Question

在使用Yocto构建的ARM交叉编译系统中，我无法在GDB的回溯中显示正确的调试符号。

abc.c是一个简单的printf（“ Hello world \ n”）;用C编写程序（没什么麻烦的）。在构建机器上：

> yocto-dir/build/tmp-angstrom-glibc/sysroots/x86_64-linux/usr/bin/arm-angstrom-linux-gnueabi/arm-angstrom-linux-gnueabi-gcc abc --sysroot=yocto-dir/build/tmp-angstrom-glibc/sysroots/imx28scm -g -O0 -o abc
> scp abc root@DEVICE-IP:~

关于ARM目标：

> gdbserver :2345 abc

在构建计算机上启动GDB（从已安装的Yocto SDK）：

> /usr/local/oecore-x86_64/sysroots/x86_64-angstromsdk-linux/usr/bin/arm-angstrom-linux-gnueabi/arm-angstrom-linux-gnueabi-gdb abc
GNU gdb (Linaro GDB) 7.8-2014.09
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 "--host=x86_64-angstromsdk-linux --target=arm-angstrom-linux-gnueabi".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://bugs.linaro.org>.
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 abc...done.
(gdb) target remote DEVICE-IP:2345
Remote debugging using DEVICE-IP:2345
warning: Unable to find dynamic linker breakpoint function.
GDB will be unable to debug shared library initializers
and track explicitly loaded dynamic code.
Cannot access memory at address 0x0
0x4ae90a20 in ?? ()
(gdb) bt
#0  0x4ae90a20 in ?? ()
#1  0x00000000 in ?? ()
Backtrace stopped: previous frame identical to this frame (corrupt stack?)
(gdb) set sysroot yocto-dir/build/tmp-angstrom-glibc/sysroots/imx28scm
Reading symbols from yocto-dir/build/tmp-angstrom-glibc/sysroots/imx28scm/lib/ld-linux.so.3...done.
Loaded symbols for yocto-dir/build/tmp-angstrom-glibc/sysroots/imx28scm/lib/ld-linux.so.3
Cannot access memory at address 0x0

设置sysroot之后，它仍然不提供符号。

(gdb) bt
#0  0x4ae90a20 in ?? ()
#1  0x00000000 in ?? ()
Backtrace stopped: previous frame identical to this frame (corrupt stack?)
(gdb) b main
Breakpoint 1 at 0x84a8: file abc.c, line 5.
(gdb) c
Continuing.

Breakpoint 1, main () at abc.c:5
5      printf("Hello world\n");

好的，当它达到断点时，它会显示符号。

(gdb) bt
Cannot access memory at address 0x0
#0  main () at abc.c:5

但是，走到那儿很奇怪。

(gdb) n
Cannot access memory at address 0x1
0x4aea6ea0 in ?? ()
(gdb) bt
#0  0x4aea6ea0 in ?? ()
#1  0x0000a014 in do_lookup_unique (Cannot access memory at address 0x1
undef_map=0x1, ref=0x0, strtab=0x56ebb27 <error: Cannot access memory at address 0x56ebb27>, sym=0x84a0 <main>, type_class=-1224757248, result=0x1, map=<optimized out>, 
    new_hash=<optimized out>, undef_name=<optimized out>) at /usr/src/debug/glibc/2.24-r0/git/elf/dl-lookup.c:332
#2  do_lookup_x (undef_name=<optimized out>, new_hash=<optimized out>, old_hash=<optimized out>, ref=0x0, result=<optimized out>, scope=0x177ff8e, i=<optimized out>, version=<optimized out>, 
    flags=-1224757248, skip=0x1, type_class=100, undef_map=0x1) at /usr/src/debug/glibc/2.24-r0/git/elf/dl-lookup.c:544
#3  0x4aec0b10 in ?? ()
Cannot access memory at address 0x1
Backtrace stopped: previous frame identical to this frame (corrupt stack?)

找不到合适的libc.so.6版本。

(gdb) info sharedlibrary
warning: .dynamic section for "yocto-dir/build/tmp-angstrom-glibc/sysroots/imx28scm/lib/libc.so.6" is not at the expected address (wrong library or version mismatch?)
From        To          Syms Read   Shared Object Library
0x000007d0  0x0001bee0  Yes         yocto-dir/build/tmp-angstrom-glibc/sysroots/imx28scm/lib/ld-linux.so.3
0x4aee73c0  0x4afe2018  No          yocto-dir/build/tmp-angstrom-glibc/sysroots/imx28scm/lib/libc.so.6
(gdb) n
Cannot find bounds of current function

它不能提供理想的调试体验。

yocto-dir sysroot（如上所用）以及/ usr / local / oecore-x86_64中都有一个gcc。它们的行为相同。 / usr / local / oecore-x86_64 SDK是全新构建和安装的。

类似地，在yocto-dir（如上所用）以及/ usr / local / oecore-x86_64中有一个imx28scm sysroot，它们的行为相同。 但是，它们显然具有不同版本的libc.so.6-yocto-dir的版本为14.8MB，/ usr / local / oecore-x86_64的版本为1.3MB。这是一个问题，但是请设置这些位置，因为sysroot无法解决问题。

一种解决方法是与-static链接。在这种情况下，GDB确实会提供符号：

(gdb) target remote DEVICE-IP:2345
Remote debugging using DEVICE-IP:2345
_start () at ../sysdeps/arm/start.S:79
79  ../sysdeps/arm/start.S: No such file or directory.
(gdb) set sysroot yocto-dir/build/tmp-angstrom-glibc/sysroots/imx28scm
(gdb) bt
#0  _start () at ../sysdeps/arm/start.S:79
(gdb) b main
Breakpoint 1 at 0x8480: file abc.c, line 5.
(gdb) c
Continuing.

Breakpoint 1, main () at abc.c:5
5      printf("Hello world\n");
(gdb) n
6      return 0;
(gdb) n
7   }

与-Wl,--verbose的链接似乎表明它与预期sysroot中的库的链接：

yocto-dir/build/tmp-angstrom-glibc/sysroots/x86_64-linux/usr/libexec/arm-angstrom-linux-gnueabi/gcc/arm-angstrom-linux-gnueabi/6.2.1/ld: Attempt to open yocto-dir/build/tmp-angstrom-glibc/sysroots/imx28scm/lib/libc.so.6 succeeded

链接器也找到了该链接器，但是它没有被称为libc.so.6，因此大概不会造成干扰。

yocto-dir/build/tmp-angstrom-glibc/sysroots/x86_64-linux/usr/libexec/arm-angstrom-linux-gnueabi/gcc/arm-angstrom-linux-gnueabi/6.2.1/ld: Attempt to open yocto-dir/build/tmp-angstrom-glibc/sysroots/imx28scm/usr/lib/libc.so succeeded

为什么在这种情况下库版本不匹配？我该如何让GDB显示期望的库中的符号？我不想静态链接。

Answer 1

请确保框中的libc与构建服务器中的libc相同。抱歉，这应该是一条评论，但是目前，我的信誉还不够。

Answer 2

显然，GDB for ARM目标在尝试在main（）（Debugging shared libraries with gdbserver）之前加载符号时遇到了麻烦：

我遇到的问题是gdbserver在main之前停在动态加载器上，并且此时动态库尚未加载，因此GDB还不知道符号在内存中的位置。

GDB似乎具有一些机制来自动加载共享库符号，并且如果我为主机编译并在本地运行gdbserver，则无需运行到main。但是对于ARM目标，这是最可靠的操作。

因此，将其设置为在击中main后加载共享符号：

> b main
> c
  <breakpoint hit>
> set sysroot <sysroot>

或者在按下main键后重新加载符号。

> set sysroot <sysroot>
...
> b main
> c
  <breakpoint hit>
> nosharedlibrary
> sharedlibrary

或者在与IDE调试器进行接口时将符号的自动加载设置为在GDB启动时关闭可能是有用的：

> set auto-solib-add off

GDB符号丢失-libc声称库或版本不匹配

2 个答案: