graal-jvmci-8: src/os/linux/vm/os

comparison src/os/linux/vm/os_linux.cpp @ 8710:9058789475af

7107135: Stack guard pages are no more protected after loading a shared library with executable stack Summary: Detect the execstack attribute of the loaded library and attempt to fix the stack guard using Safepoint op. Reviewed-by: dholmes, zgu Contributed-by: ioi.lam@oracle.com

author	iklam
date	Tue, 05 Mar 2013 13:55:56 -0800
parents	63e54c37ac64
children	6b803ba47588

comparison

equal deleted inserted replaced

-:255c0a4cb4eb
+:9058789475af
 #include "prims/jvm_misc.hpp"
 #include "runtime/arguments.hpp"
 #include "runtime/extendedPC.hpp"
 #include "runtime/globals.hpp"
 #include "runtime/interfaceSupport.hpp"
+#include "runtime/init.hpp"
 #include "runtime/java.hpp"
 #include "runtime/javaCalls.hpp"
 #include "runtime/mutexLocker.hpp"
 #include "runtime/objectMonitor.hpp"
 #include "runtime/osThread.hpp"
 #include "services/attachListener.hpp"
 #include "services/runtimeService.hpp"
 #include "utilities/decoder.hpp"
 #include "utilities/defaultStream.hpp"
 #include "utilities/events.hpp"
+#include "utilities/elfFile.hpp"
 #include "utilities/growableArray.hpp"
 #include "utilities/vmError.hpp"
 // put OS-includes here
 # include <sys/types.h>
 // Loads .dll/.so and
 // in case of error it checks if .dll/.so was built for the
 // same architecture as Hotspot is running on
+// Remember the stack's state. The Linux dynamic linker will change
+// the stack to 'executable' at most once, so we must safepoint only once.
+bool os::Linux::_stack_is_executable = false;
+// VM operation that loads a library.  This is necessary if stack protection
+// of the Java stacks can be lost during loading the library.  If we
+// do not stop the Java threads, they can stack overflow before the stacks
+// are protected again.
+class VM_LinuxDllLoad: public VM_Operation {
+private:
+const char *_filename;
+void *_lib;
+public:
+VM_LinuxDllLoad(const char *fn) :
+_filename(fn), _lib(NULL) {}
+VMOp_Type type() const { return VMOp_LinuxDllLoad; }
+void doit() {
+_lib = os::Linux::dll_load_inner(_filename);
+os::Linux::_stack_is_executable = true;
+}
+void* loaded_library() { return _lib; }
+};
 void * os::dll_load(const char *filename, char *ebuf, int ebuflen)
 {
-void * result= ::dlopen(filename, RTLD_LAZY);
+void * result = NULL;
+bool load_attempted = false;
+// Check whether the library to load might change execution rights
+// of the stack. If they are changed, the protection of the stack
+// guard pages will be lost. We need a safepoint to fix this.
+//
+// See Linux man page execstack(8) for more info.
+if (os::uses_stack_guard_pages() && !os::Linux::_stack_is_executable) {
+ElfFile ef(filename);
+if (!ef.specifies_noexecstack()) {
+if (!is_init_completed()) {
+os::Linux::_stack_is_executable = true;
+// This is OK - No Java threads have been created yet, and hence no
+// stack guard pages to fix.
+//
+// This should happen only when you are building JDK7 using a very
+// old version of JDK6 (e.g., with JPRT) and running test_gamma.
+//
+// Dynamic loader will make all stacks executable after
+// this function returns, and will not do that again.
+assert(Threads::first() == NULL, "no Java threads should exist yet.");
+} else {
+warning("You have loaded library %s which might have disabled stack guard. "
+"The VM will try to fix the stack guard now.\n"
+"It's highly recommended that you fix the library with "
+"'execstack -c <libfile>', or link it with '-z noexecstack'.",
+filename);
+assert(Thread::current()->is_Java_thread(), "must be Java thread");
+JavaThread *jt = JavaThread::current();
+if (jt->thread_state() != _thread_in_native) {
+// This happens when a compiler thread tries to load a hsdis-<arch>.so file
+// that requires ExecStack. Cannot enter safe point. Let's give up.
+warning("Unable to fix stack guard. Giving up.");
+} else {
+if (!LoadExecStackDllInVMThread) {
+// This is for the case where the DLL has an static
+// constructor function that executes JNI code. We cannot
+// load such DLLs in the VMThread.
+result = ::dlopen(filename, RTLD_LAZY);
+}
+ThreadInVMfromNative tiv(jt);
+debug_only(VMNativeEntryWrapper vew;)
+VM_LinuxDllLoad op(filename);
+VMThread::execute(&op);
+if (LoadExecStackDllInVMThread) {
+result = op.loaded_library();
+}
+load_attempted = true;
+}
+}
+}
+}
+if (!load_attempted) {
+result = ::dlopen(filename, RTLD_LAZY);
+}
 if (result != NULL) {
 // Successful loading
 return result;
 }
 arch_array[running_arch_index].name);
 }
 }
 return NULL;
+}
+void * os::Linux::dll_load_inner(const char *filename) {
+void * result = NULL;
+if (LoadExecStackDllInVMThread) {
+result = ::dlopen(filename, RTLD_LAZY);
+}
+// Since 7019808, libjvm.so is linked with -noexecstack. If the VM loads a
+// library that requires an executable stack, or which does not have this
+// stack attribute set, dlopen changes the stack attribute to executable. The
+// read protection of the guard pages gets lost.
+//
+// Need to check _stack_is_executable again as multiple VM_LinuxDllLoad
+// may have been queued at the same time.
+if (!_stack_is_executable) {
+JavaThread *jt = Threads::first();
+while (jt) {
+if (!jt->stack_guard_zone_unused() &&        // Stack not yet fully initialized
+jt->stack_yellow_zone_enabled()) {       // No pending stack overflow exceptions
+if (!os::guard_memory((char *) jt->stack_red_zone_base() - jt->stack_red_zone_size(),
+jt->stack_yellow_zone_size() + jt->stack_red_zone_size())) {
+warning("Attempt to reguard stack yellow zone failed.");
+}
+}
+jt = jt->next();
+}
+}
+return result;
 }
 /*
 * glibc-2.0 libdl is not MT safe.  If you are building with any glibc,
 * chances are you might want to run the generated bits against glibc-2.0

Mercurial > hg > graal-jvmci-8

comparison src/os/linux/vm/os_linux.cpp @ 8710:9058789475af