Use +secure-plt for powerpc-unknown-linux-gnu{,spe}

[taiki-e]

Fixes #136131
See that issue for details.

I'm not sure about the policy about baseline on these platforms (there is no platform support doc for them), but it seems that the Debian/Ubuntu's cross-compiler (powerpc-linux-gnu-gcc) already uses --enable-secureplt at least as of Debian 9 (stretch) and Ubuntu 14.04.

$ cat /etc/os-release | grep VERSION_ID
VERSION_ID="9"
$ powerpc-linux-gnu-gcc -v
Using built-in specs.
COLLECT_GCC=powerpc-linux-gnu-gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc-cross/powerpc-linux-gnu/6/lto-wrapper
Target: powerpc-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 6.3.0-18' --with-bugurl=file:///usr/share/doc/gcc-6/README.Bugs --enable-languages=c,ada,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-6 --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new --enable-gnu-unique-object --disable-libitm --disable-libquadmath --enable-plugin --with-system-zlib --disable-browser-plugin --enable-java-awt=gtk --enable-gtk-cairo --with-java-home=/usr/lib/jvm/java-1.5.0-gcj-6-powerpc-cross/jre --enable-java-home --with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-6-powerpc-cross --with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-6-powerpc-cross --with-arch-directory=ppc --with-ecj-jar=/usr/share/java/eclipse-ecj.jar --disable-libgcj --enable-objc-gc=auto --enable-secureplt --disable-softfloat --with-cpu=default32 --disable-softfloat --enable-targets=powerpc-linux,powerpc64-linux --enable-multiarch --with-long-double-128 --enable-multilib --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=powerpc-linux-gnu --program-prefix=powerpc-linux-gnu- --includedir=/usr/powerpc-linux-gnu/include
Thread model: posix
gcc version 6.3.0 20170516 (Debian 6.3.0-18) 

$ cat /etc/os-release | grep VERSION_ID
VERSION_ID="14.04"
$ cat /etc/debian_version 
jessie/sid
$ powerpc-linux-gnu-gcc -v
Using built-in specs.
COLLECT_GCC=powerpc-linux-gnu-gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc-cross/powerpc-linux-gnu/4.8/lto-wrapper
Target: powerpc-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu 4.8.4-2ubuntu1~14.04.1' --with-bugurl=file:///usr/share/doc/gcc-4.8/README.Bugs --enable-languages=c,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-4.8 --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/powerpc-linux-gnu/include/c++/4.8.4 --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --enable-gnu-unique-object --disable-libmudflap --disable-libitm --disable-libsanitizer --disable-libquadmath --enable-plugin --with-system-zlib --disable-browser-plugin --enable-java-awt=gtk --enable-gtk-cairo --with-java-home=/usr/lib/jvm/java-1.5.0-gcj-4.8-powerpc-cross/jre --enable-java-home --with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-4.8-powerpc-cross --with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-4.8-powerpc-cross --with-arch-directory=ppc --with-ecj-jar=/usr/share/java/eclipse-ecj.jar --disable-libgcj --enable-objc-gc --enable-secureplt --disable-softfloat --with-cpu=default32 --disable-softfloat --enable-targets=powerpc-linux,powerpc64-linux --enable-multiarch --disable-werror --with-long-double-128 --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=powerpc-linux-gnu --program-prefix=powerpc-linux-gnu- --includedir=/usr/powerpc-linux-gnu/include
Thread model: posix
gcc version 4.8.4 (Ubuntu 4.8.4-2ubuntu1~14.04.1) 

cc @glaubitz (who added powerpc-unknown-linux-gnuspe in #48484)

r? tgross35

@rustbot label +O-PowerPC +O-linux-gnu

try-job: dist-powerpc-linux
try-job: dist-powerpc64-linux
try-job: dist-powerpc64le-linux
try-job: dist-various-1
try-job: dist-various-2
try-job: aarch64-gnu

[rustbot]

These commits modify compiler targets.
(See the Target Tier Policy.)

[tgross35]

Thanks for the fix; this change looks reasonable to me, @nikic would you mind double checking? It seems like LLVM has had support since around 2018.

Is this easy to reproduce consistently? I'm wondering if there should be a UI test with linker_messages enabled that builds this target, to make sure other warnings don't appear in the future. (Really it should be all targets).

[nikic]

This generally seems fine. secure-plt is still compatible with objects not using it (apart from that linker warning). If Debian/Ubuntu enable it by default nowadays, it seems reasonable for Rust to do so as well.

I wonder whether secure-plt should be added to the known target features for powerpc though, so it is possible to toggle it without a warning?

[nikic]

Is this easy to reproduce consistently? I'm wondering if there should be a UI test with linker_messages enabled that builds this target, to make sure other warnings don't appear in the future. (Really it should be all targets).

Testing this would require a cross linker for the platform to be available. I guess we could add a no_core linking test if lld is available. Wouldn't help this particular issue though, as I don't think that lld emits this warning.

[tgross35]

Making it toggleable but on by default sounds reasonable. Maybe that's getting into MCP territory?

[tgross35]

I don't know enough about the background here, so

r? nikic

[nikic]

I think it's fine to land this as-is for now.

@bors r+

[bors]

📌 Commit 56c6ffb has been approved by nikic

It is now in the queue for this repository.

[workingjubilee]

This has had 5 rollups fail with it and there was an attempt to diagnose as to whether this PR failed the rollup or not that was possibly correct but inexact. Putting this through the paces of a try-job so as to make sure:

@bors r-
@bors try

[bors]

⌛ Trying commit 56c6ffb with merge 3e6f49f...

[bors]

☀️ Try build successful - checks-actions
Build commit: 3e6f49f (3e6f49f0118389662ed718eddd9cc07e28acdf6a)

[tgross35]

CI has been weird the past few days, this may just be a symptom of that.

@bors r=nikic

[bors]

📌 Commit 56c6ffb has been approved by nikic

It is now in the queue for this repository.