[lworld] RFR: 8372806: [lworld] x64: save bad values instead of rfp and lr above the extension space
Marc Chevalier
mchevalier at openjdk.org
Fri Dec 19 08:04:07 UTC 2025
That's the x86 counterpart of [JDK-8371993](https://bugs.openjdk.org/browse/JDK-8371993).
I've added some comments, using the offsets given in `frame_x86.hpp` to make sure to put the frame start at the right place. In particular, the frame start is 2 pointer sizes under the sender's sp:
https://github.com/openjdk/valhalla/blob/3c41c2aa442076827cb4480373a1d481e481cdf1/src/hotspot/cpu/x86/frame_x86.hpp#L61-L62
Unlike aarch64, with x64 we have only one copy of rbp. As with aarch64, I had to get rid of an assert that can't be checked anymore. A small price to pay.
Now, in debug, instead of
pop r13
sub rsp,0x20
push r13
we have
pop r13
sub rsp,0x20
mov DWORD PTR [rsp-0x4],0xdeadda7a
mov DWORD PTR [rsp-0x8],0xdeadda7a
sub rsp,0x8
I've kept the `pop r13` to limit the difference of behavior between debug and product builds: both will overwrite `r13` with the return address, whether it's a good idea or not.
And at runtime, on my favorite `compiler/valhalla/inlinetypes/CorrectlyRestoreRfp.java` example, instead of the stack:
0x7fd7345fe660: 0x000000042724f5d0 0x00007fd7345fe750 <-- rsp
0x7fd7345fe670: 0xffffffffffffffff 0x00007fd740acc0f7
0x7fd7345fe680: 0x00007fd700000000 0x000000042724f5d0
0x7fd7345fe690: 0x000000056f517f28 0x00007fd7390002a6
0x7fd7345fe6a0: 0x00007fd72c90c8b3 0x0000000000000078 <-- # | sp_inc
0x7fd7345fe6b0: 0x00007fd7345fe750 0x00007fd740541306 <-- rsp - 0x50 # rbp | return address
0x7fd7345fe6c0: 0x000000056f49f4e0 0x000000042724f5d0 <-- # String (arg2) | Object (arg3)
0x7fd7345fe6d0: 0x0000000000000000 0x00007fd740541306 <-- rsp - 0x70 # boolean (arg4) | return address
0x7fd7345fe6e0: 0x00007fd740541306 0x0000000000000000
0x7fd7345fe6f0: 0x000000042724f5d0 0x000000056f49f4e0
we have
0x7f93cfdfe660: 0x000000042724f5d0 0x00007f93cfdfe750 <-- rsp
0x7f93cfdfe670: 0xffffffffffffffff 0x00007f93e4acc107
0x7f93cfdfe680: 0x00007f9300000000 0x000000042724f5d0
0x7f93cfdfe690: 0x000000056f517fb0 0x00007f93dd0002a6
0x7f93cfdfe6a0: 0x00007f93d090c8b3 0x0000000000000078 <-- # | sp_inc
0x7f93cfdfe6b0: 0x00007f93cfdfe750 0xdeadda7adeadda7a <-- rsp - 0x50 # rbp | >>>> bad word <<<<
0x7f93cfdfe6c0: 0x000000056f49f540 0x000000042724f5d0 <-- # String (arg2) | Object (arg3)
0x7f93cfdfe6d0: 0x0000000000000000 0x00007f93e4541306 <-- rsp - 0x70 # boolean (arg4) | return address
0x7f93cfdfe6e0: 0x00007f93e4541306 0x0000000000000000
0x7f93cfdfe6f0: 0x000000042724f5d0 0x000000056f49f540
I had to problem list some virtual thread tests, in the same fashion as for aarch64, as it used the wrong return address. The assert I had to remove was a sign that only one of the return address is updated in case of deopt, so only one of them is reliable. To help with that, I've added `frame::compiled_frame_details` like for aarch64, that makes sure to do all the fixing internally.
Thanks,
Marc
-------------
Commit messages:
- Add frame::compiled_frame_details + problem list
- Comments and zap
Changes: https://git.openjdk.org/valhalla/pull/1839/files
Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1839&range=00
Issue: https://bugs.openjdk.org/browse/JDK-8372806
Stats: 158 lines in 7 files changed: 113 ins; 29 del; 16 mod
Patch: https://git.openjdk.org/valhalla/pull/1839.diff
Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1839/head:pull/1839
PR: https://git.openjdk.org/valhalla/pull/1839
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