Add indirect branch tracking #15122
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Add indirect branch tracking #15122
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OpenBSD 7.4+ enforces Indirect Branch Tracking but we're not yet compatible in Crystal, so we disable the feature for the time being.
This results in always reporting: ``` bin/crystal[204]: Brewfile: not found ```
This requires to pass the `-Dcf-protection=branch` flag for X86 or the `-Dbranch-protection=bti` flag for AARCH64.
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straight-shoota
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Oct 29, 2024
straight-shoota
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I guess #14026 can close too? IIRC the main blocker was indirect branch tracking and from what I can tell it's already on 1.13.2 (https://openbsd.app/?search=crystal) |
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Nov 9, 2024
Adds support for indirect branch tracking for X86[_64] (CET) and AArch64 targets through the following compile time flags (taken from gcc/clang/rust): - `-Dcf-protection=branch` (or `=return` or `=full`) for X86 - `-Dbranch-protection=bti` for AArch64 These flags are automatically set for OpenBSD, that enforces IBT or BTI on all user land applications. The patch also removes the `-Wl-znobtcfi` linker option since we don't need to disable it anymore. OpenBSD is the only OS I know to support _and_ enforce IBT or BTI in user land. Linux for example only supports it for kernel code (for the time being). I manually tested IBT in an OpenBSD VM on x86_64 with a supported CPU (Intel Raptor Lake). I can compile & recompile crystal as well as run `gmake std_spec` without running into IBT issues 👍 Notes: - I expected to have to add the ASM instructions to the fiber context switch ASM... but messing with the stack pointer isn't considered as a conditional jump apparently 🤷 - I'm using the genius idea from @straight-shoota that we can pass `-Dkey=value` then test for `flag?("key=value")` and it just worked 😲 - I can't test BTI on AArch64: I have no hardware and there are no bindings for the `aarch64-unknown-openbsd` target; there are little reasons it wouldn't work though; - I added support for shadow stack (SHSTK) on X86 (`-Dcf-protection=return`). I'm not sure we really support it though, since fibers are messing with the stacks?
straight-shoota
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Nov 13, 2024
These flags were added in crystal-lang/crystal#15122 They are put in a new section *Codegen Features*. The existing *Compiler Features* section is renamed to *Language Features*.
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Adds support for indirect branch tracking for X86[_64] (CET) and AArch64 targets through the following compile time flags (taken from gcc/clang/rust):
-Dcf-protection=branch(or=returnor=full) for X86-Dbranch-protection=btifor AArch64These flags are automatically set for OpenBSD, that enforces IBT or BTI on all user land applications. The patch also removes the
-Wl-znobtcfilinker option since we don't need to disable it anymore.OpenBSD is the only OS I know to support and enforce IBT or BTI in user land. Linux for example only supports it for kernel code (for the time being). I manually tested IBT in an OpenBSD VM on x86_64 with a supported CPU (Intel Raptor Lake). I can compile & recompile crystal as well as run
gmake std_specwithout running into IBT issues 👍Notes:
-Dkey=valuethen test forflag?("key=value")and it just worked 😲aarch64-unknown-openbsdtarget; there are little reasons it wouldn't work though;-Dcf-protection=return). I'm not sure we really support it though, since fibers are messing with the stacks?closes #13665
follow up to #15118 itself a followup of #15115