On 1/27/21 8:02 AM, Madhavan T. Venkataraman wrote:

On 10/12/20 12:26 PM, Mark Brown wrote:

quoted

This patch series aims to implement reliable stacktrace for arm64. 
Reliable stacktrace exists mainly to support live patching, it provides
a version of stacktrace that checks for consistency problems in the
traces it generates and provides an error code to callers indicating if
any problems were detected.      

This is a first cut of support for arm64, I've not really even started
testing it meaningfully at this point.  The main thing I'm looking for
here is that I'm not sure if there are any more potential indicators of
unrelabile stacks that I'm missing tests for or anything about the
interfaces that I've misunderstood.

There's more work that can be done here, mainly that we could sync our
unwinder more with what's done on S/390 and x86 which should if nothing
else help with keeping up to date with generic changes, but this should 
be what's needed to allow reliable stack trace.

Mark Brown (2):
  arm64: stacktrace: Report when we reach the end of the stack
  arm64: stacktrace: Implement reliable stacktrace

Mark Rutland (1):
  arm64: remove EL0 exception frame record

 arch/arm64/Kconfig             |  1 +
 arch/arm64/kernel/entry.S      | 10 +++----
 arch/arm64/kernel/stacktrace.c | 55 ++++++++++++++++++++++++++++------
 3 files changed, 52 insertions(+), 14 deletions(-)

This is mostly a question to improve my understanding of the current ARM64
unwinder.

Currently, ARM64 defines different stack types - task stack, IRQ stack, etc.
When it unwinds, it appears to unwind only the currently active stack.
Specifically, if an interrupt has happened and the IRQ stack is the one that
is active, only the IRQ stack is unwound. The task stack is not. Is this
accurate?

My question is - for live patching, we would need to look at the task stack
as well, right? May be, we need to pass a flag to the unwinder to check the
task stack in addition to the active task?

Typo - I meant to say "active stack" at the end of the question.
Sorry about that.

Madhavan

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