The point is to generate a hex without main function using IAR linker - xlink?
This code should be loaded into the RAM of RL78 MCU.
A quick Google search of iar generate hex from library brought me to this document, "Creating an Absolutely Placed Library", as a first result. It has all the information you need, plus some information on using a CRC for consistency checking. The document is for the IAR EWRX variant, but the concepts should all be the same.
The basic process is to compile your library as an executable, but without a main() function in it. You'll need to set your library configuration under General -> Library Options to None. You can also setup your file conversion settings at this point.
Since you don't have a main() function for a program entry point, you will need to create an entry function to call the IAR C runtime initialization function, __iar_data_init2(), and then set the linker to use this function as the entry point (which can be found under Linker Options -> Library Options).
When building a library, all the symbols will be preserved until the final link step for the application using it, but since you are building this as an executable, it is important that the symbols you want to keep have the __root keyword, or under Linker -> Extra Options you can specify --no-remove to keep all symbols.
In the next step, you need to use isymexport to export the symbols that you want. You will need a file to direct the tool what to export. In the example, they have a file that just contains the following:
show lib_*
show __checksum*
This will direct the tool to export all symbols beginning with lib_ and all symbols beginning with __checksum. They note that __iar_data_init2() should not be exported, as this would cause conflicts with the application that ultimately will use this code. You invoke the tool like so:
isymexport <path to .out file> <path to output from tool> --edit <path to file created above>
Now you should have the output from isymexport and the library file that you were looking for. For the application using this library, you'll need to add the output from isymexport as a library under Linker -> Library, and in your application, you'll need to call your entry function in the library before you attempt to use any of the library's symbols.
This should be the information you need to generate a library that lives in a hex file and can be loaded separately, as well as how to use that library. The referenced document has a lot more detail, so if it is available at that link (or can be found elsewhere by title) it will be a better reference than my summary here.
Related
test platform is on 32 bit Linux and Windows.
I am trying to identify all the user defined functions towards dynamic linked binary,
extracting their instructions and assemble them into binary again.
As for the ELF file, I use this:
nm binary | grep "T"
to extract certain functions, and I consider all the functions who don't begin with _ should be the user defined functions.
It works fine for small programs...
But when I am testing coreutils (8.5), for example like basename
Here is part of the output of nm
0804b530 T rpl_fflush
0804b590 T rpl_fseeko
0804a400 T set_char_quoting
0804a480 T set_custom_quoting
08049580 T set_program_name
0804a460 T set_quoting_flags
0804a3e0 T set_quoting_style
08049480 T strip_trailing_slashes
08048f70 T usage
0804b0f0 T version_etc
0804b6c0 T atexit
In the source code of basename, it only defines three functions as
main
usage
remove_suffix
But I use nm to find lots of functions here...
Basically I think these functions like version_etc *atexit* are defined in the header files
basename included
So my question is :
How to accurately find all the user defined functions from a ELF file?
Any answers on PE file is also welcomed!
THank you!
Basically I think these functions like version_etc atexit are defined in the header files basename included
Your mental model of how basename is built appears to be completely incorrect.
basename is built from basename.o and a whole bunch of other objects (which are part of coreutils) and a whole bunch more objects pulled in from other libraries.
Once basename is linked, there is no way to tell which functions came from where.
Besides, what does "user defined function" even mean?
This may be compiler specific, in which case I am using the IAR EWARM 5.50 compiler (firmware development for the STM32 chip).
Our project consists of a bunch of C-code libraries that we compile first, and then the main application which compiles its C-code and then links in those libraries (pretty standard stuff).
However, if I use a hex editor and open up any of the library object files produced or the final application binary, I find a whole bunch of plain text references inside the output binary to the file paths of the C files that were compiled. (eg. I see "C:\Development\trunk\Common\Encryption\SHA_1.c")
Two issues with this:
we don't really want the file paths being easily readable as that indicates our design some what
the size of the binary grows if you have your C-files located in a long subdirectory (the binary contains the full path, not just the name)...this is especially important when we're dealing with firmware that has a limited amount of code space (256KB).
Any thoughts on this? I've tried all the switches in the compiler I can think of to "remove debug information", etc., but those paths are still in there.
"The command-line option --no_path_in_file_macros has been added. It removes the path leaving only the filename for the symbols FILE and BASE_FILE."
It is defined in the release notes if IAR.
http://supp.iar.com/FilesPublic/UPDINFO/005832/arm/doc/infocenter/iccarm_history.ENU.html
Or you can look for FILE and BASE_FILE macros and remove it you do not want to use the flag.
I'm pretty new to working with libraries and I'm in the process of trying to understand some specifics regarding static libraries and object files.
Summary
The behavior I'm noticing is that I can link several objects to make an executable with no problem, but if I take an intermediate step of combining those objects into static libraries, I cannot link those static libraries to make an executable without additionally specifying the needed C Run-time library in the link command.
Also, or the record, I'm doing the compiling/linking with Visual Studio 2010 from the command line. More details of the process I'm following are below.
First, let's say I have four source files in a project: main.c, util1.c, util2.c, and util3.c.
What works
I can compile these sources with the following command:cl -c main.c util1.c util2.c util3.cAs a result, I now have four object files: main.obj, util1.obj, util2.obj, and util3.obj. These object files each contain a DEFAULTLIB statement intended to inform the linker that it should additionally check the static C Run-time library libcmt.lib for any unresolved external dependencies in these object files when linking them.
I can create an executable named "app_objs.exe" by linking these objects with the following command:
link -out:app_objs.exe main.obj util1.obj util2.obj util3.obj
As mentioned in step 1, the linker used the runtime library due to the compiler's step of adding a default library statement to the objects.
Where I'm confused
Let's say I want to have an intermediate step of combining these objects into static libraries, and then linking those resulting LIB files to create my executable. First, I can create these libraries with the following commands:
link -lib -out:main.lib main.obj
link -lib -out:util.lib util1.obj util2.obj util3.obj
Now, my original thought was that I could simply link these libraries and have the same executable that I created in step 2 of "What works". I tried the following command and received linker error LNK1561, which states that an entry point needs to be specified:
link -out:app_libs.exe main.lib util.lib
From Microsoft's documentation, it is evident that linking libraries without any object files may require entry points to be specified, so I modified the command to set the subsystem as "console" to specify that the executable in intended to be a console application (which seems to imply certain entry points, thereby resolving that error):link -out:app_libs.exe -subsystem:console main.lib util.libUnfortunately, now I get a linker error stating that mainCRTStartup is an unresolved external symbol. I understand that this is defined in the C runtime library, so I can resolve this issue by manually specifying that I want to link against libcmt.lib, and this gives me a functioning executable:link -out:app_libs.exe -subsystem:console main.lib util.lib libcmt.lib
What I'm not understanding is why the default library info that the compiler placed in each object file couldn't be used to resolve the dependency on libcmt.lib. If I can link object files without explicitly stating I want libcmt.lib, and I created static libraries that are containers for the object files, why can't I link those static libraries without having to explicitly state that I want libcmt.lib? Is this just the way things are, or is there some way I could create the static libraries so that the linker will know to check for unresolved symbols in the runtime library?
Thanks for your help. If I have some fundamentally incorrect ideas here, I'd love suggestions on good references to learn all of this correctly.
Well the answer to your misunderstanding is that .lib files are often a product in themselves, and the compiler can't make those assumptions safely. That's what "external" is for.
If I produce binaries for someone's platform because its users are totally helpless, and they want/need static linkage, I have to give them foo.h and libfoo.lib without tying them to a specific runtime entry point. They may very well have defined their own entry point already for their final product, whether DLL or EXE.
You either want the runtime, or you want your own .obj that contains your entry point. Be warned that declaring and defining mainCRTStartup on your own may mean you're not executing important instructions for the target platform.
We have a legacy library implementation and associated exposed header files. Recently we found that, some of the functions in the exposed header file, don't have corresponding definitions in the library implementation.
We want to check if there could be some more such functions. Is there any easier way of doing this rather than sifting through each and every API present in header and then checking if there is a definition for it?
You can generate C source from the header (Perl is a way to go!) that calls all the functions and try to compile it. Linker will complain about missing functions.
Try to create the ABI dump file by the abi-compliance-checker tool:
abi-compliance-checker -lib NAME -dump DESC.xml
DESC.xml file is the following:
<version>
1.0
</version>
<headers>
/path(s)/to/headers
</headers>
<libs>
/path(s)/to/libraries
</libs>
The resulting ABI dump file will contain the information you need about symbols declared in header files (SymbolInfo) and symbols exported by shared libraries (Symbols).
You can also generate ABI dump in the xml format by adding --xml option.
If this is C, you can do something like:
printf("", /* insert all functions here */);
That should pass them all as function pointers to printf. The ones that do not exist should show up as linker errors.
(In C++, you would have to list overloads explicitly, which makes it a bit more difficult.)
I'd be inclined to use ctags to generate a list of identifiers from the header file then use ar, emfar or elfdump in Unix or lib.exe or dumpbin.exe in Windows (see discussion here) to dump a list of identifiers from the library and then sort and diff the two lists.
If I have two libraries, A.lib and B.lib, both of which export foo and bar, how do I tell the linker to use the symbol foo from A.lib and the symbol bar from B.lib?
You cannot. For your example you can have definitions from foo.lib or bar.lib but not both (especially if you cannot recompile the libraries and set symbol visibility so that only the symbols you want are exported). The order you link them against your application will depend on which library's definitions are used (you'll have to use the scientific method, I think the first one linked wins). Niklas Hansson's answer is a great way to do this dynamically but it seems you don't want to modify the original application, either, to dynamically pick/choose what symbols to take out of the libraries.
If you really wanted to you could mangle the symbol tables with a hex editor so that the symbols you don't want exported have different names (hacky, but it would work). I know on Linux there is a tool called objcopy that would let you do this (not sure about Windows).
You can use LIB.EXE /EXTRACT ... to extract only the object files you want to use, and link those files into your own application.
Or you may use LIB to create one new library containing the elements you need:
First, use /REMOVE on A.LIB to remove bar.obj:
LIB.EXE /OUT:ANOBAR.LIB /REMOVE:bar.obj A.LIB
Then combine A.LIB and B.LIB, and make sure to use ANOBAR.LIB as the last on the command line to ensure its foo.obj is used instead of B.LIB's:
LIB.EXE /OUT:COMBINED.LIB B.LIB ANOBAR.LIB
Details are found here: Managing a library, especially the paragraph:
You can use LIB [...] To replace a library member with a new object, specify the library containing the member object to be replaced and the file name for the new object (or the library that contains it). When an object that has the same name exists in more than one input file, LIB puts the last object specified in the LIB command into the output library. When you replace a library member, be sure to specify the new object or library after the library that contains the old object.
I didn't test the command lines given, but I've used similar ones extensively in the past.
If you are using dynamic libraries, you could use dynamic loading and pick foo from A and bar from B when loading.