[x86/Linux] Exception Handling ABI

[wateret]

Currently there is no EH ABI defined for x86/Linux so we need one. I'm going to start with @jkotas suggested in dotnet/coreclr#9384 (comment)

Which is:

There is actually a third variant used by CoreRT on all platforms. It was intentionally designed, taking the best parts from both AMD64 and ARM/ARM64. It would be nice to snap to CoreRT convention for Linux x86 where possible.

• First argument of all funclets is establisher frame, second argument is exception object (where applicable). Same as AMD64.
• For filter funclets the VM sets the frame register to be the same as the parent function. For second pass funclets the VM restores all non-volatile registers. Similar to ARM/ARM64.
• No PSP sym (it may be hard to not have PSP sym for CoreCLR - it is ok to skip it)

[wateret]

cc: @parjong @seanshpark

[wateret]

@jkotas @parjong
About using Caller-SP or Initial-SP for establisher frame and funclets, currently x86 does not support FEATURE_FIXED_OUT_ARGS. Wouldn't it be problem with using Initial-SP?

[parjong]

@wateret When UNIX_X86_ABI is used, the jitter inserts padding to align stack, and thus it is not so trivial to obtain Initial-SP (Please refer to dotnet/coreclr#9602 for details).

[danmoseley]

@parjong @wateret with only a few days remaining, would it make sense to set an owner on this issue?

[parjong]

@danmosemsft Sorry for late response. We may close this issue. Currently, there are no further actions related with this issue. EH subsystem now works for x86/Linux (although there are several GC-related issues), and dotnet/coreclr#10023 already updated CLR ABI document.

@wateret Could you let me know your opinion?

[wateret]

@parjong I agree. I think it's good to close this issue.

[danmoseley]

thanks!