iommu: debug-pagealloc: Check mapped/unmapped kernel memory

Now, as the page_ext holds count of IOMMU mappings, we can use it to
assert that any page allocated/freed is indeed not in the IOMMU.

The sanitizer doesn’t protect against mapping/unmapping during this
period. However, that’s less harmful as the page is not used by the
kernel.

Reviewed-by: Samiullah Khawaja <skhawaja@google.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Mostafa Saleh <smostafa@google.com>
Reviewed-by: Pranjal Shrivastava <praan@google.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/include/linux/iommu-debug-pagealloc.h b/include/linux/iommu-debug-pagealloc.h
index a439d6815ca1..46c3c1f70150 100644
--- a/include/linux/iommu-debug-pagealloc.h
+++ b/include/linux/iommu-debug-pagealloc.h
@@ -13,6 +13,20 @@ DECLARE_STATIC_KEY_FALSE(iommu_debug_initialized);
 
 extern struct page_ext_operations page_iommu_debug_ops;
 
+void __iommu_debug_check_unmapped(const struct page *page, int numpages);
+
+static inline void iommu_debug_check_unmapped(const struct page *page, int numpages)
+{
+	if (static_branch_unlikely(&iommu_debug_initialized))
+		__iommu_debug_check_unmapped(page, numpages);
+}
+
+#else
+static inline void iommu_debug_check_unmapped(const struct page *page,
+					      int numpages)
+{
+}
+
 #endif /* CONFIG_IOMMU_DEBUG_PAGEALLOC */
 
 #endif /* __LINUX_IOMMU_DEBUG_PAGEALLOC_H */