feat: add Zicfiss (shadow stack) CSR support

[sudo-apt-abdullah]

Closes #560

[ThinkOpenly]

just nits. Thanks for your efforts!

[ThinkOpenly]

I'm glad you like feedback, because I have a couple more nitpicks. :-)

[ThinkOpenly]

The validation code seems to not like this combo:

priv_mode: U
length: XLEN

...but I'm not smart enough to know how to resolve that. @dhower-qc ?

[dhower-qc]

The validation code seems to not like this combo:

priv_mode: U
length: XLEN

...but I'm not smart enough to know how to resolve that. @dhower-qc ?

This is just an unhandled case by the pretty printer; it doesn't know how to say that the location of ssp.VALUE changes with the current XLEN.

Currently, it assumes that if the location changes, it's based on a particular mode (e.g., the CSR width is MXLEN or SXLEN). It needs to be extended to handle when length is XLEN.

Fixed in commit aacade9

[dhower-qc]

oops, pressed the wrong button

[sudo-apt-abdullah]

Added the SSE field to the xenvcfg CSRs to fix CI failures caused by its absence.

[dhower-qc]

Do you also want to try to implement the shadow stack instructions (by filling out the operation() field of instructions in spec/std/isa/inst/Zicfiss/*)?

You don't have to, but it might make sense since you already in here.

[sudo-apt-abdullah]

Do you also want to try to implement the shadow stack instructions (by filling out the operation() field of instructions in spec/std/isa/inst/Zicfiss/*)?

You don't have to, but it might make sense since you already in here.

I'll be happy doing this and open a separate PR for that if it's okay.

[ThinkOpenly]

Do you also want to try to implement the shadow stack instructions (by filling out the operation() field of instructions in spec/std/isa/inst/Zicfiss/*)?
You don't have to, but it might make sense since you already in here.

I'll be happy doing this and open a separate PR for that if it's okay.

Feel free to open a sub-issue for #560 (there's a "create sub-issue") button in the original text there, so we don't lose track.

[sudo-apt-abdullah]

Feel free to open a sub-issue for #560 (there's a "create sub-issue") button in the original text there, so we don't lose track.

Please assign #995 to me, thanks.

[ThinkOpenly]

I think this PR is waiting on #891, right? Just adding this comment for context.

[sudo-apt-abdullah]

I think this PR is waiting on #891, right?

Yes, it's waiting for #891 to be merged.