[aarch64-port-dev ] Simple HTTP server app crashes on JDK 11 and 8 on OSv AArch64

[Andrew Haley]

On 3/5/22 10:08, Andrew Haley wrote:
> On 3/5/22 05:25, Waldek Kozaczuk wrote:
>> Any ideas on how to debug it further?
>>
>> Any help is greatly appreciated,
>> Waldek
> 
> Is is possible to attach gdb? Is it possible to get a core dump?
> 
> I see no attached file. Please put it on a file sharing system so we
> can see it.

Having said that, it looks like there may be a problem when patching
inline cache, and that may be due to a problem with cache flushing.
Maybe __builtin___clear_cache is flaky.

The caller is here:

address MacroAssembler::ic_call(address entry, jint method_index) {
    RelocationHolder rh = virtual_call_Relocation::spec(pc(), method_index);
    movptr(rscratch2, (uintptr_t)Universe::non_oop_word());
    return trampoline_call(Address(entry, rh));
}

This generates a sequence that gets patched at runtime when a call is
resolved. The compiled sequence initially looks like this:

     0xffffa5be35e0:      mov     x9, #0xffff                     // #65535
     0xffffa5be35e4:      movk    x9, #0xffff, lsl #16
     0xffffa5be35e8:      movk    x9, #0xffff, lsl #32
     0xffffa5be35ec:      bl      0xffffa5bd23c0

then it gets patched to look like this:

     0xffffa5be35e0:      mov     x9, #0x1b58                     // #7000
     0xffffa5be35e4:      movk    x9, #0x4, lsl #16
     0xffffa5be35e8:      movk    x9, #0x8, lsl #32
     0xffffa5be35ec:      bl      0xffffa5be36e0

It looks to me as though some threads aren't seeing the patched code,
and this could well be a kernel problem.

-- 
Andrew Haley  (he/him)
Java Platform Lead Engineer
Red Hat UK Ltd. <https://www.redhat.com>
https://keybase.io/andrewhaley
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