Merge r174503 - Ensure that inline assembly Thunk functions don't con…

…flict with the section designations of the compiler

https://bugs.webkit.org/show_bug.cgi?id=137434

Patch by Akos Kiss <akiss@inf.u-szeged.hu> on 2014-10-09
Reviewed by Michael Saboff.

The ARM64 version of the defineUnaryDoubleOpWrapper macro in
ThunkGenerators.cpp contains inline assembly with .text assembler
directive followed by a static variable declaration. This macro gets
expanded several times afterwards, however, only during the compilation
of the first expansion does gcc insert a .data assembler directive
before the assembled version of the static variable. Thus, only the
first variable gets allocated in the .data section, all the others
remain in .text. If JavaScriptCore is built as a shared library then
this causes a segmentation fault during dynamic linking.

This patch puts a .previous directive at the end of the inline assembly
to ensure that the assumptions of the compiler about the sections are
not broken and the following variable goes to the right place.

* jit/ThunkGenerators.cpp:

Canonical link: https://commits.webkit.org/154760.114@webkitgtk/2.6
git-svn-id: https://svn.webkit.org/repository/webkit/releases/WebKitGTK/webkit-2.6@174966 268f45cc-cd09-0410-ab3c-d52691b4dbfc

Source/JavaScriptCore/ChangeLog

@@ -1,3 +1,26 @@
+2014-10-09  Akos Kiss  <akiss@inf.u-szeged.hu>
+
+        Ensure that inline assembly Thunk functions don't conflict with the section designations of the compiler
+        https://bugs.webkit.org/show_bug.cgi?id=137434
+
+        Reviewed by Michael Saboff.
+
+        The ARM64 version of the defineUnaryDoubleOpWrapper macro in
+        ThunkGenerators.cpp contains inline assembly with .text assembler
+        directive followed by a static variable declaration. This macro gets
+        expanded several times afterwards, however, only during the compilation
+        of the first expansion does gcc insert a .data assembler directive
+        before the assembled version of the static variable. Thus, only the
+        first variable gets allocated in the .data section, all the others
+        remain in .text. If JavaScriptCore is built as a shared library then
+        this causes a segmentation fault during dynamic linking.
+
+        This patch puts a .previous directive at the end of the inline assembly
+        to ensure that the assumptions of the compiler about the sections are
+        not broken and the following variable goes to the right place.
+
+        * jit/ThunkGenerators.cpp:
+
 2014-10-06  Oliver Hunt  <oliver@apple.com>
 
         Fix cloop build

Source/JavaScriptCore/jit/ThunkGenerators.cpp

@@ -801,6 +801,7 @@ double jsRound(double d)
         HIDE_SYMBOL(function##Thunk) "\n" \
         SYMBOL_STRING(function##Thunk) ":" "\n" \
         "b " GLOBAL_REFERENCE(function) "\n" \
+        ".previous" \
     ); \
     extern "C" { \
         MathThunkCallingConvention function##Thunk(MathThunkCallingConvention); \