[NaCl SDK] Map active fds to absolute paths.

native_client_sdk/src/libraries/nacl_io/kernel_proxy.cc

Index: native_client_sdk/src/libraries/nacl_io/kernel_proxy.cc
diff --git a/native_client_sdk/src/libraries/nacl_io/kernel_proxy.cc b/native_client_sdk/src/libraries/nacl_io/kernel_proxy.cc
index 672f51c30825aa1c9a8b4febf07f1047128e7b0c..298820026dcc3817d4a6f879d298c9923748f802 100644
--- a/native_client_sdk/src/libraries/nacl_io/kernel_proxy.cc
+++ b/native_client_sdk/src/libraries/nacl_io/kernel_proxy.cc
@@ -172,7 +172,8 @@ int KernelProxy::open_resource(const char* path) {
     return -1;
   }
 
-  return AllocateFD(handle);
+  int fd = AllocateFD(handle, path);

[binji, 2014/01/07 21:40:29]

return AllocateFD(handle, path);

is fine. Here and below

+  return fd;
 }
 
 int KernelProxy::open(const char* path, int open_flags) {
@@ -192,7 +193,8 @@ int KernelProxy::open(const char* path, int open_flags) {
     return -1;
   }
 
-  return AllocateFD(handle);
+  int fd = AllocateFD(handle, path);
+  return fd;
 }
 
 int KernelProxy::pipe(int pipefds[2]) {
@@ -209,8 +211,8 @@ int KernelProxy::pipe(int pipefds[2]) {
       return -1;
     }
 
-    pipefds[0] = AllocateFD(handle0);
-    pipefds[1] = AllocateFD(handle1);
+    pipefds[0] = AllocateFD(handle0, "");

[binji, 2014/01/07 21:40:29]

I think I'd prefer having the second parameter default to std::string(), and
making this just AllocateFD(handle0);

+    pipefds[1] = AllocateFD(handle1, "");
     return 0;
   }
 
@@ -238,8 +240,12 @@ int KernelProxy::dup(int oldfd) {
     errno = error;
     return -1;
   }
-
-  return AllocateFD(handle);
+  // Return value will be NULL if fd is not a path, which matches with the
+  // appropriate argument to AllocateFD.  Note that this will be a normalized
+  // Path.
+  std::string path = GetFDPath(oldfd);

[binji, 2014/01/07 21:40:29]

hm, I think there's a race here. The oldfd mapping can change between this call
and the handle acquired above from oldfd; this will make the dup'd fd have a
mismatched handle and path.

Here's a thought: add KernelObject::AcquireHandleAndPath that retrieves both in
the same locking of handle_lock_. You can use the same call below in fchdir.

+  int fd = AllocateFD(handle, path);
+  return fd;
 }
 
 int KernelProxy::dup2(int oldfd, int newfd) {
@@ -514,8 +520,31 @@ int KernelProxy::getdents(int fd, void* buf, unsigned int count) {
 }
 
 int KernelProxy::fchdir(int fd) {
-  errno = ENOSYS;
-  return -1;
+  ScopedKernelHandle handle;
+  Error error = AcquireHandle(fd, &handle);
+  if (error) {
+    errno = error;
+    return -1;
+  }
+
+  if (!handle->node()->IsaDir()) {
+    errno = ENOTDIR;
+    return -1;
+  }
+
+  std::string path = GetFDPath(fd);
+  if (path.empty()) {
+    errno = EBADF;
+    return -1;
+  }
+
+  error = SetCWD(path);
+  if (error) {
+    // errno is return value from SetCWD
+    errno = error;
+    return -1;
+  }
+  return 0;
 }
 
 int KernelProxy::ftruncate(int fd, off_t length) {
@@ -1202,7 +1231,7 @@ int KernelProxy::accept(int fd, struct sockaddr* addr, socklen_t* len) {
     return -1;
   }
 
-  return AllocateFD(new_handle);
+  return AllocateFD(new_handle, "");
 }
 
 int KernelProxy::bind(int fd, const struct sockaddr* addr, socklen_t len) {
@@ -1563,7 +1592,7 @@ int KernelProxy::socket(int domain, int type, int protocol) {
     return -1;
   }
 
-  return AllocateFD(handle);
+  return AllocateFD(handle, "");
 }
 
 int KernelProxy::socketpair(int domain, int type, int protocol, int* sv) {