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

Janosch Frank
2021-02-17T16:23:18Z

On 2/17/21 4:55 PM, Thomas Huth wrote:
> 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?

Don't I already do that in #2?

+ /* Store the gr15 value before we allocated the new stack */

+ lgr %r0, %r15

+ algfi %r0, 32 * 8 + 4 * 8

+ stg %r0, 13 * 8 + STACK_FRAME_INT_GRS0(%r15)

+ stg %r0, STACK_FRAME_INT_BACKCHAIN(%r15)

I can vertainly move the hunk here and improve the comment.

>
> 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
>>
>