arm64: Add support for ARCH_SUPPORTS_DEBUG_PAGEALLOC

ARCH_SUPPORTS_DEBUG_PAGEALLOC provides a hook to map and unmap
pages for debugging purposes. This requires memory be mapped
with PAGE_SIZE mappings since breaking down larger mappings
at runtime will lead to TLB conflicts. Check if debug_pagealloc
is enabled at runtime and if so, map everyting with PAGE_SIZE
pages. Implement the functions to actually map/unmap the
pages at runtime.

Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Laura Abbott <labbott@fedoraproject.org>
[catalin.marinas@arm.com: static annotation block_mappings_allowed() and #ifdef]
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

1 files changed, 36 insertions, 10 deletions

diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
index 0795c3a36d8f..ca6d268e3313 100644
--- a/arch/arm64/mm/pageattr.c
+++ b/arch/arm64/mm/pageattr.c
@@ -37,14 +37,31 @@ static int change_page_range(pte_t *ptep, pgtable_t token, unsigned long addr,
         return 0;
 }
 
+/*
+ * This function assumes that the range is mapped with PAGE_SIZE pages.
+ */
+static int __change_memory_common(unsigned long start, unsigned long size,
+                                pgprot_t set_mask, pgprot_t clear_mask)
+{
+        struct page_change_data data;
+        int ret;
+
+        data.set_mask = set_mask;
+        data.clear_mask = clear_mask;
+
+        ret = apply_to_page_range(&init_mm, start, size, change_page_range,
+                                        &data);
+
+        flush_tlb_kernel_range(start, start + size);
+        return ret;
+}
+
 static int change_memory_common(unsigned long addr, int numpages,
                                 pgprot_t set_mask, pgprot_t clear_mask)
 {
         unsigned long start = addr;
         unsigned long size = PAGE_SIZE*numpages;
         unsigned long end = start + size;
-        int ret;
-        struct page_change_data data;
         struct vm_struct *area;
 
         if (!PAGE_ALIGNED(addr)) {
@@ -75,14 +92,7 @@ static int change_memory_common(unsigned long addr, int numpages,
         if (!numpages)
                 return 0;
 
-        data.set_mask = set_mask;
-        data.clear_mask = clear_mask;
-
-        ret = apply_to_page_range(&init_mm, start, size, change_page_range,
-                                        &data);
-
-        flush_tlb_kernel_range(start, end);
-        return ret;
+        return __change_memory_common(start, size, set_mask, clear_mask);
 }
 
 int set_memory_ro(unsigned long addr, int numpages)
@@ -114,3 +124,19 @@ int set_memory_x(unsigned long addr, int numpages)
                                         __pgprot(PTE_PXN));
 }
 EXPORT_SYMBOL_GPL(set_memory_x);
+
+#ifdef CONFIG_DEBUG_PAGEALLOC
+void __kernel_map_pages(struct page *page, int numpages, int enable)
+{
+        unsigned long addr = (unsigned long) page_address(page);
+
+        if (enable)
+                __change_memory_common(addr, PAGE_SIZE * numpages,
+                                        __pgprot(PTE_VALID),
+                                        __pgprot(0));
+        else
+                __change_memory_common(addr, PAGE_SIZE * numpages,
+                                        __pgprot(0),
+                                        __pgprot(PTE_VALID));
+}
+#endif