Re: [kvm-unit-tests PATCH 3/8] lib: s390x: Print addressing related exception information

[Claudio Imbrenda <imbrenda@linux.ibm.com>]

On Fri, 13 Aug 2021 07:36:10 +0000
Janosch Frank <frankja@linux.ibm.com> wrote:

> Right now we only get told the kind of program exception as well as
> the PSW at the point where it happened.
> 
> For addressing exceptions the PSW is not always enough so let's print
> the TEID which contains the failing address and flags that tell us
> more about the kind of address exception.
> 
> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
> ---
>  lib/s390x/asm/arch_def.h |  4 +++
>  lib/s390x/interrupt.c    | 72
> ++++++++++++++++++++++++++++++++++++++++ 2 files changed, 76
> insertions(+)
> 
> diff --git a/lib/s390x/asm/arch_def.h b/lib/s390x/asm/arch_def.h
> index 4ca02c1d..39c5ba99 100644
> --- a/lib/s390x/asm/arch_def.h
> +++ b/lib/s390x/asm/arch_def.h
> @@ -41,6 +41,10 @@ struct psw {
>  	uint64_t	addr;
>  };
>  
> +/* Let's ignore spaces we don't expect to use for now. */
> +#define AS_PRIM				0
> +#define AS_HOME				3
> +
>  #define PSW_MASK_EXT			0x0100000000000000UL
>  #define PSW_MASK_IO			0x0200000000000000UL
>  #define PSW_MASK_DAT			0x0400000000000000UL
> diff --git a/lib/s390x/interrupt.c b/lib/s390x/interrupt.c
> index 01ded49d..1248bceb 100644
> --- a/lib/s390x/interrupt.c
> +++ b/lib/s390x/interrupt.c
> @@ -12,6 +12,7 @@
>  #include <sclp.h>
>  #include <interrupt.h>
>  #include <sie.h>
> +#include <asm/page.h>
>  
>  static bool pgm_int_expected;
>  static bool ext_int_expected;
> @@ -126,6 +127,73 @@ static void fixup_pgm_int(struct stack_frame_int
> *stack) /* suppressed/terminated/completed point already at the next
> address */ }
>  
> +static void decode_pgm_prot(uint64_t teid)

it is actually more complicated than this.

if you don't want to add all the possibilities because they are
unlikely and/or not relevant, maybe add a comment

> +{
> +	/* Low-address protection exception, 100 */
> +	if (test_bit_inv(56, &teid) && !test_bit_inv(60, &teid) &&
> !test_bit_inv(61, &teid)) {
> +		printf("Type: LAP\n");
> +		return;
> +	}
> +
> +	/* Instruction execution prevention, i.e. no-execute, 101 */
> +	if (test_bit_inv(56, &teid) && !test_bit_inv(60, &teid) &&
> test_bit_inv(61, &teid)) {
> +		printf("Type: IEP\n");
> +		return;
> +	}
> +
> +	/* Standard DAT exception, 001 */
> +	if (!test_bit_inv(56, &teid) && !test_bit_inv(60, &teid) &&
> test_bit_inv(61, &teid)) {
> +		printf("Type: DAT\n");
> +		return;
> +	}
> +}
> +
> +static void decode_teid(uint64_t teid)
> +{
> +	int asce_id = lc->trans_exc_id & 3;
> +	bool dat = lc->pgm_old_psw.mask & PSW_MASK_DAT;
> +
> +	printf("Memory exception information:\n");
> +	printf("TEID: %lx\n", teid);
> +	printf("DAT: %s\n", dat ? "on" : "off");
> +	printf("AS: %s\n", asce_id == AS_PRIM ? "Primary" : "Home");
> +
> +	if (lc->pgm_int_code == PGM_INT_CODE_PROTECTION)
> +		decode_pgm_prot(teid);
> +
> +	/*
> +	 * If teid bit 61 is off for these two exception the reported
> +	 * address is unpredictable.
> +	 */
> +	if ((lc->pgm_int_code == PGM_INT_CODE_SECURE_STOR_ACCESS ||
> +	     lc->pgm_int_code == PGM_INT_CODE_SECURE_STOR_VIOLATION)
> &&
> +	    !test_bit_inv(61, &teid)) {
> +		printf("Address: %lx, unpredictable\n ", teid &
> PAGE_MASK);
> +		return;
> +	}
> +	printf("Address: %lx\n\n", teid & PAGE_MASK);
> +}
> +
> +static void print_storage_exception_information(void)
> +{
> +	switch (lc->pgm_int_code) {
> +	case PGM_INT_CODE_PROTECTION:
> +	case PGM_INT_CODE_PAGE_TRANSLATION:
> +	case PGM_INT_CODE_SEGMENT_TRANSLATION:
> +	case PGM_INT_CODE_ASCE_TYPE:
> +	case PGM_INT_CODE_REGION_FIRST_TRANS:
> +	case PGM_INT_CODE_REGION_SECOND_TRANS:
> +	case PGM_INT_CODE_REGION_THIRD_TRANS:
> +	case PGM_INT_CODE_SECURE_STOR_ACCESS:
> +	case PGM_INT_CODE_NON_SECURE_STOR_ACCESS:
> +	case PGM_INT_CODE_SECURE_STOR_VIOLATION:
> +		decode_teid(lc->trans_exc_id);
> +		break;
> +	default:
> +		return;
> +	}
> +}
> +
>  static void print_int_regs(struct stack_frame_int *stack)
>  {
>  	printf("\n");
> @@ -155,6 +223,10 @@ static void print_pgm_info(struct
> stack_frame_int *stack) lc->pgm_int_code, stap(),
> lc->pgm_old_psw.addr, lc->pgm_int_id); print_int_regs(stack);
>  	dump_stack();
> +
> +	/* Dump stack doesn't end with a \n so we add it here
> instead */
> +	printf("\n");
> +	print_storage_exception_information();
>  	report_summary();
>  	abort();
>  }