[PATCH v7] rust: support for shadow call stack sanitizer

[Alice Ryhl]

On Fri, Sep 13, 2024 at 11:18 PM Conor Dooley <conor at kernel.org> wrote:
>
> On Fri, Sep 13, 2024 at 12:08:20AM +0200, Miguel Ojeda wrote:
> > On Thu, Aug 29, 2024 at 10:23 AM Alice Ryhl <aliceryhl at google.com> wrote:
> > >
> > > Add all of the flags that are needed to support the shadow call stack
> > > (SCS) sanitizer with Rust, and updates Kconfig to allow only
> > > configurations that work.
> >
> > Applied to `rust-next` -- thanks everyone!
> >
> > Paul/Palmer/Albert/RISC-V: I think you were not Cc'd (at least in this
> > version?), so please shout if you have a problem with this.
>
> For some reason I deleted the series from my mailbox, must've been in
> dt-binding review mode and hit ctrl + d. I've been away and busy, so my
> apologies Alice for not trying this out sooner.
> It's sorta annoying to test rust + scs on riscv, cos you need (unless I
> am mistaken) llvm-19. llvm-18 + rust built fine, but has no SCS.
>
> llvm-19 + rust failed to build for me riscv, producing:
>
> In file included from /stuff/linux/rust/helpers/helpers.c:22:
> /stuff/linux/rust/helpers/spinlock.c:10:23: error: call to undeclared function 'spinlock_check'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
> __raw_spin_lock_init(spinlock_check(lock), name, key, LD_WAIT_CONFIG);
> ^
> /stuff/linux/rust/helpers/spinlock.c:10:23: error: incompatible integer to pointer conversion passing 'int' to parameter of type 'raw_spinlock_t *' (aka 'struct raw_spinlock *') [-Wint-conversion]
> __raw_spin_lock_init(spinlock_check(lock), name, key, LD_WAIT_CONFIG);
> ^~~~~~~~~~~~~~~~~~~~
> /stuff/linux/include/linux/spinlock.h:101:52: note: passing argument to parameter 'lock' here
> extern void __raw_spin_lock_init(raw_spinlock_t *lock, const char *name,
> ^
> 2 errors generated.
>
> This occurs because I have DEBUG_SPINLOCK enabled. I didn't check why,
> but Andreas seems to have introduced that code - luckily he's already on
> CC here :)
>
> With that disabled, there are dozens of warnings along the lines of:
> /stuff/linux/rust/helpers/err.c:6:14: warning: symbol 'rust_helper_ERR_PTR' was not declared. Should it be static?
> If those are okay for rust code, it would be rather helpful if the
> warnings could be disabled - otherwise they should really be fixed.
>
> Following that, I got a build error:
>
> error[E0425]: cannot find function `__mutex_init` in crate `bindings`
> --> /stuff/linux/rust/kernel/sync/lock/mutex.rs:104:28
> |
> 104   |           unsafe { bindings::__mutex_init(ptr, name, key) }
> |                              ^^^^^^^^^^^^ help: a function with a similar name exists: `__mutex_rt_init`
> |
> ::: /stuff/brsdk/work/linux/rust/bindings/bindings_generated.rs:12907:5
> |
> 12907 | /     pub fn __mutex_rt_init(
> 12908 | |         lock: *mut mutex,
> 12909 | |         name: *const core::ffi::c_char,
> 12910 | |         key: *mut lock_class_key,
> 12911 | |     );
> | |_____- similarly named function `__mutex_rt_init` defined here
>
> error: aborting due to 1 previous error

This looks like an unrelated problem to me. This patch only changes
the rustc flags, but these errors have to do with the Rust
helpers/bindings, which get generated before the rustc flags are used
at all. Most likely, there is a problem under the particular
configuration you are using. Were you able to reproduce these errors
without this patch?

> I stopped there, Space Marine 2 awaits.
>
> Hopefully I'll get to say hello next week,
> Conor.

Thanks for taking a look, and see you at Plumbers!

Alice