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Re: [PATCH] backends: ppc_abi_cfi reg1 use DW_CFA_val_offset not DW_CFA_val_expression.
- From: Mark Wielaard <mjw at redhat dot com>
- To: elfutils-devel at lists dot fedorahosted dot org
- Date: Wed, 09 Oct 2013 14:35:28 +0200
- Subject: Re: [PATCH] backends: ppc_abi_cfi reg1 use DW_CFA_val_offset not DW_CFA_val_expression.
On Sun, 2013-10-06 at 17:25 +0200, Mark Wielaard wrote:
> Register rules using expressions are stored using an offset from the
> start of the .eh_frame or .debug_frame ELF section data. Since abi_cfi
> rules aren't stored in those ELF sections they should use neither
> DW_CFA_expression nor DW_CFA_val_expression. The only backend that used
> DW_CFA_val_expression was ppc_cfi.c. It was easier to express the same
> rule using DW_CFA_val_offset than to change the code to handle register
> rules using expressions. On most architectures this did work by accident.
> See the definition of struct dwarf_frame_register value in libdw/cfi.h to
> see why. But on ia64 the abi_cfi data and actual frame data were placed
> too far apart and caused a crash in tests/run-addrcfi.sh for ppc32.
I pushed this to master with Petr's suggested comment fixes.