1 files changed, 48 insertions, 0 deletions
diff --git a/arch/arm64/kernel/module.c b/arch/arm64/kernel/module.c
index b2657ac41226..51fd8abd9b74 100644
--- a/arch/arm64/kernel/module.c
+++ b/arch/arm64/kernel/module.c
@@ -15,13 +15,61 @@
 #include <linux/kernel.h>
 #include <linux/mm.h>
 #include <linux/moduleloader.h>
+#include <linux/random.h>
 #include <linux/scs.h>
 #include <linux/vmalloc.h>
+
 #include <asm/alternative.h>
 #include <asm/insn.h>
 #include <asm/scs.h>
 #include <asm/sections.h>
 
+static u64 __ro_after_init module_alloc_base = (u64)_etext - MODULES_VSIZE;
+
+#ifdef CONFIG_RANDOMIZE_BASE
+static int __init kaslr_module_init(void)
+{
+	u64 module_range;
+	u32 seed;
+
+	if (!kaslr_enabled())
+		return 0;
+
+	seed = get_random_u32();
+
+	if (IS_ENABLED(CONFIG_RANDOMIZE_MODULE_REGION_FULL)) {
+		/*
+		 * Randomize the module region over a 2 GB window covering the
+		 * kernel. This reduces the risk of modules leaking information
+		 * about the address of the kernel itself, but results in
+		 * branches between modules and the core kernel that are
+		 * resolved via PLTs. (Branches between modules will be
+		 * resolved normally.)
+		 */
+		module_range = SZ_2G - (u64)(_end - _stext);
+		module_alloc_base = max((u64)_end - SZ_2G, (u64)MODULES_VADDR);
+	} else {
+		/*
+		 * Randomize the module region by setting module_alloc_base to
+		 * a PAGE_SIZE multiple in the range [_etext - MODULES_VSIZE,
+		 * _stext) . This guarantees that the resulting region still
+		 * covers [_stext, _etext], and that all relative branches can
+		 * be resolved without veneers unless this region is exhausted
+		 * and we fall back to a larger 2GB window in module_alloc()
+		 * when ARM64_MODULE_PLTS is enabled.
+		 */
+		module_range = MODULES_VSIZE - (u64)(_etext - _stext);
+	}
+
+	/* use the lower 21 bits to randomize the base of the module region */
+	module_alloc_base += (module_range * (seed & ((1 << 21) - 1))) >> 21;
+	module_alloc_base &= PAGE_MASK;
+
+	return 0;
+}
+subsys_initcall(kaslr_module_init)
+#endif
+
 void *module_alloc(unsigned long size)
 {
 	u64 module_alloc_end = module_alloc_base + MODULES_VSIZE;