On Sun, 11 Sept 2022 at 16:26, Peter Zijlstra [off-list ref] wrote:

On Fri, Sep 09, 2022 at 11:07:04AM -0700, Josh Poimboeuf wrote:

quoted

Alternatives
------------

Another idea which has been floated in the past is for objtool to read
DWARF (or .eh_frame) to help it figure out the control flow.  That
hasn't been tried yet, but would be considerably more difficult and
fragile IMO.

I though Ard played around with that a bit on ARM64. And yes, given that
most toolchains consider DWARF itself best-effort, I'm not holding my
breath there.

I have patches out that use unwind data to locate pointer auth
sign/authenticate instructions in the code, in order to patch them to
shadow call stack pushes and pops at runtime if pointer authentication
is not supported by the hardware. This has little to do with objtool
or reliable stack traces.

I still think DWARF could help to make objtool's job a bit easier, but
I don't think it will be of any use with jump tables or noreturn
functions in particular.