This commit fixes up the handling of shadow registers quite a bit.

Removed the SK_(written_shadow_regs_values)() function.  Instead, skins that
use shadow regs can track the `post_regs_write_init' event, and set the shadow
regs from within it.  This is much more flexible, since it allows each shadow
register to be set to a separate value if necessary.  It also matches the new
shadow-reg-change events described below.

In the core, there were some places where the shadow regs were changed, and
skins had no way of knowing about it, which was a problem for some skins.
So I added a bunch of new events to notify skins about these:

  post_reg_write_syscall_return
  post_reg_write_deliver_signal
  post_reg_write_pthread_return
  post_reg_write_clientreq_return
  post_reg_write_clientcall_return

Any skin that uses shadow regs should almost certainly track these events.  The
post_reg_write_clientcall_return allows a skin to tailor the shadow reg of the
return value of a CLIENTCALL'd function appropriately;  this is especially
useful when replacing malloc() et al.

Defined some macros that should be used *whenever the core changes the value of
a shadow register* :

  SET_SYSCALL_RETVAL
  SET_SIGNAL_EDX          (maybe should be SET_SIGNAL_RETVAL? ... not sure)
  SET_SIGNAL_ESP
  SET_CLREQ_RETVAL
  SET_CLCALL_RETVAL
  SET_PTHREQ_ESP
  SET_PTHREQ_RETVAL

These replace all the old SET_EAX and SET_EDX macros, and are added in a few
places where the shadow-reg update was missing.

Added shadow registers to the machine state saved/restored when signal handlers
are pushed/popped (they were missing).

Added skin-callable functions VG_(set_return_from_syscall_shadow)() and
VG_(get_exit_status_shadow)() which are useful and abstract away from which
registers the results are in.

Also, poll() changes %ebx (it's first argument) sometimes, I don't know why.
So we notify skins about that too (with the `post_reg_write_syscall_return'
event, which isn't ideal I guess...)


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@1642 a5019735-40e9-0310-863c-91ae7b9d1cf9
11 files changed