On Wed, 3 Feb 2021 22:44:18 GMT, Gerard Ziemski <gziem...@openjdk.org> wrote:
>> Thanks for your questions Gerard. >> >>> Part of the comment said This work-around is not necessary for 10.5+, as >>> CrashReporter no longer intercedes on caught fatal signals. >> >> That comment can probably be deleted since minversion is anyway 10.9 (and >> soon 10.12 https://github.com/openjdk/jdk/pull/2268 ). >> >>> Do you know if this also apply to lldb or is it gdb only specific? How do >>> you run gdb on macOS nowadays anyhow? >> >> `lldb` is shipped with Xcode, `gdb` isn't. You would need to build and sign >> it yourself, I haven't tried that in a while. So, we should update that >> comment to talk about `lldb` 🙂 >> >>> a) why we need `EXC_MASK_ARITHMETIC` ? >> >> I _believe_ this dates back to i386. As far as I can tell this isn't needed >> for x86_64 or aarch64. I guess we can remove it, the worst case is that it >> makes the debugging experience of the runtime a little bit worse. OTOH it >> doesn't hurt either to have it here. >> >>> b) we hit signal SIGSEGV in debugger even with the code in place, any way >>> to avoid that? >> >> The equivalent for `handle SIGSEGV nostop noprint` (gdb) in lldb is `process >> handle -n false -p true -s false SIGSEGV`. >> >>> c) does `BSD aarch6` need only `EXC_MASK_BAD_INSTRUCTION` or does it need >>> `EXC_MASK_BAD_ACCESS` as well? >> >> aarch64 needs `EXC_MASK_BAD_ACCESS` at least for implicit null checking, >> there might be other cases. >> >>> d) can we `#ifdef` the `EXC_MASK_BAD_INSTRUCTION` part of the mask only to >>> apply to `aarch64`? >> >> Maybe. I don't see any value in it though, except making the code more >> complicated to read 🙂 > > I don't like the idea of using masks on architectures that do not require > them. How about something like this? > > `#if defined(__APPLE__)` > ` // lldb (gdb) installs both standard BSD signal handlers, and mach > exception` > ` // handlers. By replacing the existing task exception handler, we disable > lldb's mach` > ` // exception handling, while leaving the standard BSD signal handlers > functional.` > ` //` > ` // EXC_MASK_BAD_ACCESS needed by all architectures for NULL ptr checking` > ` // EXC_MASK_ARITHMETIC needed by i386` > ` // EXC_MASK_BAD_INSTRUCTION needed by aarch64 to initiate deoptimization` > ` kern_return_t kr;` > ` kr = task_set_exception_ports(mach_task_self(),` > ` EXC_MASK_BAD_ACCESS` > ` NOT_LP64(| EXC_MASK_ARITHMETIC)` > ` AARCH64_ONLY(| EXC_MASK_BAD_INSTRUCTION),` > ` MACH_PORT_NULL,` > ` EXCEPTION_STATE_IDENTITY,` > ` MACHINE_THREAD_STATE);` > ` ` > ` assert(kr == KERN_SUCCESS, "could not set mach task signal handler");` > `#endif` > > If I just knew why i386 needs `EXC_MASK_ARITHMETIC` and add that to the > comment I would be personally happy with that chunk of code. No idea how to insert spaces and make text align :-( ------------- PR: https://git.openjdk.java.net/jdk/pull/2200
