[Lldb-commits] [lldb] [lldb][FreeBSDKernel] Implement trapframe unwinding (PR #192184)

[Jason Molenda via lldb-commits]

jasonmolenda wrote:

@mchoo7 Hi, please include me in any future PRs related to unwinding like this. The transition between userland and kernel land via a syscall is a processor fault and the fault-catcher function in the kernel saves the register context in memory.  (I work with macOS/Darwin systems and know exactly how it works there, but I expect most systems are similar)  The correct way to get unwinds that cross this boundary are for the fault-catcher routine in the kernel (written in assembly) to have `.cfi` directives expressing where to find the saved register context via a non-volatile (aka callee-preserved) register.  Then the unwinds work cleanly across the system call.  You also see this (and it's more important) in kernel faults / timer interrupts entirely within kernel land.

https://github.com/llvm/llvm-project/pull/192184