Benjamin A. Bjørnseth bb9dee95ed add rustc option for using LLVM stack smash protection ... LLVM has built-in heuristics for adding stack canaries to functions. These heuristics can be selected with LLVM function attributes. This patch adds a rustc option `-Z stack-protector={none,basic,strong,all}` which controls the use of these attributes. This gives rustc the same stack smash protection support as clang offers through options `-fno-stack-protector`, `-fstack-protector`, `-fstack-protector-strong`, and `-fstack-protector-all`. The protection this can offer is demonstrated in test/ui/abi/stack-protector.rs. This fills a gap in the current list of rustc exploit mitigations (https://doc.rust-lang.org/rustc/exploit-mitigations.html), originally discussed in #15179. Stack smash protection adds runtime overhead and is therefore still off by default, but now users have the option to trade performance for security as they see fit. An example use case is adding Rust code in an existing C/C++ code base compiled with stack smash protection. Without the ability to add stack smash protection to the Rust code, the code base artifacts could be exploitable in ways not possible if the code base remained pure C/C++. Stack smash protection support is present in LLVM for almost all the current tier 1/tier 2 targets: see test/assembly/stack-protector/stack-protector-target-support.rs. The one exception is nvptx64-nvidia-cuda. This patch follows clang's example, and adds a warning message printed if stack smash protection is used with this target (see test/ui/stack-protector/warn-stack-protector-unsupported.rs). Support for tier 3 targets has not been checked. Since the heuristics are applied at the LLVM level, the heuristics are expected to add stack smash protection to a fraction of functions comparable to C/C++. Some experiments demonstrating how Rust code is affected by the different heuristics can be found in test/assembly/stack-protector/stack-protector-heuristics-effect.rs. There is potential for better heuristics using Rust-specific safety information. For example it might be reasonable to skip stack smash protection in functions which transitively only use safe Rust code, or which uses only a subset of functions the user declares safe (such as anything under `std.*`). Such alternative heuristics could be added at a later point. LLVM also offers a "safestack" sanitizer as an alternative way to guard against stack smashing (see #26612). This could possibly also be included as a stack-protection heuristic. An alternative is to add it as a sanitizer (#39699). This is what clang does: safestack is exposed with option `-fsanitize=safe-stack`. The options are only supported by the LLVM backend, but as with other codegen options it is visible in the main codegen option help menu. The heuristic names "basic", "strong", and "all" are hopefully sufficiently generic to be usable in other backends as well. Reviewed-by: Nikita Popov <nikic@php.net> Extra commits during review: - [address-review] make the stack-protector option unstable - [address-review] reduce detail level of stack-protector option help text - [address-review] correct grammar in comment - [address-review] use compiler flag to avoid merging functions in test - [address-review] specify min LLVM version in fortanix stack-protector test Only for Fortanix test, since this target specifically requests the `--x86-experimental-lvi-inline-asm-hardening` flag. - [address-review] specify required LLVM components in stack-protector tests - move stack protector option enum closer to other similar option enums - rustc_interface/tests: sort debug option list in tracking hash test - add an explicit `none` stack-protector option Revert "set LLVM requirements for all stack protector support test revisions" This reverts commit a49b74f92a4e7d701d6f6cf63d207a8aff2e0f68.		2021-11-22 20:06:22 +01:00
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src	add rustc option for using LLVM stack smash protection	2021-11-22 20:06:22 +01:00
Cargo.toml	Move rustc_middle::middle::cstore to rustc_session.	2021-10-03 16:08:51 +02:00