On 2/9/21 7:51 PM, Claudio Imbrenda wrote:
> In most testcases, we enter problem state (userspace) just to test if a
> privileged instruction causes a fault. In some cases, though, we need
> to test if an instruction works properly in userspace. This means that
> we do not expect a fault, and we need an orderly way to leave problem
> state afterwards.
>
> This patch introduces a simple system based on the SVC instruction.
>
> Signed-off-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
> ---
> lib/s390x/asm/arch_def.h | 5 +++++
> lib/s390x/interrupt.c | 12 ++++++++++--
> 2 files changed, 15 insertions(+), 2 deletions(-)
>
> diff --git a/lib/s390x/asm/arch_def.h b/lib/s390x/asm/arch_def.h
> index 9c4e330a..9902e9fe 100644
> --- a/lib/s390x/asm/arch_def.h
> +++ b/lib/s390x/asm/arch_def.h
> @@ -276,6 +276,11 @@ static inline void enter_pstate(void)
> load_psw_mask(mask);
> }
>
> +static inline void leave_pstate(void)
> +{
> + asm volatile(" svc 1\n");
Magic constants being magic :-)
> +}
> +
> static inline int stsi(void *addr, int fc, int sel1, int sel2)
> {
> register int r0 asm("0") = (fc << 28) | sel1;
> diff --git a/lib/s390x/interrupt.c b/lib/s390x/interrupt.c
> index 1ce36073..59e01b1a 100644
> --- a/lib/s390x/interrupt.c
> +++ b/lib/s390x/interrupt.c
> @@ -188,6 +188,14 @@ int unregister_io_int_func(void (*f)(void))
>
> void handle_svc_int(void)
> {
> - report_abort("Unexpected supervisor call interrupt: on cpu %d at %#lx",
> - stap(), lc->svc_old_psw.addr);
> + uint16_t code = lc->svc_int_code;
> +
> + switch (code) {
> + case 1:
> + lc->svc_old_psw.mask &= ~PSW_MASK_PSTATE;
> + break;
> + default:
> + report_abort("Unexpected supervisor call interrupt: code %#x on cpu %d at %#lx",
> + code, stap(), lc->svc_old_psw.addr);
> + }
> }
>
