Always set the RDRAND and RDSEED features on SGX

[jethrogb]

Not sure if this is 100% correct.

This Intel article goes in great depth regarding using (untrusted) CPUID to see whether RDRAND/RDSEED is supported, and explains what happens to the enclave if the CPUID result is faked.

I'd say that an implementation of SGX that doesn't make RDRAND available to the enclave is so severely limited/broken that it's ok if you get #UD in that case. The case is less clear for RDSEED, but it so far every processor released by Intel with SGX support also has RDSEED (including Gemini Lake).

cc @briansmith

[rust-highfive]

r? @estebank

(rust_highfive has picked a reviewer for you, use r? to override)

[jethrogb]

Actually, I'm not sure if this is the correct way to set this. This parameter seems to go directly into LLVM, but I also want to trigger #[cfg(target_feature="...")]. How can I do that?

[rust-highfive]

The job x86_64-gnu-llvm-5.0 of your PR failed on Travis (raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

travis_time:end:14ce26ba:start=1544532111472385763,finish=1544532112534669366,duration=1062283603
$ git checkout -qf FETCH_HEAD
travis_fold:end:git.checkout

Encrypted environment variables have been removed for security reasons.
See https://docs.travis-ci.com/user/pull-requests/#Pull-Requests-and-Security-Restrictions
$ export SCCACHE_BUCKET=rust-lang-ci-sccache2
$ export SCCACHE_REGION=us-west-1
Setting environment variables from .travis.yml
$ export IMAGE=x86_64-gnu-llvm-5.0
---
[00:05:28]    Compiling parking_lot v0.6.4
[00:05:28]    Compiling rustc-rayon v0.1.1
[00:05:31]    Compiling tempfile v3.0.5
[00:05:32]    Compiling rustc_data_structures v0.0.0 (/checkout/src/librustc_data_structures)
[00:05:37] error[E0560]: struct `spec::Target` has no field named `features`
[00:05:37]   --> src/librustc_target/spec/x86_64_fortanix_unknown_sgx.rs:69:9
[00:05:37]    |
[00:05:37] 69 |         features: "rdrnd,rdseed".into(),
[00:05:37]    |         ^^^^^^^^ `spec::Target` does not have this field
[00:05:37]    |
[00:05:37]    = note: available fields are: `llvm_target`, `target_endian`, `target_pointer_width`, `target_c_int_width`, `target_os` ... and 6 others
[00:05:37] error: aborting due to previous error
[00:05:37] 
[00:05:37] For more information about this error, try `rustc --explain E0560`.
[00:05:37] error: Could not compile `rustc_target`.
---
153288 ./src/tools/clang
150704 ./obj/build/bootstrap/debug/incremental
149568 ./.git
135104 ./obj/build/bootstrap/debug/incremental/bootstrap-2pgjvb3usndhe
135100 ./obj/build/bootstrap/debug/incremental/bootstrap-2pgjvb3usndhe/s-f7hob0oiws-ukbbk3-e1ql6nnu93qh
134556 ./.git/modules/src
115344 ./src/llvm/test/CodeGen
107888 ./obj/build/x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/codegen-backends
107416 ./src/tools/lldb

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

[alexcrichton]

I think this is the right place to configure, but a plus sign may be needed in front as it's llvm syntax

[jethrogb]

Yes, that's it, thanks.

[estebank]

r? @alexcrichton you are probably better suited to approve this :)

[alexcrichton]

@bors: r+ rollup

[bors]

📌 Commit 5acab2d has been approved by alexcrichton