diff mbox series

[v2,1/3] rust: make mutually exclusive with CFI_CLANG

Message ID 20240223-perjury-preshow-fc2cf73d552e@spud
State New
Headers
Series RISC-V: enable rust |

Commit Message

Conor Dooley Feb. 23, 2024, 1:38 p.m. UTC 
  From: Conor Dooley <conor.dooley@microchip.com>

On RISC-V, and presumably x86/arm64, if CFI_CLANG is enabled loading a
rust module will trigger a kernel panic. Support for sanitisers,
including kcfi (CFI_CLANG), is in the works, but for now they're
nightly-only options in rustc. Make RUST depend on !CFI_CLANG to prevent
configuring a kernel without symmetrical support for kfi.

Fixes: 2f7ab1267dc9 ("Kbuild: add Rust support")
cc: stable@vger.kernel.org
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
---
This probably needs to go to stable. The correct fixes tag for that I am
not sure of however, but since CFI_CLANG predates RUST, I blamed the
commit adding rust support.
---
 init/Kconfig | 1 +
 1 file changed, 1 insertion(+)

Comments

Miguel Ojeda Feb. 23, 2024, 2:45 p.m. UTC | #1 
On Fri, Feb 23, 2024 at 2:38 PM Conor Dooley <conor@kernel.org> wrote:
>
> configuring a kernel without symmetrical support for kfi.

Nit: typo.

> This probably needs to go to stable. The correct fixes tag for that I am
> not sure of however, but since CFI_CLANG predates RUST, I blamed the
> commit adding rust support.

Cc'ing Matthew et al. in case this is a problem for them, but I guess
we can relax it later as needed.

Cheers,
Miguel
Conor Dooley Feb. 27, 2024, 10:53 a.m. UTC | #2 
On Fri, Feb 23, 2024 at 03:45:10PM +0100, Miguel Ojeda wrote:
> On Fri, Feb 23, 2024 at 2:38 PM Conor Dooley <conor@kernel.org> wrote:
> >
> > configuring a kernel without symmetrical support for kfi.
> 
> Nit: typo.
> 
> > This probably needs to go to stable. The correct fixes tag for that I am
> > not sure of however, but since CFI_CLANG predates RUST, I blamed the
> > commit adding rust support.
> 
> Cc'ing Matthew et al. in case this is a problem for them, but I guess
> we can relax it later as needed.

I suspect that nobody has actually sat down and tried it.

I did try to test it but I ran into too many toolchain issues - my
older copies of LLVM (pre 17) are not multiarch as I built them by hand
with PGO for x86 and RISC-V. My LLVM 17 is from kernel.org and has no
libclang. And then the copy of LLVM 18 on kernel.org apparently does not
support kcfi at all. I gave up there, but I don't see how this would not
be a problem on other arches, given rustc never gets told to enable
kcfi.

Cheers,
Conor.
Miguel Ojeda Feb. 27, 2024, 12:34 p.m. UTC | #3 
On Tue, Feb 27, 2024 at 11:54 AM Conor Dooley
<conor.dooley@microchip.com> wrote:
>
> I did try to test it but I ran into too many toolchain issues - my
> older copies of LLVM (pre 17) are not multiarch as I built them by hand
> with PGO for x86 and RISC-V. My LLVM 17 is from kernel.org and has no
> libclang. And then the copy of LLVM 18 on kernel.org apparently does not
> support kcfi at all. I gave up there, but I don't see how this would not

I asked Nathan to add libclang a few days ago, and he very quickly did
it for LLVM 18 -- though I don't know the plan for the others. I just
pinged in that thread.

Cheers,
Miguel
Conor Dooley Feb. 27, 2024, 1:02 p.m. UTC | #4 
On Tue, Feb 27, 2024 at 01:34:14PM +0100, Miguel Ojeda wrote:
> On Tue, Feb 27, 2024 at 11:54 AM Conor Dooley
> <conor.dooley@microchip.com> wrote:
> >
> > I did try to test it but I ran into too many toolchain issues - my
> > older copies of LLVM (pre 17) are not multiarch as I built them by hand
> > with PGO for x86 and RISC-V. My LLVM 17 is from kernel.org and has no
> > libclang. And then the copy of LLVM 18 on kernel.org apparently does not
> > support kcfi at all. I gave up there, but I don't see how this would not
> 
> I asked Nathan to add libclang a few days ago, and he very quickly did
> it for LLVM 18 -- though I don't know the plan for the others. I just
> pinged in that thread.

I had actually said it to him on IRC already (although he is CCed here)
but I just noticed that this was my fault - I symlinked incorrectly
after downloading the toolchain. kcfi is detected fine with llvm18.
I'll give testing another try.
Conor Dooley Feb. 27, 2024, 1:30 p.m. UTC | #5 
On Tue, Feb 27, 2024 at 01:02:17PM +0000, Conor Dooley wrote:

> I'll give testing another try.

Yah, it is (as expected) broken on arm64 too:

 CFI failure at do_one_initcall+0xec/0x26c (target: __rust_minimal_init+0x0/0x64; expected type: 0x36b1c5a6)
 Internal error: Oops - CFI: 00000000f2008233 [#1] PREEMPT SMP
 Modules linked in:
 CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.8.0-rc3-00002-g724a75ac9542 #10
 Hardware name: linux,dummy-virt (DT)
 pstate: a0000005 (NzCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
 pc : do_one_initcall+0xec/0x26c
 lr : do_initcall_level+0x8c/0xb0
 sp : ffff80008000bab0
 x29: ffff80008000bda0 x28: 0000000000000000 x27: 0000000000000000
 x26: 0000000000000000 x25: 0000000000000000 x24: 0000000000000000
 x23: 0000000000000000 x22: 0000000000000000 x21: ffff18d941cb0000
 x20: ffffb8f6d6d9f000 x19: ffffb8f6d63e8b18 x18: 0000000000000002
 x17: 0000000036b1c5a6 x16: 00000000d65f03c0 x15: 0000000000000000
 x14: ffff18d9420280b1 x13: 0000000065dde380 x12: 0000000000000017
 x11: 0000000000000000 x10: 0000000000000000 x9 : d4db8c0058e7e300
 x8 : 0000000000000000 x7 : 0000000001f4c18b x6 : 0000000001f4c18b
 x5 : ffffb8f6d6d300a0 x4 : ffff80008000ba78 x3 : ffff18d942019860
 x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffffb8f6d63e8b18
 Call trace:
  do_one_initcall+0xec/0x26c
  do_initcall_level+0x8c/0xb0
  do_initcalls+0x54/0x94
  do_basic_setup+0x68/0x78
  kernel_init_freeable+0x100/0x16c
  kernel_init+0x20/0x1a0
  ret_from_fork+0x10/0x20
 Code: 7298b4d1 72a6d631 6b11021f 54000040 (d4304660) 
 ---[ end trace 0000000000000000 ]---
 note: swapper/0[1] exited with irqs disabled
 note: swapper/0[1] exited with preempt_count 1
 Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
 Kernel Offset: 0x38f655800000 from 0xffff800080000000
 PHYS_OFFSET: 0xffffe72700000000
 CPU features: 0x0,88000203,3c020000,0100421b
 Memory Limit: none
 ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b ]---

Cheers,
Conor.
diff mbox series

Patch

diff --git a/init/Kconfig b/init/Kconfig
index 8d4e836e1b6b..6cf05824859e 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1895,6 +1895,7 @@  config RUST
 	bool "Rust support"
 	depends on HAVE_RUST
 	depends on RUST_IS_AVAILABLE
+	depends on !CFI_CLANG
 	depends on !MODVERSIONS
 	depends on !GCC_PLUGINS
 	depends on !RANDSTRUCT