Re: [PATCH 08/32] s390/dis: Improve show_code() output

[Ilya Leoshkevich <iii@linux.ibm.com>]

On 10/1/26 12:32, Heiko Carstens wrote:
> Replace the '>' and '*' instruction markers with explicit 'PSW >' and
> 'PGM >' markers which identify both the PSW address and the faulting
> instruction.
> 
> Previously, '>' marked the PSW address, while '*' marked the preceding
> instruction as a guess for the faulting instruction for suppressing
> exceptions:
> 
>   Krnl Code:
>              000003ff8dc7bff8: e310f0080004 lg      %r1,8(%r15)
>             *000003ff8dc7bffe: e3a0e0000004 lg      %r10,0(%r14)
>             >000003ff8dc7c004: a7280000     lhi     %r2,0
>              000003ff8dc7c008: eb9ff0900024 stmg    %r9,%r15,144(%r15)
> 
> Now 'PGM >' explicitly marks the faulting instruction without guessing
> and 'PSW >' marks the PSW address:
> 
>   Krnl Code:
>              000003ff8dc7bff8: e310f0080004 lg      %r1,8(%r15)
>         PGM >000003ff8dc7bffe: e3a0e0000004 lg      %r10,0(%r14)
>         PSW >000003ff8dc7c004: a7280000     lhi     %r2,0
>              000003ff8dc7c008: eb9ff0900024 stmg    %r9,%r15,144(%r15)
> 
> For nullifying exceptions where both addresses are the same,
> 'PGM+PSW >' is printed instead:
> 
>   Krnl Code:
>              000003ff8dc7bff8: e310f0080004 lg      %r1,8(%r15)
>     PGM+PSW >000003ff8dc7bffe: e3a0e0000004 lg      %r10,0(%r14)
>              000003ff8dc7c004: a7280000     lhi     %r2,0
>              000003ff8dc7c008: eb9ff0900024 stmg    %r9,%r15,144(%r15)
> 
> show_code() may also be called in other contexts where pt_regs does not
> originate from a program check (e.g. system calls). Introduce and set
> PIF_PGM_CHECK to indicate when in program check context, and print the
> PGM marker only in such a context.
> 
> Note that corner cases are not taken into account. Like before kprobes is
> not considered, which means that the disassembly may contain unexpected
> instructions, or that disassembly and/or instruction length count as well
> as interruption do not match.
> 
> Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
> ---
>   arch/s390/include/asm/ptrace.h |  4 ++++
>   arch/s390/kernel/dis.c         | 16 +++++++++++-----
>   arch/s390/kernel/early.c       |  1 +
>   arch/s390/kernel/traps.c       |  4 +++-
>   4 files changed, 19 insertions(+), 6 deletions(-)

Reviewed-by: Ilya Leoshkevich <iii@linux.ibm.com>