1 files changed, 153 insertions, 0 deletions
diff --git a/sandbox/linux/seccomp/mutex.h b/sandbox/linux/seccomp/mutex.h
new file mode 100644
index 0000000..d7e1c5d
--- /dev/null
+++ b/sandbox/linux/seccomp/mutex.h
@@ -0,0 +1,153 @@
+// Copyright (c) 2010 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.
+
+#ifndef MUTEX_H__
+#define MUTEX_H__
+
+#include "sandbox_impl.h"
+
+namespace playground {
+
+class Mutex {
+ public:
+  typedef int mutex_t;
+
+  enum { kInitValue = 0 };
+
+  static void initMutex(mutex_t* mutex) {
+    // Mutex is unlocked, and nobody is waiting for it
+    *mutex = kInitValue;
+  }
+
+  static void unlockMutex(mutex_t* mutex) {
+    char status;
+    #if defined(__x86_64__) || defined(__i386__)
+    asm volatile(
+        "lock; addl %2, %0\n"
+        "setz %1"
+        : "=m"(*mutex), "=qm"(status)
+        : "ir"(0x80000000), "m"(*mutex));
+    #else
+    #error Unsupported target platform
+    #endif
+    if (status) {
+      // Mutex is zero now. No other waiters. So, we can return.
+      return;
+    }
+    // We unlocked the mutex, but still need to wake up other waiters.
+    Sandbox::SysCalls sys;
+    sys.futex(mutex, FUTEX_WAKE, 1, NULL);
+  }
+
+  static bool lockMutex(mutex_t* mutex, int timeout = 0) {
+    bool rc        = true;
+    // Increment mutex to add ourselves to the list of waiters
+    #if defined(__x86_64__) || defined(__i386__)
+    asm volatile(
+        "lock; incl %0\n"
+        : "=m"(*mutex)
+        : "m"(*mutex));
+    #else
+    #error Unsupported target platform
+    #endif
+    for (;;) {
+      // Atomically check whether the mutex is available and if so, acquire it
+      char status;
+      #if defined(__x86_64__) || defined(__i386__)
+      asm volatile(
+          "lock; btsl %3, %1\n"
+          "setc %0"
+          : "=q"(status), "=m"(*mutex)
+          : "m"(*mutex), "ir"(31));
+      #else
+      #error Unsupported target platform
+      #endif
+      if (!status) {
+     done:
+        // If the mutex was available, remove ourselves from list of waiters
+        #if defined(__x86_64__) || defined(__i386__)
+        asm volatile(
+            "lock; decl %0\n"
+            : "=m"(*mutex)
+            : "m"(*mutex));
+        #else
+        #error Unsupported target platform
+        #endif
+        return rc;
+      }
+      int value    = *mutex;
+      if (value >= 0) {
+        // Mutex has just become available, no need to call kernel
+        continue;
+      }
+      Sandbox::SysCalls sys;
+      Sandbox::SysCalls::kernel_timespec tm;
+      if (timeout) {
+        tm.tv_sec  = timeout / 1000;
+        tm.tv_nsec = (timeout % 1000) * 1000 * 1000;
+      } else {
+        tm.tv_sec  = 0;
+        tm.tv_nsec = 0;
+      }
+      if (NOINTR_SYS(sys.futex(mutex, FUTEX_WAIT, value, &tm)) &&
+          sys.my_errno == ETIMEDOUT) {
+        rc         = false;
+        goto done;
+      }
+    }
+  }
+
+  static bool waitForUnlock(mutex_t* mutex, int timeout = 0) {
+    bool rc        = true;
+    // Increment mutex to add ourselves to the list of waiters
+    #if defined(__x86_64__) || defined(__i386__)
+    asm volatile(
+        "lock; incl %0\n"
+        : "=m"(*mutex)
+        : "m"(*mutex));
+    #else
+    #error Unsupported target platform
+    #endif
+    Sandbox::SysCalls sys;
+    for (;;) {
+      mutex_t value = *mutex;
+      if (value >= 0) {
+     done:
+        // Mutex was not locked. Remove ourselves from list of waiters, notify
+        // any other waiters (if any), and return.
+        #if defined(__x86_64__) || defined(__i386__)
+        asm volatile(
+            "lock; decl %0\n"
+            : "=m"(*mutex)
+            : "m"(*mutex));
+        #else
+        #error Unsupported target platform
+        #endif
+        NOINTR_SYS(sys.futex(mutex, FUTEX_WAKE, 1, 0));
+        return rc;
+      }
+
+      // Wait for mutex to become unlocked
+      Sandbox::SysCalls::kernel_timespec tm;
+      if (timeout) {
+        tm.tv_sec   = timeout / 1000;
+        tm.tv_nsec  = (timeout % 1000) * 1000 * 1000;
+      } else {
+        tm.tv_sec   = 0;
+        tm.tv_nsec  = 0;
+      }
+
+      if (NOINTR_SYS(sys.futex(mutex, FUTEX_WAIT, value, &tm)) &&
+          sys.my_errno == ETIMEDOUT) {
+        rc          = false;
+        goto done;
+      }
+    }
+  }
+
+};
+
+} // namespace
+
+#endif // MUTEX_H__