On Wed, Nov 06, 2024 at 10:03:25AM -0800, H. Peter Anvin wrote:
> The issue is that we want the frame pointer chain to be maintained, even
> across alternatives.
If the current function doesn't have frame pointer set up yet (or is in the
epilogue after it got restored already), then the chain is still maintained,
just one frame will be missing from it. I don't see why that would be a big
deal.
> This isn't to quiet a spurious warning, rather
> objtool is throwing a legitimate warning that a level environment
> invariant is being violated.
Anyway, do you have a testcase where you saw problematic inline asm being
moved into the prologue or after the epilogue or is that just theoretical?
So that we can test if "redzone" clobber prevents that or if "=m" (dummy)
does or similar?
The rsp register var in output is something we should warn about at least,
it isn't really something kernel should keep using.
Jakub
