Nit: I think the subject needs to be updated (I assume this was written
before Nick's fix?).
On Wed, Mar 09, 2022 at 12:45:37PM -0800, Kees Cook wrote:
> Unfortunately, Clang did not have support for "sp" as a global register
> definition, and was crashing after the addition of current_stack_pointer.
> This has been fixed in Clang 15, but earlier Clang versions need to
> avoid this code, so add a versioned test and revert back to the
> open-coded asm instances. Fixes Clang build error:
>
> fatal error: error in backend: Invalid register name global variable
>
> Fixes: 200ed341b864 ("mips: Implement "current_stack_pointer"")
> Reported-by: Nathan Chancellor <nathan@xxxxxxxxxx>
> Cc: Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx>
> Cc: Marc Zyngier <maz@xxxxxxxxxx>
> Cc: Guenter Roeck <linux@xxxxxxxxxxxx>
> Cc: Yanteng Si <siyanteng01@xxxxxxxxx>
> Cc: linux-mips@xxxxxxxxxxxxxxx
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Thanks for sending this!
Reviewed-by: Nathan Chancellor <nathan@xxxxxxxxxx>
> ---
> arch/mips/Kconfig | 2 +-
> arch/mips/include/asm/thread_info.h | 2 ++
> arch/mips/kernel/irq.c | 3 ++-
> arch/mips/lib/uncached.c | 4 +++-
> 4 files changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
> index 3f58b45fc953..15769013f46e 100644
> --- a/arch/mips/Kconfig
> +++ b/arch/mips/Kconfig
> @@ -4,7 +4,7 @@ config MIPS
> default y
> select ARCH_32BIT_OFF_T if !64BIT
> select ARCH_BINFMT_ELF_STATE if MIPS_FP_SUPPORT
> - select ARCH_HAS_CURRENT_STACK_POINTER
> + select ARCH_HAS_CURRENT_STACK_POINTER if !CC_IS_CLANG || CLANG_VERSION >= 150000
Nit: This can be 140000, as release/14.x has received the fix:
https://github.com/llvm/llvm-project/commit/0826716786cd4a8c7cbcb8c01e4d9fac46b7a17a
> select ARCH_HAS_DEBUG_VIRTUAL if !64BIT
> select ARCH_HAS_FORTIFY_SOURCE
> select ARCH_HAS_KCOV
> diff --git a/arch/mips/include/asm/thread_info.h b/arch/mips/include/asm/thread_info.h
> index 4463348d2372..ecae7470faa4 100644
> --- a/arch/mips/include/asm/thread_info.h
> +++ b/arch/mips/include/asm/thread_info.h
> @@ -69,7 +69,9 @@ static inline struct thread_info *current_thread_info(void)
> return __current_thread_info;
> }
>
> +#ifdef CONFIG_ARCH_HAS_CURRENT_STACK_POINTER
> register unsigned long current_stack_pointer __asm__("sp");
> +#endif
>
> #endif /* !__ASSEMBLY__ */
>
> diff --git a/arch/mips/kernel/irq.c b/arch/mips/kernel/irq.c
> index fc313c49a417..5e11582fe308 100644
> --- a/arch/mips/kernel/irq.c
> +++ b/arch/mips/kernel/irq.c
> @@ -75,8 +75,9 @@ void __init init_IRQ(void)
> #ifdef CONFIG_DEBUG_STACKOVERFLOW
> static inline void check_stack_overflow(void)
> {
> - unsigned long sp = current_stack_pointer;
> + unsigned long sp;
>
> + __asm__ __volatile__("move %0, $sp" : "=r" (sp));
> sp &= THREAD_MASK;
>
> /*
> diff --git a/arch/mips/lib/uncached.c b/arch/mips/lib/uncached.c
> index f8d4ca046c3e..f80a67c092b6 100644
> --- a/arch/mips/lib/uncached.c
> +++ b/arch/mips/lib/uncached.c
> @@ -40,7 +40,9 @@ unsigned long run_uncached(void *func)
> register long ret __asm__("$2");
> long lfunc = (long)func, ufunc;
> long usp;
> - long sp = current_stack_pointer;
> + long sp;
> +
> + __asm__("move %0, $sp" : "=r" (sp));
>
> if (sp >= (long)CKSEG0 && sp < (long)CKSEG2)
> usp = CKSEG1ADDR(sp);
> --
> 2.32.0
>
