[uml-devel] question about UML sigcontext in tt mode

[uml-devel] question about UML sigcontext in tt mode

[Alex LIU]

Hi,all:

I have a question about the sigcontext in tt mode.The union uml_pt_regs is defined as below(in uml-2.6.7):

--------------------------------
union uml_pt_regs {
#ifdef UML_CONFIG_MODE_TT
	struct tt_regs {
		long syscall;
		void *sc;
	} tt;
#endif
#ifdef UML_CONFIG_MODE_SKAS
	struct skas_regs {
		unsigned long regs[HOST_FRAME_SIZE];
		unsigned long fp[HOST_FP_SIZE];
		unsigned long xfp[HOST_XFP_SIZE];
		unsigned long fault_addr;
		unsigned long fault_type;
		unsigned long trap_type;
		long syscall;
		int is_user;
	} skas;
#endif
};
-------------------------------------

Then why the tt.sc is defined as void while not as struct sigcontext? Thanks!

Alex 





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Re: [uml-devel] question about UML sigcontext in tt mode

[Blaisorblade]

On Thursday 31 March 2005 12:03, Alex LIU wrote:
> Hi,all:
>
> I have a question about the sigcontext in tt mode.The union uml_pt_regs is
> defined as below(in uml-2.6.7):
>
> --------------------------------
> union uml_pt_regs {
> #ifdef UML_CONFIG_MODE_TT
>  struct tt_regs {
>   long syscall;
>   void *sc;
>  } tt;
> #endif
> #ifdef UML_CONFIG_MODE_SKAS
>  struct skas_regs {
>   unsigned long regs[HOST_FRAME_SIZE];
>   unsigned long fp[HOST_FP_SIZE];
>   unsigned long xfp[HOST_XFP_SIZE];
>   unsigned long fault_addr;
>   unsigned long fault_type;
>   unsigned long trap_type;
>   long syscall;
>   int is_user;
>  } skas;
> #endif
> };
> -------------------------------------
>
> Then why the tt.sc is defined as void while not as struct sigcontext?
> Thanks!

I think because of header inclusion problems... you can't include userspace 
header in kernelspace files and so on. And the above can be included by both 
kind of files, being in arch/um/include.

This could be solved however with a:
struct sigcontext;
...
struct sigcontext * sc;

instead of

void* sc;

I've not checked however if sc is actually a sigcontext - I rely on what you 
say.
-- 
Paolo Giarrusso, aka Blaisorblade
Linux registered user n. 292729
http://www.user-mode-linux.org/~blaisorblade





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Re: [uml-devel] question about UML sigcontext in tt mode

[Jeff Dike]

On Thu, Mar 31, 2005 at 06:03:34PM +0800, Alex LIU wrote:
> union uml_pt_regs {
> #ifdef UML_CONFIG_MODE_TT
> 	struct tt_regs {
> 		long syscall;
> 		void *sc;
> 	} tt;
> #endif
> };
> -------------------------------------
> 
> Then why the tt.sc is defined as void while not as struct sigcontext? Thanks!

Probably because you can't get a definition of struct sigcontext into 
processor.h and have it still compile.

Try #including sigcontext.h there and you'll see what I mean.

				Jeff


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Re: [uml-devel] question about UML sigcontext in tt mode

[Rob Landley]

On Monday 04 April 2005 10:00 am, Jeff Dike wrote:
> On Thu, Mar 31, 2005 at 06:03:34PM +0800, Alex LIU wrote:
> > union uml_pt_regs {
> > #ifdef UML_CONFIG_MODE_TT
> > 	struct tt_regs {
> > 		long syscall;
> > 		void *sc;
> > 	} tt;
> > #endif
> > };
> > -------------------------------------
> >
> > Then why the tt.sc is defined as void while not as struct sigcontext?
> > Thanks!
>
> Probably because you can't get a definition of struct sigcontext into
> processor.h and have it still compile.
>
> Try #including sigcontext.h there and you'll see what I mean.

I don't know about can't.

#define sigcontext WALRUS
#include <processor.h>
thingy
#undef WALRUS

Adviseable is another matter entirely.  (Did I mention I have a knack for 
coming up with disgusting solutions to impossible problems?)

Rob


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Re: [uml-devel] question about UML sigcontext in tt mode

[Blaisorblade]

On Tuesday 05 April 2005 19:20, Rob Landley wrote:
> On Monday 04 April 2005 10:00 am, Jeff Dike wrote:
> > On Thu, Mar 31, 2005 at 06:03:34PM +0800, Alex LIU wrote:
> > > union uml_pt_regs {
> > > #ifdef UML_CONFIG_MODE_TT
> > >  struct tt_regs {
> > >   long syscall;
> > >   void *sc;
> > >  } tt;
> > > #endif
> > > };
> > > -------------------------------------
> > >
> > > Then why the tt.sc is defined as void while not as struct sigcontext?
> > > Thanks!
> >
> > Probably because you can't get a definition of struct sigcontext into
> > processor.h and have it still compile.
> >
> > Try #including sigcontext.h there and you'll see what I mean.
>
> I don't know about can't.
>
> #define sigcontext WALRUS
> #include <processor.h>
> thingy
> #undef WALRUS
>
> Adviseable is another matter entirely.  (Did I mention I have a knack for
> coming up with disgusting solutions to impossible problems?)
I've not tested if it's impossible in this very case, however: if any host 
header includes kernel headers on the host, and we include it from a 
kernelspace file, we run into trouble.

So, defining away like you do above every and each identifier present in every 
possible versions of glibc / kernel headers would indeed work. Is this still 
a solution?

So, we cut the problem by excluding the unusable headers from the compiler 
search path. arch/um/include are includable everywhere, /usr/include from 
userspace files, <currentTreeRoot>/include/{asm,linux,*}/ from kernelspace 
only.

If you really come up with a general solution, let us know. Please. Thanks for 
you effort anyway.
-- 
Paolo Giarrusso, aka Blaisorblade
Linux registered user n. 292729
http://www.user-mode-linux.org/~blaisorblade




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