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List:       user-mode-linux-devel
Subject:    Re: [uml-devel] sys_sigreturn
From:       Jeff Dike <jdike () karaya ! com>
Date:       2001-09-11 22:21:05
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cemerson@chiark.greenend.org.uk said:
> Ok, I've looked into arch/ppc/kernel/entry.S.  0x7777 is treated as a
> special case, which bypasses the system call tracing and calls
> sys_sigreturn directly (and similarly for rt_sigreturn).  That's a
> pain.

Bleah.  That's annoying.

> I'll see what I can do to work around it, or failing that try to fix
> the host. 

When the tracing thread gets the "return me to userspace" SIGUSR1, you 
could have it fake the sys_sigreturn by munging the appropriate registers 
and calling do_syscall.

You'd need to munge them into the process rather than into 
current->thread.process_regs because do_syscall fills that in itself.

AFAICS that would work.  However, delivering and returing from signals is 
tricky so I don't guarantee anything.

				Jeff




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