Re: [RFC] rust: kernel: Add KUnit tests for ARCH_WARN_ASM bug table emission

[Heiko Carstens]

On Thu, Sep 24, 2026 at 01:15:57PM +0200, Peter Zijlstra wrote:
> Untested thingies for arm64 and s390x.
...
> diff --git a/arch/s390/kernel/traps.c b/arch/s390/kernel/traps.c
> index b6ba4465f59d..8bbb082fd5e3 100644
> --- a/arch/s390/kernel/traps.c
> +++ b/arch/s390/kernel/traps.c
> @@ -26,6 +26,7 @@
>  #include <linux/entry-common.h>
>  #include <linux/kmsan.h>
>  #include <linux/bug.h>
> +#include <linux/uaccess.h>
>  #include <asm/entry-percpu.h>
>  #include <asm/asm-extable.h>
>  #include <asm/irqflags.h>
> @@ -55,7 +56,12 @@ static inline void __user *get_trap_ip(struct pt_regs *regs)
>  #ifdef CONFIG_GENERIC_BUG
>  int is_valid_bugaddr(unsigned long addr)
>  {
> -	return 1;
> +	u16 insn;
> +
> +	if (get_kernel_nofault(insn, (u16 *)addr))
> +		return 0;
> +
> +	return insn == 0x0001 || insn == 0x000e;

I have no idea why anybody wants to do this, but it looks like I'm not
alone :) In any case: the check is wrong.
s390 uses only the monitor call instruction and this should be

	return insn == 0xaf00;

At least it is not possible to set a kprobe on bug instructions, which
would make this "interesting".