[PATCH] JDK-8214122 Prevent name mangling of jdwpTransport_OnLoad in Windows 32-bit DLL name decoration

Alexey Ivanov alexey.ivanov at oracle.com
Tue Nov 20 15:49:50 UTC 2018


Hi Ali, Magnus,

I absolutely agree this change has to be reviewed by someone from 
serviceability.

There are several options:

1. Add -export:jdwpTransport_OnLoad to LDFLAGS for Windows
http://mail.openjdk.java.net/pipermail/build-dev/2018-November/023935.html
so it partially reverts the changes from
https://bugs.openjdk.java.net/browse/JDK-8200178

2. Remove JNICALL (__stdcall) modifier, eventually changing the calling 
convention to __cdecl.
http://mail.openjdk.java.net/pipermail/build-dev/2018-November/023969.html

3. Use inline /export option via #pragma:
#pragma comment(linker, "/export:jdwpTransport_OnLoad= 
_jdwpTransport_OnLoad at 16")
as referenced in
https://docs.microsoft.com/en-ie/cpp/cpp/dllexport-dllimport?view=vs-2017
https://docs.microsoft.com/en-ie/cpp/build/reference/exports?view=vs-2017

The third options still needs to be tested to make sure it does not 
break other platforms builds.


Regards,
Alexey

On 19/11/2018 12:19, Magnus Ihse Bursie wrote:
> Hi Ali,
>
> From a build perspective this change looks OK. I'm not aware of the 
> finer details on the OnLoad mechanism, like what calling convention is 
> to be used. So maybe this is a no-go from that view.
>
> I'm cc:ing servicability so they can have a look at it.
>
> /Magnus
>
> On 2018-11-18 13:07, Ali İnce wrote:
>> Hi Alexey,
>>
>> Below is a new patch content that removes JNICALL modifiers from the exported functions of interest. This results in exported functions not to be name decorated and use __cdecl calling convention.
>>
>> Do you have any more suggestions, or would you please guide me on next steps?
>>
>> Thanks,
>>
>> Ali
>>
>> # HG changeset patch
>> # User Ali Ince<ali.ince at gmail.com>
>> # Date 1542542415 0
>> #      Sun Nov 18 12:00:15 2018 +0000
>> # Node ID a41df44e13e1b761f4b3f05a17ed18953067ae39
>> # Parent  16d5ec7dbbb49ef3f969e34be870e3f917ea89ff
>> Remove JNICALL modifiers to prevent name decoration on 32-bit windows builds
>>
>> diff -r 16d5ec7dbbb4 -r a41df44e13e1 src/jdk.jdi/share/native/libdt_shmem/shmemBack.c
>> --- a/src/jdk.jdi/share/native/libdt_shmem/shmemBack.c	Tue Aug 14 14:28:23 2018 +0200
>> +++ b/src/jdk.jdi/share/native/libdt_shmem/shmemBack.c	Sun Nov 18 12:00:15 2018 +0000
>> @@ -339,7 +339,7 @@
>>       return JDWPTRANSPORT_ERROR_NONE;
>>   }
>>   
>> -JNIEXPORT jint JNICALL
>> +JNIEXPORT jint
>>   jdwpTransport_OnLoad(JavaVM *vm, jdwpTransportCallback* cbTablePtr,
>>                        jint version, jdwpTransportEnv** result)
>>   {
>> diff -r 16d5ec7dbbb4 -r a41df44e13e1 src/jdk.jdwp.agent/share/native/include/jdwpTransport.h
>> --- a/src/jdk.jdwp.agent/share/native/include/jdwpTransport.h	Tue Aug 14 14:28:23 2018 +0200
>> +++ b/src/jdk.jdwp.agent/share/native/include/jdwpTransport.h	Sun Nov 18 12:00:15 2018 +0000
>> @@ -140,7 +140,7 @@
>>       void (*free)(void *buffer);      /* Call this for all deallocations */
>>   } jdwpTransportCallback;
>>   
>> -typedef jint (JNICALL *jdwpTransport_OnLoad_t)(JavaVM *jvm,
>> +typedef jint (*jdwpTransport_OnLoad_t)(JavaVM *jvm,
>>                                                  jdwpTransportCallback *callback,
>>                                                  jint version,
>>                                                  jdwpTransportEnv** env);
>> diff -r 16d5ec7dbbb4 -r a41df44e13e1 src/jdk.jdwp.agent/share/native/libdt_socket/socketTransport.c
>> --- a/src/jdk.jdwp.agent/share/native/libdt_socket/socketTransport.c	Tue Aug 14 14:28:23 2018 +0200
>> +++ b/src/jdk.jdwp.agent/share/native/libdt_socket/socketTransport.c	Sun Nov 18 12:00:15 2018 +0000
>> @@ -1019,7 +1019,7 @@
>>       return JDWPTRANSPORT_ERROR_NONE;
>>   }
>>   
>> -JNIEXPORT jint JNICALL
>> +JNIEXPORT jint
>>   jdwpTransport_OnLoad(JavaVM *vm, jdwpTransportCallback* cbTablePtr,
>>                        jint version, jdwpTransportEnv** env)
>>   {
>>
>>
>>
>>> On 16 Nov 2018, at 23:03, Alexey Ivanov<alexey.ivanov at oracle.com>  wrote:
>>>
>>> Hi Ali,
>>>
>>> It's exactly what I referred to.
>>>
>>> Yes, it does change the calling convention.
>>> Yet it's not a (big) problem because both parties will use the same calling convention.
>>>
>>> Using a DLL from another build will not be possible. But it's not a good idea to do so anyway.
>>>
>>>
>>> Mapfiles and export options have been removed byhttps://bugs.openjdk.java.net/browse/JDK-8200178  to simplify managing exported functions. So that to add or remove an exported function, you don't have modify makefiles and/or mapfiles. You just edit the source files.
>>>
>>> Regards,
>>> Alexey
>>>
>>> On 16/11/2018 22:42, Ali İnce wrote:
>>>> Hi Alexey,
>>>>
>>>> Thanks for your reply.
>>>>
>>>> I will definitely give it a try though I’m not sure if that’ll be a breaking change. This is because JNICALL modifier is defined to be __stdcall on windows which is both specified on jdwpTransport_OnLoad exported functions both for dt_socket.dll and dt_shmem.dll.
>>>>
>>>> The __stdcall is ignored on x64 platforms and also name decoration is not applied (https://docs.microsoft.com/en-gb/cpp/build/reference/decorated-names?view=vs-2017). I believe that’s why we don’t experience any problems on x64 builds.
>>>>
>>>> Removing JNICALL (thus __stdcall) modifier (apparently only applies to x86 builds) will result in the calling convention to be changed, and thus will change how parameters are ordered and also the stack cleanup rules. I think this may result in problems in programs that are designed to load shared libraries and its exported functions at runtime (not bound by link time which probably won’t cause any issues - assuming that they use the shared function signature) - as inhttps://github.com/AdoptOpenJDK/openjdk-jdk11u/blob/5f01925b80ed851b133ee26fbcb07026ac04149e/src/jdk.jdwp.agent/share/native/libjdwp/transport.c#L99.
>>>>
>>>> Any thoughts?
>>>>
>>>> Regards,
>>>>
>>>> Ali
>>>>
>>>>> On 15 Nov 2018, at 22:14, Alexey Ivanov<alexey.ivanov at oracle.com>  wrote:
>>>>>
>>>>> Hi Ali,
>>>>>
>>>>> Can the issue be resolved by using different call modifiers on the affected functions?
>>>>>
>>>>> Some build / link issues were resolved by adding / removing JNICALL modifier, see
>>>>> https://bugs.openjdk.java.net/browse/JDK-8201226
>>>>> http://mail.openjdk.java.net/pipermail/build-dev/2018-April/021553.html
>>>>>
>>>>> https://bugs.openjdk.java.net/browse/JDK-8202476
>>>>> http://mail.openjdk.java.net/pipermail/build-dev/2018-May/021913.html
>>>>>
>>>>> Regards,
>>>>> Alexey
>>>>>
>>>>> On 15/11/2018 21:43, Ali İnce wrote:
>>>>>> Hi,
>>>>>>
>>>>>> An issue (https://github.com/AdoptOpenJDK/openjdk-build/issues/709) raised against AdoptOpenJDK jdk11 32-bit windows builds led us to the name decoration problem on built 32-bit dlls - specifically dt_socket.dll and dt_shmem.dll. Whereas 64-bit MSVC builds don’t apply any name decorations on exported functions, 32-bit builds apply them - which requires either def files or /export flags to be specified on the linker arguments.
>>>>>>
>>>>>> Although the expected linker arguments were present on previous jdk makefiles, they were removed in jdk11 makefiles.
>>>>>>
>>>>>> Below is the proposed patch, which can also be browsed athttps://github.com/AdoptOpenJDK/openjdk-jdk11u/pull/1.
>>>>>>
>>>>>> Would you please have a look and let me know of any points I may have missed (I don’t have any background information about why the export flags were removed in jdk11)?
>>>>>>
>>>>>> Regards,
>>>>>>
>>>>>> Ali
>>>>>>
>>>>>> diff --git a/make/lib/Lib-jdk.jdi.gmk b/make/lib/Lib-jdk.jdi.gmk
>>>>>> index 197b95c2e2..ac6ebf5591 100644
>>>>>> --- a/make/lib/Lib-jdk.jdi.gmk
>>>>>> +++ b/make/lib/Lib-jdk.jdi.gmk
>>>>>> @@ -37,6 +37,7 @@ ifeq ($(OPENJDK_TARGET_OS), windows)
>>>>>>             jdk.jdwp.agent:include \
>>>>>>             jdk.jdwp.agent:libjdwp/export, \
>>>>>>         LDFLAGS := $(LDFLAGS_JDKLIB), \
>>>>>> +      LDFLAGS_windows := -export:jdwpTransport_OnLoad, \
>>>>>>         LIBS := $(JDKLIB_LIBS), \
>>>>>>     ))
>>>>>>
>>>>>> diff --git a/make/lib/Lib-jdk.jdwp.agent.gmk b/make/lib/Lib-jdk.jdwp.agent.gmk
>>>>>> index 0bc93e0d35..0382e55325 100644
>>>>>> --- a/make/lib/Lib-jdk.jdwp.agent.gmk
>>>>>> +++ b/make/lib/Lib-jdk.jdwp.agent.gmk
>>>>>> @@ -37,6 +37,7 @@ $(eval $(call SetupJdkLibrary, BUILD_LIBDT_SOCKET, \
>>>>>>           libjdwp/export, \
>>>>>>       LDFLAGS := $(LDFLAGS_JDKLIB) \
>>>>>>           $(call SET_SHARED_LIBRARY_ORIGIN), \
>>>>>> +    LDFLAGS_windows := -export:jdwpTransport_OnLoad, \
>>>>>>       LIBS_linux := -lpthread, \
>>>>>>       LIBS_solaris := -lnsl -lsocket, \
>>>>>>       LIBS_windows := $(JDKLIB_LIBS) ws2_32.lib, \
>



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