[Xen-devel] [PATCH 2/3] tools/libxencalls: add new function to query hypercall buffer safety

[Juergen Gross <jgross@xxxxxxxx>]

Add a new function to query whether hypercall buffers are always safe
to access by the hypervisor or might result in EFAULT.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
 tools/libs/call/Makefile          | 2 +-
 tools/libs/call/freebsd.c         | 5 +++++
 tools/libs/call/include/xencall.h | 7 +++++++
 tools/libs/call/libxencall.map    | 5 +++++
 tools/libs/call/linux.c           | 5 +++++
 tools/libs/call/minios.c          | 5 +++++
 tools/libs/call/netbsd.c          | 5 +++++
 tools/libs/call/solaris.c         | 5 +++++
 8 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/tools/libs/call/Makefile b/tools/libs/call/Makefile
index 39dd207428..252d3973fc 100644
--- a/tools/libs/call/Makefile
+++ b/tools/libs/call/Makefile
@@ -2,7 +2,7 @@ XEN_ROOT = $(CURDIR)/../../..
 include $(XEN_ROOT)/tools/Rules.mk
 
 MAJOR    = 1
-MINOR    = 0
+MINOR    = 1
 SHLIB_LDFLAGS += -Wl,--version-script=libxencall.map
 
 CFLAGS   += -Werror -Wmissing-prototypes
diff --git a/tools/libs/call/freebsd.c b/tools/libs/call/freebsd.c
index cadd313c04..28bfd852c1 100644
--- a/tools/libs/call/freebsd.c
+++ b/tools/libs/call/freebsd.c
@@ -107,6 +107,11 @@ void osdep_free_pages(xencall_handle *xcall, void *ptr, 
size_t npages)
     errno = saved_errno;
 }
 
+int xencall_buffers_never_fault(xencall_handle *xcall)
+{
+    return 1;
+}
+
 /*
  * Local variables:
  * mode: C
diff --git a/tools/libs/call/include/xencall.h 
b/tools/libs/call/include/xencall.h
index bafacdd2ba..0d09bc8eae 100644
--- a/tools/libs/call/include/xencall.h
+++ b/tools/libs/call/include/xencall.h
@@ -115,6 +115,13 @@ void xencall_free_buffer_pages(xencall_handle *xcall, void 
*p, size_t nr_pages);
 void *xencall_alloc_buffer(xencall_handle *xcall, size_t size);
 void xencall_free_buffer(xencall_handle *xcall, void *p);
 
+/*
+ * Are allocated hypercall buffers safe to be accessed by the hypervisor all
+ * the time?
+ * Returns 0 if EFAULT might be possible.
+ */
+int xencall_buffers_never_fault(xencall_handle *xcall);
+
 #endif
 
 /*
diff --git a/tools/libs/call/libxencall.map b/tools/libs/call/libxencall.map
index 2f96144f40..c482195b95 100644
--- a/tools/libs/call/libxencall.map
+++ b/tools/libs/call/libxencall.map
@@ -17,3 +17,8 @@ VERS_1.0 {
                xencall_free_buffer_pages;
        local: *; /* Do not expose anything by default */
 };
+
+VERS_1.1 {
+       global:
+               xencall_buffers_never_fault;
+} VERS_1.0;
diff --git a/tools/libs/call/linux.c b/tools/libs/call/linux.c
index fc1125972d..809fd19d2e 100644
--- a/tools/libs/call/linux.c
+++ b/tools/libs/call/linux.c
@@ -152,6 +152,11 @@ void osdep_free_pages(xencall_handle *xcall, void *ptr, 
size_t npages)
     errno = saved_errno;
 }
 
+int xencall_buffers_never_fault(xencall_handle *xcall)
+{
+    return xcall->buf_fd >= 0;
+}
+
 /*
  * Local variables:
  * mode: C
diff --git a/tools/libs/call/minios.c b/tools/libs/call/minios.c
index f04688f63c..9f7a96995f 100644
--- a/tools/libs/call/minios.c
+++ b/tools/libs/call/minios.c
@@ -70,6 +70,11 @@ void osdep_free_pages(xencall_handle *xcall, void *ptr, 
size_t npages)
     free(ptr);
 }
 
+int xencall_buffers_never_fault(xencall_handle *xcall)
+{
+    return 1;
+}
+
 /*
  * Local variables:
  * mode: C
diff --git a/tools/libs/call/netbsd.c b/tools/libs/call/netbsd.c
index e96fbf16f7..a5502da377 100644
--- a/tools/libs/call/netbsd.c
+++ b/tools/libs/call/netbsd.c
@@ -110,6 +110,11 @@ int do_xen_hypercall(xencall_handle *xcall, 
privcmd_hypercall_t *hypercall)
         return hypercall->retval;
 }
 
+int xencall_buffers_never_fault(xencall_handle *xcall)
+{
+    return 1;
+}
+
 /*
  * Local variables:
  * mode: C
diff --git a/tools/libs/call/solaris.c b/tools/libs/call/solaris.c
index 5aa330e4eb..c63b6a329a 100644
--- a/tools/libs/call/solaris.c
+++ b/tools/libs/call/solaris.c
@@ -86,6 +86,11 @@ int do_xen_hypercall(xencall_handle *xcall, 
privcmd_hypercall_t *hypercall)
     return ioctl(fd, IOCTL_PRIVCMD_HYPERCALL, hypercall);
 }
 
+int xencall_buffers_never_fault(xencall_handle *xcall)
+{
+    return 1;
+}
+
 /*
  * Local variables:
  * mode: C
-- 
2.13.7


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