Allow multiple modifications in same call

[fzakaria]

patchelf previously would incorrectly patch the ELF header if it was called with multiple changes at once such as add & replace.

In order to support that, rewrite the sections in between each section modification.

Please see the issue for the bug and here is now the fix:

> ./src/patchelf --replace-needed libruby-2.7.so.2.7 /lib/x86_64-linux-gnu/libruby-2.7.so.2.7 \
--replace-needed libc.so.6 /lib/x86_64-linux-gnu/libc.so.6 \
--add-needed /lib/x86_64-linux-gnu/libcrypt.so.1 \
--add-needed /lib/x86_64-linux-gnu/libdl.so.2 \
--add-needed /lib/x86_64-linux-gnu/libgmp.so.10 \
--add-needed /lib/x86_64-linux-gnu/libm.so.6 \
--add-needed /lib/x86_64-linux-gnu/libpthread.so.0 \
--add-needed /lib/x86_64-linux-gnu/librt.so.1 /tmp/ruby

> ./src/patchelf --print-needed /tmp/ruby
/lib/x86_64-linux-gnu/libcrypt.so.1
/lib/x86_64-linux-gnu/libdl.so.2
/lib/x86_64-linux-gnu/libgmp.so.10
/lib/x86_64-linux-gnu/libm.so.6
/lib/x86_64-linux-gnu/libpthread.so.0
/lib/x86_64-linux-gnu/librt.so.1
/lib/x86_64-linux-gnu/libruby-2.7.so.2.7
/lib/x86_64-linux-gnu/libc.so.6

Fix #359

Thank you @trws for the idea of the fix.

CC @Mic92

[fzakaria]

Interestingly discussed with @trws that if the shared object doesn't have a DT_SONAME, it won't make use of the previously discovered loaded shared object.

This was discovered while writing this test. You can see below that libbar.so was not found, even though its set with an absolute path.

ldd ~/code/github.com/NixOS/patchelf/tests/scratch/replace-add-needed/simple
	linux-vdso.so.1 (0x00007ffc90565000)
	/home/fmzakari/code/github.com/NixOS/patchelf/tests/scratch/replace-add-needed/libbar.so (0x00007f532a4c4000)
	/home/fmzakari/code/github.com/NixOS/patchelf/tests/scratch/replace-add-needed/libfoo.so (0x00007f532a4bf000)
	libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f532a2da000)
	/nix/store/jsp3h3wpzc842j0rz61m5ly71ak6qgdn-glibc-2.32-54/lib/ld-linux-x86-64.so.2 => /lib64/ld-linux-x86-64.so.2 (0x00007f532a4cb000)
	libbar.so => not found

[Mic92]

The test error for musl looks legit FAIL: replace-add-needed.sh

[fzakaria]

@Mic92 ah -- my test tries to grep for glibc ! I didn't know we build musl libraries lol.
I'll figure out a new thing to do for the test + make the changes you recommend.

[fzakaria]

Okay I started alpine locally and see that the issue is that the musl linker is working differently than glibc.

/app/tests # ./replace-add-needed.sh
Error loading shared library libbar.so: No such file or directory (needed by /app/tests/scratch/replace-add-needed/libfoo.so)
	/lib/ld-musl-x86_64.so.1 (0x7f3e0f527000)
	/app/tests/scratch/replace-add-needed/libfoo.so => /app/tests/scratch/replace-add-needed/libfoo.so (0x7f3e0e51a000)
	/app/tests/scratch/replace-add-needed/libbar.so => /app/tests/scratch/replace-add-needed/libbar.so (0x7f3e0e514000)
	libc.musl-x86_64.so.1 => /lib/ld-musl-x86_64.so.1 (0x7f3e0f527000)
Error loading shared library libbar.so: No such file or directory (needed by /app/tests/scratch/replace-add-needed/libfoo.so)

/app/tests # ../src/patchelf --print-soname scratch/replace-add-needed/libbar.so
libbar.so

It's failing to skip the libbar.so NEEDED since it already linked it.

This is quite interesting; tagging @trws

[fzakaria]

@Mic92 please read the linked mailing issue I opened for why we have to do this for musl
https://www.openwall.com/lists/musl/2021/12/21/1

This should now succeed on musl and glibc proving the fix of the bug.

[Mic92]

Thanks!