RFR: 8319747: galoisCounterMode_AESCrypt stack walking broken [v2]

[Daniel Jeliński]

On Fri, 10 Nov 2023 07:59:42 GMT, Daniel Jeliński <djelinski at openjdk.org> wrote:

>> src/hotspot/cpu/x86/stubGenerator_x86_64_aes.cpp line 243:
>> 
>>> 241:   const Register state = r13;
>>> 242:   const Address subkeyH_mem(rbp, 8 * wordSize);
>>> 243:   const Register subkeyHtbl = r11;
>> 
>> Changing the register from r14 to r11 here doesn't look correct. As aesgcm_encrypt() uses r11 as temporary for windows at line 3046 and overwrites it at line 3074 etc in the original code.  
>> 3046 const Register ghash_pos = NOT_WIN64( r14) WIN64_ONLY( r11 );
>> 3074   __ movl(ghash_pos, 0); // Pointer for ghash read and store operations
>
> Ah, you're right! I missed that. I was looking for `#ifdef`s, and forgot that we have the `*_ONLY` macros.
> 
> The code works correctly because `subkeyHtbl` and `ghash_pos` have non-overlapping lifetimes; `subkeyHtbl` is last used in line:
> 3072 __ call(GENERATE_HTBL_48_BLKS, relocInfo::none);
> 
> I'd like to make this explicit by changing the code like:
> 
>   // reuse subkeyHtbl register - the lifetimes do not overlap
>   const Register ghash_pos = subkeyHtbl;
> 
> but I can also revert the register renaming changes. What's your preference?

I reverted register renaming to keep this PR focused on stack walking. Tests still pass.

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/16567#discussion_r1392139380