sandbox/linux/seccomp-bpf/syscall.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef SANDBOX_LINUX_SECCOMP_BPF_SYSCALL_H__
   6 #define SANDBOX_LINUX_SECCOMP_BPF_SYSCALL_H__
   7
   8 #include <signal.h>
   9 #include <stdint.h>
  10
  11 #include "base/macros.h"
  12 #include "sandbox/linux/system_headers/linux_signal.h"
  13 #include "sandbox/sandbox_export.h"
  14
  15 namespace sandbox {
  16
  17 // This purely static class can be used to perform system calls with some
  18 // low-level control.
  19 class SANDBOX_EXPORT Syscall {
  20  public:
  21   // InvalidCall() invokes Call() with a platform-appropriate syscall
  22   // number that is guaranteed to not be implemented (i.e., normally
  23   // returns -ENOSYS).
  24   // This is primarily meant to be useful for writing sandbox policy
  25   // unit tests.
  26   static intptr_t InvalidCall();
  27
  28   // System calls can take up to six parameters (up to eight on some
  29   // architectures). Traditionally, glibc
  30   // implements this property by using variadic argument lists. This works, but
  31   // confuses modern tools such as valgrind, because we are nominally passing
  32   // uninitialized data whenever we call through this function and pass less
  33   // than the full six arguments.
  34   // So, instead, we use C++'s template system to achieve a very similar
  35   // effect. C++ automatically sets the unused parameters to zero for us, and
  36   // it also does the correct type expansion (e.g. from 32bit to 64bit) where
  37   // necessary.
  38   // We have to use C-style cast operators as we want to be able to accept both
  39   // integer and pointer types.
  40   template <class T0,
  41             class T1,
  42             class T2,
  43             class T3,
  44             class T4,
  45             class T5,
  46             class T6,
  47             class T7>
  48   static inline intptr_t
  49   Call(int nr, T0 p0, T1 p1, T2 p2, T3 p3, T4 p4, T5 p5, T6 p6, T7 p7) {
  50     return Call(nr,
  51                 (intptr_t)p0,
  52                 (intptr_t)p1,
  53                 (intptr_t)p2,
  54                 (intptr_t)p3,
  55                 (intptr_t)p4,
  56                 (intptr_t)p5,
  57                 (intptr_t)p6,
  58                 (intptr_t)p7);
  59   }
  60
  61   template <class T0,
  62             class T1,
  63             class T2,
  64             class T3,
  65             class T4,
  66             class T5,
  67             class T6>
  68   static inline intptr_t
  69   Call(int nr, T0 p0, T1 p1, T2 p2, T3 p3, T4 p4, T5 p5, T6 p6) {
  70     return Call(nr,
  71                 (intptr_t)p0,
  72                 (intptr_t)p1,
  73                 (intptr_t)p2,
  74                 (intptr_t)p3,
  75                 (intptr_t)p4,
  76                 (intptr_t)p5,
  77                 (intptr_t)p6,
  78                 0);
  79   }
  80
  81   template <class T0, class T1, class T2, class T3, class T4, class T5>
  82   static inline intptr_t
  83   Call(int nr, T0 p0, T1 p1, T2 p2, T3 p3, T4 p4, T5 p5) {
  84     return Call(nr,
  85                 (intptr_t)p0,
  86                 (intptr_t)p1,
  87                 (intptr_t)p2,
  88                 (intptr_t)p3,
  89                 (intptr_t)p4,
  90                 (intptr_t)p5,
  91                 0,
  92                 0);
  93   }
  94
  95   template <class T0, class T1, class T2, class T3, class T4>
  96   static inline intptr_t Call(int nr, T0 p0, T1 p1, T2 p2, T3 p3, T4 p4) {
  97     return Call(nr, p0, p1, p2, p3, p4, 0, 0, 0);
  98   }
  99
 100   template <class T0, class T1, class T2, class T3>
 101   static inline intptr_t Call(int nr, T0 p0, T1 p1, T2 p2, T3 p3) {
 102     return Call(nr, p0, p1, p2, p3, 0, 0, 0, 0);
 103   }
 104
 105   template <class T0, class T1, class T2>
 106   static inline intptr_t Call(int nr, T0 p0, T1 p1, T2 p2) {
 107     return Call(nr, p0, p1, p2, 0, 0, 0, 0, 0);
 108   }
 109
 110   template <class T0, class T1>
 111   static inline intptr_t Call(int nr, T0 p0, T1 p1) {
 112     return Call(nr, p0, p1, 0, 0, 0, 0, 0, 0);
 113   }
 114
 115   template <class T0>
 116   static inline intptr_t Call(int nr, T0 p0) {
 117     return Call(nr, p0, 0, 0, 0, 0, 0, 0, 0);
 118   }
 119
 120   static inline intptr_t Call(int nr) {
 121     return Call(nr, 0, 0, 0, 0, 0, 0, 0, 0);
 122   }
 123
 124   // Set the registers in |ctx| to match what they would be after a system call
 125   // returning |ret_val|. |ret_val| must follow the Syscall::Call() convention
 126   // of being -errno on errors.
 127   static void PutValueInUcontext(intptr_t ret_val, ucontext_t* ctx);
 128
 129  private:
 130   // This performs system call |nr| with the arguments p0 to p7 from a constant
 131   // userland address, which is for instance observable by seccomp-bpf filters.
 132   // The constant userland address from which these system calls are made will
 133   // be returned if |nr| is passed as -1.
 134   // On error, this function will return a value between -1 and -4095 which
 135   // should be interpreted as -errno.
 136   static intptr_t Call(int nr,
 137                        intptr_t p0,
 138                        intptr_t p1,
 139                        intptr_t p2,
 140                        intptr_t p3,
 141                        intptr_t p4,
 142                        intptr_t p5,
 143                        intptr_t p6,
 144                        intptr_t p7);
 145
 146 #if defined(__mips__)
 147   // This function basically does on MIPS what SandboxSyscall() is doing on
 148   // other architectures. However, because of specificity of MIPS regarding
 149   // handling syscall errors, SandboxSyscall() is made as a wrapper for this
 150   // function in order for SandboxSyscall() to behave more like on other
 151   // architectures on places where return value from SandboxSyscall() is used
 152   // directly (like in most tests).
 153   // The syscall "nr" is called with arguments that are set in an array on which
 154   // pointer "args" points to and an information weather there is an error or no
 155   // is returned to SandboxSyscall() by err_stat.
 156   static intptr_t SandboxSyscallRaw(int nr,
 157                                     const intptr_t* args,
 158                                     intptr_t* err_stat);
 159 #endif  // defined(__mips__)
 160
 161   DISALLOW_IMPLICIT_CONSTRUCTORS(Syscall);
 162 };
 163
 164 }  // namespace sandbox
 165
 166 #endif  // SANDBOX_LINUX_SECCOMP_BPF_SYSCALL_H__