cf-protection
The tracking issue for this feature is: #93754.
This option enables control-flow enforcement technology (CET) on x86; a more detailed description of
CET is available here. Similar to clang
, this flag takes one of the following values:
none
- Disable CET completely (this is the default).branch
- Enable indirect branch tracking (IBT
).return
- Enable shadow stack (SHSTK
).full
- Enable bothbranch
andreturn
.
This flag only applies to the LLVM backend: it sets the cf-protection-branch
and
cf-protection-return
flags on LLVM modules. Note, however, that all compiled modules linked
together must have the flags set for the compiled output to be CET-enabled. Currently, Rust's
standard library does not ship with CET enabled by default, so you may need to rebuild all standard
modules with a cargo
command like:
$ RUSTFLAGS="-Z cf-protection=full" cargo +nightly build -Z build-std --target x86_64-unknown-linux-gnu
Detection
An ELF binary is CET-enabled if it has the IBT
and SHSTK
tags, e.g.:
$ readelf -a target/x86_64-unknown-linux-gnu/debug/example | grep feature:
Properties: x86 feature: IBT, SHSTK
Troubleshooting
To display modules that are not CET enabled, examine the linker errors available when cet-report
is enabled:
$ RUSTC_LOG=rustc_codegen_ssa::back::link=info rustc-custom -v -Z cf-protection=full -C link-arg="-Wl,-z,cet-report=warning" -o example example.rs
...
/usr/bin/ld: /.../build/x86_64-unknown-linux-gnu/stage1/lib/rustlib/x86_64-unknown-linux-gnu/lib/libstd-d73f7266be14cb8b.rlib(std-d73f7266be14cb8b.std.f7443020-cgu.12.rcgu.o): warning: missing IBT and SHSTK properties