Date: Tue, 16 Jun 2015 15:38:59 +0900 From: Yoshinori Sato <ysato@...rs.sourceforge.jp> To: Rich Felker <dalias@...c.org> Cc: musl@...ts.openwall.com, "D. Jeff Dionne" <Jeff@...inux.org>, shumpei.kawasaki@...wc.com Subject: Re: Moving forward with sh2/nommu On Fri, 12 Jun 2015 13:28:21 +0900, Rich Felker wrote: > > On Fri, Jun 12, 2015 at 01:08:05PM +0900, Yoshinori Sato wrote: > > > > >> 4. Syscall trap numbers differ on SH2 vs SH3/4. Presumably the reason > > > > >> is that these two SH2A hardware traps overlap with the syscall > > > > >> range used by SH3/4 ABI: > > > > > > > > > > I haven't patched this yet. I'd like to use 31 (0x1f) as the new > > > > > universal SH syscall trap number, instead of 22. More details on the > > > > > reasons later. > > > > > > > > I've cc'd Yoshinori Sato (who did most of the historical sh2 work) and > > > > Shumpei Kawasaki (the original superh architect). They'll probably have > > > > an opinion on your "more reasons" for changing sh2 system call numbers > > > > to match sh4. > > > > It histrical reason. > > SH3/4 is assigned #0x10 to #0x17 for system call entry. > > But SH2A system using this vector. > > So we moved to #0x20 to #0x27 for SH2A. > > (SH2A specification is #0x20 to #0x3f allocated for user application.) > > > > And SH2 port is based on SH2A port. > > It have same systemcall interface. > > > > > Thank you. I'd really like to make progress at least on the matter of > > > determining if this is feasible. I now have a new musl/sh2 patch that > > > simply uses "trapa #31" unconditionally, and it's a lot > > > simpler/cleaner and working on my patched kernel. The big question is > > > just whether this is an unacceptable constraint on hardware. > > > > SH2A reserved system for vector 31. > > But not assigned now. > > I think no problem. > > Thank you for the feedback. This sounds promising. > > We still need whoever ends up being the new kernel maintainer for SH > to be okay with adding trap 31 syscall support for sh2 and declaring > it supported/stable for sh3/4 too, but at least it looks like there > arent technical problems for doing this. > > Rich Yes. I think test necessary by SH2A, but there would be no problems. -- Yoshinori Sato <ysato@...rs.sourceforge.jp>
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