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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
// Use "dyld interposing" to hook methods imported from other libraries in the
// plugin child process. The basic technique is described at
// http://books.google.com/books?id=K8vUkpOXhN4C&pg=PA73&lpg=PA73&dq=__interpose&source=bl&ots=OJnnXZYpZC&sig=o7I3lXvoduUi13SrPfOON7o3do4&hl=en&ei=AoehS9brCYGQNrvsmeUM&sa=X&oi=book_result&ct=result&resnum=6&ved=0CBsQ6AEwBQ#v=onepage&q=__interpose&f=false.
// The idea of doing it for the plugin child process comes from Chromium code,
// particularly from plugin_carbon_interpose_mac.cc
// (http://codesearch.google.com/codesearch/p?hl=en#OAMlx_jo-ck/src/chrome/browser/plugin_carbon_interpose_mac.cc&q=nscursor&exact_package=chromium&d=1&l=168)
// and from PluginProcessHost::Init() in plugin_process_host.cc
// (http://codesearch.google.com/codesearch/p?hl=en#OAMlx_jo-ck/src/content/browser/plugin_process_host.cc&q=nscursor&exact_package=chromium&d=1&l=222).
// These hooks are needed to make certain OS calls work from the child process
// (a background process) that would normally only work when called in the
// parent process (the foreground process). They allow us to serialize
// information from the child process to the parent process, so that the same
// (or equivalent) calls can be made from the parent process.
// This file lives in a seperate module (libplugin_child_interpose.dylib),
// which will get loaded by the OS before any other modules when the plugin
// child process is launched (from GeckoChildProcessHost::
// PerformAsyncLaunchInternal()). For this reason it shouldn't link in other
// browser modules when loaded. Instead it should use dlsym() to load
// pointers to the methods it wants to call in other modules.
#if !defined(__LP64__)
#include <dlfcn.h>
#import <Carbon/Carbon.h>
// The header file QuickdrawAPI.h is missing on OS X 10.7 and up (though the
// QuickDraw APIs defined in it are still present) -- so we need to supply the
// relevant parts of its contents here. It's likely that Apple will eventually
// remove the APIs themselves (probably in OS X 10.8), so we need to make them
// weak imports, and test for their presence before using them.
#if !defined(__QUICKDRAWAPI__)
struct Cursor;
extern "C" void SetCursor(const Cursor * crsr) __attribute__((weak_import));
#endif /* __QUICKDRAWAPI__ */
BOOL (*OnSetThemeCursorPtr) (ThemeCursor) = NULL;
BOOL (*OnSetCursorPtr) (const Cursor*) = NULL;
BOOL (*OnHideCursorPtr) () = NULL;
BOOL (*OnShowCursorPtr) () = NULL;
static BOOL loadXULPtrs()
{
if (!OnSetThemeCursorPtr) {
// mac_plugin_interposing_child_OnSetThemeCursor(ThemeCursor cursor) is in
// PluginInterposeOSX.mm
OnSetThemeCursorPtr = (BOOL(*)(ThemeCursor))
dlsym(RTLD_DEFAULT, "mac_plugin_interposing_child_OnSetThemeCursor");
}
if (!OnSetCursorPtr) {
// mac_plugin_interposing_child_OnSetCursor(const Cursor* cursor) is in
// PluginInterposeOSX.mm
OnSetCursorPtr = (BOOL(*)(const Cursor*))
dlsym(RTLD_DEFAULT, "mac_plugin_interposing_child_OnSetCursor");
}
if (!OnHideCursorPtr) {
// mac_plugin_interposing_child_OnHideCursor() is in PluginInterposeOSX.mm
OnHideCursorPtr = (BOOL(*)())
dlsym(RTLD_DEFAULT, "mac_plugin_interposing_child_OnHideCursor");
}
if (!OnShowCursorPtr) {
// mac_plugin_interposing_child_OnShowCursor() is in PluginInterposeOSX.mm
OnShowCursorPtr = (BOOL(*)())
dlsym(RTLD_DEFAULT, "mac_plugin_interposing_child_OnShowCursor");
}
return (OnSetCursorPtr && OnSetThemeCursorPtr && OnHideCursorPtr && OnShowCursorPtr);
}
static OSStatus MacPluginChildSetThemeCursor(ThemeCursor cursor)
{
if (loadXULPtrs()) {
OnSetThemeCursorPtr(cursor);
}
return ::SetThemeCursor(cursor);
}
static void MacPluginChildSetCursor(const Cursor* cursor)
{
if (::SetCursor) {
if (loadXULPtrs()) {
OnSetCursorPtr(cursor);
}
::SetCursor(cursor);
}
}
static CGError MacPluginChildCGDisplayHideCursor(CGDirectDisplayID display)
{
if (loadXULPtrs()) {
OnHideCursorPtr();
}
return ::CGDisplayHideCursor(display);
}
static CGError MacPluginChildCGDisplayShowCursor(CGDirectDisplayID display)
{
if (loadXULPtrs()) {
OnShowCursorPtr();
}
return ::CGDisplayShowCursor(display);
}
#pragma mark -
struct interpose_substitution {
const void* replacement;
const void* original;
};
#define INTERPOSE_FUNCTION(function) \
{ reinterpret_cast<const void*>(MacPluginChild##function), \
reinterpret_cast<const void*>(function) }
__attribute__((used)) static const interpose_substitution substitutions[]
__attribute__((section("__DATA, __interpose"))) = {
INTERPOSE_FUNCTION(SetThemeCursor),
INTERPOSE_FUNCTION(CGDisplayHideCursor),
INTERPOSE_FUNCTION(CGDisplayShowCursor),
// SetCursor() and other QuickDraw APIs will probably be removed in OS X
// 10.8. But this will make 'SetCursor' NULL, which will just stop the OS
// from interposing it (tested using an INTERPOSE_FUNCTION_BROKEN macro
// that just sets the second address of each tuple to NULL).
INTERPOSE_FUNCTION(SetCursor),
};
#endif // !__LP64__
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