Add support for s390x architecture.

[PiotrSikora]

Description of changes:

Add support for s390x architecture.

This is pretty trivial change (a few defines), since the big-endian support was previously added for PowerPC architectures.

Call-outs:

There is a false-positive error when compiling using s390x-linux-gnu-gcc-11 with -O3 (i.e. Release profile):

crypto/pem/pem_lib.c:705:11: error: ‘strncmp’ of strings of length 1 and 9 and bound of 9 evaluates to nonzero [-Werror=string-compare]
 705 |       if (strncmp(buf, "-----END ", 9) == 0) {
     |           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors

but there are no issues when using -O2 or when building with s390x-linux-gnu-gcc-12.

Testing:

All tests from run_cross_tests.sh, i.e.

crypto/crypto_test --gtest_also_run_disabled_tests
crypto/urandom_test
crypto/mem_test
crypto/mem_set_test
crypto/dynamic_loading_test

ssl/ssl_test
ssl/integration_test

passed, with the exception of BIOTest.InvokeConnectCallback, which fails for me on all platforms.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license and the ISC license.

cc @andrewhop @justsmth

[justsmth]

Could this be added to our cross-tests? (After fixing BIOTest.InvokeConnectCallback?)

[PiotrSikora]

Could this be added to our cross-tests?

It can be added, but I believe that someone from your team has to upload the cross-compiling toolchain for s390x, which is downloaded as part of the CI (see: tests/ci/run_cross_tests.sh#L34).

(After fixing BIOTest.InvokeConnectCallback?)

As mentioned in the original message, this test is always failing for me without any code changes in all the configurations I've tested (i.e. when running unmodified main branch on native x86-64 system, and also when cross-compiling to different architectures), and I don't believe there is anything s390x-specific about this failure.

Anyway, it looks that the test was broken: #1433.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 76.94%. Comparing base (67cf4cc) to head (853b015).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1431      +/-   ##
==========================================
- Coverage   76.95%   76.94%   -0.02%     
==========================================
  Files         425      425              
  Lines       71587    71587              
==========================================
- Hits        55093    55080      -13     
- Misses      16494    16507      +13     

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[justsmth]

Sorry for the delay in reviewing this. I plan to build a toolchain to perform testing for this platform. I'll hopefully have an update on it soon.

[justsmth]

CI tests for the s390x passed: https://github.com/aws/aws-lc/actions/runs/8116237276/job/22185808912?pr=1431