8173941 Re: SA does not work if executable is DSO

[Yasumasa Suenaga]

Hi Andrew,

I checked with GDB, readelf and libsaproc debug message.
I found that we should calculate .dynamic address from entry point in ELF.

I uploaded webrev. This patch works fine on JDK 9 and JDK 10.

   http://cr.openjdk.java.net/~ysuenaga/JDK-8173941/webrev.00/


Thanks,

Yasumasa


On 2017/02/08 23:21, Yasumasa Suenaga wrote:
> Hi Andrew,
>
> I could reproduce it in my environment.
>
>
> * libsaproc debug
> ```
> libsaproc DEBUG: address of _DYNAMIC is 0x563bc6dd8d28
> ```
>
> * Address of .dynamic in GDB
> ```
>         0x0000563bc6dd7d28 - 0x0000563bc6dd7f68 is .dynamic
> ```
>
> It differs 1 page (0x1000).
> In this case, according to GDB, `java` was loaded 0x563bc6dd7000.
> According to readelf of `java`, offset of dynamic section is 0x1d28.
> So I want to investigate why we found 1 memory page difference.
> (Is it caused by ASLR? Do you have any idea?)
>
>
> Thanks,
>
> Yasumasa
>
>
> On 2017/02/08 20:46, Andrew Haley wrote:
>> Okay, thanks.
>>
>> The patch will have to be submitted to JDK 9 first and then back-
>> ported to earlier releases.  Unfortunately it doesn't work on JDK 9.
>> I don't know why: I spent some time looking at it, but I couldn't
>> figure out what was wrong.
>>
>> Is there any way you could have a look?  This is using hg.openjdk.java.net/jdk9/hs
>> on F25.
>>
>> Thanks,
>>
>> Andrew.
>>
>>
>> [aph at localhost hs-8173941]$ LIBSAPROC_DEBUG=1 ./build/linux-x86_64-normal-server-fastdebug/images/jdk/bin/jhsdb jstack --core core.63600 --exe build/linux-x86_64-normal-server-fastdebug/images/jdk/bin/java
>> Attaching to core core.63600 from executable build/linux-x86_64-normal-server-fastdebug/images/jdk/bin/java, please wait...
>> libsaproc DEBUG: Note header with n_type = 3 and n_descsz = 136
>> libsaproc DEBUG: Note header with n_type = 1 and n_descsz = 336
>> libsaproc DEBUG: got integer regset for lwp 63600
>> libsaproc DEBUG: integer regset
>> ...
>> libsaproc DEBUG: Note address of NT_FILE is 0x564be32e5000
>> libsaproc DEBUG: ELF interpreter /lib64/ld-linux-x86-64.so.2
>> libsaproc DEBUG: address of _DYNAMIC p_vaddr is 0x201d28
>> libsaproc DEBUG: address of _DYNAMIC is 0x564be32e6d28
>> libsaproc DEBUG: ---- sorted virtual address map ----
>> ...
>> libsaproc DEBUG: base = 0x7fe62227c000  size = 4096
>> libsaproc DEBUG: base = 0x7ffeabb33000  size = 135168
>> libsaproc DEBUG: base = 0x7ffeabbc0000  size = 8192
>> libsaproc DEBUG: base = 0xffffffffff600000      size = 4096
>> libsaproc DEBUG: can't locate map_info at 0x564be32e7000
>> libsaproc DEBUG: core read failed for 16 byte(s) @ 0x564be32e7000 (8 more bytes)
>> libsaproc DEBUG: 1: can't read debug info from _DYNAMIC
>> Error attaching to core file: Can't attach to the core file
>> sun.jvm.hotspot.debugger.DebuggerException: Can't attach to the core file
>>         at jdk.hotspot.agent/sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal.attach0(Native Method)
>>         at jdk.hotspot.agent/sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal.attach(LinuxDebuggerLocal.java:286)
>>         at jdk.hotspot.agent/sun.jvm.hotspot.HotSpotAgent.attachDebugger(HotSpotAgent.java:679)
>>         at jdk.hotspot.agent/sun.jvm.hotspot.HotSpotAgent.setupDebuggerLinux(HotSpotAgent.java:617)
>>