Add support for virtualized (xen) platforms (i.e. amazon ec2)

build/config.rb

@@ -35,6 +35,7 @@
 # Should be included last in the command string, even after PlatformInfo.portability_cflags.
 EXTRA_CXXFLAGS = "-Wextra -Wno-unused-parameter -Wno-parentheses -Wpointer-arith -Wwrite-strings -Wno-long-long"
 EXTRA_CXXFLAGS << " -Wno-missing-field-initializers" if PlatformInfo.compiler_supports_wno_missing_field_initializers_flag?
+EXTRA_CXXFLAGS << " -mno-tls-direct-seg-refs" if PlatformInfo.requires_no_tls_direct_seg_refs? && PlatformInfo.compiler_supports_no_tls_direct_seg_refs_option?
 EXTRA_CXXFLAGS << " #{OPTIMIZATION_FLAGS}" if !OPTIMIZATION_FLAGS.empty?
 
 # Extra linker flags that should always be passed to the linker.

lib/phusion_passenger/platform_info/compiler.rb

@@ -66,6 +66,11 @@ def self.compiler_supports_wno_missing_field_initializers_flag?
 	end
 	memoize :compiler_supports_wno_missing_field_initializers_flag?
 
+	def self.compiler_supports_no_tls_direct_seg_refs_option?
+		return try_compile(:c, '', '-mno-tls-direct-seg-refs')
+	end
+	memoize :compiler_supports_no_tls_direct_seg_refs_option?, true
+
 	# Returns whether compiling C++ with -fvisibility=hidden might result
 	# in tons of useless warnings, like this:
 	# http://code.google.com/p/phusion-passenger/issues/detail?id=526

lib/phusion_passenger/platform_info/operating_system.rb

@@ -153,6 +153,11 @@ def self.supports_lfence_instruction?
 			}))
 	end
 	memoize :supports_lfence_instruction?, true
+
+	def self.requires_no_tls_direct_seg_refs?
+		return File.exists?("/proc/xen/capabilities")
+	end
+	memoize :requires_no_tls_direct_seg_refs?, true
 end
 
 end # module PhusionPassenger