x86/entry: Fix ORC unwinder for PUSH_REGS with save_ret=1

PUSH_REGS with save_ret=1 is used by interrupt entry helper functions that
initially start with a UNWIND_HINT_FUNC ORC state.

However, save_ret=1 means that we clobber the helper function's return
address (and then later restore the return address further down on the
stack); after that point, the only thing on the stack we can unwind through
is the IRET frame, so use UNWIND_HINT_IRET_REGS until we have a full
pt_regs frame.

( An alternate approach would be to move the pt_regs->di overwrite down
  such that it is the final step of pt_regs setup; but I don't want to
  rearrange entry code just to make unwinding a tiny bit more elegant. )

Fixes: 9e809d15d6b6 ("x86/entry: Reduce the code footprint of the 'idtentry' macro")
Signed-off-by: Jann Horn <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Brian Gerst <[email protected]>
Cc: Juergen Gross <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

0 files changed, 0 insertions, 0 deletions