Request: MUSL x-compilation target

[sempervictus]

The currently supported targets list includes a bunch of GNU target toolchains, but none on MUSL. In order to build fully static binaries - like something one might want to run inside the initramfs, we need to separate from whatever libc is used by the rest of the host inside that target as it might change and break critical paths accessing the TPM before a full userspace is available. The crate page has a link to how cross compiles are set up in the buildbots, but leads to a missing page - We include cross-compilation builds as a nightly check in Github Actions - you can find them here as an example of the steps needed
Is there a writeup somewhere on how to set this up, or possibly a way to include pre-built targets?

[hug-dev]

Hey 👋!
Thanks for the issue!

First about the link, it should point to this file. Looks like relative links to file do not work well with crates.io! Fixed it in #225

About target support, I guess yo ugot the panic message saying that the target is not supported? We modified the way we check for supported targets only verifying for the target architecture and OS (see #219) but not making any difference if the target has a GNU or MUSL environment. That would mean that both x86_64-unknown-linux-gnu and x86_64-unknown-linux-musl for example would be treated the same way by our build script. If the bindings for those two targets would be different, maybe they should be treated differently btw. We did not yet release that change however!

I hope that would help? Feel free to say if I am wrong or you were having a totally different problem 😋

[nightmared]

FWIW I was able to successfully build a static binary using the following Dockerfile (that builds atop the "famous" clux/muslrust):

# Note: for safety, please build the mulsrust image yourselves (this will help against supply chain attacks):
# https://github.com/clux/muslrust/blob/main/Dockerfile
FROM clux/muslrust:stable

RUN apt update && apt install -y libclang-15-dev clang-15 git meson ninja-build bison gettext autopoint libltdl-dev pkg-config autoconf-archive && rm -rf /var/lib/apt/lists/*
WORKDIR /
RUN curl -sSL https://s3.amazonaws.com/json-c_releases/releases/json-c-0.17-nodoc.tar.gz | tar xz && mkdir json-c-0.17/build && cd json-c-0.17/build && cmake .. -DBUILD_STATIC_LIBS=ON -DBUILD_SHARED_LIBS=OFF -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=$PREFIX && make -j8 && make install && cd .. && rm -rf json-c-0.17
RUN git clone --depth 1 https://github.com/util-linux/util-linux.git && cd util-linux && ./autogen.sh && ./configure --enable-static --prefix=$PREFIX --host=x86_64-unknown-linux-musl --disable-shared --disable-all-programs --enable-libuuid && make -j8 && make install && cd .. && rm -rf util-linux
RUN git clone --depth 1 -b 4.0.x https://github.com/tpm2-software/tpm2-tss.git && cd tpm2-tss && ./bootstrap && CFLAGS="-Wno-error" ./configure --disable-doxygen-doc --enable-static --prefix=$PREFIX --host=x86_64-unknown-linux-musl --disable-shared && make -j8 && make install && cd .. && rm -rf tpm2-tss
WORKDIR /volume

And then building my binary works as follows:

docker build -t musl_with_tss .
docker run -v $PWD:/volume --rm -t -v cargo-cache:/root/.cargo/registry musl_with_tss cargo build

So I don't believe there is any blocking problem for building static binaries with this crate, even though I guess a more integrated solution wouldn't be scorned at.

[nightmared]

EDIT: turns out it's not that simple, because you need to build tpm-tss with the --enable-nodl flag, otherwise your program will attempt to perform dlopen of the tcti backend (e.g. device), and it won't work with musl