RFR: 8277489: Rewrite JAAS UnixLoginModule with FFM [v2]

[Martin Doerr]

On Thu, 1 Jan 2026 04:37:38 GMT, Weijun Wang <weijun at openjdk.org> wrote:

>> src/jdk.security.auth/share/classes/com/sun/security/auth/module/UnixSystem.java line 152:
>> 
>>> 150:             int out = (int) getpwuid_r.invokeExact(
>>> 151:                     tmpUid, resbuf, pwd_buf, GETPW_R_SIZE_MAX, pwd);
>>> 152:             if (out != 0 || pwd.get(ValueLayout.ADDRESS, 0).equals(MemorySegment.NULL)) {
>> 
>> The additional `|| pwd.get(ValueLayout.ADDRESS, 0).equals(MemorySegment.NULL)` breaks AIX. The included test passes when we remove it and we get the correct username.
>> @JoKern65, @varada1110: Do you know why `getpwuid_r` writes nullptr (or nothing) to `result` on a successful query?
>
> First, thank you so much for the experiments.
> 
> Here, I think I follow the C checks in the old `Unix.c`:
> 
>     if (getpwuid_r(getuid(), &resbuf, pwd_buf, sizeof(pwd_buf), &pwd) == 0 &&
>             pwd != NULL) {
> 
> How did it run in AIX?

The old C code works on AIX. I haven't figured out what causes different behavior with the new code. Note that the new code works on linux on ppc64 (big and little endian).

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PR Review Comment: https://git.openjdk.org/jdk/pull/28931#discussion_r2657691333