问题描述
尝试从 gdb 运行 java 应用程序会导致段错误，但单独运行应用程序不会.这个应用程序是一个 .JAR，它使用 JOGL 和一些内存映射来与 GPU 对话.
Attempting to run java app from gdb results in segfault, yet running app alone does not. This app is a .JAR which uses JOGL and a bit of memory-mapping to talk to the GPU.
下面的 Stacktrace 暗示了某种内存访问问题，但我不明白为什么它会出现在 GDB 中而不是在现实生活中.是否有一些环境因素 gdb 需要知道才能正确执行?
Stacktrace below hints at some sort of memory access problem but I don't understand why it manifests in GDB but not in real life. Could there be some environment factor gdb needs to know to allow proper execution?
此问题在 JVM OpenJDK 6 和 7 以及 Oracle JRE 7 之间仍然存在.oracle JRE 在段错误之前运行得更远一些.在其他方面，所有段错误在试验之间的发生和位置上都是一致的.
This issue persists between JVMs OpenJDK 6 and 7, as well as Oracle JRE 7. The oracle JRE runs a little farther into startup before segfault. All segfaults are otherwise consistent in occurrence and location between trials.
GPU 和驱动程序之间仍然存在段错误(！！):nvidia、radeon、fglrx current 和 fglrx beta (14.xx).GDB 将成功附加到我的程序的一个已经运行的实例，但是 gDEBugger 似乎不可能做到这一点，这最终需要工作.
Segfault persists between GPUs and drivers(!!): nvidia, radeon, fglrx current and fglrx beta (14.xx). GDB will successfully attach to an already-running instance of my program, however it doesn't seem possible for gDEBugger to do this, which is ultimately what needs to work.
无意使用 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 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 来隔离问题.
There is no intent to actually debug with gdb. Rather I am trying to use gDEBugger to perform OpenGL debugging. gDEBugger apparently relies on GDB as part of its backend, so if GDB fails, so does gDEBugger. This resulted in attempts to run gdb alone to isolate the issue.
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:改用 AMD CodeXL(基本上是 gDEBugger 的最新形式)并且情况没有太大变化.
UPDATE: Switched to AMD CodeXL (basically the most recent form of gDEBugger) and situation hasn't changed much.
推荐答案
因为它不会实际上崩溃.
Java 使用推测加载.如果指针指向可寻址内存，则加载成功.很少有指针不指向可寻址内存，并且尝试加载会生成 SIGSEGV ... java 运行时拦截它，使内存再次可寻址，并重新启动加载指令.
Java uses speculative loads. If a pointer points to addressable memory, the load succeeds. Rarely the pointer does not point to addressable memory, and the attempted load generates SIGSEGV ... which java runtime intercepts, makes the memory addressable again, and restarts the load instruction.
在调试java程序时，一般必须这样做:
When debugging java programs, one has to generally do this:
(gdb) handle SIGSEGV nostop noprint pass
不幸的是，如果涉及到一些 JNI 代码，并且那个代码 SIGSEGVs，GDB 也会很乐意忽略该信号，从而导致劣质(被调试)过程.对于后一个问题，我还没有找到可接受的解决方案.
Unfortunately, if there is some JNI code involved, and that code SIGSEGVs, GDB will happily ignore that signal as well, resulting in the death of inferior (being debugged) process. I have not found an acceptable solution for that latter problem.
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