[Lldb-commits] [PATCH] D61733: Breakpad: Generate unwind plans from STACK CFI records

[Pavel Labath via Phabricator via lldb-commits]

labath created this revision.
labath added reviewers: amccarth, clayborg, markmentovai.
Herald added a subscriber: aprantl.

This patch implements the GetUnwindPlan interface (added in the previous
patch) for SymbolFileBreakpad, and uses it to generate unwind plans from
STACK CFI records in breakpad files.

We first perform a light-weight parse of the breakpad in order to build
up a map of regions covered by the unwind info so that we can later jump
to the right record when we need to unwind a specific function.

The actual parsing is relatively straight-forward, as the STACK CFI records
are just another (text) form of the eh_frame unwind instructions, and
the same goes for lldb's UnwindPlans. The newly-introduced
PostfixExpression API is used to convert the breakpad postfix
expressions into DWARF. The generated dwarf expressions are stored in a
BumpPtrAllocator, as the UnwindPlan does not take ownership of the
expression data it references (usually this is static data in an object
file, so special ownership is needed).

At this moment the generated unwind plans aren't used in the actual
unwind machinery (only in the image show-unwind command), but that is
coming in a separate patch.


https://reviews.llvm.org/D61733

Files:
  lit/SymbolFile/Breakpad/Inputs/stack-cfi-parsing.dmp
  lit/SymbolFile/Breakpad/Inputs/stack-cfi-parsing.syms
  lit/SymbolFile/Breakpad/stack-cfi-parsing.test
  source/Plugins/SymbolFile/Breakpad/SymbolFileBreakpad.cpp
  source/Plugins/SymbolFile/Breakpad/SymbolFileBreakpad.h

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