
/*--------------------------------------------------------------------*/
/*--- Create/destroy signal delivery frames.                       ---*/
/*---                                        sigframe-x86-darwin.c ---*/
/*--------------------------------------------------------------------*/

/*
   This file is part of Valgrind, a dynamic binary instrumentation
   framework.

   Copyright (C) 2006-2012 OpenWorks Ltd
      info@open-works.co.uk

   This program is free software; you can redistribute it and/or
   modify it under the terms of the GNU General Public License as
   published by the Free Software Foundation; either version 2 of the
   License, or (at your option) any later version.

   This program is distributed in the hope that it will be useful, but
   WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307, USA.

   The GNU General Public License is contained in the file COPYING.
*/

#if defined(VGP_x86_darwin)

#include "pub_core_basics.h"
#include "pub_core_vki.h"
#include "pub_core_vkiscnums.h"
#include "pub_core_libcsetjmp.h"    // to keep _threadstate.h happy
#include "pub_core_threadstate.h"
#include "pub_core_aspacemgr.h"
#include "pub_core_libcbase.h"
#include "pub_core_libcassert.h"
#include "pub_core_libcprint.h"
#include "pub_core_machine.h"
#include "pub_core_options.h"
#include "pub_core_signals.h"
#include "pub_core_tooliface.h"
#include "pub_core_trampoline.h"
#include "pub_core_sigframe.h"      /* self */


/* Cheap-ass hack copied from ppc32-aix5 code, just to get started.
   Produce a frame with layout entirely of our own choosing. */

/* This module creates and removes signal frames for signal deliveries
   on x86-darwin.  Kludgey; the machine state ought to be saved in a
   ucontext and retrieved from it later, so the handler can modify it
   and return.  However .. for now .. just stick the vex guest state
   in the frame and snarf it again later.

   Also, don't bother with creating siginfo and ucontext in the
   handler, although do point them somewhere non-faulting.

   Frame should have a 16-aligned size, just in case that turns out to
   be important for Darwin.  (be conservative)
*/
struct hacky_sigframe {
   /* first four words look like a call to a 3-arg x86 function */
   UInt             returnAddr;
   UInt             a1_signo;
   UInt             a2_siginfo;
   UInt             a3_ucontext;
   UChar            lower_guardzone[512];  // put nothing here
   VexGuestX86State gst;
   VexGuestX86State gshadow1;
   VexGuestX86State gshadow2;
   vki_siginfo_t    fake_siginfo;
   struct vki_ucontext fake_ucontext;
   UInt             magicPI;
   UInt             sigNo_private;
   vki_sigset_t     mask; // saved sigmask; restore when hdlr returns
   UInt             __pad[1];
   UChar            upper_guardzone[512]; // put nothing here
   // and don't zero it, since that might overwrite the client's
   // stack redzone, at least on archs which have one
};


/* Extend the stack segment downwards if needed so as to ensure the
   new signal frames are mapped to something.  Return a Bool
   indicating whether or not the operation was successful.
*/
static Bool extend ( ThreadState *tst, Addr addr, SizeT size )
{
   ThreadId tid = tst->tid;
   /* For tracking memory events, indicate the entire frame has been
      allocated.  Except, don't mess with the area which
      overlaps the previous frame's redzone. */
   /* XXX is the following call really right?  compared with the
      amd64-linux version, this doesn't appear to handle the redzone
      in the same way. */
   VG_TRACK( new_mem_stack_signal,
             addr - VG_STACK_REDZONE_SZB, size, tid );
   return True;
}


/* Create a signal frame for thread 'tid'.  Make a 3-arg frame
   regardless of whether the client originally requested a 1-arg
   version (no SA_SIGINFO) or a 3-arg one (SA_SIGINFO) since in the
   former case, the x86 calling conventions will simply cause the
   extra 2 args to be ignored (inside the handler). */
void VG_(sigframe_create) ( ThreadId tid,
                            Addr sp_top_of_frame,
                            const vki_siginfo_t *siginfo,
                            const struct vki_ucontext *siguc,
                            void *handler,
                            UInt flags,
                            const vki_sigset_t *mask,
                            void *restorer )
{
   ThreadState* tst;
   Addr esp;
   struct hacky_sigframe* frame;
   Int sigNo = siginfo->si_signo;

   vg_assert(VG_IS_16_ALIGNED(sizeof(struct hacky_sigframe)));

   sp_top_of_frame &= ~0xf;
   esp = sp_top_of_frame - sizeof(struct hacky_sigframe);
   esp -= 4; /* ELF ABI says that esp+4 must be 16 aligned on
                entry to a function. */

   tst = VG_(get_ThreadState)(tid);
   if (!extend(tst, esp, sp_top_of_frame - esp))
      return;

   vg_assert(VG_IS_16_ALIGNED(esp+4));

   frame = (struct hacky_sigframe *) esp;

   /* clear it (very conservatively) (why so conservatively??) */
   VG_(memset)(&frame->lower_guardzone, 0, 512);
   VG_(memset)(&frame->gst,      0, sizeof(VexGuestX86State));
   VG_(memset)(&frame->gshadow1, 0, sizeof(VexGuestX86State));
   VG_(memset)(&frame->gshadow2, 0, sizeof(VexGuestX86State));
   VG_(memset)(&frame->fake_siginfo,  0, sizeof(frame->fake_siginfo));
   VG_(memset)(&frame->fake_ucontext, 0, sizeof(frame->fake_ucontext));

   /* save stuff in frame */
   frame->gst           = tst->arch.vex;
   frame->gshadow1      = tst->arch.vex_shadow1;
   frame->gshadow2      = tst->arch.vex_shadow2;
   frame->sigNo_private = sigNo;
   frame->mask          = tst->sig_mask;
   frame->magicPI       = 0x31415927;

   /* Minimally fill in the siginfo and ucontext.  Note, utter
      lameness prevails.  Be underwhelmed, be very underwhelmed. */
   frame->fake_siginfo.si_signo = sigNo;
   frame->fake_siginfo.si_code  = siginfo->si_code;

   /* Set up stack pointer */
   vg_assert(esp == (Addr)&frame->returnAddr);
   VG_(set_SP)(tid, esp);
   VG_TRACK( post_reg_write, Vg_CoreSignal, tid, VG_O_STACK_PTR, sizeof(UInt));

   /* Set up program counter */
   VG_(set_IP)(tid, (UInt)handler);
   VG_TRACK( post_reg_write, Vg_CoreSignal, tid, VG_O_INSTR_PTR, sizeof(UInt));

   /* Set up RA and args for the frame */
   VG_TRACK( pre_mem_write, Vg_CoreSignal, tid, "signal handler frame",
             (Addr)frame, 4*sizeof(UInt) );
   frame->returnAddr  = (UInt)&VG_(x86_darwin_SUBST_FOR_sigreturn);
   frame->a1_signo    = sigNo;
   frame->a2_siginfo  = (UInt)&frame->fake_siginfo;  /* oh well */
   frame->a3_ucontext = (UInt)&frame->fake_ucontext; /* oh well */
   VG_TRACK( post_mem_write, Vg_CoreSignal, tid,
             (Addr)frame, 4*sizeof(UInt) );
   VG_TRACK( post_mem_write, Vg_CoreSignal, tid,
             (Addr)&frame->fake_siginfo, sizeof(frame->fake_siginfo));
   VG_TRACK( post_mem_write, Vg_CoreSignal, tid,
             (Addr)&frame->fake_ucontext, sizeof(frame->fake_ucontext));

   if (VG_(clo_trace_signals))
      VG_(message)(Vg_DebugMsg,
                   "sigframe_create (thread %d): "
                   "next EIP=%#lx, next ESP=%#lx\n",
                   tid, (Addr)handler, (Addr)frame );
}


/* Remove a signal frame from thread 'tid's stack, and restore the CPU
   state from it.  Note, isRT is irrelevant here. */
void VG_(sigframe_destroy)( ThreadId tid, Bool isRT )
{
   ThreadState *tst;
   Addr esp;
   Int sigNo;
   struct hacky_sigframe* frame;
 
   vg_assert(VG_(is_valid_tid)(tid));
   tst = VG_(get_ThreadState)(tid);

   /* Check that the stack frame looks valid */
   esp = VG_(get_SP)(tid);

   /* why -4 ? because the signal handler's return will have popped
      the return address off the stack; and the return address is the
      lowest-addressed element of hacky_sigframe. */
   frame = (struct hacky_sigframe*)(esp - 4);
   vg_assert(frame->magicPI == 0x31415927);

   /* This +8 is because of the -4 referred to in the ELF ABI comment
      in VG_(sigframe_create) just above. */
   vg_assert(VG_IS_16_ALIGNED((Addr)frame + 4));

   /* restore the entire guest state, and shadows, from the
      frame.  Note, as per comments above, this is a kludge - should
      restore it from saved ucontext.  Oh well. */
   tst->arch.vex = frame->gst;
   tst->arch.vex_shadow1 = frame->gshadow1;
   tst->arch.vex_shadow2 = frame->gshadow2;
   tst->sig_mask = frame->mask;
   tst->tmp_sig_mask = frame->mask;
   sigNo = frame->sigNo_private;

   if (VG_(clo_trace_signals))
      VG_(message)(Vg_DebugMsg,
                   "sigframe_destroy (thread %d): "
                   "valid magic; next EIP=%#x\n",
                   tid, tst->arch.vex.guest_EIP);

   VG_TRACK( die_mem_stack_signal, 
             (Addr)frame - VG_STACK_REDZONE_SZB, 
             sizeof(struct hacky_sigframe) );

   /* tell the tools */
   VG_TRACK( post_deliver_signal, tid, sigNo );
}

#endif // defined(VGP_x86_darwin)

/*--------------------------------------------------------------------*/
/*--- end                                                          ---*/
/*--------------------------------------------------------------------*/
