ppc64 unwinding problem

Richard Henderson rth@redhat.com
Fri Jul 11 22:38:00 GMT 2003

On Fri, Jul 11, 2003 at 10:57:37PM +0200, Jakub Jelinek wrote:
> This is very bad, not only because some libgcj stuff does not work
> (there are other bugs on ppc64 in gcj), but because NPTL relies on this.

Hum.  Well, IMO the best solution to the unwinding problem is
to have signal trampolines that have proper unwind info.  Does
ppc64-linux allow for an sa_restorer that glibc could set up?
If so, then at least NPTL is set.

> (I don't think if (*($r1 + 16) == 0xE8410028) DW_CFA_offset (2, -40);
> else do nothing is expressible in Dwarf2)

Well, if we can assume that R2 has an entry at top-level (i.e.
in _Unwind_RaiseException etc), then I would think that

	// CFA == $r1, which is at TOS on entry

	DW_OP_plus_uconst 16
	DW_OP_deref_size 4
	DW_OP_const4u 0xE8410028
	DW_OP_bra 1f
	DW_OP_skip 2f
1:	DW_OP_const1u 40
2:	DW_OP_nop

would do that job.  No idea where you'd put this...

The test case looks ok.


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