question about ucontext_t and friends

From: Etienne Robillard (granted14_at_yahoo.com)
Date: 02/08/05

  • Next message: John-Mark Gurney: "buildenv target" 
    Date: Mon, 7 Feb 2005 20:19:17 -0500 (EST)
To: freebsd-arch@freebsd.org

    Hi,

    I have a c++ application implementing a user-level
    hardware abstraction (L4 ­µ-kernel in user-mode linux)
    bu I am missing a few arch backbones.

    Afaiu, the application must find some ways to
    manipulate registers in user-context, after having the
    request traced by ptrace(2).

    So far, interfaces are prototyped in similar manners:

    ...
    kernel_entry( *context, ... )

    Where *context is a pointer to a `struct ucontext',
    but I suspect its because the relevant ucontext_t
    type wasnt available for some reasons.

    Question 1:

    Concerning the 'missing members' in ucontext_t, may I
    suspect that conformant applications needs not to
    alter things in uc_mcontext (machine context) ?? [1]

    The docs are saying that:

    "The ucontext_t type that ucp points to defines the
    user context and includes the contents of the calling
    thread's machine registers, the signal mask, and the
    current execution stack."
     
    Therefore this is almost okay but doesnt work on
    freebsd as-is:

    // save it to <machine/reg.h>
    regs.foo = context->uc_mcontext.gregs[REG_FOO]

    TIA
    -erob

    1.
    http://www.opengroup.org/onlinepubs/009695399/functions/getcontext.html
     

    =====
    JabberID: incidah (at) njs (dot) netlab (dot) cz

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