[PATCH v4 0/2] Rust and the shadow call stack sanitizer

[PATCH v4 0/2] Rust and the shadow call stack sanitizer

[Alice Ryhl]

This patch series makes it possible to use Rust together with the shadow
call stack sanitizer. The first patch is intended to be backported to
ensure that people don't try to use SCS with Rust on older kernel
versions. The second patch makes it possible to use Rust with the shadow
call stack sanitizer.

The second patch in this series depends on the next version of [1],
which Miguel will send soon.

Link: https://lore.kernel.org/rust-for-linux/20240709160615.998336-12-ojeda@kernel.org/ [1]
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
---
Changes in v4:
- Move `depends on` to CONFIG_RUST.
- Rewrite commit messages to include more context.
- Link to v3: https://lore.kernel.org/r/20240704-shadow-call-stack-v3-0-d11c7a6ebe30@google.com

Changes in v3:
- Use -Zfixed-x18.
- Add logic to reject unsupported rustc versions.
- Also include a fix to be backported.
- Link to v2: https://lore.kernel.org/rust-for-linux/20240305-shadow-call-stack-v2-1-c7b4a3f4d616@google.com/

Changes in v2:
- Add -Cforce-unwind-tables flag.
- Link to v1: https://lore.kernel.org/rust-for-linux/20240304-shadow-call-stack-v1-1-f055eaf40a2c@google.com/

---
Alice Ryhl (2):
      rust: SHADOW_CALL_STACK is incompatible with Rust
      rust: support for shadow call stack sanitizer

 Makefile            | 1 +
 arch/arm64/Makefile | 3 +++
 init/Kconfig        | 1 +
 3 files changed, 5 insertions(+)
---
base-commit: 9cde54ad2f7ac3cf84f65df605570c5a00afc82f
change-id: 20240304-shadow-call-stack-9c197a4361d9

Best regards,
-- 
Alice Ryhl <aliceryhl@google.com>

[PATCH v4 1/2] rust: SHADOW_CALL_STACK is incompatible with Rust

[Alice Ryhl]

When using the shadow call stack sanitizer, all code must be compiled
with the -ffixed-x18 flag, but this flag is not currently being passed
to Rust. This results in crashes that are extremely difficult to debug.

To ensure that nobody else has to go through the same debugging session
that I had to, prevent configurations that enable both SHADOW_CALL_STACK
and RUST.

It is rather common for people to backport 724a75ac9542 ("arm64: rust:
Enable Rust support for AArch64"), so I recommend applying this fix all
the way back to 6.1.

Cc: <stable@vger.kernel.org> # 6.1 and later
Fixes: 724a75ac9542 ("arm64: rust: Enable Rust support for AArch64")
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
---
 init/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/init/Kconfig b/init/Kconfig
index b0238c4b6e79..914edf51b068 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1909,6 +1909,7 @@ config RUST
 	depends on !MODVERSIONS
 	depends on !GCC_PLUGINS
 	depends on !RANDSTRUCT
+	depends on !SHADOW_CALL_STACK
 	depends on !DEBUG_INFO_BTF || PAHOLE_HAS_LANG_EXCLUDE
 	help
 	  Enables Rust support in the kernel.

-- 
2.46.0.rc1.232.g9752f9e123-goog

Re: [PATCH v4 1/2] rust: SHADOW_CALL_STACK is incompatible with Rust

[Miguel Ojeda]

On Mon, Jul 29, 2024 at 4:23 PM Alice Ryhl <aliceryhl@google.com> wrote:
>
> When using the shadow call stack sanitizer, all code must be compiled
> with the -ffixed-x18 flag, but this flag is not currently being passed
> to Rust. This results in crashes that are extremely difficult to debug.
>
> To ensure that nobody else has to go through the same debugging session
> that I had to, prevent configurations that enable both SHADOW_CALL_STACK
> and RUST.
>
> It is rather common for people to backport 724a75ac9542 ("arm64: rust:
> Enable Rust support for AArch64"), so I recommend applying this fix all
> the way back to 6.1.

It should not hurt, and it is useful out-of-tree just in case -- if
arm64 is picking it up (which would be ideal):

Acked-by: Miguel Ojeda <ojeda@kernel.org>

Otherwise, please let us know. Thanks!

Cheers,
Miguel

Re: (subset) [PATCH v4 0/2] Rust and the shadow call stack sanitizer

[Catalin Marinas]

On Mon, 29 Jul 2024 14:22:48 +0000, Alice Ryhl wrote:
> This patch series makes it possible to use Rust together with the shadow
> call stack sanitizer. The first patch is intended to be backported to
> ensure that people don't try to use SCS with Rust on older kernel
> versions. The second patch makes it possible to use Rust with the shadow
> call stack sanitizer.
> 
> The second patch in this series depends on the next version of [1],
> which Miguel will send soon.
> 
> [...]

Applied to arm64 (for-next/fixes), thanks!

[1/2] rust: SHADOW_CALL_STACK is incompatible with Rust
      https://git.kernel.org/arm64/c/f126745da817

-- 
Catalin