[Xen-devel] [PATCH v2 2/8] libxc: Provide access to internal handles

[Ian Jackson <ian.jackson@xxxxxxxxxxxxx>]

In order to support auditing of qemu depriv, my audit tool wants to
know the fd of a privcmd handle on which it can easily make
hypercalls.  xencall provides such a handle, but has no cooked
facilities for making hypercalls.  So I open a libxc handle.  That
means I need to get the privcmd fd out of the libxc handle.

ISTM that it is best to do this by providing an interface to get the
underlying library handles for a libxc handle.  This kind of interface
is quite common elsewhere and has not caused problems.

libxc is not a stable API so the downside risk of providing this
access is not significant.

Signed-off-by: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
Acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>

---
v2: Actually provide the fmem and dmod handle functions that the
    declarations in the .h file promise.
---
 tools/libxc/include/xenctrl.h | 10 ++++++++++
 tools/libxc/xc_private.c      | 15 +++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/tools/libxc/include/xenctrl.h b/tools/libxc/include/xenctrl.h
index 408fa1c..d7733aa 100644
--- a/tools/libxc/include/xenctrl.h
+++ b/tools/libxc/include/xenctrl.h
@@ -183,6 +183,16 @@ enum xc_open_flags {
  */
 int xc_interface_close(xc_interface *xch);
 
+/**
+ * Return the handles which xch has opened and will use for
+ * hypercalls, foreign memory accesses and device model operations.
+ * These may be used with the corresponding libraries so long as the
+ * xch itself remains open.
+ */
+struct xencall_handle *xc_interface_xcall_handle(xc_interface *xch);
+struct xenforeignmemory_handle *xc_interface_fmem_handle(xc_interface *xch);
+struct xendevicemodel_handle *xc_interface_dmod_handle(xc_interface *xch);
+
 /*
  * HYPERCALL SAFE MEMORY BUFFER
  *
diff --git a/tools/libxc/xc_private.c b/tools/libxc/xc_private.c
index fcda981..5a2efe7 100644
--- a/tools/libxc/xc_private.c
+++ b/tools/libxc/xc_private.c
@@ -104,6 +104,21 @@ int xc_interface_close(xc_interface *xch)
     return rc;
 }
 
+xencall_handle *xc_interface_xcall_handle(xc_interface *xch)
+{
+    return xch->xcall;
+}
+
+struct xenforeignmemory_handle *xc_interface_fmem_handle(xc_interface *xch)
+{
+    return xch->fmem;
+}
+
+struct xendevicemodel_handle *xc_interface_dmod_handle(xc_interface *xch)
+{
+    return xch->dmod;
+}
+
 static pthread_key_t errbuf_pkey;
 static pthread_once_t errbuf_pkey_once = PTHREAD_ONCE_INIT;
 
-- 
2.1.4


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