Add cross-compilation example to nightly

This commit adds cross-compilation to armv7 and aarch64 to the nightly
build. This involves modifications to the way `pkg-config` is used
as described in #204.

Signed-off-by: Ionut Mihalcea <[email protected]>

.github/workflows/nightly.yml

@@ -41,13 +41,15 @@ jobs:
         run: cargo audit
 
   coverage:
-    name: Calculate code coverage
+    name: Calculate code coverage and cross compile
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
       - name: Build the container
         run: docker build -t ubuntucontainer tss-esapi/tests/ --file tss-esapi/tests/Dockerfile-ubuntu
-      - name: Run the container
+      - name: Run the code coverage script
         run: docker run -v $(pwd):/tmp/rust-tss-esapi -w /tmp/rust-tss-esapi/tss-esapi --security-opt seccomp=unconfined ubuntucontainer /tmp/rust-tss-esapi/tss-esapi/tests/coverage.sh
       - name: Collect coverage results
         run: bash <(curl -s https://codecov.io/bash)
+      - name: Run the cross-compilation script
+        run: docker run -v $(pwd):/tmp/rust-tss-esapi -w /tmp/rust-tss-esapi/tss-esapi ubuntucontainer /tmp/rust-tss-esapi/tss-esapi/tests/cross-compile.sh

tss-esapi-sys/.cargo/config

@@ -0,0 +1,7 @@
+# Cargo seems to expect the -gcc variant instead of -ld
+
+[target.armv7-unknown-linux-gnueabi]
+linker = "arm-linux-gnueabihf-gcc"
+
+[target.aarch64-unknown-linux-gnu]
+linker = "aarch64-linux-gnu-gcc"

tss-esapi-sys/README.md

@@ -38,4 +38,22 @@ NOTE: Only a limited set of bindings are committed and their target triplet
 is included in the name of the file - if the triplet you require is not
 available, feel free to raise a Pull Request to add it or to use build-time
 generation of bindings. All the committed bindings **MUST** be generated from
-the library version found under the `vendor` submodule.
+the library version found under the `vendor` submodule.
+
+## Cross compiling
+
+Cross-compilation can be done as long as you have on your build system the TSS 
+libraries compiled for your target system of choice. We rely on `pkg-config` to
+identify the libraries which we link against. Installing `tpm2-tss` yields `.pc`
+files which can be used for this purpose, but depending on the exact build
+environment setup, you might need to be careful when configuring the `tpm2-tss`
+build.
+
+We include cross-compilation builds as a nightly check in Github Actions - you
+can find them [here](../tss-esapi/tests/cross-compile.sh) as an example of the
+steps needed. You can find more information on using `pkg-config` when cross-compiling
+[here](https://github.com/parallaxsecond/rust-tss-esapi/issues/204). Our wrapper
+script around `pkg-config` can be seen [here](../tss-esapi/tests/pkg-config).
+
+Be advised that in most cases the linker used might need to be set manually in
+`.cargo/config` (some entries already exist there as an example).