Linux sandbox: add space for 8 parameters to the Syscall() class

sandbox/linux/seccomp-bpf/syscall.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "sandbox/linux/seccomp-bpf/syscall.h"
 
 #include <asm/unistd.h>
 #include <errno.h>
 
 #include "base/basictypes.h"
@@ skipping 163 matching lines @@
     );  // asm
 
 }  // namespace
 
 intptr_t Syscall::Call(int nr,
                        intptr_t p0,
                        intptr_t p1,
                        intptr_t p2,
                        intptr_t p3,
                        intptr_t p4,
-                       intptr_t p5) {
+                       intptr_t p5,
+                       intptr_t p6,
+                       intptr_t p7) {
   // We rely on "intptr_t" to be the exact size as a "void *". This is
   // typically true, but just in case, we add a check. The language
   // specification allows platforms some leeway in cases, where
   // "sizeof(void *)" is not the same as "sizeof(void (*)())". We expect
   // that this would only be an issue for IA64, which we are currently not
   // planning on supporting. And it is even possible that this would work
   // on IA64, but for lack of actual hardware, I cannot test.
   COMPILE_ASSERT(sizeof(void*) == sizeof(intptr_t),
                  pointer_types_and_intptr_must_be_exactly_the_same_size);
 
+  // TODO(nedeljko): Enable use of more than six parameters on architectures

[mdempsky, 2014/07/01 21:53:17]

Would it make sense to add DCHECK()s to make sure p6 == 0 and p7 == 0 until
support is added?

[nedeljko, 2014/07/02 10:46:19]

Done.

+  //                 where that makes sense.
   const intptr_t args[6] = {p0, p1, p2, p3, p4, p5};
 
 // Invoke our file-scope assembly code. The constraints have been picked
 // carefully to match what the rest of the assembly code expects in input,
 // output, and clobbered registers.
 #if defined(__i386__)
   intptr_t ret = nr;
   asm volatile(
       "call SyscallAsm\n"
       // N.B. These are not the calling conventions normally used by the ABI.
@@ skipping 54 matching lines @@
         );
     ret = inout;
   }
 #else
 #error "Unimplemented architecture"
 #endif
   return ret;
 }
 
 }  // namespace sandbox