[all-commits] [llvm/llvm-project] fd1bd5: [lldb/aarch64] Fix unwinding when signal interrupt...

[Pavel Labath via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: fd1bd53ba5a06f344698a55578f6a5d79c457e30
      https://github.com/llvm/llvm-project/commit/fd1bd53ba5a06f344698a55578f6a5d79c457e30
  Author: Pavel Labath <pavel at labath.sk>
  Date:   2024-05-09 (Thu, 09 May 2024)

  Changed paths:
    M lldb/source/Plugins/Instruction/ARM64/EmulateInstructionARM64.cpp
    M lldb/source/Plugins/UnwindAssembly/InstEmulation/UnwindAssemblyInstEmulation.cpp
    M lldb/source/Target/RegisterContextUnwind.cpp
    A lldb/test/Shell/Unwind/Inputs/signal-in-leaf-function-aarch64.c
    A lldb/test/Shell/Unwind/signal-in-leaf-function-aarch64.test
    M lldb/unittests/UnwindAssembly/ARM64/TestArm64InstEmulation.cpp

  Log Message:
  -----------
  [lldb/aarch64] Fix unwinding when signal interrupts a leaf function (#91321)

A leaf function may not store the link register to stack, but we it can
still end up being a non-zero frame if it gets interrupted by a signal.
Currently, we were unable to unwind past this function because we could
not read the link register value.

To make this work, this patch:
- changes the function-entry unwind plan to include the `fp|lr = <same>`
rules. This in turn necessitated an adjustment in the generic
instruction emulation logic to ensure that `lr=[sp-X]` can override the
`<same>` rule.
- allows the `<same>` rule for pc and lr in all
`m_all_registers_available` frames (and not just frame zero).

The test verifies that we can unwind in a situation like this, and that
the backtrace matches the one we computed before getting a signal.



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