1
2/*--------------------------------------------------------------------*/
3/*--- Create/destroy signal delivery frames.                       ---*/
4/*---                                        sigframe-x86-darwin.c ---*/
5/*--------------------------------------------------------------------*/
6
7/*
8   This file is part of Valgrind, a dynamic binary instrumentation
9   framework.
10
11   Copyright (C) 2006-2012 OpenWorks Ltd
12      info@open-works.co.uk
13
14   This program is free software; you can redistribute it and/or
15   modify it under the terms of the GNU General Public License as
16   published by the Free Software Foundation; either version 2 of the
17   License, or (at your option) any later version.
18
19   This program is distributed in the hope that it will be useful, but
20   WITHOUT ANY WARRANTY; without even the implied warranty of
21   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
22   General Public License for more details.
23
24   You should have received a copy of the GNU General Public License
25   along with this program; if not, write to the Free Software
26   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
27   02111-1307, USA.
28
29   The GNU General Public License is contained in the file COPYING.
30*/
31
32#if defined(VGP_x86_darwin)
33
34#include "pub_core_basics.h"
35#include "pub_core_vki.h"
36#include "pub_core_vkiscnums.h"
37#include "pub_core_libcsetjmp.h"    // to keep _threadstate.h happy
38#include "pub_core_threadstate.h"
39#include "pub_core_aspacemgr.h"
40#include "pub_core_libcbase.h"
41#include "pub_core_libcassert.h"
42#include "pub_core_libcprint.h"
43#include "pub_core_machine.h"
44#include "pub_core_options.h"
45#include "pub_core_signals.h"
46#include "pub_core_tooliface.h"
47#include "pub_core_trampoline.h"
48#include "pub_core_sigframe.h"      /* self */
49
50
51/* Cheap-ass hack copied from ppc32-aix5 code, just to get started.
52   Produce a frame with layout entirely of our own choosing. */
53
54/* This module creates and removes signal frames for signal deliveries
55   on x86-darwin.  Kludgey; the machine state ought to be saved in a
56   ucontext and retrieved from it later, so the handler can modify it
57   and return.  However .. for now .. just stick the vex guest state
58   in the frame and snarf it again later.
59
60   Also, don't bother with creating siginfo and ucontext in the
61   handler, although do point them somewhere non-faulting.
62
63   Frame should have a 16-aligned size, just in case that turns out to
64   be important for Darwin.  (be conservative)
65*/
66struct hacky_sigframe {
67   /* first four words look like a call to a 3-arg x86 function */
68   UInt             returnAddr;
69   UInt             a1_signo;
70   UInt             a2_siginfo;
71   UInt             a3_ucontext;
72   UChar            lower_guardzone[512];  // put nothing here
73   VexGuestX86State gst;
74   VexGuestX86State gshadow1;
75   VexGuestX86State gshadow2;
76   vki_siginfo_t    fake_siginfo;
77   struct vki_ucontext fake_ucontext;
78   UInt             magicPI;
79   UInt             sigNo_private;
80   vki_sigset_t     mask; // saved sigmask; restore when hdlr returns
81   UInt             __pad[1];
82   UChar            upper_guardzone[512]; // put nothing here
83   // and don't zero it, since that might overwrite the client's
84   // stack redzone, at least on archs which have one
85};
86
87
88/* Extend the stack segment downwards if needed so as to ensure the
89   new signal frames are mapped to something.  Return a Bool
90   indicating whether or not the operation was successful.
91*/
92static Bool extend ( ThreadState *tst, Addr addr, SizeT size )
93{
94   ThreadId tid = tst->tid;
95   /* For tracking memory events, indicate the entire frame has been
96      allocated.  Except, don't mess with the area which
97      overlaps the previous frame's redzone. */
98   /* XXX is the following call really right?  compared with the
99      amd64-linux version, this doesn't appear to handle the redzone
100      in the same way. */
101   VG_TRACK( new_mem_stack_signal,
102             addr - VG_STACK_REDZONE_SZB, size, tid );
103   return True;
104}
105
106
107/* Create a signal frame for thread 'tid'.  Make a 3-arg frame
108   regardless of whether the client originally requested a 1-arg
109   version (no SA_SIGINFO) or a 3-arg one (SA_SIGINFO) since in the
110   former case, the x86 calling conventions will simply cause the
111   extra 2 args to be ignored (inside the handler). */
112void VG_(sigframe_create) ( ThreadId tid,
113                            Addr sp_top_of_frame,
114                            const vki_siginfo_t *siginfo,
115                            const struct vki_ucontext *siguc,
116                            void *handler,
117                            UInt flags,
118                            const vki_sigset_t *mask,
119                            void *restorer )
120{
121   ThreadState* tst;
122   Addr esp;
123   struct hacky_sigframe* frame;
124   Int sigNo = siginfo->si_signo;
125
126   vg_assert(VG_IS_16_ALIGNED(sizeof(struct hacky_sigframe)));
127
128   sp_top_of_frame &= ~0xf;
129   esp = sp_top_of_frame - sizeof(struct hacky_sigframe);
130   esp -= 4; /* ELF ABI says that esp+4 must be 16 aligned on
131                entry to a function. */
132
133   tst = VG_(get_ThreadState)(tid);
134   if (!extend(tst, esp, sp_top_of_frame - esp))
135      return;
136
137   vg_assert(VG_IS_16_ALIGNED(esp+4));
138
139   frame = (struct hacky_sigframe *) esp;
140
141   /* clear it (very conservatively) (why so conservatively??) */
142   VG_(memset)(&frame->lower_guardzone, 0, 512);
143   VG_(memset)(&frame->gst,      0, sizeof(VexGuestX86State));
144   VG_(memset)(&frame->gshadow1, 0, sizeof(VexGuestX86State));
145   VG_(memset)(&frame->gshadow2, 0, sizeof(VexGuestX86State));
146   VG_(memset)(&frame->fake_siginfo,  0, sizeof(frame->fake_siginfo));
147   VG_(memset)(&frame->fake_ucontext, 0, sizeof(frame->fake_ucontext));
148
149   /* save stuff in frame */
150   frame->gst           = tst->arch.vex;
151   frame->gshadow1      = tst->arch.vex_shadow1;
152   frame->gshadow2      = tst->arch.vex_shadow2;
153   frame->sigNo_private = sigNo;
154   frame->mask          = tst->sig_mask;
155   frame->magicPI       = 0x31415927;
156
157   /* Minimally fill in the siginfo and ucontext.  Note, utter
158      lameness prevails.  Be underwhelmed, be very underwhelmed. */
159   frame->fake_siginfo.si_signo = sigNo;
160   frame->fake_siginfo.si_code  = siginfo->si_code;
161
162   /* Set up stack pointer */
163   vg_assert(esp == (Addr)&frame->returnAddr);
164   VG_(set_SP)(tid, esp);
165   VG_TRACK( post_reg_write, Vg_CoreSignal, tid, VG_O_STACK_PTR, sizeof(UInt));
166
167   /* Set up program counter */
168   VG_(set_IP)(tid, (UInt)handler);
169   VG_TRACK( post_reg_write, Vg_CoreSignal, tid, VG_O_INSTR_PTR, sizeof(UInt));
170
171   /* Set up RA and args for the frame */
172   VG_TRACK( pre_mem_write, Vg_CoreSignal, tid, "signal handler frame",
173             (Addr)frame, 4*sizeof(UInt) );
174   frame->returnAddr  = (UInt)&VG_(x86_darwin_SUBST_FOR_sigreturn);
175   frame->a1_signo    = sigNo;
176   frame->a2_siginfo  = (UInt)&frame->fake_siginfo;  /* oh well */
177   frame->a3_ucontext = (UInt)&frame->fake_ucontext; /* oh well */
178   VG_TRACK( post_mem_write, Vg_CoreSignal, tid,
179             (Addr)frame, 4*sizeof(UInt) );
180   VG_TRACK( post_mem_write, Vg_CoreSignal, tid,
181             (Addr)&frame->fake_siginfo, sizeof(frame->fake_siginfo));
182   VG_TRACK( post_mem_write, Vg_CoreSignal, tid,
183             (Addr)&frame->fake_ucontext, sizeof(frame->fake_ucontext));
184
185   if (VG_(clo_trace_signals))
186      VG_(message)(Vg_DebugMsg,
187                   "sigframe_create (thread %d): "
188                   "next EIP=%#lx, next ESP=%#lx\n",
189                   tid, (Addr)handler, (Addr)frame );
190}
191
192
193/* Remove a signal frame from thread 'tid's stack, and restore the CPU
194   state from it.  Note, isRT is irrelevant here. */
195void VG_(sigframe_destroy)( ThreadId tid, Bool isRT )
196{
197   ThreadState *tst;
198   Addr esp;
199   Int sigNo;
200   struct hacky_sigframe* frame;
201
202   vg_assert(VG_(is_valid_tid)(tid));
203   tst = VG_(get_ThreadState)(tid);
204
205   /* Check that the stack frame looks valid */
206   esp = VG_(get_SP)(tid);
207
208   /* why -4 ? because the signal handler's return will have popped
209      the return address off the stack; and the return address is the
210      lowest-addressed element of hacky_sigframe. */
211   frame = (struct hacky_sigframe*)(esp - 4);
212   vg_assert(frame->magicPI == 0x31415927);
213
214   /* This +8 is because of the -4 referred to in the ELF ABI comment
215      in VG_(sigframe_create) just above. */
216   vg_assert(VG_IS_16_ALIGNED((Addr)frame + 4));
217
218   /* restore the entire guest state, and shadows, from the
219      frame.  Note, as per comments above, this is a kludge - should
220      restore it from saved ucontext.  Oh well. */
221   tst->arch.vex = frame->gst;
222   tst->arch.vex_shadow1 = frame->gshadow1;
223   tst->arch.vex_shadow2 = frame->gshadow2;
224   tst->sig_mask = frame->mask;
225   tst->tmp_sig_mask = frame->mask;
226   sigNo = frame->sigNo_private;
227
228   if (VG_(clo_trace_signals))
229      VG_(message)(Vg_DebugMsg,
230                   "sigframe_destroy (thread %d): "
231                   "valid magic; next EIP=%#x\n",
232                   tid, tst->arch.vex.guest_EIP);
233
234   VG_TRACK( die_mem_stack_signal,
235             (Addr)frame - VG_STACK_REDZONE_SZB,
236             sizeof(struct hacky_sigframe) );
237
238   /* tell the tools */
239   VG_TRACK( post_deliver_signal, tid, sigNo );
240}
241
242#endif // defined(VGP_x86_darwin)
243
244/*--------------------------------------------------------------------*/
245/*--- end                                                          ---*/
246/*--------------------------------------------------------------------*/
247