[all-commits] [llvm/llvm-project] 4b2b8b: Re-land Unwind past an interrupt handler correctly...

[Jason Molenda via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 4b2b8b96db2837a95e8c3ceca3f31ac5641ca001
      https://github.com/llvm/llvm-project/commit/4b2b8b96db2837a95e8c3ceca3f31ac5641ca001
  Author: Jason Molenda <jmolenda at apple.com>
  Date:   2020-02-25 (Tue, 25 Feb 2020)

  Changed paths:
    M lldb/source/Plugins/Process/Utility/RegisterContextLLDB.cpp

  Log Message:
  -----------
  Re-land Unwind past an interrupt handler correctly on arm or at pc==0

Updated the patch to only fetch $pc on a Return Address-using
target only if we're in a trap frame *and* if there is a saved
location for $pc in the trap frame's unwind rules.  If not,
we fall back to fetching the Return Address register (eg $lr).

Original commit msg:

    Unwind past an interrupt handler correctly on arm or at pc==0

    Fix RegisterContextLLDB::InitializeNonZerothFrame so that it
    will fetch a FullUnwindPlan instead of falling back to the
    architectural default unwind plan -- GetFullUnwindPlan knows
    how to spot a jmp 0x0 that results in a fault, which may be
    the case when we see a trap handler on the stack.

    Fix RegisterContextLLDB::SavedLocationForRegister so that when
    the pc value is requested from a trap handler frame, where we
    have a complete register context available to us, don't provide
    the Return Address register (lr) instead of the pc.  We have
    an actual pc value here, and it's pointing to the instruction
    that faulted.

    Differential revision: https://reviews.llvm.org/D75007
    <rdar://problem/59416588>