cvs commit: src/sys/ia64/ia64 machdep.c syscall.S src/sys/ia64/include ucontext.h

[Marcel Moolenaar]

marcel      2003/11/09 14:17:36 PST

  FreeBSD src repository

  Modified files:
    sys/ia64/ia64        machdep.c syscall.S 
    sys/ia64/include     ucontext.h 
  Log:
  Use get_mcontext() to construct the signal context in sendsig() and
  use set_mcontext() to restore the context in sigreturn(). Since we
  put the syscall number and the syscall arguments in the trapframe
  (we don't save the scratch registers for syscalls, which allows us
  to reuse the space to our advantage), create a MD specific flag so
  that we save the scratch registers even for syscalls. We would not
  be able to restart a syscall otherwise.
  
  The signal trampoline does not need to flush the regiters anymore,
  because get_mcontext() already handles that. In fact, if we set up
  the context correctly, we do not need to have a trampoline at all.
  This change however only minimally changes the trampoline code. In
  follow-up commits this can be further optimized.
  
  Note that normally we preserve cfm and iip in the trapframe created
  by the EPC syscall path when we restore a context in set_mcontext()
  because those fields are not normally set for a synchronuous context.
  The kernel puts the return address and frame info of the syscall
  stub in there. By preserving these fields we hide this detail from
  userland which allows us to use setcontext(2) for user created
  contexts. However, sigreturn() is commonly called from the trampoline,
  which means that if we preserve cfm and iip in all cases, we would
  return to the trampoline after the sigreturn(), which means we hit
  the safety net: we call exit(2). So, we do not preserve cfm and iip
  when we have a synchronous context that also has scratch registers
  (the uncommon context created by sendsig() only), under the assumption
  that if such a context is created in userland, something special is
  going on and the use of cfm and iip is then just another quirk. All
  this is invisible in the common case.
  
  Revision  Changes    Path
  1.165     +34 -72    src/sys/ia64/ia64/machdep.c
  1.10      +10 -36    src/sys/ia64/ia64/syscall.S
  1.6       +6 -1      src/sys/ia64/include/ucontext.h