Re: [PATCH] libgcc: Fix uninitialized RA signing on AArch64 [PR107678]

["Martin Liška" <mliska@suse.cz>]

On 1/12/23 19:57, Jakub Jelinek via Gcc-patches wrote:
> On Tue, Jan 10, 2023 at 04:33:59PM +0000, Wilco Dijkstra via Gcc-patches wrote:
>> Hi Szabolcs,
>>
>>> i would keep the assert: how[reg] must be either UNSAVED or UNDEFINED
>>> here, other how[reg] means the toggle cfi instruction is mixed with
>>> incompatible instructions for the pseudo reg.
>>>
>>> and i would add a comment about this e.g. saying that UNSAVED/UNDEFINED
>>> how[reg] is used for tracking the return address signing status and
>>> other how[reg] is not allowed here.
>>
>> I've added the assert back and updated the comment.
> 
> BTW, the patch doesn't apply to trunk cleanly (since the January 2nd
> r13-4955-gcb775ecd6e437 commit).

@Wilco, can you please send the rebased patch for patch review? We would
need in out openSUSE package soon.

Thank you,
Martin

> 
>> v3: Improve comments, add assert.
>>
>> A recent change only initializes the regs.how[] during Dwarf unwinding
>> which resulted in an uninitialized offset used in return address signing
>> and random failures during unwinding.  The fix is to encode the return
>> address signing state in REG_UNSAVED and REG_UNDEFINED.
>>
>> Passes bootstrap & regress, OK for commit?
>>
>> libgcc/
>>         PR target/107678
>>         * unwind-dw2.c (execute_cfa_program): Use REG_UNSAVED/UNDEFINED
>>         to encode return address signing state.
>>         * config/aarch64/aarch64-unwind.h (aarch64_demangle_return_addr)
>>         Check current return address signing state.
>>         (aarch64_frob_update_contex): Remove.
> 
> 	Jakub
>