On 15/06/23 17:40, Nicholas Piggin wrote:
On Thu Jun 15, 2023 at 7:10 PM AEST, Aditya Gupta wrote:
ppc_save_regs() skips one stack frame while saving the CPU register states.
Instead of saving current R1, it pulls the previous stack frame pointer.
...
So this now saves regs as though it was an interrupt taken in the
caller, at the instruction after the call to ppc_save_regs, whereas
previously the NIP was there, but R1 came from the caller's caller
and that mismatch is what causes gdb's dwarf unwinder to go haywire.
Nice catch, and I think I follow the fix and I think I agree with it.
Before the bug was introduced, NIP also came from the grandparent.
Which is what xmon presumably wanted, but since then I think maybe it
makes more sense to just have the parent caller.
Reivewed-by: Nicholas Piggin <npig...@gmail.com>
Fixes: d16a58f8854b1 ("powerpc: Improve ppc_save_regs()")
Thanks for reviewing this, and providing a Fixes tag too.
Thanks
- Aditya
