I need to add a custom segment to standard ELF file. Even I find some manual, I cannot do it. Could anyone give some help? Thanks.
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I'm trying to create some debug scripts with compiled programs, for this I'm trying to create something where I prepare my variables in some code I generate and then jump into another program.
Is there a way to do that ? For example by having some C code and then jumping to a label or place in the executable. For now I'm focusing on ELF programs, but if something exists on Windows I'm also interested !
Thanks !
I've tried to bring back the ELF file into a .s for GCC and recompile, however this doesn't seem to work well for all ELF files (e.g non-PIE binaries). And I've looked to see if there were tools that would create a .s but they are either buggy, incomplete or both.
Background:
I am generating a JIT code (which generates x86-64 code). After the end of JIT process, I have a .text section, a .data section and a .eh_frame section generated (.eh_frame is used for stack unwinding). I am able to execute this JIT code successfully. But the issue is GDB. I want to be able to debug this JIT code using GDB (specifically the 'backtrace' command of GDB should work).
Problem:
I need to tell GDB about this loaded JIT code (in particular I need to tell GDB about .eh_frame so it can use that frame for stack-unwinding). I see that GDB has a JIT interface: https://sourceware.org/gdb/current/onlinedocs/gdb/JIT-Interface.html
Possible Solutions:
There are two options here:
Hand over a ELF file to GDB
Write a Customer Jit-Reader plugin to handle debugging of custom object file.
Right now I have a custom object file (just bunch of three independent sections loaded into memory). I don't want to write my own Jit Reader plugin.
Blocking Issue:
Does anyone knows existing code that will help me package these three independent sections into a simple ELF file (which I can then register with GDB by calling __jit_debug_register_code())? I am guessing all I need to do is write some header (conforming to ELF specifications) which have names and pointers to the section. Is there existing open source code for this or if not, can someone point me towards how to do this packaging myself?
I need bare minimum ELF file so that GDB is happy (I don't need to Load the ELF file as .text and .data section are already loaded)
libelf could be of help for constructing an ELF object. There are open-source implementations available at:
elftoolchain (BSD licensed)
elfutils (GPL).
I'm afraid my question is a bit complex. Appreciate anyone who can help.
Some background:
I have a 3rd party SW package that compile both kernel modules and user space applications.
Unfortunately, this 3rd party is very complex, and doesn't use Kbuild for building kernel modules (I tried without success)
When compiling the kernel modules, I add -I{path to kernel headers}, but I see the .config file is not being parsed in the compilation, which, of course, causes many errors.
I tried to manually add all flags from .config to gcc in command line (using a script to generate the command line) but that was a very very long line and gcc couldn't handle it.
So my question would be: Is there a way to force all these flags to gcc somehow?
Appreciate your ideas :)
Clarification:
The 3rd party SW can compile on older kernels (2.6, 2.4) I'm trying to compile it for 3.2
Maybe if someone can explain how the original kernel Makefile manages the .config file, I can mimic that behavior.
After digging in the kernel sources, I found the answer. Here it is in case someone needs it.
There's an automatically generated h file called autoconf.h which contains all the relevant definitions in C pre processor format. Just need to include it manually when compiling the module.
Also in theory, I could use my script to create such a file and include it from the sources.
Hope this helps someone. Now on to the next problem :)
I am working with a project that was handed off to me and some of the building and linking concepts are new to me. I have a makefile, several assembly and C source files, an ELF file and binary file. When I load the ELF file onto my target, I am only able to step-through the C files, not the assembly files.
When I do a readelf on the ELF file, I see that the assembly (.S) files are missing from the symbol table. Likewise, my debugger (RealView Debugger 4.1) doesn't list those .S files in the "sources from image" tree. I can see that some of the symbols from those files are included (i.e. label names) in my readelf output, but not the file type symbols themselves. I've been going over the makefile to try to spot what may be failing to include them, but I'm not sure what I'm looking for. Can anyone please point me in the right direction? Thanks!
You mentioned using the RealView debugger so I'm making an educated guess that you have RVDS. If so, have you tried using the readelf equivalent that ships with RVDS, fromelf. I have no way to confirm this now but I recall there were subtle differences between assembly code generated by the ARM compiler and gcc.
Can any one of you help me in converting an windows dll file in a .so file.
You might try re-compiling the source code to the dll to a shared object. This may help you get started, after ensuring the code is indeed portable.
Edit:
Here is yet another link that can help guide you through the process of creating a shared library using GCC and other parts of the GNU tool chain. This link will help you to discover pitfalls that other people had when undertaking a project similar to this.
There is only so much help that can be provided for such a specific task, especially with so many unknowns. If you elect to provide more information in your question, please leave a comment.
NB: I'm pulling these links right out of Google.
If you don't have the source, or can't recompile, you may be able to run the code under Wine.
You need to recompile again into an .so file.