(buf, O_RDONLY);
+    if (fd < 0)
+      continue;
+    bool read_ret =
+        file_util::ReadFromFD(fd, syscall_data.get(), expected_data.length());
+    close(fd);
+    if (!read_ret)
+      continue;
+
+    if (0 == strncmp(expected_data.c_str(), syscall_data.get(),
+                     expected_data.length())) {
+      return current_tid;
+    }
+  }
+  return -1;
+}
+
 }  // namespace base
diff --git a/base/linux_util.h b/base/linux_util.h
index e810674..a4ba9b6 100644
--- a/base/linux_util.h
+++ b/base/linux_util.h
@@ -29,6 +29,12 @@ bool FileDescriptorGetInode(ino_t* inode_out, int fd);
 // multiple processes hold the socket, this function returns false.
 bool FindProcessHoldingSocket(pid_t* pid_out, ino_t socket_inode);
 
+// For a given process |pid|, look through all its threads and find the first
+// thread with /proc/[pid]/task/[thread_id]/syscall whose first N bytes matches
+// |expected_data|, where N is the length of |expected_data|.
+// Returns the thread id or -1 on error.
+pid_t FindThreadIDWithSyscall(pid_t pid, const std::string& expected_data);
+
 }  // namespace base
 
 #endif  // BASE_LINUX_UTIL_H_