RFR: 8282306: os::is_first_C_frame(frame*) crashes on invalid link access [v3]

[David Holmes]

On Thu, 24 Feb 2022 02:41:25 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> Johannes Bechberger has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Use safefetch
>
> src/hotspot/share/runtime/os.cpp line 1192:
> 
>> 1190: 
>> 1191:   uintptr_t usp    = (uintptr_t)fr->sp();
>> 1192:   if ((usp & sp_align_mask) != 0 || SafeFetchN(fr->sp(), 0) == 0) return true;
> 
> This doesn't quite make sense to me. If the SafeFetchN were to fail then the load in the previous line would already have crashed wouldn't it?

Sorry ignore that. The SafeFetch loads `*fr->sp()`.

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PR: https://git.openjdk.java.net/jdk/pull/7591