1 files changed, 479 insertions, 0 deletions
diff --git a/mm/execmem.c b/mm/execmem.c
new file mode 100644
index 000000000000..317b6a8d35be
--- /dev/null
+++ b/mm/execmem.c
@@ -0,0 +1,479 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2002 Richard Henderson
+ * Copyright (C) 2001 Rusty Russell, 2002, 2010 Rusty Russell IBM.
+ * Copyright (C) 2023 Luis Chamberlain <mcgrof@kernel.org>
+ * Copyright (C) 2024 Mike Rapoport IBM.
+ */
+
+#define pr_fmt(fmt) "execmem: " fmt
+
+#include <linux/mm.h>
+#include <linux/mutex.h>
+#include <linux/vmalloc.h>
+#include <linux/execmem.h>
+#include <linux/maple_tree.h>
+#include <linux/set_memory.h>
+#include <linux/moduleloader.h>
+#include <linux/text-patching.h>
+
+#include <asm/tlbflush.h>
+
+#include "internal.h"
+
+static struct execmem_info *execmem_info __ro_after_init;
+static struct execmem_info default_execmem_info __ro_after_init;
+
+#ifdef CONFIG_MMU
+static void *execmem_vmalloc(struct execmem_range *range, size_t size,
+			     pgprot_t pgprot, unsigned long vm_flags)
+{
+	bool kasan = range->flags & EXECMEM_KASAN_SHADOW;
+	gfp_t gfp_flags = GFP_KERNEL | __GFP_NOWARN;
+	unsigned int align = range->alignment;
+	unsigned long start = range->start;
+	unsigned long end = range->end;
+	void *p;
+
+	if (kasan)
+		vm_flags |= VM_DEFER_KMEMLEAK;
+
+	if (vm_flags & VM_ALLOW_HUGE_VMAP)
+		align = PMD_SIZE;
+
+	p = __vmalloc_node_range(size, align, start, end, gfp_flags,
+				 pgprot, vm_flags, NUMA_NO_NODE,
+				 __builtin_return_address(0));
+	if (!p && range->fallback_start) {
+		start = range->fallback_start;
+		end = range->fallback_end;
+		p = __vmalloc_node_range(size, align, start, end, gfp_flags,
+					 pgprot, vm_flags, NUMA_NO_NODE,
+					 __builtin_return_address(0));
+	}
+
+	if (!p) {
+		pr_warn_ratelimited("unable to allocate memory\n");
+		return NULL;
+	}
+
+	if (kasan && (kasan_alloc_module_shadow(p, size, GFP_KERNEL) < 0)) {
+		vfree(p);
+		return NULL;
+	}
+
+	return p;
+}
+
+struct vm_struct *execmem_vmap(size_t size)
+{
+	struct execmem_range *range = &execmem_info->ranges[EXECMEM_MODULE_DATA];
+	struct vm_struct *area;
+
+	area = __get_vm_area_node(size, range->alignment, PAGE_SHIFT, VM_ALLOC,
+				  range->start, range->end, NUMA_NO_NODE,
+				  GFP_KERNEL, __builtin_return_address(0));
+	if (!area && range->fallback_start)
+		area = __get_vm_area_node(size, range->alignment, PAGE_SHIFT, VM_ALLOC,
+					  range->fallback_start, range->fallback_end,
+					  NUMA_NO_NODE, GFP_KERNEL, __builtin_return_address(0));
+
+	return area;
+}
+#else
+static void *execmem_vmalloc(struct execmem_range *range, size_t size,
+			     pgprot_t pgprot, unsigned long vm_flags)
+{
+	return vmalloc(size);
+}
+#endif /* CONFIG_MMU */
+
+#ifdef CONFIG_ARCH_HAS_EXECMEM_ROX
+struct execmem_cache {
+	struct mutex mutex;
+	struct maple_tree busy_areas;
+	struct maple_tree free_areas;
+};
+
+static struct execmem_cache execmem_cache = {
+	.mutex = __MUTEX_INITIALIZER(execmem_cache.mutex),
+	.busy_areas = MTREE_INIT_EXT(busy_areas, MT_FLAGS_LOCK_EXTERN,
+				     execmem_cache.mutex),
+	.free_areas = MTREE_INIT_EXT(free_areas, MT_FLAGS_LOCK_EXTERN,
+				     execmem_cache.mutex),
+};
+
+static inline unsigned long mas_range_len(struct ma_state *mas)
+{
+	return mas->last - mas->index + 1;
+}
+
+static int execmem_set_direct_map_valid(struct vm_struct *vm, bool valid)
+{
+	unsigned int nr = (1 << get_vm_area_page_order(vm));
+	unsigned int updated = 0;
+	int err = 0;
+
+	for (int i = 0; i < vm->nr_pages; i += nr) {
+		err = set_direct_map_valid_noflush(vm->pages[i], nr, valid);
+		if (err)
+			goto err_restore;
+		updated += nr;
+	}
+
+	return 0;
+
+err_restore:
+	for (int i = 0; i < updated; i += nr)
+		set_direct_map_valid_noflush(vm->pages[i], nr, !valid);
+
+	return err;
+}
+
+static void execmem_cache_clean(struct work_struct *work)
+{
+	struct maple_tree *free_areas = &execmem_cache.free_areas;
+	struct mutex *mutex = &execmem_cache.mutex;
+	MA_STATE(mas, free_areas, 0, ULONG_MAX);
+	void *area;
+
+	mutex_lock(mutex);
+	mas_for_each(&mas, area, ULONG_MAX) {
+		size_t size = mas_range_len(&mas);
+
+		if (IS_ALIGNED(size, PMD_SIZE) &&
+		    IS_ALIGNED(mas.index, PMD_SIZE)) {
+			struct vm_struct *vm = find_vm_area(area);
+
+			execmem_set_direct_map_valid(vm, true);
+			mas_store_gfp(&mas, NULL, GFP_KERNEL);
+			vfree(area);
+		}
+	}
+	mutex_unlock(mutex);
+}
+
+static DECLARE_WORK(execmem_cache_clean_work, execmem_cache_clean);
+
+static int execmem_cache_add(void *ptr, size_t size)
+{
+	struct maple_tree *free_areas = &execmem_cache.free_areas;
+	struct mutex *mutex = &execmem_cache.mutex;
+	unsigned long addr = (unsigned long)ptr;
+	MA_STATE(mas, free_areas, addr - 1, addr + 1);
+	unsigned long lower, upper;
+	void *area = NULL;
+	int err;
+
+	lower = addr;
+	upper = addr + size - 1;
+
+	mutex_lock(mutex);
+	area = mas_walk(&mas);
+	if (area && mas.last == addr - 1)
+		lower = mas.index;
+
+	area = mas_next(&mas, ULONG_MAX);
+	if (area && mas.index == addr + size)
+		upper = mas.last;
+
+	mas_set_range(&mas, lower, upper);
+	err = mas_store_gfp(&mas, (void *)lower, GFP_KERNEL);
+	mutex_unlock(mutex);
+	if (err)
+		return err;
+
+	return 0;
+}
+
+static bool within_range(struct execmem_range *range, struct ma_state *mas,
+			 size_t size)
+{
+	unsigned long addr = mas->index;
+
+	if (addr >= range->start && addr + size < range->end)
+		return true;
+
+	if (range->fallback_start &&
+	    addr >= range->fallback_start && addr + size < range->fallback_end)
+		return true;
+
+	return false;
+}
+
+static void *__execmem_cache_alloc(struct execmem_range *range, size_t size)
+{
+	struct maple_tree *free_areas = &execmem_cache.free_areas;
+	struct maple_tree *busy_areas = &execmem_cache.busy_areas;
+	MA_STATE(mas_free, free_areas, 0, ULONG_MAX);
+	MA_STATE(mas_busy, busy_areas, 0, ULONG_MAX);
+	struct mutex *mutex = &execmem_cache.mutex;
+	unsigned long addr, last, area_size = 0;
+	void *area, *ptr = NULL;
+	int err;
+
+	mutex_lock(mutex);
+	mas_for_each(&mas_free, area, ULONG_MAX) {
+		area_size = mas_range_len(&mas_free);
+
+		if (area_size >= size && within_range(range, &mas_free, size))
+			break;
+	}
+
+	if (area_size < size)
+		goto out_unlock;
+
+	addr = mas_free.index;
+	last = mas_free.last;
+
+	/* insert allocated size to busy_areas at range [addr, addr + size) */
+	mas_set_range(&mas_busy, addr, addr + size - 1);
+	err = mas_store_gfp(&mas_busy, (void *)addr, GFP_KERNEL);
+	if (err)
+		goto out_unlock;
+
+	mas_store_gfp(&mas_free, NULL, GFP_KERNEL);
+	if (area_size > size) {
+		void *ptr = (void *)(addr + size);
+
+		/*
+		 * re-insert remaining free size to free_areas at range
+		 * [addr + size, last]
+		 */
+		mas_set_range(&mas_free, addr + size, last);
+		err = mas_store_gfp(&mas_free, ptr, GFP_KERNEL);
+		if (err) {
+			mas_store_gfp(&mas_busy, NULL, GFP_KERNEL);
+			goto out_unlock;
+		}
+	}
+	ptr = (void *)addr;
+
+out_unlock:
+	mutex_unlock(mutex);
+	return ptr;
+}
+
+static int execmem_cache_populate(struct execmem_range *range, size_t size)
+{
+	unsigned long vm_flags = VM_ALLOW_HUGE_VMAP;
+	unsigned long start, end;
+	struct vm_struct *vm;
+	size_t alloc_size;
+	int err = -ENOMEM;
+	void *p;
+
+	alloc_size = round_up(size, PMD_SIZE);
+	p = execmem_vmalloc(range, alloc_size, PAGE_KERNEL, vm_flags);
+	if (!p)
+		return err;
+
+	vm = find_vm_area(p);
+	if (!vm)
+		goto err_free_mem;
+
+	/* fill memory with instructions that will trap */
+	execmem_fill_trapping_insns(p, alloc_size, /* writable = */ true);
+
+	start = (unsigned long)p;
+	end = start + alloc_size;
+
+	vunmap_range(start, end);
+
+	err = execmem_set_direct_map_valid(vm, false);
+	if (err)
+		goto err_free_mem;
+
+	err = vmap_pages_range_noflush(start, end, range->pgprot, vm->pages,
+				       PMD_SHIFT);
+	if (err)
+		goto err_free_mem;
+
+	err = execmem_cache_add(p, alloc_size);
+	if (err)
+		goto err_free_mem;
+
+	return 0;
+
+err_free_mem:
+	vfree(p);
+	return err;
+}
+
+static void *execmem_cache_alloc(struct execmem_range *range, size_t size)
+{
+	void *p;
+	int err;
+
+	p = __execmem_cache_alloc(range, size);
+	if (p)
+		return p;
+
+	err = execmem_cache_populate(range, size);
+	if (err)
+		return NULL;
+
+	return __execmem_cache_alloc(range, size);
+}
+
+static bool execmem_cache_free(void *ptr)
+{
+	struct maple_tree *busy_areas = &execmem_cache.busy_areas;
+	struct mutex *mutex = &execmem_cache.mutex;
+	unsigned long addr = (unsigned long)ptr;
+	MA_STATE(mas, busy_areas, addr, addr);
+	size_t size;
+	void *area;
+
+	mutex_lock(mutex);
+	area = mas_walk(&mas);
+	if (!area) {
+		mutex_unlock(mutex);
+		return false;
+	}
+	size = mas_range_len(&mas);
+
+	mas_store_gfp(&mas, NULL, GFP_KERNEL);
+	mutex_unlock(mutex);
+
+	execmem_fill_trapping_insns(ptr, size, /* writable = */ false);
+
+	execmem_cache_add(ptr, size);
+
+	schedule_work(&execmem_cache_clean_work);
+
+	return true;
+}
+#else /* CONFIG_ARCH_HAS_EXECMEM_ROX */
+static void *execmem_cache_alloc(struct execmem_range *range, size_t size)
+{
+	return NULL;
+}
+
+static bool execmem_cache_free(void *ptr)
+{
+	return false;
+}
+#endif /* CONFIG_ARCH_HAS_EXECMEM_ROX */
+
+void *execmem_alloc(enum execmem_type type, size_t size)
+{
+	struct execmem_range *range = &execmem_info->ranges[type];
+	bool use_cache = range->flags & EXECMEM_ROX_CACHE;
+	unsigned long vm_flags = VM_FLUSH_RESET_PERMS;
+	pgprot_t pgprot = range->pgprot;
+	void *p;
+
+	if (use_cache)
+		p = execmem_cache_alloc(range, size);
+	else
+		p = execmem_vmalloc(range, size, pgprot, vm_flags);
+
+	return kasan_reset_tag(p);
+}
+
+void execmem_free(void *ptr)
+{
+	/*
+	 * This memory may be RO, and freeing RO memory in an interrupt is not
+	 * supported by vmalloc.
+	 */
+	WARN_ON(in_interrupt());
+
+	if (!execmem_cache_free(ptr))
+		vfree(ptr);
+}
+
+void *execmem_update_copy(void *dst, const void *src, size_t size)
+{
+	return text_poke_copy(dst, src, size);
+}
+
+bool execmem_is_rox(enum execmem_type type)
+{
+	return !!(execmem_info->ranges[type].flags & EXECMEM_ROX_CACHE);
+}
+
+static bool execmem_validate(struct execmem_info *info)
+{
+	struct execmem_range *r = &info->ranges[EXECMEM_DEFAULT];
+
+	if (!r->alignment || !r->start || !r->end || !pgprot_val(r->pgprot)) {
+		pr_crit("Invalid parameters for execmem allocator, module loading will fail");
+		return false;
+	}
+
+	if (!IS_ENABLED(CONFIG_ARCH_HAS_EXECMEM_ROX)) {
+		for (int i = EXECMEM_DEFAULT; i < EXECMEM_TYPE_MAX; i++) {
+			r = &info->ranges[i];
+
+			if (r->flags & EXECMEM_ROX_CACHE) {
+				pr_warn_once("ROX cache is not supported\n");
+				r->flags &= ~EXECMEM_ROX_CACHE;
+			}
+		}
+	}
+
+	return true;
+}
+
+static void execmem_init_missing(struct execmem_info *info)
+{
+	struct execmem_range *default_range = &info->ranges[EXECMEM_DEFAULT];
+
+	for (int i = EXECMEM_DEFAULT + 1; i < EXECMEM_TYPE_MAX; i++) {
+		struct execmem_range *r = &info->ranges[i];
+
+		if (!r->start) {
+			if (i == EXECMEM_MODULE_DATA)
+				r->pgprot = PAGE_KERNEL;
+			else
+				r->pgprot = default_range->pgprot;
+			r->alignment = default_range->alignment;
+			r->start = default_range->start;
+			r->end = default_range->end;
+			r->flags = default_range->flags;
+			r->fallback_start = default_range->fallback_start;
+			r->fallback_end = default_range->fallback_end;
+		}
+	}
+}
+
+struct execmem_info * __weak execmem_arch_setup(void)
+{
+	return NULL;
+}
+
+static void __init __execmem_init(void)
+{
+	struct execmem_info *info = execmem_arch_setup();
+
+	if (!info) {
+		info = execmem_info = &default_execmem_info;
+		info->ranges[EXECMEM_DEFAULT].start = VMALLOC_START;
+		info->ranges[EXECMEM_DEFAULT].end = VMALLOC_END;
+		info->ranges[EXECMEM_DEFAULT].pgprot = PAGE_KERNEL_EXEC;
+		info->ranges[EXECMEM_DEFAULT].alignment = 1;
+	}
+
+	if (!execmem_validate(info))
+		return;
+
+	execmem_init_missing(info);
+
+	execmem_info = info;
+}
+
+#ifdef CONFIG_ARCH_WANTS_EXECMEM_LATE
+static int __init execmem_late_init(void)
+{
+	__execmem_init();
+	return 0;
+}
+core_initcall(execmem_late_init);
+#else
+void __init execmem_init(void)
+{
+	__execmem_init();
+}
+#endif