service_runtime/sel_rt.h

   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 Secure Runtime
  34  */
  35
  36 #ifndef __SEL_RT_H__
  37 #define __SEL_RT_H__    1
  38
  39 #include "native_client/include/portability.h"
  40
  41 uint16_t NaClGetCs(void);
  42 /* setting CS is done using an lcall */
  43
  44 uint16_t NaClGetDs(void);
  45
  46 void    NaClSetDs(uint16_t v);
  47
  48 uint16_t NaClGetEs(void);
  49
  50 void    NaClSetEs(uint16_t v);
  51
  52 uint16_t NaClGetFs(void);
  53
  54 void    NaClSetFs(uint16_t v);
  55
  56 uint16_t NaClGetGs(void);
  57
  58 void    NaClSetGs(uint16_t v);
  59
  60 uint16_t NaClGetSs(void);
  61
  62 /* not really a segment registers, but ... */
  63
  64 uint32_t NaClGetEsp(void);
  65
  66 uint32_t NaClGetEbx(void);
  67
  68 /*
  69  * On a context switch through the syscall interface, not all
  70  * registers are saved.  We assume that C calling convention is used,
  71  * so %ecx and %edx are caller-saved and the NaCl service runtime do
  72  * not have to bother saving them; %eax (or %edx:%eax pair) should
  73  * have the return value, so its old value is also not saved.  (We
  74  * should, however, ensure that there is not an accidental covert
  75  * channel leaking information via these registers on syscall return.)
  76  * The eflags register is also caller saved.
  77  *
  78  * TODO if/when we do pre-emptive thread switching (to multiplex
  79  * user threads on top of kernel threads, for example), we will have
  80  * to add the full CPU state back in and figure out how to do a full
  81  * context switch completely in ring 3 code.
  82  *
  83  * We assume that the following is packed.  This is true for gcc and
  84  * msvc for x86, but we will include a check that sizeof(struct
  85  * NaClThreadContext) == 9*4 == 36 bytes.
  86  */
  87 struct NaClThreadContext {
  88   uint32_t    ebx, esi, edi, ebp, esp;  /* ecx, edx, eax, eflags not saved */
  89   /*          0    4    8    c    10 */
  90   uint32_t    eip;  /* return addr */
  91   /*          14 */
  92   uint16_t    cs, ds, es, fs, gs, ss;
  93   /*          18  1a  1c  1e  20  22 */
  94   /*
  95    * gs is our TLS base in the app; on the host side it's either fs or gs.
  96    */
  97 };
  98
  99 /*
 100  * A sanity check -- should be invoked in some early function, e.g.,
 101  * main, or something that main invokes early.
 102  */
 103 #define NACL_THREAD_CHECK do {                    \
 104     CHECK(sizeof(struct NaClThreadContext)==36);  \
 105   } while (0)
 106
 107 struct NaClApp;  /* fwd */
 108
 109 int NaClThreadContextCtor(struct NaClThreadContext  *ntcp,
 110                           uintptr_t                 eip,
 111                           uintptr_t                 esp,
 112                           uint16_t                  des_seg,
 113                           uint16_t                  gs,
 114                           uint16_t                  cs);
 115
 116 void NaClThreadContextDtor(struct NaClThreadContext *ntcp);
 117
 118 #endif