Re: [PATCH v5] ARM: imx: Fix suspend/resume crash with Clang CFI

On Sun, Aug 30, 2026 at 8:51 AM Yo'av Moshe [off-list ref] wrote:

The suspend code that runs from OCRAM is copied there with fncpy(),
which does not copy the kCFI type hash preceding the function. With
CONFIG_CFI=y the indirect call through imx6_suspend_in_ocram_fn
therefore panics.

Keep the call covered by CFI instead of exempting it:

- Add SYM_TYPED_FUNC_START_ALIGNED(), a variant of
  SYM_TYPED_FUNC_START() that aligns the function entry rather than
  the type hash preceding it, and use it to declare imx6_suspend():
  fncpy() requires the entry point of the function it copies to be
  8-byte aligned. The macro lives in arch/arm/include/asm/linkage.h
  since the requirement comes from arm's fncpy().

- Add a cfi_type member at the end of struct imx6_cpu_pm_info, which
  directly precedes the OCRAM copy of the function. It fits in the
  struct's tail padding, so no sizes or offsets change. Fill it using
  cfi_get_func_hash(), putting the hash where the caller's CFI check
  expects it: four bytes before the function entry.

Also mark ccm_base, suspend_ocram_base and imx6_suspend_in_ocram_fn
as __ro_after_init: they are only written during __init, and the
function pointer in particular should not be writable afterwards.

Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Yo'av Moshe <redacted>

Reviewed-by: Sami Tolvanen <samitolvanen@google.com>

Sami