Re: [kvm-unit-tests PATCH v2 1/3] lib: s390x: Print addressing related exception information

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

On Fri, 20 Aug 2021 11:39:58 +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>

Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>

(but see a small nit below)

> ---
>  lib/s390x/asm/arch_def.h |  5 +++
>  lib/s390x/fault.c        | 76 ++++++++++++++++++++++++++++++++++++++++
>  lib/s390x/fault.h        | 44 +++++++++++++++++++++++
>  lib/s390x/interrupt.c    | 29 +++++++++++++--
>  s390x/Makefile           |  1 +
>  5 files changed, 153 insertions(+), 2 deletions(-)
>  create mode 100644 lib/s390x/fault.c
>  create mode 100644 lib/s390x/fault.h
> 
> diff --git a/lib/s390x/asm/arch_def.h b/lib/s390x/asm/arch_def.h
> index 302ef1ff..ab5a9043 100644
> --- a/lib/s390x/asm/arch_def.h
> +++ b/lib/s390x/asm/arch_def.h
> @@ -41,6 +41,11 @@ struct psw {
>  	uint64_t	addr;
>  };
>  
> +#define AS_PRIM				0
> +#define AS_ACCR				1
> +#define AS_SECN				2
> +#define AS_HOME				3
> +
>  #define PSW_MASK_EXT			0x0100000000000000UL
>  #define PSW_MASK_IO			0x0200000000000000UL
>  #define PSW_MASK_DAT			0x0400000000000000UL
> diff --git a/lib/s390x/fault.c b/lib/s390x/fault.c
> new file mode 100644
> index 00000000..fd1490e3
> --- /dev/null
> +++ b/lib/s390x/fault.c
> @@ -0,0 +1,76 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Library to decode addressing related exceptions
> + *
> + * Copyright 2021 IBM Corp.
> + *
> + * Authors:
> + *    Janosch Frank <frankja@linux.ibm.com>
> + */
> +#include <libcflat.h>
> +#include <bitops.h>
> +#include <asm/arch_def.h>
> +#include <asm/page.h>
> +#include <fault.h>
> +
> +static struct lowcore *lc = (struct lowcore *)0x0;
> +
> +/* Decodes the protection exceptions we'll most likely see */
> +static void decode_pgm_prot(uint64_t teid)

I think this is also a "print_decode_pgm_prot", but it's static
so I guess we don't really care too much

> +{
> +	if (prot_is_lap(teid)) {
> +		printf("Type: LAP\n");
> +		return;
> +	}
> +
> +	if (prot_is_iep(teid)) {
> +		printf("Type: IEP\n");
> +		return;
> +	}
> +
> +	if (prot_is_datp(teid)) {
> +		printf("Type: DAT\n");
> +		return;
> +	}
> +}
> +
> +void print_decode_teid(uint64_t teid)
> +{
> +	int asce_id = teid & 3;
> +	bool dat = lc->pgm_old_psw.mask & PSW_MASK_DAT;
> +
> +	printf("Memory exception information:\n");
> +	printf("DAT: %s\n", dat ? "on" : "off");
> +
> +	printf("AS: ");
> +	switch (asce_id) {
> +	case AS_PRIM:
> +		printf("Primary\n");
> +		break;
> +	case AS_ACCR:
> +		printf("Access Register\n");
> +		break;
> +	case AS_SECN:
> +		printf("Secondary\n");
> +		break;
> +	case AS_HOME:
> +		printf("Home\n");
> +		break;
> +	}
> +
> +	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("TEID: %lx\n", teid);
> +	printf("Address: %lx\n\n", teid & PAGE_MASK);
> +}
> diff --git a/lib/s390x/fault.h b/lib/s390x/fault.h
> new file mode 100644
> index 00000000..726da2f0
> --- /dev/null
> +++ b/lib/s390x/fault.h
> @@ -0,0 +1,44 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +/*
> + * Headers for fault.c
> + *
> + * Copyright 2021 IBM Corp.
> + *
> + * Authors:
> + *    Janosch Frank <frankja@linux.ibm.com>
> + */
> +#ifndef _S390X_FAULT_H_
> +#define _S390X_FAULT_H_
> +
> +#include <bitops.h>
> +
> +/* Instruction execution prevention, i.e. no-execute, 101 */
> +static inline bool prot_is_iep(uint64_t teid)
> +{
> +	if (test_bit_inv(56, &teid) && !test_bit_inv(60, &teid) && test_bit_inv(61, &teid))
> +		return true;
> +
> +	return false;
> +}
> +
> +/* Standard DAT exception, 001 */
> +static inline bool prot_is_datp(uint64_t teid)
> +{
> +	if (!test_bit_inv(56, &teid) && !test_bit_inv(60, &teid) && test_bit_inv(61, &teid))
> +		return true;
> +
> +	return false;
> +}
> +
> +/* Low-address protection exception, 100 */
> +static inline bool prot_is_lap(uint64_t teid)
> +{
> +	if (test_bit_inv(56, &teid) && !test_bit_inv(60, &teid) && !test_bit_inv(61, &teid))
> +		return true;
> +
> +	return false;
> +}
> +
> +void print_decode_teid(uint64_t teid);
> +
> +#endif /* _S390X_FAULT_H_ */
> diff --git a/lib/s390x/interrupt.c b/lib/s390x/interrupt.c
> index 01ded49d..721e6758 100644
> --- a/lib/s390x/interrupt.c
> +++ b/lib/s390x/interrupt.c
> @@ -12,6 +12,8 @@
>  #include <sclp.h>
>  #include <interrupt.h>
>  #include <sie.h>
> +#include <fault.h>
> +#include <asm/page.h>
>  
>  static bool pgm_int_expected;
>  static bool ext_int_expected;
> @@ -76,8 +78,7 @@ static void fixup_pgm_int(struct stack_frame_int *stack)
>  		break;
>  	case PGM_INT_CODE_PROTECTION:
>  		/* Handling for iep.c test case. */
> -		if (lc->trans_exc_id & 0x80UL && lc->trans_exc_id & 0x04UL &&
> -		    !(lc->trans_exc_id & 0x08UL))
> +		if (prot_is_iep(lc->trans_exc_id))
>  			/*
>  			 * We branched to the instruction that caused
>  			 * the exception so we can use the return
> @@ -126,6 +127,26 @@ static void fixup_pgm_int(struct stack_frame_int *stack)
>  	/* suppressed/terminated/completed point already at the next address */
>  }
>  
> +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:
> +		print_decode_teid(lc->trans_exc_id);
> +		break;
> +	default:
> +		return;
> +	}
> +}
> +
>  static void print_int_regs(struct stack_frame_int *stack)
>  {
>  	printf("\n");
> @@ -155,6 +176,10 @@ 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();
>  }
> diff --git a/s390x/Makefile b/s390x/Makefile
> index ef8041a6..5d1a33a0 100644
> --- a/s390x/Makefile
> +++ b/s390x/Makefile
> @@ -72,6 +72,7 @@ cflatobjs += lib/s390x/css_lib.o
>  cflatobjs += lib/s390x/malloc_io.o
>  cflatobjs += lib/s390x/uv.o
>  cflatobjs += lib/s390x/sie.o
> +cflatobjs += lib/s390x/fault.o
>  
>  OBJDIRS += lib/s390x
>