Hi On Wed, Nov 27, 2013 at 10:31 PM, Greg KH <gre...@linuxfoundation.org> wrote: > On Wed, Nov 27, 2013 at 07:48:39PM +0100, David Herrmann wrote: >> In several situations we want to link a binary file into our executable >> and access it from our C code. The easiest way is to transform it into a >> C-array and compile it as usual. However, for large files (>1MB) such >> compilations can take a considerable amount of time or even fail on >> low-memory systems. >> >> This adds a new automake-target to link binary sources directly. Instead >> of transforming it into a C-array, we simply use "ld -r" to create an >> object file via: >> ld -r -o my-source.bin.o --format=binary my-source.bin >> We also use "-z noexecstack" to mark "my-source.bin.o" to not require an >> executable stack. >> >> As we only want to support read-only data sources here, we do some >> post-processing to mark the object as read-only via: >> objcopy --rename-section .data=.rodata,alloc,load,readonly,data,contents >> my-source.bin.o >> >> As libtool requires "*.lo" files, we cannot link this object-file >> directly. Thus, we also create a fake "*.lo" file for such objects which >> libtool can use. Note that libtool actually *requires* the comment-section >> in "*.lo" files (ugh?!) so we need to fake that, too. >> >> How to use this helper? >> - put your binary source file into the tree as: >> src/somewhere/something.bin >> - for the library you want to link that to, add this to mylib_LIBADD: >> src/somewhere/something.bin.lo >> This causes the helper to create src/somewhere/something.bin.[o,lo] and >> it will be linked as a normal object file. >> >> GNU-ld automatically creates 3 symbols for such objects, but the important >> symbols are: >> extern const char _binary_src_somewhere_something_bin_start[]; >> extern const char _binary_src_somewhere_something_bin_end[]; >> Use these to access start/end of the binary section. >> >> I tested this with in-tree and out-of-tree builds, with GNU-ld and >> GNU-gold and cross-compilation. All worked fine.. > > That's crazy, very nice job in doing this :) > > I tried to do this a while ago, and gave up and just used a perl script > and a .c file with a big array, like 'xxd -i' can create. I think I'll > "steal" this idea for other projects if you don't mind, as it makes > things easier just to use the linker.
I figured that out about 1 year ago, took me way too long to get working. Please, go ahead and copy it! And if any issue comes up, let me know. Thanks David _______________________________________________ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
