From: "Mike Rapoport (Microsoft)" <r...@kernel.org> Using large pages to map text areas reduces iTLB pressure and improves performance.
Extend execmem_alloc() with an ability to use huge pages with ROX permissions as a cache for smaller allocations. To populate the cache, a writable large page is allocated from vmalloc with VM_ALLOW_HUGE_VMAP, filled with invalid instructions and then remapped as ROX. Portions of that large page are handed out to execmem_alloc() callers without any changes to the permissions. When the memory is freed with execmem_free() it is invalidated again so that it won't contain stale instructions. The cache is enabled when an architecture sets EXECMEM_ROX_CACHE flag in definition of an execmem_range. Signed-off-by: Mike Rapoport (Microsoft) <r...@kernel.org> --- include/linux/execmem.h | 2 + mm/execmem.c | 289 +++++++++++++++++++++++++++++++++++++++- 2 files changed, 286 insertions(+), 5 deletions(-) diff --git a/include/linux/execmem.h b/include/linux/execmem.h index dfdf19f8a5e8..7436aa547818 100644 --- a/include/linux/execmem.h +++ b/include/linux/execmem.h @@ -77,12 +77,14 @@ struct execmem_range { /** * struct execmem_info - architecture parameters for code allocations + * @fill_trapping_insns: set memory to contain instructions that will trap * @ranges: array of parameter sets defining architecture specific * parameters for executable memory allocations. The ranges that are not * explicitly initialized by an architecture use parameters defined for * @EXECMEM_DEFAULT. */ struct execmem_info { + void (*fill_trapping_insns)(void *ptr, size_t size, bool writable); struct execmem_range ranges[EXECMEM_TYPE_MAX]; }; diff --git a/mm/execmem.c b/mm/execmem.c index 0f6691e9ffe6..f547c1f3c93d 100644 --- a/mm/execmem.c +++ b/mm/execmem.c @@ -7,28 +7,88 @@ */ #include <linux/mm.h> +#include <linux/mutex.h> #include <linux/vmalloc.h> #include <linux/execmem.h> +#include <linux/maple_tree.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; -static void *__execmem_alloc(struct execmem_range *range, size_t size) +#ifdef CONFIG_MMU +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 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; + + if (!xa_is_value(area)) + continue; + + size = xa_to_value(area); + + if (IS_ALIGNED(size, PMD_SIZE) && + IS_ALIGNED(mas.index, PMD_SIZE)) { + void *ptr = (void *)mas.index; + + mas_erase(&mas); + vfree(ptr); + } + } + mutex_unlock(mutex); +} + +static DECLARE_WORK(execmem_cache_clean_work, execmem_cache_clean); + +static void execmem_fill_trapping_insns(void *ptr, size_t size, bool writable) +{ + if (execmem_info->fill_trapping_insns) + execmem_info->fill_trapping_insns(ptr, size, writable); + else + memset(ptr, 0, size); +} + +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; - unsigned long vm_flags = VM_FLUSH_RESET_PERMS; gfp_t gfp_flags = GFP_KERNEL | __GFP_NOWARN; + unsigned int align = range->alignment; unsigned long start = range->start; unsigned long end = range->end; - unsigned int align = range->alignment; - pgprot_t pgprot = range->pgprot; 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)); @@ -50,8 +110,225 @@ static void *__execmem_alloc(struct execmem_range *range, size_t size) return NULL; } + return p; +} + +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, lower_size = 0; + unsigned long upper, upper_size = 0; + unsigned long area_size; + void *area = NULL; + int err; + + lower = addr; + upper = addr + size - 1; + + mutex_lock(mutex); + area = mas_walk(&mas); + if (area && xa_is_value(area) && mas.last == addr - 1) { + lower = mas.index; + lower_size = xa_to_value(area); + } + + area = mas_next(&mas, ULONG_MAX); + if (area && xa_is_value(area) && mas.index == addr + size) { + upper = mas.last; + upper_size = xa_to_value(area); + } + + mas_set_range(&mas, lower, upper); + area_size = lower_size + upper_size + size; + err = mas_store_gfp(&mas, xa_mk_value(area_size), GFP_KERNEL); + mutex_unlock(mutex); + if (err) + return -ENOMEM; + + 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 = xa_to_value(area); + + 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, xa_mk_value(size), GFP_KERNEL); + if (err) + goto out_unlock; + + mas_erase(&mas_free); + if (area_size > size) { + /* + * re-insert remaining free size to free_areas at range + * [addr + size, last] + */ + mas_set_range(&mas_free, addr + size, last); + size = area_size - size; + err = mas_store_gfp(&mas_free, xa_mk_value(size), GFP_KERNEL); + if (err) { + mas_erase(&mas_busy); + 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_FLUSH_RESET_PERMS | 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 = 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 = xa_to_value(area); + mas_erase(&mas); + mutex_unlock(mutex); + + execmem_fill_trapping_insns(ptr, size, /* writable = */ false); + + execmem_cache_add(ptr, size); + + schedule_work(&execmem_cache_clean_work); + + return true; +} + +static void *__execmem_alloc(struct execmem_range *range, size_t size) +{ + 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); } +#else +static void *__execmem_alloc(struct execmem_range *range, size_t size) +{ + return vmalloc(size); +} + +static bool execmem_cache_free(void *ptr) +{ + return false; +} +#endif void *execmem_alloc(enum execmem_type type, size_t size) { @@ -67,7 +344,9 @@ void execmem_free(void *ptr) * supported by vmalloc. */ WARN_ON(in_interrupt()); - vfree(ptr); + + if (!execmem_cache_free(ptr)) + vfree(ptr); } void *execmem_update_copy(void *dst, const void *src, size_t size) -- 2.43.0 _______________________________________________ linux-snps-arc mailing list linux-snps-arc@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-snps-arc