爲什麼java應用程序在gdb中崩潰，但在現實生活中正常運行？

Question

嘗試從gdb運行java應用程序會導致段錯誤，但單獨運行應用程序卻不行。這個應用程序是一個.JAR，它使用JOGL和一些內存映射來與GPU對話。

Stacktrace下面提示某種內存訪問問題，但我不明白它爲什麼會在GDB中顯示，但不在現實生活中。 gdb是否需要知道一些環境因素才能正確執行？

在JVM的OpenJDK 6和7以及Oracle JRE 7之間，此問題仍然存在。在JDefault之前，Oracle JRE運行時間稍遠。所有段錯誤在試驗之間的發生和位置方面是一致的。

Segfault在GPU和驅動程序（!!）之間仍然存在：nvidia，radeon，fglrx current和fglrx beta（14.xx）。 GDB將成功附加到我的程序的一個已經運行的實例，但是gDEBugger似乎不可能這樣做，這最終是需要工作的。

沒有意圖用gdb進行實際調試。相反，我試圖使用gDEBugger來執行OpenGL調試。 gDEBugger顯然依賴於GDB作爲其後端的一部分，所以如果GDB失敗，gDEBugger也會失敗。這導致嘗試單獨運行gdb來隔離問題。

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 

UPDATE：切換到AMD CodeXL（基本上是最近gDEBugger的形式），情況並沒有太大的改變。

Answer 1

爲什麼java應用程序在gdb中崩潰，但在現實生活中正常運行？

因爲它沒有實際上崩潰。

Java使用推測性加載。如果指針指向可尋址內存，則加載成功。很少指針指向可尋址的內存，並且嘗試的負載生成SIGSEGV ... java運行時攔截，使內存重新尋址，並重新啓動加載指令。

當調試Java程序，一個具有普遍做到這一點：

(gdb) handle SIGSEGV nostop noprint pass 

不幸的是，如果有一些涉及的JNI代碼，那代碼SIGSEGV S，GDB會很樂意忽略信號爲好，導致劣質（被調試）過程的死亡。對於後一個問題，我還沒有找到可以接受的解決方案。