dev, virtio: Use of Unix socket for virtIO 9P device

This commit adds support for diod to use a unix socket, rather
than a TCP port.  We don't rely on the IP-based connection as we
directly use pipes to interact with diod.  This allows it to work
on any system, even if the specific port is taken by another diod
instance (or similar).  Secondly, the Unix socket could in theory
be used to debug.  However, this functionality has not been
tested.

Change-Id: I616e0ad8768da1dfc867de3af98cdfbb22a72d63
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Sascha Bischoff <sascha.bischoff@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/2820
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>

2 files changed, 39 insertions, 3 deletions

diff --git a/src/dev/virtio/VirtIO9P.py b/src/dev/virtio/VirtIO9P.py
index a13107db4..623403d1d 100644
--- a/src/dev/virtio/VirtIO9P.py
+++ b/src/dev/virtio/VirtIO9P.py
@@ -1,6 +1,6 @@
 # -*- mode:python -*-
 
-# Copyright (c) 2014 ARM Limited
+# Copyright (c) 2014,2017 ARM Limited
 # All rights reserved.
 #
 # The license below extends only to copyright in the software and shall
@@ -61,6 +61,7 @@ class VirtIO9PDiod(VirtIO9PProxy):
 
     diod = Param.String("/usr/sbin/diod", "Path to diod")
     root = Param.String("/tmp", "Path to export through diod")
+    socketPath = Param.String("Unused socket to diod")
 
 class VirtIO9PSocket(VirtIO9PProxy):
     type = 'VirtIO9PSocket'
diff --git a/src/dev/virtio/fs9p.cc b/src/dev/virtio/fs9p.cc
index a8d1ee779..7dac79ca0 100644
--- a/src/dev/virtio/fs9p.cc
+++ b/src/dev/virtio/fs9p.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2014-2015 ARM Limited
+ * Copyright (c) 2014-2017 ARM Limited
  * All rights reserved
  *
  * The license below extends only to copyright in the software and shall
@@ -44,8 +44,12 @@
 #include <netinet/in.h>
 #include <sys/socket.h>
 #include <sys/types.h>
+#include <sys/un.h>
 #include <unistd.h>
 
+#include <fstream>
+
+#include "base/output.hh"
 #include "debug/VIO9P.hh"
 #include "debug/VIO9PData.hh"
 #include "params/VirtIO9PBase.hh"
@@ -334,6 +338,8 @@ VirtIO9PDiod::startDiod()
 
     const char *diod(p->diod.c_str());
 
+    DPRINTF(VIO9P, "Using diod at %s \n", p->diod.c_str());
+
     if (pipe(pipe_rfd) == -1 || pipe(pipe_wfd) == -1)
         panic("Failed to create DIOD pipes: %i\n", errno);
 
@@ -353,6 +359,33 @@ VirtIO9PDiod::startDiod()
                   errno);
         }
 
+        // Create Unix domain socket
+        int socket_id = socket(AF_UNIX, SOCK_STREAM, 0);
+        if (socket_id == -1) {
+            panic("Socket creation failed %i \n", errno);
+        }
+        // Bind the socket to a path which will not be read
+        struct sockaddr_un socket_address;
+        memset(&socket_address, 0, sizeof(struct sockaddr_un));
+        socket_address.sun_family = AF_UNIX;
+
+        const std::string socket_path = simout.resolve(p->socketPath);
+        fatal_if(!OutputDirectory::isAbsolute(socket_path), "Please make the" \
+                 " output directory an absolute path, else diod will fail!\n");
+
+        // Prevent overflow in strcpy
+        fatal_if(sizeof(socket_address.sun_path) <= socket_path.length(),
+                 "Incorrect length of socket path");
+        strncpy(socket_address.sun_path, socket_path.c_str(),
+                sizeof(socket_address.sun_path));
+
+        if (bind(socket_id, (struct sockaddr*) &socket_address,
+                 sizeof(struct sockaddr_un)) == -1){
+            perror("Socket binding");
+            panic("Socket binding to %i failed - most likely the output dir" \
+                  " and hence unused socket already exists \n", socket_id);
+        }
+
         execlp(diod, diod,
                "-f", // start in foreground
                "-r", "3", // setup read FD
@@ -360,8 +393,10 @@ VirtIO9PDiod::startDiod()
                "-e", p->root.c_str(), // path to export
                "-n", // disable security
                "-S", // squash all users
+               "-l", socket_path.c_str(), // pass the socket
                (char *)NULL);
-        panic("Failed to execute diod: %i\n", errno);
+        perror("Starting DIOD");
+        panic("Failed to execute diod to %s: %i\n",socket_path, errno);
     } else {
         close(pipe_rfd[0]);
         close(pipe_wfd[1]);