Question

我编写了一个旨在通过LD_PRELOAD加载的库。在某些Linux系统上，这会导致动态库加载器在初始化期间发生段错误。

我有一个展示此行为的简单测试用例，但仅当我与-lm链接时。例如：

# Works fine
gcc -o vecadd.normal -std=c99 vecadd.c -lOpenCL
LD_PRELOAD=/path/to/my/library.so ./vecadd.normal

# Causes segmentation fault
gcc -o vecadd.broken -std=c99 vecadd.c -lOpenCL -lm
LD_PRELOAD=/path/to/my/library.so ./vecadd.broken

关于这一点的奇怪之处在于libm.so似乎包含在两个版本中：ldd显示完全相同的库集，只是以不同的顺序：

vecadd.normal:
  linux-vdso.so.1 =>  (0x00007fffed9ff000)
  libOpenCL.so => /usr/lib64/libOpenCL.so (0x00007f135c9b1000)
  libc.so.6 => /lib64/libc.so.6 (0x00007f135c61c000)
  libdl.so.2 => /lib64/libdl.so.2 (0x00007f135c418000)
  libnuma.so.1 => /usr/lib64/libnuma.so.1 (0x00007f135c20f000)
  libstdc++.so.6 => /usr/lib64/libstdc++.so.6 (0x00007f135bf08000)
  libm.so.6 => /lib64/libm.so.6 (0x00007f135bc84000)
  libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00007f135ba6e000)
  /lib64/ld-linux-x86-64.so.2 (0x00007f135cbd4000)
vecadd.broken:
  linux-vdso.so.1 =>  (0x00007fff25c74000)
  libOpenCL.so => /usr/lib64/libOpenCL.so (0x00007fb8c071e000)
  libm.so.6 => /lib64/libm.so.6 (0x00007fb8c0499000)
  libc.so.6 => /lib64/libc.so.6 (0x00007fb8c0105000)
  libdl.so.2 => /lib64/libdl.so.2 (0x00007fb8bff01000)
  libnuma.so.1 => /usr/lib64/libnuma.so.1 (0x00007fb8bfcf7000)
  libstdc++.so.6 => /usr/lib64/libstdc++.so.6 (0x00007fb8bf9f1000)
  libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00007fb8bf7db000)
  /lib64/ld-linux-x86-64.so.2 (0x00007fb8c0941000)

Google将我定向到LD_DEBUG，该问题也指向libm.so作为问题的一部分：

 14143: symbol=fma;  lookup in file=./vecadd.broken [0]
 14143: symbol=fma;  lookup in file=/path/to/my/library.so [0]
 14143: symbol=fma;  lookup in file=/usr/lib64/libOpenCL.so [0]
 14143: symbol=fma;  lookup in file=/lib64/libm.so.6 [0]
 14143: binding file /path/to/my/library.so [0] to /lib64/libm.so.6 [0]: normal symbol `fma' [GLIBC_2.2.5]
Segmentation fault (core dumped)

不幸的是，我可以重现此问题的唯一机器似乎没有可用的动态库加载器的调试符号（并且我没有任何管理权限），因此GDB不会产生任何有用的东西：< / p>

gdb ./vecadd.broken
(gdb) set environment LD_PRELOAD /path/to/my/library.so
(gdb) run
Starting program: vecadd.broken 

Program received signal SIGSEGV, Segmentation fault.
0x0000000000003dce in ?? ()
Missing separate debuginfos, use: debuginfo-install glibc-2.12-1.132.el6_5.1.x86_64
(gdb) bt
#0  0x0000000000003dce in ?? ()
#1  0x00007fff7f755369 in ?? ()
#2  0x00007fffffffd840 in ?? ()
#3  0x00007fff7fde9e91 in _dl_relocate_object ()
   from /lib64/ld-linux-x86-64.so.2
#4  0x00007fff7fde18a3 in dl_main () from /lib64/ld-linux-x86-64.so.2
#5  0x00007fff7fdf3a0e in _dl_sysdep_start () from /lib64/ld-linux-x86-64.so.2
#6  0x00007fff7fddf4a4 in _dl_start () from /lib64/ld-linux-x86-64.so.2
#7  0x00007fff7fddeb08 in _start () from /lib64/ld-linux-x86-64.so.2
#8  0x0000000000000001 in ?? ()
#9  0x00007fffffffde01 in ?? ()
#10 0x0000000000000000 in ?? ()

找到问题根源的最佳方法是什么？

Answer 1

您可以上传自己使用符号构建的动态加载程序，并将其调用以链接您的应用，例如：

var token = configuration.Get<string>("AppData:CompanyName");

LD_PRELOAD在动态库加载器中导致分段错误

1 个答案: