Linux: set the process title (that shows in "ps" etc.) of renderers correctly when using the zygote.

BUG=none
TEST=none

Review URL: http://codereview.chromium.org/196009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@25877 0039d316-1c4b-4281-b951-d872f2087c98

5 files changed, 191 insertions, 3 deletions

diff --git a/base/base.gyp b/base/base.gyp
index f6a7192..8c0ed39 100644
--- a/base/base.gyp
+++ b/base/base.gyp
@@ -261,6 +261,8 @@
         'scoped_variant_win.cc',
         'scoped_variant_win.h',
         'scoped_vector.h',
+        'setproctitle_linux.c',
+        'setproctitle_linux.h',
         'sha2.cc',
         'sha2.h',
         'shared_memory.h',
@@ -398,8 +400,8 @@
             'cflags': [
               '-Wno-write-strings',
             ],
-	    'link_settings': {
-	      'libraries': [
+            'link_settings': {
+              'libraries': [
                 # We need rt for clock_gettime().
                 '-lrt',
               ],
@@ -424,7 +426,15 @@
               'nss_init.h',
               'time_posix.cc',
             ],
-          }
+          },
+        ],
+        [ 'OS != "linux"', {
+            'sources!': [
+              # Not automatically excluded by the *linux.cc rules.
+              'setproctitle_linux.c',
+              'setproctitle_linux.h',
+            ],
+          },
         ],
         [ 'GENERATOR == "quentin"', {
             # Quentin builds don't have a recent enough glibc to include the
diff --git a/base/command_line.cc b/base/command_line.cc
index 43b068c..04c1ece 100644
--- a/base/command_line.cc
+++ b/base/command_line.cc
@@ -7,6 +7,9 @@
 #if defined(OS_WIN)
 #include <windows.h>
 #include <shellapi.h>
+#elif defined(OS_FREEBSD)
+#include <stdlib.h>
+#include <unistd.h>
 #endif
 
 #include <algorithm>
@@ -17,6 +20,11 @@
 #include "base/string_util.h"
 #include "base/sys_string_conversions.h"
 
+#if defined(OS_LINUX)
+// Linux/glibc doesn't natively have setproctitle().
+#include "base/setproctitle_linux.h"
+#endif
+
 CommandLine* CommandLine::current_process_commandline_ = NULL;
 
 // Since we use a lazy match, make sure that longer versions (like L"--")
@@ -194,6 +202,29 @@ void CommandLine::Init(const std::vector<std::string>& argv) {
 #endif
 }
 
+#if defined(OS_LINUX) || defined(OS_FREEBSD)
+// static
+void CommandLine::SetProcTitle() {
+  // Build a single string which consists of all the arguments separated
+  // by spaces. We can't actually keep them separate due to the way the
+  // setproctitle() function works.
+  std::string title;
+  for (size_t i = 1; i < current_process_commandline_->argv_.size(); ++i) {
+    if (!title.empty())
+      title += " ";
+    title += current_process_commandline_->argv_[i];
+  }
+  setproctitle("%s", title.c_str());
+}
+
+// static
+void CommandLine::SetTrueArgv(char** argv) {
+#if defined(OS_LINUX)
+  setproctitle_init(argv);
+#endif
+}
+#endif
+
 void CommandLine::Terminate() {
   DCHECK(current_process_commandline_ != NULL);
   delete current_process_commandline_;
diff --git a/base/command_line.h b/base/command_line.h
index 121eb8c..78f3862 100644
--- a/base/command_line.h
+++ b/base/command_line.h
@@ -55,6 +55,16 @@ class CommandLine {
   static void Init(int argc, const char* const* argv);
   static void Init(const std::vector<std::string>& argv);
 
+#if defined(OS_LINUX) || defined(OS_FREEBSD)
+  // Sets the current process' arguments that show in "ps" etc. to those
+  // in |current_process_commandline_|. Used by the zygote host so that
+  // renderers show up with --type=renderer.
+  static void SetProcTitle();
+
+  // Needed to support SetProcTitle() on Linux. Should be called by main().
+  static void SetTrueArgv(char** argv);
+#endif
+
   // Destroys the current process CommandLine singleton. This is necessary if
   // you want to reset the base library to its initial state (for example in an
   // outer library that needs to be able to terminate, and be re-initialized).
diff --git a/base/setproctitle_linux.c b/base/setproctitle_linux.c
new file mode 100644
index 0000000..205be2b
--- /dev/null
+++ b/base/setproctitle_linux.c
@@ -0,0 +1,112 @@
+// Copyright (c) 2009 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// This file implements BSD-style setproctitle() for Linux.
+// It is written such that it can easily be compiled outside Chromium.
+//
+// The Linux kernel sets up two locations in memory to pass arguments and
+// environment variables to processes. First, there are two char* arrays stored
+// one after another: argv and environ. A pointer to argv is passed to main(),
+// while glibc sets the global variable |environ| to point at the latter. Both
+// of these arrays are terminated by a NULL pointer; the environment array is
+// also followed by some empty space to allow additional variables to be added.
+//
+// These arrays contain pointers to a second location in memory, where the
+// strings themselves are stored one after another: first all the arguments,
+// then the environment variables. The kernel will allocate a single page of
+// memory for this purpose, so the end of the page containing argv[0] is the
+// end of the storage potentially available to store the process title.
+//
+// When the kernel reads the command line arguments for a process, it looks at
+// the range of memory within this page that it initially used for the argument
+// list. If the terminating '\0' character is still where it expects, nothing
+// further is done. If it has been overwritten, the kernel will scan up to the
+// size of a page looking for another. (Note, however, that in general not that
+// much space is actually mapped, since argv[0] is rarely page-aligned and only
+// one page is mapped.)
+//
+// Thus to change the process title, we must move any environment variables out
+// of the way to make room for a potentially longer title, and then overwrite
+// the memory pointed to by argv[0] with a single replacement string, making
+// sure its size does not exceed the available space.
+//
+// It is perhaps worth noting that patches to add a system call to Linux for
+// this, like in BSD, have never made it in: this is the "official" way to do
+// this on Linux. Presumably it is not in glibc due to some disagreement over
+// this position within the glibc project, leaving applications caught in the
+// middle. (Also, only a very few applications need or want this anyway.)
+
+#include "base/setproctitle_linux.h"
+
+#include <stdarg.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+extern char** environ;
+
+static char** g_main_argv = NULL;
+static char* g_orig_argv0 = NULL;
+
+void setproctitle(const char* fmt, ...) {
+  va_list ap;
+  size_t i, avail_size;
+  uintptr_t page_size, page, page_end;
+  // Sanity check before we try and set the process title.
+  // The BSD version allows fmt == NULL to restore the original title.
+  if (!g_main_argv || !environ || !fmt)
+    return;
+  if (!g_orig_argv0) {
+    // Save the original argv[0].
+    g_orig_argv0 = strdup(g_main_argv[0]);
+    if (!g_orig_argv0)
+      return;
+  }
+  page_size = sysconf(_SC_PAGESIZE);
+  // Get the page on which the argument list and environment live.
+  page = (uintptr_t) g_main_argv[0];
+  page -= page % page_size;
+  page_end = page + page_size;
+  // Move the environment out of the way. Note that we are moving the values,
+  // not the environment array itself (which may not be on the page we need
+  // to overwrite anyway).
+  for (i = 0; environ[i]; ++i) {
+    uintptr_t env_i = (uintptr_t) environ[i];
+    // Only move the value if it's actually in the way. This avoids
+    // leaking copies of the values if this function is called again.
+    if (page <= env_i && env_i < page_end) {
+      char* copy = strdup(environ[i]);
+      // Be paranoid. Check for allocation failure and bail out.
+      if (!copy)
+        return;
+      environ[i] = copy;
+    }
+  }
+  // Put the title in argv[0]. We have to zero out the space first since the
+  // kernel doesn't actually look for a null terminator unless we make the
+  // argument list longer than it started.
+  avail_size = page_end - (uintptr_t) g_main_argv[0];
+  memset(g_main_argv[0], 0, avail_size);
+  va_start(ap, fmt);
+  if (fmt[0] == '-') {
+    vsnprintf(g_main_argv[0], avail_size, fmt, ap);
+  } else {
+    size_t size = snprintf(g_main_argv[0], avail_size, "%s ", g_orig_argv0);
+    if (size < avail_size)
+      vsnprintf(g_main_argv[0] + size, avail_size - size, fmt, ap);
+  }
+  va_end(ap);
+  g_main_argv[1] = NULL;
+}
+
+// A version of this built into glibc would not need this function, since
+// it could stash the argv pointer in __libc_start_main(). But we need it.
+void setproctitle_init(char** main_argv) {
+  uintptr_t page_size = sysconf(_SC_PAGESIZE);
+  // Check that the argv array is in fact on the same page of memory
+  // as the environment array just as an added measure of protection.
+  if (((uintptr_t) environ) / page_size == ((uintptr_t) main_argv) / page_size)
+    g_main_argv = main_argv;
+}
diff --git a/base/setproctitle_linux.h b/base/setproctitle_linux.h
new file mode 100644
index 0000000..32cc297
--- /dev/null
+++ b/base/setproctitle_linux.h
@@ -0,0 +1,25 @@
+// Copyright (c) 2009 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_SETPROCTITLE_LINUX_H_
+#define BASE_SETPROCTITLE_LINUX_H_
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// Set the process title that will show in "ps" and similar tools. Takes
+// printf-style format string and arguments. After calling setproctitle()
+// the original main() argv[] array should not be used.
+void setproctitle(const char* fmt, ...);
+
+// Initialize state needed for setproctitle() on Linux. Pass the argv pointer
+// from main() to setproctitle_init() before calling setproctitle().
+void setproctitle_init(char** main_argv);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif  // BASE_SETPROCTITLE_LINUX_H_