为什么java应用程序在gdb中崩溃但在现实生活中正常运行？

Question

尝试从gdb运行java应用程序导致segfault,但单独运行app却没有.这个应用程序是.JAR,它使用JOGL和一些内存映射来与GPU通信.

下面的Stacktrace暗示了某种内存访问问题,但我不明白它为什么会出现在GDB中而不是现实生活中.是否有一些环境因素gdb需要知道才能正确执行？

这个问题在JVM OpenJDK 6和7以及Oracle JRE 7之间仍然存在.在启用segfault之前,oracle JRE在启动时运行得更远.所有段错误在试验之间的发生和位置都是一致的.

Segfault在GPU和驱动程序之间持续存在(!!):nvidia,radeon,fglrx current和fglrx beta(14.xx).GDB将成功附加到已经运行的程序实例,但是gDEBugger似乎不可能这样做,这最终需要工作.

没有意图使用gdb进行实际调试.相反,我试图使用gDEBugger来执行OpenGL调试.gDEBugger显然依赖于GDB作为其后端的一部分,因此如果GDB失败,gDEBugger也会失败.这导致尝试单独运行gdb以隔离问题.

gDEBugger output:
GDB String:  [Thread debugging using libthread_db enabled]  
GDB String:  Using host libthread_db library  /lib/x86_64-linux-gnu/libthread_db.so.1 .  
Thread Created: 140737353893632 (LWP: 3265)
Thread Created: 140737294624512 (LWP: 3266)
Thread Created: 140737293571840 (LWP: 3267)
Thread Created: 140737292519168 (LWP: 3268)
Thread Created: 140737155180288 (LWP: 3269)
Thread Created: 140737154127616 (LWP: 3270)
Thread Created: 140736913602304 (LWP: 3271)
Thread Created: 140736909629184 (LWP: 3272)
Thread Created: 140736908576512 (LWP: 3273)
Thread Created: 140736907523840 (LWP: 3274)
Thread Created: 140736906471168 (LWP: 3275)
Thread Created: 140736905418496 (LWP: 3276)
Thread Created: 140736278275840 (LWP: 3277)
Thread Created: 140736272963328 (LWP: 3278)
Thread Created: 140736271910656 (LWP: 3279)
Thread Created: 140736270857984 (LWP: 3280)
Thread Created: 140736269805312 (LWP: 3281)
Thread Created: 140737287657216 (LWP: 3285)
Thread Created: 140736261945088 (LWP: 3289)
GDB String:  [Thread 0x7fffb6e67700 (LWP 3289) exited]  
Thread Created: 140736261945088 (LWP: 3290)
API Connection Established: gDEBugger Servers Manager
Thread Created: 140736234641152 (LWP: 3291)
GDB String:  [Thread 0x7fffb6e67700 (LWP 3290) exited]  
API Connection Established: gDEBugger OpenGL Server
GDB String:  [Thread 0x7fffb77e8700 (LWP 3279) exited]  
GDB String:  [Thread 0x7fffb76e7700 (LWP 3280) exited]  
Debug String: gDEBugger OpenGL Server was initialized
Thread Created: 140736270857984 (LWP: 3292)
Thread Created: 140735692441344 (LWP: 3294)
Thread Created: 140735582430976 (LWP: 3295)
Thread Created: 140735574038272 (LWP: 3296)
OpenGL Render Context 1 Created
Signal: SIGSEGV
Process Exit


$ java -versionjava version "1.6.0_33"
OpenJDK Runtime Environment (IcedTea6 1.13.5) (6b33-1.13.5-1ubuntu0.14.04)
OpenJDK 64-Bit Server VM (build 23.25-b01, mixed mode)

$ gdb -version
GNU gdb (Ubuntu 7.7.1-0ubuntu5~14.04.2) 7.7.1

$ cat /etc/lsb-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=14.04
DISTRIB_CODENAME=trusty
DISTRIB_DESCRIPTION="Ubuntu 14.04.1 LTS"

$ fglrxinfo
display: :0.0  screen: 0
OpenGL vendor string: Advanced Micro Devices, Inc.
OpenGL renderer string: AMD Radeon HD 5570     
OpenGL version string: 4.4.12967 Compatibility Profile Context 14.20


$ gdb --args java -jar RunMe.jar
GNU gdb (Ubuntu 7.7.1-0ubuntu5~14.04.2) 7.7.1
Copyright (C) 2014 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from java...Reading symbols from /usr/lib/debug//usr/lib/jvm/java-6-openjdk-amd64/jre/bin/java...done.
done.
(gdb) show configuration
This GDB was configured as follows:
   configure --host=x86_64-linux-gnu --target=x86_64-linux-gnu
             --with-auto-load-dir=$debugdir:$datadir/auto-load
             --with-auto-load-safe-path=$debugdir:$datadir/auto-load
             --with-expat
             --with-gdb-datadir=/usr/share/gdb (relocatable)
             --with-jit-reader-dir=/usr/lib/gdb (relocatable)
             --without-libunwind-ia64
             --with-lzma
             --with-python=/usr (relocatable)
             --with-separate-debug-dir=/usr/lib/debug (relocatable)
             --with-system-gdbinit=/etc/gdb/gdbinit
             --with-zlib
             --without-babeltrace
(gdb) run
Starting program: /usr/bin/java -jar RunMe.jar
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
process 6866 is executing new program: /usr/lib/jvm/java-6-openjdk-amd64/jre/bin/java
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[New Thread 0x7ffff7fc4700 (LWP 6870)]
[New Thread 0x7ffff486c700 (LWP 6871)]
[New Thread 0x7ffff476b700 (LWP 6872)]
[New Thread 0x7ffff466a700 (LWP 6873)]
[New Thread 0x7fffea2d6700 (LWP 6874)]
[New Thread 0x7fffea1d5700 (LWP 6875)]
[New Thread 0x7fffea0d4700 (LWP 6876)]
[New Thread 0x7fffe9d0a700 (LWP 6877)]
[New Thread 0x7fffe9c09700 (LWP 6878)]
[New Thread 0x7fffe9b08700 (LWP 6879)]
[New Thread 0x7fffe9a07700 (LWP 6880)]
[New Thread 0x7fffe9906700 (LWP 6881)]
...
[New Thread 0x7fffe8110700 (LWP 6882)]
[New Thread 0x7fffe3169700 (LWP 6883)]
[New Thread 0x7fffe3068700 (LWP 6884)]
[New Thread 0x7fffe2f67700 (LWP 6885)]
[New Thread 0x7fffe2e66700 (LWP 6886)]
[New Thread 0x7fffe2d65700 (LWP 6887)]
[Thread 0x7fffe2d65700 (LWP 6887) exited]
[New Thread 0x7fffe2d65700 (LWP 6891)]
[Thread 0x7fffe2d65700 (LWP 6891) exited]
[New Thread 0x7fffe2d65700 (LWP 6895)]
[Thread 0x7fffe2d65700 (LWP 6895) exited]
[New Thread 0x7fffe2d65700 (LWP 6896)]
[New Thread 0x7fffe0efd700 (LWP 6897)]
libEGL warning: DRI2: failed to authenticate
[New Thread 0x7fff9799f700 (LWP 6898)]
[New Thread 0x7fff9719e700 (LWP 6899)]
[New Thread 0x7fff9699d700 (LWP 6900)]
[Thread 0x7fffe2d65700 (LWP 6896) exited]
[New Thread 0x7fffe2d65700 (LWP 6901)]
[New Thread 0x7fffe01ab700 (LWP 6902)]
[New Thread 0x7fff92f00700 (LWP 6903)]
[New Thread 0x7fff92dff700 (LWP 6904)]
[New Thread 0x7fff92cfe700 (LWP 6905)]
Setting up sound system...[New Thread 0x7fff92bfd700 (LWP 6906)]

[New Thread 0x7fff92afc700 (LWP 6907)]
[New Thread 0x7fff929fb700 (LWP 6908)]
[New Thread 0x7fff928fa700 (LWP 6909)]
[New Thread 0x7fff927f9700 (LWP 6910)]
[New Thread 0x7fff926f8700 (LWP 6911)]
[New Thread 0x7fff925f7700 (LWP 6912)]

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7fffe2f67700 (LWP 6885)]
0x00007ffff6b3a770 in acl_CopyRight ()
   from /usr/lib/jvm/java-6-openjdk-amd64/jre/lib/amd64/server/libjvm.so
(gdb) where
#0  0x00007ffff6b3a770 in acl_CopyRight ()
   from /usr/lib/jvm/java-6-openjdk-amd64/jre/lib/amd64/server/libjvm.so
#1  0x00007ffff6d51309 in Unsafe_CopyMemory2 (env=<optimized out>, 
    unsafe=<optimized out>, srcObj=0x0, srcOffset=140737008618496, dstObj=0x0, 
    dstOffset=140737006779392, size=1024)
    at /build/buildd/openjdk-6-6b33-1.13.5/build/openjdk/hotspot/src/share/vm/prims/unsafe.cpp:689
#2  0x00007fffed011790 in ?? ()
#3  0x0000000000000400 in ?? ()
#4  0x0000000000000000 in ?? ()
Warning: the current language does not match this frame.
(gdb) quit
A debugging session is active.

    Inferior 1 [process 6866] will be killed.

Quit anyway? (y or n) y

更新:切换到AMD CodeXL(基本上是最新形式的gDEBugger),情况没有太大变化.

Answer 1

为什么java应用程序在gdb中崩溃但在现实生活中正常运行？

因为它实际上并没有崩溃.

Java使用推测性负载.如果指针指向可寻址内存,则加载成功.很少指针不指向可寻址的内存,并且尝试的加载生成SIGSEGV...哪个java运行时截获,使内存再次可寻址,并重新启动加载指令.

在调试java程序时,通常必须这样做:

(gdb) handle SIGSEGV nostop noprint pass

不幸的是,如果有一些JNI代码参与,并且该代码SIGSEGVS,GDB将愉快地忽略该信号为好,导致不良的(被调试)处理的死亡.对于后一个问题我没有找到可接受的解决方案.