Re: [kvm-unit-tests PATCH v2 4/8] s390x: Introduce and use CALL_INT_HANDLER macro

Thomas Huth
2021-02-17T15:56:53Z

On 17/02/2021 15.41, Janosch Frank wrote:
> The ELF ABI dictates that we need to allocate 160 bytes of stack space
> for the C functions we're calling. Since we would need to do that for
> every interruption handler which, combined with the new stack argument
> being saved in GR2, makes cstart64.S look a bit messy.
>
> So let's introduce the CALL_INT_HANDLER macro that handles all of
> that, calls the C interrupt handler and handles cleanup afterwards.
>
> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
> ---
> s390x/cstart64.S | 28 +++++-----------------------
> s390x/macros.S | 17 +++++++++++++++++
> 2 files changed, 22 insertions(+), 23 deletions(-)
>
> diff --git a/s390x/cstart64.S b/s390x/cstart64.S
> index 35d20293..666a9567 100644
> --- a/s390x/cstart64.S
> +++ b/s390x/cstart64.S
> @@ -92,37 +92,19 @@ memsetxc:
>
> .section .text
> pgm_int:
> - SAVE_REGS_STACK
> - lgr %r2, %r15
> - brasl %r14, handle_pgm_int
> - RESTORE_REGS_STACK
> - lpswe GEN_LC_PGM_OLD_PSW
> + CALL_INT_HANDLER handle_pgm_int, GEN_LC_PGM_OLD_PSW
>
> ext_int:
> - SAVE_REGS_STACK
> - lgr %r2, %r15
> - brasl %r14, handle_ext_int
> - RESTORE_REGS_STACK
> - lpswe GEN_LC_EXT_OLD_PSW
> + CALL_INT_HANDLER handle_ext_int, GEN_LC_EXT_OLD_PSW
>
> mcck_int:
> - SAVE_REGS_STACK
> - brasl %r14, handle_mcck_int
> - RESTORE_REGS_STACK
> - lpswe GEN_LC_MCCK_OLD_PSW
> + CALL_INT_HANDLER handle_mcck_int, GEN_LC_MCCK_OLD_PSW
>
> io_int:
> - SAVE_REGS_STACK
> - lgr %r2, %r15
> - brasl %r14, handle_io_int
> - RESTORE_REGS_STACK
> - lpswe GEN_LC_IO_OLD_PSW
> + CALL_INT_HANDLER handle_io_int, GEN_LC_IO_OLD_PSW
>
> svc_int:
> - SAVE_REGS_STACK
> - brasl %r14, handle_svc_int
> - RESTORE_REGS_STACK
> - lpswe GEN_LC_SVC_OLD_PSW
> + CALL_INT_HANDLER handle_svc_int, GEN_LC_SVC_OLD_PSW
>
> .align 8
> initial_psw:
> diff --git a/s390x/macros.S b/s390x/macros.S
> index a7d62c6f..212a3823 100644
> --- a/s390x/macros.S
> +++ b/s390x/macros.S
> @@ -11,6 +11,23 @@
> * David Hildenbrand <david@redhat.com>
> */
> #include <asm/asm-offsets.h>
> +/*
> + * Exception handler macro that saves registers on the stack,
> + * allocates stack space and calls the C handler function. Afterwards
> + * we re-load the registers and load the old PSW.
> + */
> + .macro CALL_INT_HANDLER c_func, old_psw
> + SAVE_REGS_STACK
> + /* Save the stack address in GR2 which is the first function argument */
> + lgr %r2, %r15
> + /* Allocate stack pace for called C function, as specified in s390 ELF ABI */
> + slgfi %r15, 160

By the way, don't you have to store a back chain pointer at the bottom of
that area, too, if you want to use -mbackchoin in the next patch?

Thomas

> + brasl %r14, \c_func
> + algfi %r15, 160
> + RESTORE_REGS_STACK
> + lpswe \old_psw
> + .endm
> +
> .macro SAVE_REGS
> /* save grs 0-15 */
> stmg %r0, %r15, GEN_LC_SW_INT_GRS
>