From 355f44f373e765f4eb2bbfc91ade0735525e3a31 Mon Sep 17 00:00:00 2001 From: Daan Date: Sun, 17 Mar 2024 08:44:11 -0700 Subject: [PATCH] split free routines in a separate file --- src/alloc.c | 511 +-------------------------------------------------- src/free.c | 519 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 520 insertions(+), 510 deletions(-) create mode 100644 src/free.c diff --git a/src/alloc.c b/src/alloc.c index 2576206f..76d68d13 100644 --- a/src/alloc.c +++ b/src/alloc.c @@ -18,6 +18,7 @@ terms of the MIT license. A copy of the license can be found in the file #define MI_IN_ALLOC_C #include "alloc-override.c" +#include "free.c" #undef MI_IN_ALLOC_C // ------------------------------------------------------ @@ -194,516 +195,6 @@ mi_decl_nodiscard mi_decl_restrict void* mi_zalloc(size_t size) mi_attr_noexcept } -// ------------------------------------------------------ -// Check for double free in secure and debug mode -// This is somewhat expensive so only enabled for secure mode 4 -// ------------------------------------------------------ - -#if (MI_ENCODE_FREELIST && (MI_SECURE>=4 || MI_DEBUG!=0)) -// linear check if the free list contains a specific element -static bool mi_list_contains(const mi_page_t* page, const mi_block_t* list, const mi_block_t* elem) { - while (list != NULL) { - if (elem==list) return true; - list = mi_block_next(page, list); - } - return false; -} - -static mi_decl_noinline bool mi_check_is_double_freex(const mi_page_t* page, const mi_block_t* block) { - // The decoded value is in the same page (or NULL). - // Walk the free lists to verify positively if it is already freed - if (mi_list_contains(page, page->free, block) || - mi_list_contains(page, page->local_free, block) || - mi_list_contains(page, mi_page_thread_free(page), block)) - { - _mi_error_message(EAGAIN, "double free detected of block %p with size %zu\n", block, mi_page_block_size(page)); - return true; - } - return false; -} - -#define mi_track_page(page,access) { size_t psize; void* pstart = _mi_page_start(_mi_page_segment(page),page,&psize); mi_track_mem_##access( pstart, psize); } - -static inline bool mi_check_is_double_free(const mi_page_t* page, const mi_block_t* block) { - bool is_double_free = false; - mi_block_t* n = mi_block_nextx(page, block, page->keys); // pretend it is freed, and get the decoded first field - if (((uintptr_t)n & (MI_INTPTR_SIZE-1))==0 && // quick check: aligned pointer? - (n==NULL || mi_is_in_same_page(block, n))) // quick check: in same page or NULL? - { - // Suspicous: decoded value a in block is in the same page (or NULL) -- maybe a double free? - // (continue in separate function to improve code generation) - is_double_free = mi_check_is_double_freex(page, block); - } - return is_double_free; -} -#else -static inline bool mi_check_is_double_free(const mi_page_t* page, const mi_block_t* block) { - MI_UNUSED(page); - MI_UNUSED(block); - return false; -} -#endif - -// --------------------------------------------------------------------------- -// Check for heap block overflow by setting up padding at the end of the block -// --------------------------------------------------------------------------- - -#if MI_PADDING // && !MI_TRACK_ENABLED -static bool mi_page_decode_padding(const mi_page_t* page, const mi_block_t* block, size_t* delta, size_t* bsize) { - *bsize = mi_page_usable_block_size(page); - const mi_padding_t* const padding = (mi_padding_t*)((uint8_t*)block + *bsize); - mi_track_mem_defined(padding,sizeof(mi_padding_t)); - *delta = padding->delta; - uint32_t canary = padding->canary; - uintptr_t keys[2]; - keys[0] = page->keys[0]; - keys[1] = page->keys[1]; - bool ok = ((uint32_t)mi_ptr_encode(page,block,keys) == canary && *delta <= *bsize); - mi_track_mem_noaccess(padding,sizeof(mi_padding_t)); - return ok; -} - -// Return the exact usable size of a block. -static size_t mi_page_usable_size_of(const mi_page_t* page, const mi_block_t* block) { - size_t bsize; - size_t delta; - bool ok = mi_page_decode_padding(page, block, &delta, &bsize); - mi_assert_internal(ok); mi_assert_internal(delta <= bsize); - return (ok ? bsize - delta : 0); -} - -// When a non-thread-local block is freed, it becomes part of the thread delayed free -// list that is freed later by the owning heap. If the exact usable size is too small to -// contain the pointer for the delayed list, then shrink the padding (by decreasing delta) -// so it will later not trigger an overflow error in `mi_free_block`. -void _mi_padding_shrink(const mi_page_t* page, const mi_block_t* block, const size_t min_size) { - size_t bsize; - size_t delta; - bool ok = mi_page_decode_padding(page, block, &delta, &bsize); - mi_assert_internal(ok); - if (!ok || (bsize - delta) >= min_size) return; // usually already enough space - mi_assert_internal(bsize >= min_size); - if (bsize < min_size) return; // should never happen - size_t new_delta = (bsize - min_size); - mi_assert_internal(new_delta < bsize); - mi_padding_t* padding = (mi_padding_t*)((uint8_t*)block + bsize); - mi_track_mem_defined(padding,sizeof(mi_padding_t)); - padding->delta = (uint32_t)new_delta; - mi_track_mem_noaccess(padding,sizeof(mi_padding_t)); -} -#else -static size_t mi_page_usable_size_of(const mi_page_t* page, const mi_block_t* block) { - MI_UNUSED(block); - return mi_page_usable_block_size(page); -} - -void _mi_padding_shrink(const mi_page_t* page, const mi_block_t* block, const size_t min_size) { - MI_UNUSED(page); - MI_UNUSED(block); - MI_UNUSED(min_size); -} -#endif - -#if MI_PADDING && MI_PADDING_CHECK - -static bool mi_verify_padding(const mi_page_t* page, const mi_block_t* block, size_t* size, size_t* wrong) { - size_t bsize; - size_t delta; - bool ok = mi_page_decode_padding(page, block, &delta, &bsize); - *size = *wrong = bsize; - if (!ok) return false; - mi_assert_internal(bsize >= delta); - *size = bsize - delta; - if (!mi_page_is_huge(page)) { - uint8_t* fill = (uint8_t*)block + bsize - delta; - const size_t maxpad = (delta > MI_MAX_ALIGN_SIZE ? MI_MAX_ALIGN_SIZE : delta); // check at most the first N padding bytes - mi_track_mem_defined(fill, maxpad); - for (size_t i = 0; i < maxpad; i++) { - if (fill[i] != MI_DEBUG_PADDING) { - *wrong = bsize - delta + i; - ok = false; - break; - } - } - mi_track_mem_noaccess(fill, maxpad); - } - return ok; -} - -static void mi_check_padding(const mi_page_t* page, const mi_block_t* block) { - size_t size; - size_t wrong; - if (!mi_verify_padding(page,block,&size,&wrong)) { - _mi_error_message(EFAULT, "buffer overflow in heap block %p of size %zu: write after %zu bytes\n", block, size, wrong ); - } -} - -#else - -static void mi_check_padding(const mi_page_t* page, const mi_block_t* block) { - MI_UNUSED(page); - MI_UNUSED(block); -} - -#endif - -// only maintain stats for smaller objects if requested -#if (MI_STAT>0) -static void mi_stat_free(const mi_page_t* page, const mi_block_t* block) { -#if (MI_STAT < 2) - MI_UNUSED(block); -#endif - mi_heap_t* const heap = mi_heap_get_default(); - const size_t bsize = mi_page_usable_block_size(page); -#if (MI_STAT>1) - const size_t usize = mi_page_usable_size_of(page, block); - mi_heap_stat_decrease(heap, malloc, usize); -#endif - if (bsize <= MI_LARGE_OBJ_SIZE_MAX) { - mi_heap_stat_decrease(heap, normal, bsize); -#if (MI_STAT > 1) - mi_heap_stat_decrease(heap, normal_bins[_mi_bin(bsize)], 1); -#endif - } -#if !MI_HUGE_PAGE_ABANDON - else { - const size_t bpsize = mi_page_block_size(page); - if (bpsize <= MI_HUGE_OBJ_SIZE_MAX) { - mi_heap_stat_decrease(heap, huge, bpsize); - } - else { - mi_heap_stat_decrease(heap, giant, bpsize); - } - } -#endif -} -#else -static void mi_stat_free(const mi_page_t* page, const mi_block_t* block) { - MI_UNUSED(page); MI_UNUSED(block); -} -#endif - -#if MI_HUGE_PAGE_ABANDON -#if (MI_STAT>0) -// maintain stats for huge objects -static void mi_stat_huge_free(const mi_page_t* page) { - mi_heap_t* const heap = mi_heap_get_default(); - const size_t bsize = mi_page_block_size(page); // to match stats in `page.c:mi_page_huge_alloc` - if (bsize <= MI_HUGE_OBJ_SIZE_MAX) { - mi_heap_stat_decrease(heap, huge, bsize); - } - else { - mi_heap_stat_decrease(heap, giant, bsize); - } -} -#else -static void mi_stat_huge_free(const mi_page_t* page) { - MI_UNUSED(page); -} -#endif -#endif - -// ------------------------------------------------------ -// Free -// ------------------------------------------------------ - -// forward declaration of multi-threaded free (`_mt`) (or free in huge block if compiled with MI_HUGE_PAGE_ABANDON) -static mi_decl_noinline void mi_free_block_mt(mi_segment_t* segment, mi_page_t* page, mi_block_t* block); - -// regular free of a (thread local) block pointer -// fast path written carefully to prevent spilling on the stack -static inline void mi_free_block_local(mi_page_t* page, mi_block_t* block, bool check_full) -{ - // owning thread can free a block directly - if mi_unlikely(mi_check_is_double_free(page, block)) return; - mi_check_padding(page, block); - mi_stat_free(page, block); - #if (MI_DEBUG>0) && !MI_TRACK_ENABLED && !MI_TSAN - memset(block, MI_DEBUG_FREED, mi_page_block_size(page)); - #endif - mi_track_free_size(p, mi_page_usable_size_of(page,block)); // faster then mi_usable_size as we already know the page and that p is unaligned - mi_block_set_next(page, block, page->local_free); - page->local_free = block; - if mi_unlikely(--page->used == 0) { // using this expression generates better code than: page->used--; if (mi_page_all_free(page)) - _mi_page_retire(page); - } - else if mi_unlikely(check_full && mi_page_is_in_full(page)) { - _mi_page_unfull(page); - } -} - -// Adjust a block that was allocated aligned, to the actual start of the block in the page. -mi_block_t* _mi_page_ptr_unalign(const mi_segment_t* segment, const mi_page_t* page, const void* p) { - mi_assert_internal(page!=NULL && p!=NULL); - const size_t diff = (uint8_t*)p - _mi_page_start(segment, page, NULL); - const size_t adjust = (diff % mi_page_block_size(page)); - return (mi_block_t*)((uintptr_t)p - adjust); -} - -// free a local pointer -static void mi_decl_noinline mi_free_generic_local(const mi_segment_t* segment, mi_page_t* page, void* p) mi_attr_noexcept { - mi_block_t* const block = (mi_page_has_aligned(page) ? _mi_page_ptr_unalign(segment, page, p) : (mi_block_t*)p); - mi_free_block_local(page, block, true); -} - -// free a pointer owned by another thread -static void mi_decl_noinline mi_free_generic_mt(const mi_segment_t* segment, mi_page_t* page, void* p) mi_attr_noexcept { - mi_block_t* const block = _mi_page_ptr_unalign(segment, page, p); // don't check `has_aligned` flag to avoid a race (issue #865) - mi_free_block_mt(segment, page, block); -} - -// generic free (for runtime integration) -void mi_decl_noinline _mi_free_generic(const mi_segment_t* segment, mi_page_t* page, bool is_local, void* p) mi_attr_noexcept { - if (is_local) mi_free_generic_local(segment,page,p); - else mi_free_generic_mt(segment,page,p); -} - -// Get the segment data belonging to a pointer -// This is just a single `and` in release mode but does further checks in debug mode -// (and secure mode) to see if this was a valid pointer. -static inline mi_segment_t* mi_checked_ptr_segment(const void* p, const char* msg) -{ - MI_UNUSED(msg); - mi_assert(p != NULL); - -#if (MI_DEBUG>0) - if mi_unlikely(((uintptr_t)p & (MI_INTPTR_SIZE - 1)) != 0) { - _mi_error_message(EINVAL, "%s: invalid (unaligned) pointer: %p\n", msg, p); - return NULL; - } -#endif - - mi_segment_t* const segment = _mi_ptr_segment(p); - mi_assert_internal(segment != NULL); - -#if (MI_DEBUG>0) - if mi_unlikely(!mi_is_in_heap_region(p)) { - _mi_warning_message("%s: pointer might not point to a valid heap region: %p\n" - "(this may still be a valid very large allocation (over 64MiB))\n", msg, p); - if mi_likely(_mi_ptr_cookie(segment) == segment->cookie) { - _mi_warning_message("(yes, the previous pointer %p was valid after all)\n", p); - } - } -#endif -#if (MI_DEBUG>0 || MI_SECURE>=4) - if mi_unlikely(_mi_ptr_cookie(segment) != segment->cookie) { - _mi_error_message(EINVAL, "%s: pointer does not point to a valid heap space: %p\n", msg, p); - return NULL; - } -#endif - - return segment; -} - -// Free a block -// Fast path written carefully to prevent register spilling on the stack -void mi_free(void* p) mi_attr_noexcept -{ - if mi_unlikely(p == NULL) return; - mi_segment_t* const segment = mi_checked_ptr_segment(p,"mi_free"); - const bool is_local= (_mi_prim_thread_id() == mi_atomic_load_relaxed(&segment->thread_id)); - mi_page_t* const page = _mi_segment_page_of(segment, p); - - if mi_likely(is_local) { // thread-local free? - if mi_likely(page->flags.full_aligned == 0) { // and it is not a full page (full pages need to move from the full bin), nor has aligned blocks (aligned blocks need to be unaligned) - // thread-local, aligned, and not a full page - mi_block_t* const block = (mi_block_t*)p; - mi_free_block_local(page,block,false /* no need to check if the page is full */); - } - else { - // page is full or contains (inner) aligned blocks; use generic path - mi_free_generic_local(segment, page, p); - } - } - else { - // not thread-local; use generic path - mi_free_generic_mt(segment, page, p); - } -} - -// return true if successful -bool _mi_free_delayed_block(mi_block_t* block) { - // get segment and page - const mi_segment_t* const segment = _mi_ptr_segment(block); - mi_assert_internal(_mi_ptr_cookie(segment) == segment->cookie); - mi_assert_internal(_mi_thread_id() == segment->thread_id); - mi_page_t* const page = _mi_segment_page_of(segment, block); - - // Clear the no-delayed flag so delayed freeing is used again for this page. - // This must be done before collecting the free lists on this page -- otherwise - // some blocks may end up in the page `thread_free` list with no blocks in the - // heap `thread_delayed_free` list which may cause the page to be never freed! - // (it would only be freed if we happen to scan it in `mi_page_queue_find_free_ex`) - if (!_mi_page_try_use_delayed_free(page, MI_USE_DELAYED_FREE, false /* dont overwrite never delayed */)) { - return false; - } - - // collect all other non-local frees to ensure up-to-date `used` count - _mi_page_free_collect(page, false); - - // and free the block (possibly freeing the page as well since used is updated) - mi_free_block_local(page, block, true); - return true; -} - -// ------------------------------------------------------ -// Multi-threaded Free (`_mt`) -// ------------------------------------------------------ - -// Push a block that is owned by another thread on its page-local thread free -// list or it's heap delayed free list. Such blocks are later collected by -// the owning thread in `_mi_free_delayed_block`. -static void mi_decl_noinline mi_free_block_delayed_mt( mi_page_t* page, mi_block_t* block ) -{ - // Try to put the block on either the page-local thread free list, - // or the heap delayed free list (if this is the first non-local free in that page) - mi_thread_free_t tfreex; - bool use_delayed; - mi_thread_free_t tfree = mi_atomic_load_relaxed(&page->xthread_free); - do { - use_delayed = (mi_tf_delayed(tfree) == MI_USE_DELAYED_FREE); - if mi_unlikely(use_delayed) { - // unlikely: this only happens on the first concurrent free in a page that is in the full list - tfreex = mi_tf_set_delayed(tfree,MI_DELAYED_FREEING); - } - else { - // usual: directly add to page thread_free list - mi_block_set_next(page, block, mi_tf_block(tfree)); - tfreex = mi_tf_set_block(tfree,block); - } - } while (!mi_atomic_cas_weak_release(&page->xthread_free, &tfree, tfreex)); - - // If this was the first non-local free, we need to push it on the heap delayed free list instead - if mi_unlikely(use_delayed) { - // racy read on `heap`, but ok because MI_DELAYED_FREEING is set (see `mi_heap_delete` and `mi_heap_collect_abandon`) - mi_heap_t* const heap = (mi_heap_t*)(mi_atomic_load_acquire(&page->xheap)); //mi_page_heap(page); - mi_assert_internal(heap != NULL); - if (heap != NULL) { - // add to the delayed free list of this heap. (do this atomically as the lock only protects heap memory validity) - mi_block_t* dfree = mi_atomic_load_ptr_relaxed(mi_block_t, &heap->thread_delayed_free); - do { - mi_block_set_nextx(heap,block,dfree, heap->keys); - } while (!mi_atomic_cas_ptr_weak_release(mi_block_t,&heap->thread_delayed_free, &dfree, block)); - } - - // and reset the MI_DELAYED_FREEING flag - tfree = mi_atomic_load_relaxed(&page->xthread_free); - do { - tfreex = tfree; - mi_assert_internal(mi_tf_delayed(tfree) == MI_DELAYED_FREEING); - tfreex = mi_tf_set_delayed(tfree,MI_NO_DELAYED_FREE); - } while (!mi_atomic_cas_weak_release(&page->xthread_free, &tfree, tfreex)); - } -} - -// Multi-threaded free (`_mt`) (or free in huge block if compiled with MI_HUGE_PAGE_ABANDON) -static mi_decl_noinline void mi_free_block_mt(mi_segment_t* segment, mi_page_t* page, mi_block_t* block) -{ - // first see if the segment was abandoned and if we can reclaim it into our thread - if (mi_option_is_enabled(mi_option_abandoned_reclaim_on_free) && - #if MI_HUGE_PAGE_ABANDON - segment->page_kind != MI_PAGE_HUGE && - #endif - mi_atomic_load_relaxed(&segment->thread_id) == 0) - { - // the segment is abandoned, try to reclaim it into our heap - if (_mi_segment_attempt_reclaim(mi_heap_get_default(), segment)) { - mi_assert_internal(_mi_prim_thread_id() == mi_atomic_load_relaxed(&segment->thread_id)); - mi_free(block); // recursively free as now it will be a local free in our heap - return; - } - } - - // The padding check may access the non-thread-owned page for the key values. - // that is safe as these are constant and the page won't be freed (as the block is not freed yet). - mi_check_padding(page, block); - - // adjust stats (after padding check and potential recursive `mi_free` above) - mi_stat_free(page, block); // stat_free may access the padding - mi_track_free_size(block, mi_page_usable_size_of(page,block)); - - // for small size, ensure we can fit the delayed thread pointers without triggering overflow detection - _mi_padding_shrink(page, block, sizeof(mi_block_t)); - - if (segment->page_kind == MI_PAGE_HUGE) { - #if MI_HUGE_PAGE_ABANDON - // huge page segments are always abandoned and can be freed immediately - mi_stat_huge_free(page); - _mi_segment_huge_page_free(segment, page, block); - return; - #else - // huge pages are special as they occupy the entire segment - // as these are large we reset the memory occupied by the page so it is available to other threads - // (as the owning thread needs to actually free the memory later). - _mi_segment_huge_page_reset(segment, page, block); - #endif - } - else { - #if (MI_DEBUG>0) && !MI_TRACK_ENABLED && !MI_TSAN // note: when tracking, cannot use mi_usable_size with multi-threading - memset(block, MI_DEBUG_FREED, mi_usable_size(block)); - #endif - } - - // and finally free the actual block by pushing it on the owning heap - // thread_delayed free list (or heap delayed free list) - mi_free_block_delayed_mt(page,block); -} - - -// ------------------------------------------------------ -// Usable size -// ------------------------------------------------------ - -// Bytes available in a block -mi_decl_noinline static size_t mi_page_usable_aligned_size_of(const mi_segment_t* segment, const mi_page_t* page, const void* p) mi_attr_noexcept { - const mi_block_t* block = _mi_page_ptr_unalign(segment, page, p); - const size_t size = mi_page_usable_size_of(page, block); - const ptrdiff_t adjust = (uint8_t*)p - (uint8_t*)block; - mi_assert_internal(adjust >= 0 && (size_t)adjust <= size); - return (size - adjust); -} - -static inline size_t _mi_usable_size(const void* p, const char* msg) mi_attr_noexcept { - if (p == NULL) return 0; - const mi_segment_t* const segment = mi_checked_ptr_segment(p, msg); - const mi_page_t* const page = _mi_segment_page_of(segment, p); - if mi_likely(!mi_page_has_aligned(page)) { - const mi_block_t* block = (const mi_block_t*)p; - return mi_page_usable_size_of(page, block); - } - else { - // split out to separate routine for improved code generation - return mi_page_usable_aligned_size_of(segment, page, p); - } -} - -mi_decl_nodiscard size_t mi_usable_size(const void* p) mi_attr_noexcept { - return _mi_usable_size(p, "mi_usable_size"); -} - - -// ------------------------------------------------------ -// Allocation extensions -// ------------------------------------------------------ - -void mi_free_size(void* p, size_t size) mi_attr_noexcept { - MI_UNUSED_RELEASE(size); - mi_assert(p == NULL || size <= _mi_usable_size(p,"mi_free_size")); - mi_free(p); -} - -void mi_free_size_aligned(void* p, size_t size, size_t alignment) mi_attr_noexcept { - MI_UNUSED_RELEASE(alignment); - mi_assert(((uintptr_t)p % alignment) == 0); - mi_free_size(p,size); -} - -void mi_free_aligned(void* p, size_t alignment) mi_attr_noexcept { - MI_UNUSED_RELEASE(alignment); - mi_assert(((uintptr_t)p % alignment) == 0); - mi_free(p); -} - mi_decl_nodiscard extern inline mi_decl_restrict void* mi_heap_calloc(mi_heap_t* heap, size_t count, size_t size) mi_attr_noexcept { size_t total; if (mi_count_size_overflow(count,size,&total)) return NULL; diff --git a/src/free.c b/src/free.c new file mode 100644 index 00000000..7761cb6a --- /dev/null +++ b/src/free.c @@ -0,0 +1,519 @@ +/* ---------------------------------------------------------------------------- +Copyright (c) 2018-2024, Microsoft Research, Daan Leijen +This is free software; you can redistribute it and/or modify it under the +terms of the MIT license. A copy of the license can be found in the file +"LICENSE" at the root of this distribution. +-----------------------------------------------------------------------------*/ +#if !defined(MI_IN_ALLOC_C) +#error "this file should be included from 'alloc.c' (so aliases can work from alloc-override)" +#endif + +// ------------------------------------------------------ +// Check for double free in secure and debug mode +// This is somewhat expensive so only enabled for secure mode 4 +// ------------------------------------------------------ + +#if (MI_ENCODE_FREELIST && (MI_SECURE>=4 || MI_DEBUG!=0)) +// linear check if the free list contains a specific element +static bool mi_list_contains(const mi_page_t* page, const mi_block_t* list, const mi_block_t* elem) { + while (list != NULL) { + if (elem==list) return true; + list = mi_block_next(page, list); + } + return false; +} + +static mi_decl_noinline bool mi_check_is_double_freex(const mi_page_t* page, const mi_block_t* block) { + // The decoded value is in the same page (or NULL). + // Walk the free lists to verify positively if it is already freed + if (mi_list_contains(page, page->free, block) || + mi_list_contains(page, page->local_free, block) || + mi_list_contains(page, mi_page_thread_free(page), block)) + { + _mi_error_message(EAGAIN, "double free detected of block %p with size %zu\n", block, mi_page_block_size(page)); + return true; + } + return false; +} + +#define mi_track_page(page,access) { size_t psize; void* pstart = _mi_page_start(_mi_page_segment(page),page,&psize); mi_track_mem_##access( pstart, psize); } + +static inline bool mi_check_is_double_free(const mi_page_t* page, const mi_block_t* block) { + bool is_double_free = false; + mi_block_t* n = mi_block_nextx(page, block, page->keys); // pretend it is freed, and get the decoded first field + if (((uintptr_t)n & (MI_INTPTR_SIZE-1))==0 && // quick check: aligned pointer? + (n==NULL || mi_is_in_same_page(block, n))) // quick check: in same page or NULL? + { + // Suspicous: decoded value a in block is in the same page (or NULL) -- maybe a double free? + // (continue in separate function to improve code generation) + is_double_free = mi_check_is_double_freex(page, block); + } + return is_double_free; +} +#else +static inline bool mi_check_is_double_free(const mi_page_t* page, const mi_block_t* block) { + MI_UNUSED(page); + MI_UNUSED(block); + return false; +} +#endif + +// --------------------------------------------------------------------------- +// Check for heap block overflow by setting up padding at the end of the block +// --------------------------------------------------------------------------- + +#if MI_PADDING // && !MI_TRACK_ENABLED +static bool mi_page_decode_padding(const mi_page_t* page, const mi_block_t* block, size_t* delta, size_t* bsize) { + *bsize = mi_page_usable_block_size(page); + const mi_padding_t* const padding = (mi_padding_t*)((uint8_t*)block + *bsize); + mi_track_mem_defined(padding,sizeof(mi_padding_t)); + *delta = padding->delta; + uint32_t canary = padding->canary; + uintptr_t keys[2]; + keys[0] = page->keys[0]; + keys[1] = page->keys[1]; + bool ok = ((uint32_t)mi_ptr_encode(page,block,keys) == canary && *delta <= *bsize); + mi_track_mem_noaccess(padding,sizeof(mi_padding_t)); + return ok; +} + +// Return the exact usable size of a block. +static size_t mi_page_usable_size_of(const mi_page_t* page, const mi_block_t* block) { + size_t bsize; + size_t delta; + bool ok = mi_page_decode_padding(page, block, &delta, &bsize); + mi_assert_internal(ok); mi_assert_internal(delta <= bsize); + return (ok ? bsize - delta : 0); +} + +// When a non-thread-local block is freed, it becomes part of the thread delayed free +// list that is freed later by the owning heap. If the exact usable size is too small to +// contain the pointer for the delayed list, then shrink the padding (by decreasing delta) +// so it will later not trigger an overflow error in `mi_free_block`. +void _mi_padding_shrink(const mi_page_t* page, const mi_block_t* block, const size_t min_size) { + size_t bsize; + size_t delta; + bool ok = mi_page_decode_padding(page, block, &delta, &bsize); + mi_assert_internal(ok); + if (!ok || (bsize - delta) >= min_size) return; // usually already enough space + mi_assert_internal(bsize >= min_size); + if (bsize < min_size) return; // should never happen + size_t new_delta = (bsize - min_size); + mi_assert_internal(new_delta < bsize); + mi_padding_t* padding = (mi_padding_t*)((uint8_t*)block + bsize); + mi_track_mem_defined(padding,sizeof(mi_padding_t)); + padding->delta = (uint32_t)new_delta; + mi_track_mem_noaccess(padding,sizeof(mi_padding_t)); +} +#else +static size_t mi_page_usable_size_of(const mi_page_t* page, const mi_block_t* block) { + MI_UNUSED(block); + return mi_page_usable_block_size(page); +} + +void _mi_padding_shrink(const mi_page_t* page, const mi_block_t* block, const size_t min_size) { + MI_UNUSED(page); + MI_UNUSED(block); + MI_UNUSED(min_size); +} +#endif + +#if MI_PADDING && MI_PADDING_CHECK + +static bool mi_verify_padding(const mi_page_t* page, const mi_block_t* block, size_t* size, size_t* wrong) { + size_t bsize; + size_t delta; + bool ok = mi_page_decode_padding(page, block, &delta, &bsize); + *size = *wrong = bsize; + if (!ok) return false; + mi_assert_internal(bsize >= delta); + *size = bsize - delta; + if (!mi_page_is_huge(page)) { + uint8_t* fill = (uint8_t*)block + bsize - delta; + const size_t maxpad = (delta > MI_MAX_ALIGN_SIZE ? MI_MAX_ALIGN_SIZE : delta); // check at most the first N padding bytes + mi_track_mem_defined(fill, maxpad); + for (size_t i = 0; i < maxpad; i++) { + if (fill[i] != MI_DEBUG_PADDING) { + *wrong = bsize - delta + i; + ok = false; + break; + } + } + mi_track_mem_noaccess(fill, maxpad); + } + return ok; +} + +static void mi_check_padding(const mi_page_t* page, const mi_block_t* block) { + size_t size; + size_t wrong; + if (!mi_verify_padding(page,block,&size,&wrong)) { + _mi_error_message(EFAULT, "buffer overflow in heap block %p of size %zu: write after %zu bytes\n", block, size, wrong ); + } +} + +#else + +static void mi_check_padding(const mi_page_t* page, const mi_block_t* block) { + MI_UNUSED(page); + MI_UNUSED(block); +} + +#endif + +// only maintain stats for smaller objects if requested +#if (MI_STAT>0) +static void mi_stat_free(const mi_page_t* page, const mi_block_t* block) { +#if (MI_STAT < 2) + MI_UNUSED(block); +#endif + mi_heap_t* const heap = mi_heap_get_default(); + const size_t bsize = mi_page_usable_block_size(page); +#if (MI_STAT>1) + const size_t usize = mi_page_usable_size_of(page, block); + mi_heap_stat_decrease(heap, malloc, usize); +#endif + if (bsize <= MI_LARGE_OBJ_SIZE_MAX) { + mi_heap_stat_decrease(heap, normal, bsize); +#if (MI_STAT > 1) + mi_heap_stat_decrease(heap, normal_bins[_mi_bin(bsize)], 1); +#endif + } +#if !MI_HUGE_PAGE_ABANDON + else { + const size_t bpsize = mi_page_block_size(page); + if (bpsize <= MI_HUGE_OBJ_SIZE_MAX) { + mi_heap_stat_decrease(heap, huge, bpsize); + } + else { + mi_heap_stat_decrease(heap, giant, bpsize); + } + } +#endif +} +#else +static void mi_stat_free(const mi_page_t* page, const mi_block_t* block) { + MI_UNUSED(page); MI_UNUSED(block); +} +#endif + +#if MI_HUGE_PAGE_ABANDON +#if (MI_STAT>0) +// maintain stats for huge objects +static void mi_stat_huge_free(const mi_page_t* page) { + mi_heap_t* const heap = mi_heap_get_default(); + const size_t bsize = mi_page_block_size(page); // to match stats in `page.c:mi_page_huge_alloc` + if (bsize <= MI_HUGE_OBJ_SIZE_MAX) { + mi_heap_stat_decrease(heap, huge, bsize); + } + else { + mi_heap_stat_decrease(heap, giant, bsize); + } +} +#else +static void mi_stat_huge_free(const mi_page_t* page) { + MI_UNUSED(page); +} +#endif +#endif + +// ------------------------------------------------------ +// Free +// ------------------------------------------------------ + +// forward declaration of multi-threaded free (`_mt`) (or free in huge block if compiled with MI_HUGE_PAGE_ABANDON) +static mi_decl_noinline void mi_free_block_mt(mi_segment_t* segment, mi_page_t* page, mi_block_t* block); + +// regular free of a (thread local) block pointer +// fast path written carefully to prevent spilling on the stack +static inline void mi_free_block_local(mi_page_t* page, mi_block_t* block, bool check_full) +{ + // owning thread can free a block directly + if mi_unlikely(mi_check_is_double_free(page, block)) return; + mi_check_padding(page, block); + mi_stat_free(page, block); + #if (MI_DEBUG>0) && !MI_TRACK_ENABLED && !MI_TSAN + memset(block, MI_DEBUG_FREED, mi_page_block_size(page)); + #endif + mi_track_free_size(p, mi_page_usable_size_of(page,block)); // faster then mi_usable_size as we already know the page and that p is unaligned + mi_block_set_next(page, block, page->local_free); + page->local_free = block; + if mi_unlikely(--page->used == 0) { // using this expression generates better code than: page->used--; if (mi_page_all_free(page)) + _mi_page_retire(page); + } + else if mi_unlikely(check_full && mi_page_is_in_full(page)) { + _mi_page_unfull(page); + } +} + +// Adjust a block that was allocated aligned, to the actual start of the block in the page. +mi_block_t* _mi_page_ptr_unalign(const mi_segment_t* segment, const mi_page_t* page, const void* p) { + mi_assert_internal(page!=NULL && p!=NULL); + const size_t diff = (uint8_t*)p - _mi_page_start(segment, page, NULL); + const size_t adjust = (diff % mi_page_block_size(page)); + return (mi_block_t*)((uintptr_t)p - adjust); +} + +// free a local pointer +static void mi_decl_noinline mi_free_generic_local(const mi_segment_t* segment, mi_page_t* page, void* p) mi_attr_noexcept { + mi_block_t* const block = (mi_page_has_aligned(page) ? _mi_page_ptr_unalign(segment, page, p) : (mi_block_t*)p); + mi_free_block_local(page, block, true); +} + +// free a pointer owned by another thread +static void mi_decl_noinline mi_free_generic_mt(const mi_segment_t* segment, mi_page_t* page, void* p) mi_attr_noexcept { + mi_block_t* const block = _mi_page_ptr_unalign(segment, page, p); // don't check `has_aligned` flag to avoid a race (issue #865) + mi_free_block_mt(segment, page, block); +} + +// generic free (for runtime integration) +void mi_decl_noinline _mi_free_generic(const mi_segment_t* segment, mi_page_t* page, bool is_local, void* p) mi_attr_noexcept { + if (is_local) mi_free_generic_local(segment,page,p); + else mi_free_generic_mt(segment,page,p); +} + +// Get the segment data belonging to a pointer +// This is just a single `and` in release mode but does further checks in debug mode +// (and secure mode) to see if this was a valid pointer. +static inline mi_segment_t* mi_checked_ptr_segment(const void* p, const char* msg) +{ + MI_UNUSED(msg); + mi_assert(p != NULL); + +#if (MI_DEBUG>0) + if mi_unlikely(((uintptr_t)p & (MI_INTPTR_SIZE - 1)) != 0) { + _mi_error_message(EINVAL, "%s: invalid (unaligned) pointer: %p\n", msg, p); + return NULL; + } +#endif + + mi_segment_t* const segment = _mi_ptr_segment(p); + mi_assert_internal(segment != NULL); + +#if (MI_DEBUG>0) + if mi_unlikely(!mi_is_in_heap_region(p)) { + _mi_warning_message("%s: pointer might not point to a valid heap region: %p\n" + "(this may still be a valid very large allocation (over 64MiB))\n", msg, p); + if mi_likely(_mi_ptr_cookie(segment) == segment->cookie) { + _mi_warning_message("(yes, the previous pointer %p was valid after all)\n", p); + } + } +#endif +#if (MI_DEBUG>0 || MI_SECURE>=4) + if mi_unlikely(_mi_ptr_cookie(segment) != segment->cookie) { + _mi_error_message(EINVAL, "%s: pointer does not point to a valid heap space: %p\n", msg, p); + return NULL; + } +#endif + + return segment; +} + +// Free a block +// Fast path written carefully to prevent register spilling on the stack +void mi_free(void* p) mi_attr_noexcept +{ + if mi_unlikely(p == NULL) return; + mi_segment_t* const segment = mi_checked_ptr_segment(p,"mi_free"); + const bool is_local= (_mi_prim_thread_id() == mi_atomic_load_relaxed(&segment->thread_id)); + mi_page_t* const page = _mi_segment_page_of(segment, p); + + if mi_likely(is_local) { // thread-local free? + if mi_likely(page->flags.full_aligned == 0) { // and it is not a full page (full pages need to move from the full bin), nor has aligned blocks (aligned blocks need to be unaligned) + // thread-local, aligned, and not a full page + mi_block_t* const block = (mi_block_t*)p; + mi_free_block_local(page,block,false /* no need to check if the page is full */); + } + else { + // page is full or contains (inner) aligned blocks; use generic path + mi_free_generic_local(segment, page, p); + } + } + else { + // not thread-local; use generic path + mi_free_generic_mt(segment, page, p); + } +} + +// return true if successful +bool _mi_free_delayed_block(mi_block_t* block) { + // get segment and page + const mi_segment_t* const segment = _mi_ptr_segment(block); + mi_assert_internal(_mi_ptr_cookie(segment) == segment->cookie); + mi_assert_internal(_mi_thread_id() == segment->thread_id); + mi_page_t* const page = _mi_segment_page_of(segment, block); + + // Clear the no-delayed flag so delayed freeing is used again for this page. + // This must be done before collecting the free lists on this page -- otherwise + // some blocks may end up in the page `thread_free` list with no blocks in the + // heap `thread_delayed_free` list which may cause the page to be never freed! + // (it would only be freed if we happen to scan it in `mi_page_queue_find_free_ex`) + if (!_mi_page_try_use_delayed_free(page, MI_USE_DELAYED_FREE, false /* dont overwrite never delayed */)) { + return false; + } + + // collect all other non-local frees to ensure up-to-date `used` count + _mi_page_free_collect(page, false); + + // and free the block (possibly freeing the page as well since used is updated) + mi_free_block_local(page, block, true); + return true; +} + +// ------------------------------------------------------ +// Multi-threaded Free (`_mt`) +// ------------------------------------------------------ + +// Push a block that is owned by another thread on its page-local thread free +// list or it's heap delayed free list. Such blocks are later collected by +// the owning thread in `_mi_free_delayed_block`. +static void mi_decl_noinline mi_free_block_delayed_mt( mi_page_t* page, mi_block_t* block ) +{ + // Try to put the block on either the page-local thread free list, + // or the heap delayed free list (if this is the first non-local free in that page) + mi_thread_free_t tfreex; + bool use_delayed; + mi_thread_free_t tfree = mi_atomic_load_relaxed(&page->xthread_free); + do { + use_delayed = (mi_tf_delayed(tfree) == MI_USE_DELAYED_FREE); + if mi_unlikely(use_delayed) { + // unlikely: this only happens on the first concurrent free in a page that is in the full list + tfreex = mi_tf_set_delayed(tfree,MI_DELAYED_FREEING); + } + else { + // usual: directly add to page thread_free list + mi_block_set_next(page, block, mi_tf_block(tfree)); + tfreex = mi_tf_set_block(tfree,block); + } + } while (!mi_atomic_cas_weak_release(&page->xthread_free, &tfree, tfreex)); + + // If this was the first non-local free, we need to push it on the heap delayed free list instead + if mi_unlikely(use_delayed) { + // racy read on `heap`, but ok because MI_DELAYED_FREEING is set (see `mi_heap_delete` and `mi_heap_collect_abandon`) + mi_heap_t* const heap = (mi_heap_t*)(mi_atomic_load_acquire(&page->xheap)); //mi_page_heap(page); + mi_assert_internal(heap != NULL); + if (heap != NULL) { + // add to the delayed free list of this heap. (do this atomically as the lock only protects heap memory validity) + mi_block_t* dfree = mi_atomic_load_ptr_relaxed(mi_block_t, &heap->thread_delayed_free); + do { + mi_block_set_nextx(heap,block,dfree, heap->keys); + } while (!mi_atomic_cas_ptr_weak_release(mi_block_t,&heap->thread_delayed_free, &dfree, block)); + } + + // and reset the MI_DELAYED_FREEING flag + tfree = mi_atomic_load_relaxed(&page->xthread_free); + do { + tfreex = tfree; + mi_assert_internal(mi_tf_delayed(tfree) == MI_DELAYED_FREEING); + tfreex = mi_tf_set_delayed(tfree,MI_NO_DELAYED_FREE); + } while (!mi_atomic_cas_weak_release(&page->xthread_free, &tfree, tfreex)); + } +} + +// Multi-threaded free (`_mt`) (or free in huge block if compiled with MI_HUGE_PAGE_ABANDON) +static mi_decl_noinline void mi_free_block_mt(mi_segment_t* segment, mi_page_t* page, mi_block_t* block) +{ + // first see if the segment was abandoned and if we can reclaim it into our thread + if (mi_option_is_enabled(mi_option_abandoned_reclaim_on_free) && + #if MI_HUGE_PAGE_ABANDON + segment->page_kind != MI_PAGE_HUGE && + #endif + mi_atomic_load_relaxed(&segment->thread_id) == 0) + { + // the segment is abandoned, try to reclaim it into our heap + if (_mi_segment_attempt_reclaim(mi_heap_get_default(), segment)) { + mi_assert_internal(_mi_prim_thread_id() == mi_atomic_load_relaxed(&segment->thread_id)); + mi_free(block); // recursively free as now it will be a local free in our heap + return; + } + } + + // The padding check may access the non-thread-owned page for the key values. + // that is safe as these are constant and the page won't be freed (as the block is not freed yet). + mi_check_padding(page, block); + + // adjust stats (after padding check and potential recursive `mi_free` above) + mi_stat_free(page, block); // stat_free may access the padding + mi_track_free_size(block, mi_page_usable_size_of(page,block)); + + // for small size, ensure we can fit the delayed thread pointers without triggering overflow detection + _mi_padding_shrink(page, block, sizeof(mi_block_t)); + + if (segment->page_kind == MI_PAGE_HUGE) { + #if MI_HUGE_PAGE_ABANDON + // huge page segments are always abandoned and can be freed immediately + mi_stat_huge_free(page); + _mi_segment_huge_page_free(segment, page, block); + return; + #else + // huge pages are special as they occupy the entire segment + // as these are large we reset the memory occupied by the page so it is available to other threads + // (as the owning thread needs to actually free the memory later). + _mi_segment_huge_page_reset(segment, page, block); + #endif + } + else { + #if (MI_DEBUG>0) && !MI_TRACK_ENABLED && !MI_TSAN // note: when tracking, cannot use mi_usable_size with multi-threading + memset(block, MI_DEBUG_FREED, mi_usable_size(block)); + #endif + } + + // and finally free the actual block by pushing it on the owning heap + // thread_delayed free list (or heap delayed free list) + mi_free_block_delayed_mt(page,block); +} + + +// ------------------------------------------------------ +// Usable size +// ------------------------------------------------------ + +// Bytes available in a block +mi_decl_noinline static size_t mi_page_usable_aligned_size_of(const mi_segment_t* segment, const mi_page_t* page, const void* p) mi_attr_noexcept { + const mi_block_t* block = _mi_page_ptr_unalign(segment, page, p); + const size_t size = mi_page_usable_size_of(page, block); + const ptrdiff_t adjust = (uint8_t*)p - (uint8_t*)block; + mi_assert_internal(adjust >= 0 && (size_t)adjust <= size); + return (size - adjust); +} + +static inline size_t _mi_usable_size(const void* p, const char* msg) mi_attr_noexcept { + if (p == NULL) return 0; + const mi_segment_t* const segment = mi_checked_ptr_segment(p, msg); + const mi_page_t* const page = _mi_segment_page_of(segment, p); + if mi_likely(!mi_page_has_aligned(page)) { + const mi_block_t* block = (const mi_block_t*)p; + return mi_page_usable_size_of(page, block); + } + else { + // split out to separate routine for improved code generation + return mi_page_usable_aligned_size_of(segment, page, p); + } +} + +mi_decl_nodiscard size_t mi_usable_size(const void* p) mi_attr_noexcept { + return _mi_usable_size(p, "mi_usable_size"); +} + + +// ------------------------------------------------------ +// Allocation extensions +// ------------------------------------------------------ + +void mi_free_size(void* p, size_t size) mi_attr_noexcept { + MI_UNUSED_RELEASE(size); + mi_assert(p == NULL || size <= _mi_usable_size(p,"mi_free_size")); + mi_free(p); +} + +void mi_free_size_aligned(void* p, size_t size, size_t alignment) mi_attr_noexcept { + MI_UNUSED_RELEASE(alignment); + mi_assert(((uintptr_t)p % alignment) == 0); + mi_free_size(p,size); +} + +void mi_free_aligned(void* p, size_t alignment) mi_attr_noexcept { + MI_UNUSED_RELEASE(alignment); + mi_assert(((uintptr_t)p % alignment) == 0); + mi_free(p); +}