[PATCH 00/10] arm64: stacktrace: improve unwind reporting

[Mark Rutland]

On Fri, Oct 11, 2024 at 05:19:15PM +0200, Miroslav Benes wrote:
> On Thu, 10 Oct 2024, Mark Rutland wrote:
> 
> > This series improves arm64's unwinder to explicitly identify exception
> > boundaries, reporting both pt_regs::pc and pt_regs::lr and explicitly
> > identifying the source of elements in the stacktrace. This is useful to
> > humans when reviewing a stacktrace, and serves as infrastructure that
> > can be used for RELIABLE_STACKTRACE in future.

[...]

> > ... where:
> > 
> > * "C" indicates that the first element of the trace was the caller of an unwind
> >   function (vs "T" for a blocked task's stave PC, or "P" for a pt_regs::pc).

Ugh, s/stave/saved/, at least that was correct in the actual commit
message that introduced it.

[...]

> >   arm64: pt_regs: assert pt_regs is a multiple of 16 bytes
> >   arm64: pt_regs: remove stale big-endian layout
> >   arm64: pt_regs: rename "pmr_save" -> "pmr"
> >   arm64: pt_regs: swap 'unused' and 'pmr' fields
> >   arm64: use a common struct frame_record
> >   arm64: stacktrace: move dump_backtrace() to kunwind_stack_walk()
> >   arm64: stacktrace: report source of unwind data
> >   arm64: stacktrace: report recovered PCs
> >   arm64: stacktrace: split unwind_consume_stack()
> >   arm64: stacktrace: unwind exception boundaries
> > 
> >  arch/arm64/include/asm/daifflags.h         |   2 +-
> >  arch/arm64/include/asm/processor.h         |   2 +-
> >  arch/arm64/include/asm/ptrace.h            |  22 ++-
> >  arch/arm64/include/asm/stacktrace/common.h |  74 +++++----
> >  arch/arm64/include/asm/stacktrace/frame.h  |  48 ++++++
> >  arch/arm64/kernel/asm-offsets.c            |   3 +-
> >  arch/arm64/kernel/entry.S                  |  16 +-
> >  arch/arm64/kernel/head.S                   |   3 +
> >  arch/arm64/kernel/probes/stBV5U5j          |   0
> >  arch/arm64/kernel/process.c                |   5 +-
> >  arch/arm64/kernel/signal.c                 |   5 -
> >  arch/arm64/kernel/stacktrace.c             | 176 +++++++++++++++++++--
> >  12 files changed, 287 insertions(+), 69 deletions(-)
> >  create mode 100644 arch/arm64/include/asm/stacktrace/frame.h
> 
> Very nice!
> 
> Reviewed-by: Miroslav Benes <mbenes at suse.cz>

Thanks!

> >  create mode 100644 arch/arm64/kernel/probes/stBV5U5j
> 
> but this should probably disappear :)

Ack; gone.

I'll hold off sending a v2 with the fixups until middle/late next week
so that people get a chance to respond with anything more significant
and so that I can look over this with fresh eyes and clear out any more
typos...

In the mean time I've pushed out the fixed-up version to:

  https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git/log/?h=arm64/stacktrace/metadata

Mark.