Clean up ZygoteForkDelegate API a little

We always pass channel_switch as "--channel=XYZ" and then the
recipient pointlessly verifies that it still starts with "--channel=".
So instead rename AckChild() parameter to channel_id and just pass the
"XYZ" part to remove a possible failure case, and simplify the
receiving code a little bit.

BUG=357670

Review URL: https://codereview.chromium.org/239333009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@264681 0039d316-1c4b-4281-b951-d872f2087c98

6 files changed, 16 insertions, 24 deletions

diff --git a/components/nacl/loader/nacl_helper_linux.cc b/components/nacl/loader/nacl_helper_linux.cc
index 1026feb..70de656 100644
--- a/components/nacl/loader/nacl_helper_linux.cc
+++ b/components/nacl/loader/nacl_helper_linux.cc
@@ -150,21 +150,15 @@ void ChildNaClLoaderInit(const std::vector<int>& child_fds,
   // sandbox does) until then, because that can interfere with the
   // parent's discovery of our PID.
   const ssize_t nread = HANDLE_EINTR(read(parent_fd, buffer, kMaxReadSize));
-  const std::string switch_prefix = std::string("--") +
-      switches::kProcessChannelID + std::string("=");
-  const size_t len = switch_prefix.length();
 
   if (nread < 0) {
     perror("read");
     LOG(ERROR) << "read returned " << nread;
-  } else if (static_cast<size_t>(nread) > len) {
-    if (switch_prefix.compare(0, len, buffer, 0, len) == 0) {
-      VLOG(1) << "NaCl loader is synchronised with Chrome zygote";
-      CommandLine::ForCurrentProcess()->AppendSwitchASCII(
-          switches::kProcessChannelID,
-          std::string(&buffer[len], nread - len));
-      validack = true;
-    }
+  } else if (nread > 0) {
+    VLOG(1) << "NaCl loader is synchronised with Chrome zygote";
+    CommandLine::ForCurrentProcess()->AppendSwitchASCII(
+        switches::kProcessChannelID, std::string(buffer, nread));
+    validack = true;
   }
   if (IGNORE_EINTR(close(dummy_fd)) != 0)
     LOG(ERROR) << "close(dummy_fd) failed";
diff --git a/components/nacl/zygote/nacl_fork_delegate_linux.cc b/components/nacl/zygote/nacl_fork_delegate_linux.cc
index 049d6f3..558344d 100644
--- a/components/nacl/zygote/nacl_fork_delegate_linux.cc
+++ b/components/nacl/zygote/nacl_fork_delegate_linux.cc
@@ -329,11 +329,10 @@ pid_t NaClForkDelegate::Fork(const std::string& process_type,
   return nacl_child;
 }
 
-bool NaClForkDelegate::AckChild(const int fd,
-                                const std::string& channel_switch) {
-  int nwritten = HANDLE_EINTR(write(fd, channel_switch.c_str(),
-                                    channel_switch.length()));
-  if (nwritten != static_cast<int>(channel_switch.length())) {
+bool NaClForkDelegate::AckChild(const int fd, const std::string& channel_id) {
+  ssize_t nwritten =
+      HANDLE_EINTR(write(fd, channel_id.c_str(), channel_id.length()));
+  if (static_cast<size_t>(nwritten) != channel_id.length()) {
     return false;
   }
   return true;
diff --git a/components/nacl/zygote/nacl_fork_delegate_linux.h b/components/nacl/zygote/nacl_fork_delegate_linux.h
index 4158a5a..a0860b69 100644
--- a/components/nacl/zygote/nacl_fork_delegate_linux.h
+++ b/components/nacl/zygote/nacl_fork_delegate_linux.h
@@ -30,8 +30,7 @@ class NaClForkDelegate : public content::ZygoteForkDelegate {
                           int* uma_sample, int* uma_boundary_value) OVERRIDE;
   virtual pid_t Fork(const std::string& process_type,
                      const std::vector<int>& fds) OVERRIDE;
-  virtual bool AckChild(int fd,
-                        const std::string& channel_switch) OVERRIDE;
+  virtual bool AckChild(int fd, const std::string& channel_id) OVERRIDE;
   virtual bool GetTerminationStatus(pid_t pid, bool known_dead,
                                     base::TerminationStatus* status,
                                     int* exit_code) OVERRIDE;
diff --git a/content/public/common/zygote_fork_delegate_linux.h b/content/public/common/zygote_fork_delegate_linux.h
index f4c8e7b..999721c 100644
--- a/content/public/common/zygote_fork_delegate_linux.h
+++ b/content/public/common/zygote_fork_delegate_linux.h
@@ -66,8 +66,8 @@ class ZygoteForkDelegate {
 
   // After a successful fork, signal the child to indicate that
   // the child's PID has been received. Also communicate the
-  // channel switch as a part of acknowledgement message.
-  virtual bool AckChild(int fd, const std::string& channel_switch) = 0;
+  // channel ID as a part of acknowledgement message.
+  virtual bool AckChild(int fd, const std::string& channel_id) = 0;
 
   // The fork delegate must also assume the role of waiting for its children
   // since the caller will not be their parents and cannot do it. |pid| here
diff --git a/content/zygote/zygote_linux.cc b/content/zygote/zygote_linux.cc
index 8ea9714..04e9d83 100644
--- a/content/zygote/zygote_linux.cc
+++ b/content/zygote/zygote_linux.cc
@@ -296,7 +296,7 @@ void Zygote::HandleGetTerminationStatus(int fd,
 
 int Zygote::ForkWithRealPid(const std::string& process_type,
                             const base::GlobalDescriptors::Mapping& fd_mapping,
-                            const std::string& channel_switch,
+                            const std::string& channel_id,
                             std::string* uma_name,
                             int* uma_sample,
                             int* uma_boundary_value) {
@@ -411,7 +411,7 @@ int Zygote::ForkWithRealPid(const std::string& process_type,
     process_info_map_[real_pid].started_from_helper = use_helper;
 
     if (use_helper) {
-      if (!helper_->AckChild(pipe_fds[1], channel_switch)) {
+      if (!helper_->AckChild(pipe_fds[1], channel_id)) {
         LOG(ERROR) << "Failed to synchronise with zygote fork helper";
         goto error;
       }
@@ -467,7 +467,7 @@ base::ProcessId Zygote::ReadArgsAndFork(const Pickle& pickle,
       return -1;
     args.push_back(arg);
     if (arg.compare(0, channel_id_prefix.length(), channel_id_prefix) == 0)
-      channel_id = arg;
+      channel_id = arg.substr(channel_id_prefix.length());
   }
 
   if (!pickle.ReadInt(&iter, &numfds))
diff --git a/content/zygote/zygote_linux.h b/content/zygote/zygote_linux.h
index 37e89b5..140dfa67 100644
--- a/content/zygote/zygote_linux.h
+++ b/content/zygote/zygote_linux.h
@@ -79,7 +79,7 @@ class Zygote {
   // UMA_HISTOGRAM_ENUMERATION.
   int ForkWithRealPid(const std::string& process_type,
                       const base::GlobalDescriptors::Mapping& fd_mapping,
-                      const std::string& channel_switch,
+                      const std::string& channel_id,
                       std::string* uma_name,
                       int* uma_sample,
                       int* uma_boundary_value);