[Lldb-commits] [PATCH] D66638: Unwind: Add a stack scanning mechanism to support win32 unwinding

[Greg Clayton via Phabricator via lldb-commits]

clayborg added a comment.

So made a "sbt" command in a Python module as a way to get a backtrace when our backtracing fails because Android almost never makes it back to the first frame for any stacks. This code just grabs the current SP, looks up the memory region using the SP, and then it uses this as the address range (current SP back to the base of the stack) to scan for any pointers with an address aligned address that falls into executable sections. What it doesn't do, is to try and backup one instruction from the potential RA values to see if there is a branch to the current function. This avoids having to know anything about stack parameter sizes and just scan the stack for all executable memory region pointers, and then ask each architecture to backup one instruction from each proposed RA and see if there is a function call to the current function. For ARM this is easy: backup by 4 for ARM and 2 or 4 for Thumb and see if there is a branch and link. For x64, it would be trickier, but it might be as easy as backup up by 1 + address size and looking for a callq. If we can successfully do this, we could really improve stack backtracing for all architectures and OSs. Thoughts?


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  https://reviews.llvm.org/D66638/new/

https://reviews.llvm.org/D66638