1 files changed, 39 insertions, 9 deletions

diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c
index 37db264866b6..3c306de52fd4 100644
--- a/arch/x86/mm/kaslr.c
+++ b/arch/x86/mm/kaslr.c
@@ -22,7 +22,7 @@
 
 #include <linux/kernel.h>
 #include <linux/init.h>
-#include <linux/random.h>
+#include <linux/prandom.h>
 #include <linux/memblock.h>
 #include <linux/pgtable.h>
 
@@ -47,13 +47,28 @@ static const unsigned long vaddr_end = CPU_ENTRY_AREA_BASE;
  */
 static __initdata struct kaslr_memory_region {
 	unsigned long *base;
+	unsigned long *end;
 	unsigned long size_tb;
 } kaslr_regions[] = {
-	{ &page_offset_base, 0 },
-	{ &vmalloc_base, 0 },
-	{ &vmemmap_base, 0 },
+	{
+		.base	= &page_offset_base,
+		.end	= &direct_map_physmem_end,
+	},
+	{
+		.base	= &vmalloc_base,
+	},
+	{
+		.base	= &vmemmap_base,
+	},
 };
 
+/*
+ * The end of the physical address space that can be mapped directly by the
+ * kernel. This starts out at (1<<MAX_PHYSMEM_BITS) - 1), but KASLR may reduce
+ * that in order to increase the available entropy for mapping other regions.
+ */
+unsigned long direct_map_physmem_end __ro_after_init;
+
 /* Get size in bytes used by the memory region */
 static inline unsigned long get_padding(struct kaslr_memory_region *region)
 {
@@ -82,6 +97,8 @@ void __init kernel_randomize_memory(void)
 	BUILD_BUG_ON(vaddr_end != CPU_ENTRY_AREA_BASE);
 	BUILD_BUG_ON(vaddr_end > __START_KERNEL_map);
 
+	/* Preset the end of the possible address space for physical memory */
+	direct_map_physmem_end = ((1ULL << MAX_PHYSMEM_BITS) - 1);
 	if (!kaslr_memory_enabled())
 		return;
 
@@ -96,8 +113,14 @@ void __init kernel_randomize_memory(void)
 	memory_tb = DIV_ROUND_UP(max_pfn << PAGE_SHIFT, 1UL << TB_SHIFT) +
 		CONFIG_RANDOMIZE_MEMORY_PHYSICAL_PADDING;
 
-	/* Adapt physical memory region size based on available memory */
-	if (memory_tb < kaslr_regions[0].size_tb)
+	/*
+	 * Adapt physical memory region size based on available memory,
+	 * except when CONFIG_PCI_P2PDMA is enabled. P2PDMA exposes the
+	 * device BAR space assuming the direct map space is large enough
+	 * for creating a ZONE_DEVICE mapping in the direct map corresponding
+	 * to the physical BAR address.
+	 */
+	if (!IS_ENABLED(CONFIG_PCI_P2PDMA) && (memory_tb < kaslr_regions[0].size_tb))
 		kaslr_regions[0].size_tb = memory_tb;
 
 	/*
@@ -128,11 +151,18 @@ void __init kernel_randomize_memory(void)
 		vaddr += entropy;
 		*kaslr_regions[i].base = vaddr;
 
+		/* Calculate the end of the region */
+		vaddr += get_padding(&kaslr_regions[i]);
 		/*
-		 * Jump the region and add a minimum padding based on
-		 * randomization alignment.
+		 * KASLR trims the maximum possible size of the
+		 * direct-map. Update the direct_map_physmem_end boundary.
+		 * No rounding required as the region starts
+		 * PUD aligned and size is in units of TB.
 		 */
-		vaddr += get_padding(&kaslr_regions[i]);
+		if (kaslr_regions[i].end)
+			*kaslr_regions[i].end = __pa_nodebug(vaddr - 1);
+
+		/* Add a minimum padding based on randomization alignment. */
 		vaddr = round_up(vaddr + 1, PUD_SIZE);
 		remain_entropy -= entropy;
 	}