service_runtime/nacl_switch_to_app.c

   1 /*
   2  * Copyright 2008, Google Inc.
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions are
   7  * met:
   8  *
   9  *     * Redistributions of source code must retain the above copyright
  10  * notice, this list of conditions and the following disclaimer.
  11  *     * Redistributions in binary form must reproduce the above
  12  * copyright notice, this list of conditions and the following disclaimer
  13  * in the documentation and/or other materials provided with the
  14  * distribution.
  15  *     * Neither the name of Google Inc. nor the names of its
  16  * contributors may be used to endorse or promote products derived from
  17  * this software without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  20  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  21  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  22  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  23  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  24  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  25  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  26  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  27  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  28  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  29  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  30  */
  31
  32 /*
  33  * NaCl Service Runtime, C-level context switch code.
  34  */
  35
  36 #include "native_client/service_runtime/sel_ldr.h"
  37 #include "native_client/service_runtime/sel_rt.h"
  38 #include "native_client/service_runtime/nacl_globals.h"
  39 #include "native_client/service_runtime/nacl_switch_to_app.h"
  40
  41 NORETURN void NaClStartThreadInApp(struct NaClAppThread *natp,
  42                                    uint32_t             new_eip)
  43 {
  44   struct NaClApp  *nap;
  45   /*
  46    * Save service runtime segment registers; fs/gs is used for TLS
  47    * on Windows and Linux respectively, so will change.  The others
  48    * should be global, but we save them from the thread anyway.
  49    */
  50 #if 0 /* restored by trampoline code */
  51   natp->sys.cs = NaClGetCs();
  52   natp->sys.ds = NaClGetDs();
  53 #endif
  54   natp->sys.es = NaClGetEs();
  55   natp->sys.fs = NaClGetFs();
  56   natp->sys.gs = NaClGetGs();
  57   natp->sys.ss = NaClGetSs();
  58   /*
  59    * Preserves stack alignment.  The trampoline code loads this value
  60    * to %esp, then pushes the thread ID (LDT index) onto the stack as
  61    * argument to NaClSyscallCSegHook.  See nacl_syscall.S.
  62    */
  63   natp->sys.esp = (NaClGetEsp() & ~0xf) + 4;
  64
  65   nap = natp->nap;
  66
  67   NaClSwitch(
  68       new_eip,
  69       natp->user.ebp,
  70       natp->user.edi,
  71       natp->user.esi,
  72       natp->user.ebx,
  73       (uint32_t) natp->user.gs,
  74       (uint32_t) natp->user.fs,
  75       (uint32_t) natp->user.es,
  76       nap->springboard_addr,
  77       (uint32_t) natp->user.cs,
  78       /* rest popped by NaCl_springboard */
  79       (uint32_t) natp->user.ds,
  80       0,  /* %eax not used to return */
  81       natp->user.esp,
  82       (uint32_t) natp->user.ss);
  83 }
  84
  85 /*
  86  * syscall return
  87  */
  88 NORETURN void NaClSwitchToApp(struct NaClAppThread *natp,
  89                               uint32_t             new_eip)
  90 {
  91   struct NaClApp  *nap;
  92
  93   nap = natp->nap;
  94   NaClSwitch(
  95       new_eip,
  96       natp->user.ebp,
  97       natp->user.edi,
  98       natp->user.esi,
  99       natp->user.ebx,
 100       (uint32_t) natp->user.gs,
 101       (uint32_t) natp->user.fs,
 102       (uint32_t) natp->user.es,
 103       nap->springboard_addr,
 104       (uint32_t) natp->user.cs,
 105       /* rest popped by NaCl_springboard */
 106       (uint32_t) natp->user.ds,
 107       natp->sysret,
 108       natp->user.esp,
 109       (uint32_t) natp->user.ss);
 110 }