问题
I am using gdbserver on target and CodeSourcery IDE. My hardware is a gumstix with a omap3530.
I can step through code in my main application but if I attempt to step into a function in a shared library I get memory address and a debugger terminates.
This is my library that is compiled and copied to the /lib folder on the target system.(it does have debug symbols) I have attempted to use the .gbdinit file to set solib-absolute-prefix /lib
Here are the warnings from the gdb trace:
903,056 13-gdb-set sysroot-on-target /lib
903,065 13^done
903,065 (gdb)
903,065 14-target-select remote 192.168.1.101:2345
903,114 =thread-group-started,id="i1",pid="42000"
903,114 =thread-created,id="1",group-id="i1"
903,115 15-list-thread-groups --available
903,120 16-list-thread-groups
903,128 &"warning: Unable to find dynamic linker breakpoint function.\nGDB will be unable to debug shared library initializers\nand track explicitly loaded dynamic code."
903,128 &"\n"
Which leads to
903,395 &"Error while mapping shared library sections:\n"
903,397 &"/lib/libCoreLib.so: Invalid argument.\n"
903,399 =library-loaded,id="/lib/libCoreLib.so",target-name="/lib/libCoreLib.so",hostname="/lib/libCoreLib.so",low-address="0x0",high-address="0x0",symbols-loaded="0",thread-group="i1"
回答1:
You can debug with the library installed on your host, provided the debugging machine is also the development machine. In that case, you use set sysroot instead of set sysroot-on-target. For example :
set sysroot /home/username/.../rootfs/
where /home/username/.../rootfs/ contains a copy of your target filesystem
I think you should also specify / instead of /lib
回答2:
Target with debug symbols
This is the simplest method to get working, and it is specially useful when you are developing one particular shared library.
First copy the test executable and shared library to the target with debug information:
- check with
readelf ----debug-dump=decodedline libmyib.so: How can I tell if a library was compiled with -g? - I recommend using an NFS server on host, so that the compiled output gets automatically uploaded after compilation
Then on target:
gdbserver --multi :1234 ./executable_name
Host:
arm-linux-gnueabihf-gdb -q -nh \
-ex "target extended-remote target-hostname-or-ip:1234" \
-ex "file ./executable_name" \
-ex 'tb main' \
-ex 'c' \
-ex 'set solib-search-path .'
sharedlibrary libmylib.so also works.
The problem I had was that gdbserver stops at the dynamic loader, before main, and the dynamic libraries are not yet loaded at that point, and so GDB does not know where the symbols will go in memory yet.
GDB appears to have some mechanisms to automatically load shared library symbols, and if I compile for host, and run gdbserver locally, running to main is not needed. But on the ARM target, that is the most reliable thing to do.
Target gdbserver 7.12-6, host arm-linux-gnueabihf-gdb 7.6.1 from Linaro.
Target libraries without debug symbols
It is common to strip target libraries before deployment on embedded targets, since debug information makes them way larger.
For example, Buildroot does that by default, but you can disable it with BR2_STRIP_none=y.
You can identify this scenario by running:
info shared
Which shows something like:
From To Syms Read Shared Object Library
0x00007ffff7df7f90 0x00007ffff7dfcdd7 Yes (*) target:/lib/ld64-uClibc.so.0
0x00007ffff7b3a9b0 0x00007ffff7bbe05d Yes (*) target:/lib/libc.so.0
(*): Shared library is missing debugging information.
so there are asterisks (*) for both of the libraries which says that debug information is missing.
If that is the case, then you have to tell GDB to use the shared libraries on host before they were stripped.
Buildroot for example makes that easy for us, as it maintains the staging directory which contains the shared libraries before they were stripped and in the same relative paths as in the target:
set sysroot buildroot/output/staging/
When this option is set, gdb immediately searches for libraries in the host instead of target, and finds /lib/libc.so.0 at the path buildroot/output/staging/ + /lib/libc.so.0:
Reading symbols from buildroot/output/staging/lib/ld64-uClibc.so.0...done.
Reading symbols from buildroot/output/staging/lib/libc.so.0...done.
TODO: I don't think you can set more than one sysroot, so all your shared libraries must be placed in their correct relative paths as in the target image.
If you check the bad default sysroot, you will see:
show sysroot
give:
target:
which means that gdb searches for shared libraries on the target root / by default.
回答3:
Similar issue was encountered while debugging. The debug was hanging up. Configuration is as follows
Host: Ubuntu 12.04LTS
IDE: Eclipse Kepler
Target: Beaglebone Black / ARM A8
OS: Angstrom
Solution
Update libraries and includes
Select properties for project in Eclipse
C/C++ General > Paths and Symbols > (include TAB) GNU C > Add > Files systems > / > usr Change from /usr/lib/gcc/i686-linux-gnu/4/6/include to /usr/arm-linux-gnueabi/include
C/C++ General > Paths and Symbols > (Include TAB) GNU C++> Add >
Files systems > / > usr /usr/arm-linux-gnueabi/include/c++/4.6.3/arm-linux-gnueabiC/C++ General > Paths and Symbols > (Library Paths TAB) > Add > Files systems > / > usr /usr/arm-linux-gnueabi/lib
回答4:
Good day,
If the 'debug-file-directory' variable in GDB is set incorrectly, then the reported error messages contains: warning: Unable to find dynamic linker breakpoint function.
The root filesystem of the target is located on my host PC at /opt/arm-linux-gnueabihf-rootfs
The following two commands helped me to get remote debugging working via gdbserver using GDB (v7.11.1):
set debug-file-directory /opt/arm-linux-gnueabihf-rootfs/usr/lib/debug
set sysroot /opt/arm-linux-gnueabihf-rootfs
I've noticed that if 'sysroot' has a trailing slash in the path, then GDB fails to use it.You will see this (incorrect output) after connecting to the remote target:
Reading /lib/ld-linux-armhf.so.3 from remote target...
or
Reading symbols from /opt/arm-linux-gnueabihf-rootfs/lib/ld-linux-
armhf.so.3...(no debugging symbols found)...done
instead of the correct output:
Reading symbols from /opt/arm-linux-gnueabihf-rootfs/lib/ld-linux-
armhf.so.3...
Reading symbols from /opt/arm-linux-gnueabihf-rootfs/usr/lib/debug/
lib/arm-linux-gnueabihf/ld-2.23.so...done.
Regards, Frikkie Thirion
来源：https://stackoverflow.com/questions/8611194/debugging-shared-libraries-with-gdbserver