Looking at the size of ld.bfd binary I see: $ bloaty /usr/bin/ld.bfd FILE SIZE VM SIZE -------------- -------------- 89.5% 7.78Mi 89.5% 7.78Mi .rodata 7.0% 623Ki 7.0% 623Ki .text 1.2% 103Ki 1.2% 103Ki .rela.dyn Where the .rodata section is full of linker scripts: $ strings /usr/bin/ld.bfd | grep 'this script' | wc -l 927 So there are almost 1000 linker scripts. Would it be possible to save the scripts in a more compressed form? $ du -hs ld.bfd 8.7M ld.bfd $ xz ld.bfd $ du -hs ld.bfd.xz 316K ld.bfd.xz So one can easily compress the binary size 30x.
I've just tried to use eu-elfcompress, but it does not work for some reason: $ eu-elfcompress -n '.*rodata' -t zlib ld.bfd -o ld.xxx -v processing: ld.bfd [17] .rodata ignoring allocated section @Mark: Can you please take a look?
> $ eu-elfcompress -n '.*rodata' -t zlib ld.bfd -o ld.xxx -v > processing: ld.bfd > [17] .rodata ignoring allocated section It is as the message says. .rodata is an allocated section (SHF_ALLOC) and so cannot be ELF section compressed. This is explicitly not allowed by the spec because it would make mapping such a section into memory awkward (there is no corresponding program header flag, so it would be unclear how the dynamic linker should map a segment that contains a compressed section, especially since the segment/section mapping isn't 1-on-1 and can be about partial sections).
Created attachment 13152 [details] A POC On Linux/x86-64 text data bss dec hex filename 2606362 8376 6072 2620810 27fd8a ld.orig 1901779 8296 6072 1916147 1d3cf3 ld.compressed Use zstd may use less space.
(In reply to H.J. Lu from comment #3) > Created attachment 13152 [details] > A POC > > On Linux/x86-64 > > text data bss dec hex filename > 2606362 8376 6072 2620810 27fd8a ld.orig > 1901779 8296 6072 1916147 1d3cf3 ld.compressed > > Use zstd may use less space. Thank you for the work H.J. I can see the approach helps a bit, but we would get a better compression ratio if all linker scripts are compressed at once. Btw. why are the scripts embedded in ld.bfd? Can't be they distributed as a list of configuration files?
Whether scripts are compiled in or not is supposed to be under control of ld/genscripts.sh COMPILE_IN, but there are problems in these files modified: ld/emulparams/alphavms.sh modified: ld/emulparams/elf64_ia64_vms.sh modified: ld/emulparams/elf64mmix.sh modified: ld/emulparams/elf_iamcu.sh modified: ld/emulparams/elf_k1om.sh modified: ld/emulparams/elf_l1om.sh modified: ld/emulparams/mmo.sh modified: ld/emulparams/pdp11.sh modified: ld/emultempl/beos.em modified: ld/emultempl/pdp11.em modified: ld/emultempl/pe.em modified: ld/emultempl/pep.em and yes, I have a patch under test.
(In reply to Martin Liska from comment #4) > (In reply to H.J. Lu from comment #3) > > Created attachment 13152 [details] > > A POC > > > > On Linux/x86-64 > > > > text data bss dec hex filename > > 2606362 8376 6072 2620810 27fd8a ld.orig > > 1901779 8296 6072 1916147 1d3cf3 ld.compressed > > > > Use zstd may use less space. > > Thank you for the work H.J. I can see the approach helps a bit, but we would > get a better compression ratio if all linker scripts are compressed at once. That will require non-trivial changes in ld. > Btw. why are the scripts embedded in ld.bfd? Can't be they distributed as a > list of configuration files? You can just copy ld to another machine.
The master branch has been updated by Alan Modra <amodra@sourceware.org>: https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=1c9c9b9b55520b36c15af94ee0803f0922b3ca09 commit 1c9c9b9b55520b36c15af94ee0803f0922b3ca09 Author: Alan Modra <amodra@gmail.com> Date: Tue Jan 26 10:48:09 2021 +1030 PR27226, ld.bfd contains huge .rodata section This makes it possible to build ld without any compiled-in scripts, by setting COMPILE_IN=no in the environment. pe, beos and pdp11 targets didn't support scripts from the file system, with pdp11 nastily editing the ld/ldscripts file so that the built-in script didn't match. PR 27226 * emulparams/alphavms.sh: Don't set COMPILE_IN. * emulparams/elf64_ia64_vms.sh: Likewise. * emulparams/elf64mmix.sh: Likewise. * emulparams/elf_iamcu.sh: Likewise. * emulparams/elf_k1om.sh: Likewise. * emulparams/elf_l1om.sh: Likewise. * emulparams/mmo.sh: Likewise. * emulparams/pdp11.sh: Set DATA_SEG_ADDR. * scripttempl/pdp11.sc: Use it. * emultempl/pdp11.em: Don't edit .xn script for separate_code, instead use .xe script. Support scripts from file system. * emultempl/beos.em: Support scripts from file system. * emultempl/pe.em: Likewise. * emultempl/pep.em: Likewise. * testsuite/ld-bootstrap/bootstrap.exp: Make tmpdir/ldscripts link.