In my build chain, I need to do this:
objcopy -I binary -O $BFDNAME -B $BFDARCH <this> <that>
in order to get a binary file into library form. Because I want other people to be able to use this, I need to know how to get $BFDNAME and $BFDARCH from their toolchain when they run the build. I can get the values locally by running objdump -f against a file I've already built, but is there a better way which won't leave me compiling throw-away files just to get configuration values?
Thank you for pointing this out, regularfry! Your answer helped me to find another solution which works without specifying the architecture at all:
ld -r -b binary -o data.o data.txt
On my system (Ubuntu Linux, binutils 2.22) both objcopy and ld approaches produce identical object files.
All credit goes to:
http://stupefydeveloper.blogspot.de/2008/08/cc-embed-binary-data-into-elf.html
For future reference, the answer seems to be this: the first entry in the output of objdump -i is the default, native format of the system.
Related
I'm experimenting a bit with building DLLs on windows using MINGW.
A very good summary (in my opinion) can be found at:
https://www.transmissionzero.co.uk/computing/building-dlls-with-mingw/
There is even a basic project which can be used for the purpose of this discussion:
https://github.com/TransmissionZero/MinGW-DLL-Example/releases/tag/rel%2Fv1.1
Note there is a cosmetic mistake in this project which will make it fail out of the box: the Makefile does not create an "obj" directory - Either adjust the Makefile or create it manually.
So here is the real question.
How to change the Windows DLL name so it differs from the actual DLL file name ??
Essentially I'm trying to achieve on Windows, the effect which is very well described here on Linux:
https://www.man7.org/conf/lca2006/shared_libraries/slide4b.html
Initially I tried changing "InternalName" and ""OriginalFilename" in the resource file used to create the DLL but that does not work.
In a second step, I tried adding "-Wl,-soname,SoName.dll" on the command that performs the final link, to change the Windows DLL name.
However, that does not seem to have the expected effect (I'm using MingW 7.3.0, x86_64-posix-seh-rev0).
Two things makes me say that:
1/ The test executable still works (I would expect it to fail, because it tries to locate SoName.dll but can't find it).
2/ "pexports.exe AddLib.dll" produces the output below, where the library name hasn't changed:
LIBRARY "AddLib.dll"
EXPORTS
Add
bar DATA
foo DATA
Am I doing anything wrong ? Are my expectations wrong perhaps ?
Thanks for your help !
David
First of all, I would like to say it's important to use either a .def file for specifying the exported symbols or use __declspec(dllexport) / __declspec(dllimport), but never mix these two methods. There is also another method using the -Wl,--export-all-symbols linker flag, but I think that's ugly and should only be used when quick and dirty is what you want.
It is possible to tell MinGW to use a DLL filename that does not match the library name. In the link step use -o to specify the DLL and use -Wl,--out-implib, to specify the library file.
Let me illustrate by showing how to build chebyshev as a both static and shared library. Its sources consist of only only 2 files: chebyshev.h and chebyshev.c.
Compile
gcc -c -o chebyshev.o chebyshev.c -I. -O3
Create static library
ar cr libchebyshev.a chebyshev.o
Create a .def file (as it wasn't supplied and __declspec(dllexport) / __declspec(dllimport) wasn't used either). Note that this file doesn't contain a line with LIBRARY allowing the linker to specify the DLL filename later.
There are several ways to do this if the .def file wasn't supplied by the project:
3.1. Get the symbols from the .h file(s). This may be hard as sometimes you need to distinguish for example between type definitions (like typedef, enum, struct) and actual functions and variables that need to be exported;
echo "EXPORTS" > chebyshev.def
sed -n -e "s/^.* \**\(chebyshev_.*\) *(.*$/\1/p" chebyshev.h >> chebyshev.def
3.2. Use nm to list symbols in the library file and filter out the type of symbols you need.
echo "EXPORTS" > chebyshev.def
nm -f posix --defined-only -p libchebyshev.a | sed -n -e "s/^_*\([^ ]*\) T .*$/\1/p" >> chebyshev.def
Link the static library into the shared library.
gcc -shared -s -mwindows -def chebyshev.def -o chebyshev-0.dll -Wl,--out-implib,libchebyshev.dll.a libchebyshev.a
If you have a project that uses __declspec(dllexport) / __declspec(dllimport) things are a lot easier. And you can even have the link step generate a .def file using the -Wl,--output-def, linker flag like this:
gcc -shared -s -mwindows -o myproject.dll -Wl,--out-implib,myproject.dll.a -Wl,--output-def,myproject.def myproject.o
This answer is based on my experiences with C. For C++ you really should use __declspec(dllexport) / __declspec(dllimport).
I believe I have found one mechanism to achieve on Windows, the effect described for Linux in https://www.man7.org/conf/lca2006/shared_libraries/slide4b.html
This involves dll_tool
In the example Makefile there was originally this line:
gcc -o AddLib.dll obj/add.o obj/resource.o -shared -s -Wl,--subsystem,windows,--out-implib,libaddlib.a
I simply replaced it with the 2 lines below instead:
dlltool -e obj/exports.o --dllname soname.dll -l libAddLib.a obj/resource.o obj/add.o
gcc -o AddLib.dll obj/resource.o obj/add.o obj/exports.o -shared -s -Wl,--subsystem,windows
Really, the key seems to be the creation with dlltool of an exports file in conjunction with dllname. This exports file is linked with the object files that make up the body of the DLL and it handles the interface between the DLL and the outside world. Note that dlltool also creates the "import library" at the same time
Now I get the expected effect, and I can see that the "Internal DLL name" (not sure what the correct terminology is) has changed:
First evidence:
>> dlltool.exe -I libAddLib.a
soname.dll
Second evidence:
>> pexports.exe AddLib.dll
LIBRARY "soname.dll"
EXPORTS
Add
bar DATA
foo DATA
Third evidence:
>> AddTest.exe
Error: the code execution cannot proceed because soname.dll was not found.
Although the desired effect is achieved, this still seems to be some sort of workaround. My understanding (but I could well be wrong) is that the gcc option "-Wl,-soname" should achieve exactly the same thing. At least it does on Linux, but is this broken on Windows perhaps ??
I would like to create a symbol definition table to be used in a separate application during linking. ARM's armlink linker has the following flag but I'm using arm-eabi:
--symdefs=filename
The GNU objcopy utility has an option --extract-symbol that may do what you want. It generates an object file with only symbol data - no actual code or data.
It is specifically intended to generate a .sym file for use in the VxWorks RTOS which has a command shell and dynamic linker/loader that uses this information. It is also used by the VxWorks host shell and source-level debugger.
The binutils nm utility on the other hand generates output very similar to armlink's --symdefs which you might easily post-process into exactly the form you need.
-Wl,-Map -Wl,mapfile -Wl,--cref
added to the final gcc (link) command line should do the trick.
This the correct answer from arm gnu launchpad:
Do you intend to load the symdef file with the GNU toolchain or with armcc one? If the former I think using nm on the object file and then linking with -R <filename> would work. So you would do arm-none-eabi-nm -D ./prog > ./prog.defsym after linking prog and then arm-none-eabi-gcc -Wl,-R,./prog.defsym when you want to use this.
I have been trying to compile openssl 1.0.0g with the following rpath:
$ORIGIN/../lib64
Everytime I readelf -d apps/openssl, I am getting results like the following depending on what escaping variation I tried:
\RIGIN/../lib64
RIGIN/../lib64
ORIGIN/../lib64
I want to setup my rpath without using external tools like chrpath. Is it at all possible? I will basically accept anything that does not involve using external tools like chrpath (though I would already be done with that).
Ideally, I would like to do it by passing options on the command line (any form of -Wl,-rpath,$ORIGIN/../lib64).
I don't mind editing the generated Makefile, which is what I have been trying last. If only I could get it to print a stupid dollar sign!!! I tried modifying LIBRPATH under the BUILDENV= block with no luck. My best results so far:
LIBRPATH=$$'ORIGIN/../lib64 # result: /../lib64
LIBRPATH=$$$$'ORIGIN/../lib64 # result: 12345<pid>/../lib64
I have read various rpath related questions and tried various escaping and quoting tricks but nothing worked so far!
In your makefile try:
-Wl,-rpath,${ORIGIN}/../lib64
I am assuming that the ORIGIN is a shell variable.
EDIT
I have just found an answer to your question (better late then never):
You need to prevent make from interpolating variables, to do that you need to use $$ (double dolar sign):
-Wl,-rpath,'$$ORIGIN/../lib64'
I know that it works because I have tested it with my own application, enjoy :)
I went the chrpath way.
http://enchildfone.wordpress.com/2010/03/23/a-description-of-rpath-origin-ld_library_path-and-portable-linux-binaries/
It is quite complicated to counter shell expansion of `$$ORIGIN`` in openssl. Sooner or later, it gets expanded because of the dollar sign. If you really want to go this way, you can do it. I have found the following to work with openssl 1.0.1g on Linux. In Makefile.shared, look for this line:
DO_GNU_APP=LDFLAGS="$(CFLAGS) -Wl,-rpath,$(LIBRPATH)"
Replace it with the following. This quoting-fu neutralize the expansion of $. The double $$ is the way to get a single dollar sign in makefiles.
DO_GNU_APP=LDFLAGS="$(CFLAGS) -Wl,-rpath,'"'$$'"ORIGIN/../lib64'"
After compiling:
readelf -d apps/openssl | grep RPATH
0x000000000000000f (RPATH) Library rpath: ['$ORIGIN/../lib64']
OK I spent several hours fighting with this same issue and trying all manner of crazy escaping, at one point I was up to eight $ signs, at which point I decided that there must be another way.
In fact, it appears that there is, at least with GNU ld.
Instead of -Wl,-rpath,\\$$$\$\$\$$$\$\\\\$ or some other elder god invoking monstrosity, just do this:
echo '-rpath=$ORIGIN/../lib64' > rpathorigin
./config -Wl,#$(pwd)/rpathorigin ...
I don't see that ld.gold documents the # flag, and I have no idea about, say, lld. But if you are using GCC and it is invoking BFD ld, the above may just work for you.
Of course, the actual path used with origin should be customized as needed, and I have no opinion on ./config vs ./Configure. But using the response file trick seems to entirely sidestep the shell/make escaping nightmare.
I don't mind editing the generated Makefile, which is what I have been trying last...
I'm not sure you can set it with a shell variable and relative path. I don't think ldd expands the $ORIGIN in $ORIGIN/../lib64. In this case, I think you need to use ldconfig to add $ORIGIN/../lib64 to the library search paths. See finding ldd search path on Server Fault for more details.
Since I'm not sure, I'll provide the instructions anyway. You don't need to change the Makefiles. As a matter of fact, I did not have any luck doing so in the past because things get overwritten, and other things like CFLAGS and LDFLAGS get ignored.
Also see Build OpenSSL with RPATH? Your question and the cited question are different question that converge on similar answers (no duplicates between them). But it provides the OpenSSL dev's position on RPATHs. It was a private email, so I shared the relevant details rather than the whole message.
If you manage to embed $ORIGIN/../lib64 in the ELF section and it works, then please report back. Below, I am using /usr/local/ssl/lib for my RPATH. You should substitute $ORIGIN/../lib64 for /usr/local/ssl/lib.
OpenSSL supports RPATH's out of the box for BSD targets (but not others). From Configure:
# Unlike other OSes (like Solaris, Linux, Tru64, IRIX) BSD run-time
# linkers (tested OpenBSD, NetBSD and FreeBSD) "demand" RPATH set on
# .so objects. Apparently application RPATH is not global and does
# not apply to .so linked with other .so. Problem manifests itself
# when libssl.so fails to load libcrypto.so. One can argue that we
# should engrave this into Makefile.shared rules or into BSD-* config
# lines above. Meanwhile let's try to be cautious and pass -rpath to
# linker only when --prefix is not /usr.
if ($target =~ /^BSD\-/)
{
$shared_ldflag.=" -Wl,-rpath,\$(LIBRPATH)" if ($prefix !~ m|^/usr[/]*$|);
}
The easiest way to do it for OpenSSL 1.0.2 appears to be add it to linker flags during configuration
./config -Wl,-rpath=/usr/local/ssl/lib
You can also edit Configure line and hard code the rpath. For example, I am working on Debian x86_64. So I opened the file Configure in an editor, copied linux-x86_64, named it linux-x86_64-rpath, and made the following change to add the -rpath option:
"linux-x86_64-rpath", "gcc:-m64 -DL_ENDIAN -O3 -Wall -Wl,-rpath=/usr/local/ssl/lib::
-D_REENTRANT::-Wl,-rpath=/usr/local/ssl/lib -ldl:SIXTY_FOUR_BIT_LONG RC4_CHUNK DES_INT DES_UNROLL:
${x86_64_asm}:elf:dlfcn:linux-shared:-fPIC:-m64:.so.\$(SHLIB_MAJOR).\$(SHLIB_MINOR):::64",
Above, fields 2 and 6 were changed. They correspond to $cflag and $ldflag in OpenSSL's builds system.
Then, Configure with the new configuration:
$ ./Configure linux-x86_64-rpath shared no-ssl2 no-ssl3 no-comp \
--openssldir=/usr/local/ssl enable-ec_nistp_64_gcc_128
Finally, after make, verify the settings stuck:
$ readelf -d ./libssl.so | grep -i rpath
0x000000000000000f (RPATH) Library rpath: [/usr/local/ssl/lib]
$ readelf -d ./libcrypto.so | grep -i rpath
0x000000000000000f (RPATH) Library rpath: [/usr/local/ssl/lib]
$ readelf -d ./apps/openssl | grep -i rpath
0x000000000000000f (RPATH) Library rpath: [/usr/local/ssl/lib]
Once you perform make install, then ldd will produce expected results:
$ ldd /usr/local/ssl/lib/libssl.so
linux-vdso.so.1 => (0x00007ffceff6c000)
libcrypto.so.1.0.0 => /usr/local/ssl/lib/libcrypto.so.1.0.0 (0x00007ff5eff96000)
...
$ ldd /usr/local/ssl/bin/openssl
linux-vdso.so.1 => (0x00007ffc30d3a000)
libssl.so.1.0.0 => /usr/local/ssl/lib/libssl.so.1.0.0 (0x00007f9e8372e000)
libcrypto.so.1.0.0 => /usr/local/ssl/lib/libcrypto.so.1.0.0 (0x00007f9e832c0000)
...
Don't ask me why but this worked for me in OpenSSL 1.1.1i in getting around the $ sign issue:
\$\$\$$ORIGIN
Example:
./Configure linux-x86_64 '-Wl,-rpath,\$\$\$$ORIGIN'
Alternatively, if this command line hack isn't congruent with you, you can always use chrpath after building as others have suggested:
./Configure linux-x86_64 '-Wl,-rpath,XORIGIN'
make depend
make all
chrpath -r "\$ORIGIN" libssl.so
I've got a binary "CeeloPartyServer" that needs to find libFoundation.so at runtime, on a FreeBSD machine. They're both in the same directory. I compile (on another platform, using a cross compiler) CeeloPartyServer using linker flag -rpath=$ORIGIN.
> readelf -d CeeloPartyServer |grep -i rpath
0x0000000f (RPATH) Library rpath: [$ORIGIN]
> ls
CeeloPartyServer Contents Foundation.framework libFoundation.so
> ./CeeloPartyServer
/libexec/ld-elf.so.1: Shared object "libFoundation.so" not found, required by "CeeloPartyServer"
Why isn't it finding the library when I try to run it?
My exact linker line is: -lm -lmysql -rpath=$ORIGIN.
I am pretty sure I don't have to escape $ or anything like that since my readelf analysis does in fact show that library rpath is set to $ORIGIN. What am I missing?
I'm assuming you are using gcc and binutils.
If you do
readelf -d CeeloPartyServer | grep ORIGIN
You should get back the RPATH line you found above, but you should also see some entries about flags. The following is from a library that I built.
0x000000000000000f (RPATH) Library rpath: [$ORIGIN/../lib]
0x000000000000001e (FLAGS) ORIGIN
0x000000006ffffffb (FLAGS_1) Flags: ORIGIN
If you aren't seeing some sort of FLAGS entries, you probably haven't told the linker to mark the object as requiring origin processing. With binutils ld, you do this by passing the -z origin flag.
I'm guessing you are using gcc to drive the link though, so in that case you will need to pass flag through the compiler by adding -Wl,-z,origin to your gcc link line.
Depending on how many layers this flag passes through before the linker sees it, you may need to use $$ORIGIN or even \$$ORIGIN. You will know that you have it right when readelf shows an RPATH header that looks like $ORIGIN/../lib or similar. The extra $ and the backslash are just to prevent the $ from being processed by other tools in the chain.
\$\ORIGIN if you are using chrpath and \$\$ORIGIN if you are providing directly in LDFLAGS
using ldd CeeloPartyServer to check the dependency .so is starting with ./ or not. (e.g. libFoundation.so and ./libFoundation.so)
For common situation it should be libFoundation.so and without the prefix ./
if ./ prefix is necessary for some uncommon case, make sure the CWD is the same folder with libFoundation.so, and the $ORIGIN would be invalid.
=======
For example:
g++ --shared -Wl,--rpath="\$ORIGIN" ./libFoundation.so -o lib2.so
would got a library lib2.so with ./libFoundation.so
g++ --shared -Wl,--rpath="\$ORIGIN" libFoundation.so -o lib2.so
would got libFoundation.so instead.
I'm building ubuntu-8.04 with gcc 3.4 and I need to generate the .i files, which are the output of the gcc preprocessor. I have tried adding the --save-temps flag but this only generates the .i files for the top level directory, i.e. source, and does not seem to get passed recursively to the child directories. I also tried the -E flag, which is supposed to output preprocessed files and stop compilation, but this did not generate the files either.
I'm specifically looking to generate the .i files for the source in net/core.
Any help is appreciated. Thanks!!
There is no support for bulk preprocessing.
For single file use "make net/core/foo.i"
For bulk, workaround is "make C=2 CHECK="cc -E"".
I know that is an old post, but maybe can be useful; for me this works:
gcc -E filename.c -o outputfile.i