Re: [PATCH 07/32] s390/traps: Handle nullifying program checks in get_trap_ip()

[Ilya Leoshkevich]

On 10/1/26 12:32, Heiko Carstens wrote:
> get_trap_ip() always rewinds the PSW address by the instruction length
> from the interruption code. For nullifying program checks the PSW
> already points at the faulting instruction, so rewinding is wrong.
>
> Add a nullified[] bitmap and return the unchanged PSW address for
> nullifying cases, or if PIF_PSW_ADDR_ADJUSTED is set.
>
> No functional change for existing callers, which only deal with
> suppressing, terminating, or completing program checks.
>
> Signed-off-by: Heiko Carstens <hca@xxxxxxxxxxxxx>
> ---
>   arch/s390/kernel/traps.c | 21 +++++++++++++--------
>   1 file changed, 13 insertions(+), 8 deletions(-)
>
> diff --git a/arch/s390/kernel/traps.c b/arch/s390/kernel/traps.c
> index bfcab4592299..5e63032a56db 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 <asm/pgmcheck-defs.h>
>   #include <asm/entry-percpu.h>
>   #include <asm/asm-extable.h>
>   #include <asm/irqflags.h>
> @@ -41,15 +42,19 @@ struct pgm_stat {
>   
>   static DEFINE_PER_CPU_SHARED_ALIGNED(struct pgm_stat, pgm_stat);
>   
> -static inline void __user *get_trap_ip(struct pt_regs *regs)
> +static inline unsigned long get_trap_ip(struct pt_regs *regs)
>   {
> -	unsigned long address;
> +	static const unsigned long nullified[2] = { PGM_CHECKS_NULLIFIED };

Maybe just [], to deal with the possibility of expansion in the future?

[...]

> @@ -152,7 +157,7 @@ static void illegal_op(struct pt_regs *regs)
>   	int signal = 0;
>   	u16 opcode;
>   
> -	location = get_trap_ip(regs);
> +	location = (void __user *)get_trap_ip(regs);

Should location be moved inside the "if"? Now it reads weirdly: we cast
the pointer to __user before checking for user mode.

>   	if (user_mode(regs)) {
>   		if (get_user(opcode, location))
>   			return;

Regardless:

Reviewed-by: Ilya Leoshkevich <iii@xxxxxxxxxxxxx>