On Wed, 3 Feb 2021 20:04:18 GMT, Gerard Ziemski <gziem...@openjdk.org> wrote:
>> See comment above about `gdb`, the same applies to `lldb` today. The AArch64 >> backend uses `SIGILL` (~= `EXC_MASK_BAD_INSTRUCTION`) to initiate a >> deoptimization. Without this change you cannot continue debugging once you >> the debuggee receives `SIGILL`. This wasn't needed before as x86 doesn't use >> `SIGILL`. > > Part of the comment said `This work-around is not necessary for 10.5+, as > CrashReporter no longer intercedes on caught fatal signals.` so I thought it > was no longer needed, but it sounds like the part about `gdb` still applies > then. > > We should update the comment to just say the `gdb` relevant part perhaps (and > evaluate which of the EXC_MASK_BAD_ACCESS | EXC_MASK_BAD_INSTRUCTION | > EXC_MASK_ARITHMETIC) we actually need for gdb: > > `// gdb installs both standard BSD signal handlers, and mach exception` > `// handlers. By replacing the existing task exception handler, we disable > gdb's mach` > `// exception handling, while leaving the standard BSD signal handlers > functional.` > > Do you know if this also apply to `lldb` or is it `gdb` only specific? How do > you run `gdb` on macOS nowadays anyhow? To answer my own question, it seems that code is still needed on `x86_64` for `lldb` with `EXC_MASK_BAD_ACCESS` or we keep tripping over `EXC_BAD_ACCESS` Remaining questions: a) why we need `EXC_MASK_ARITHMETIC` ? b) we hit `signal SIGSEGV` in debugger even with the code in place, any way to avoid that? c) does `BSD aarch64` need only `EXC_MASK_BAD_INSTRUCTION` or does it need `EXC_MASK_BAD_ACCESS` as well? d) can we `#ifdef` the `EXC_MASK_BAD_INSTRUCTION` part of the mask only to apply to `aarch64`? ------------- PR: https://git.openjdk.java.net/jdk/pull/2200
