xenfb: map framebuffer read-only and handle unmap errors
The framebuffer is needlessly mapped (PROT_READ | PROT_WRITE), map it
PROT_READ instead.
The framebuffer is unmapped by replacing the framebuffer pages with
anonymous shared memory, calling mmap. Check for return errors and print
a warning.
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
diff --git a/hw/display/xenfb.c b/hw/display/xenfb.c
index f0333a0..cb9d456 100644
--- a/hw/display/xenfb.c
+++ b/hw/display/xenfb.c
@@ -495,7 +495,7 @@
munmap(map, n_fbdirs * XC_PAGE_SIZE);
xenfb->pixels = xc_map_foreign_pages(xen_xc, xenfb->c.xendev.dom,
- PROT_READ | PROT_WRITE, fbmfns, xenfb->fbpages);
+ PROT_READ, fbmfns, xenfb->fbpages);
if (xenfb->pixels == NULL)
goto out;
@@ -903,6 +903,11 @@
fb->pixels = mmap(fb->pixels, fb->fbpages * XC_PAGE_SIZE,
PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANON,
-1, 0);
+ if (fb->pixels == MAP_FAILED) {
+ xen_be_printf(xendev, 0,
+ "Couldn't replace the framebuffer with anonymous memory errno=%d\n",
+ errno);
+ }
common_unbind(&fb->c);
fb->feature_update = 0;
fb->bug_trigger = 0;
