[RFC PATCH 07/13] um: nommu: configure fs register on host syscall invocation

[Hajime Tazaki]

On Sat, 26 Oct 2024 00:22:48 +0900,
Johannes Berg wrote:
> 
> On Fri, 2024-10-25 at 22:27 +0900, Hajime Tazaki wrote:
> > 
> > On Fri, 25 Oct 2024 18:28:01 +0900,
> > Johannes Berg wrote:
> > > 
> > > On Thu, 2024-10-24 at 21:09 +0900, Hajime Tazaki wrote:
> > > > 
> > > > +static void sigill(int sig, siginfo_t *si, void *ctx_void)
> > > > +{
> > > > +	longjmp(jmpbuf, 1);
> > > > +}
> > > 
> > > Should this code use sigsetjmp/siglongjmp?
> > 
> > the code is referred from tools/testing/selftests/x86/fsgsbase.c and
> > the original code uses sigsetjmp/siglongjmp indeed.
> 
> :)
> 
> > I was struggling to pull the definition of sigsetjmp & co from host
> > headers as it conflicts with UML definitions of jmp_buf, etc.
> > 
> > Will look into detail again but would be nice if you have an
> > experience on this.
> 
> Hm. This is a userspace side so there shouldn't be much trouble with
> that? Worst case put it into its own file in os-Linux/ and don't include
> so many shared headers, I guess?

thanks, I'll try with this approach.

> > > > +int os_has_fsgsbase(void)
> > > > +{
> > > > +	return has_fsgsbase;
> > > > +}
> > > 
> > > Why should this be a function rather than just exposing the variable?
> > 
> > as it is referred in arch/x86/um code.
> 
> Yeah but you have to also declare the function somewhere in a header
> file - could as well declare "extern int host_has_fsgsbase;" or so?

agreed.  I'll update that part.

-- Hajime