[Xen-devel] [PATCH] mmap on /dev/mem support in stubdoms

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

Hi all,
this patch adds support for mmap on /dev/mem in a stubdom; it is secure
because it only works for memory areas that have been explicitly
allowed by the toolstack (xc_domain_iomem_permission).
Incidentally this is all that is needed to make MSI-X passthrough work
with stubdoms.


Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>

---


diff -r eaa7d75a82b6 extras/mini-os/include/lib.h
--- a/extras/mini-os/include/lib.h      Tue Oct 20 16:18:43 2009 +0100
+++ b/extras/mini-os/include/lib.h      Wed Oct 21 11:08:39 2009 +0100
@@ -145,6 +145,7 @@
     FTYPE_BLK,
     FTYPE_KBD,
     FTYPE_FB,
+    FTYPE_MEM,
 };
 
 #define MAX_EVTCHN_PORTS 16
diff -r eaa7d75a82b6 extras/mini-os/lib/sys.c
--- a/extras/mini-os/lib/sys.c  Tue Oct 20 16:18:43 2009 +0100
+++ b/extras/mini-os/lib/sys.c  Wed Oct 21 11:08:39 2009 +0100
@@ -188,6 +188,11 @@
     if (!strncmp(pathname,LOG_PATH,strlen(LOG_PATH))) {
        fd = alloc_fd(FTYPE_CONSOLE);
         printk("open(%s) -> %d\n", pathname, fd);
+        return fd;
+    }
+    if (!strncmp(pathname, "/dev/mem", strlen("/dev/mem"))) {
+        fd = alloc_fd(FTYPE_MEM);
+        printk("open(/dev/mem) -> %d\n", fd);
         return fd;
     }
     if (!strncmp(pathname, "/dev/ptmx", strlen("/dev/ptmx")))
@@ -1244,13 +1249,18 @@
     ASSERT(prot == (PROT_READ|PROT_WRITE));
     ASSERT((fd == -1 && (flags == (MAP_SHARED|MAP_ANON) || flags == 
(MAP_PRIVATE|MAP_ANON)))
         || (fd != -1 && flags == MAP_SHARED));
-    ASSERT(offset == 0);
 
     if (fd == -1)
         return map_zero(n, 1);
     else if (files[fd].type == FTYPE_XC) {
         unsigned long zero = 0;
         return map_frames_ex(&zero, n, 0, 0, 1, DOMID_SELF, 0, 0);
+    } else if (files[fd].type == FTYPE_MEM) {
+        int i;
+        unsigned long mfns[n];
+        for (i = 0; i < n; i++)
+            mfns[i] = ((unsigned long) offset + (i * PAGE_SIZE)) >> PAGE_SHIFT;
+        return map_frames_ex(mfns, n, 1, 0, 1, DOMID_IO, 0, 
_PAGE_PRESENT|_PAGE_RW);
     } else ASSERT(0);
 }
 

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