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https://github.com/GrapheneOS/hardened_malloc.git
synced 2024-10-01 01:36:01 -04:00
calculate slab size class instead of array loop
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commit
81cf2f27a0
22
h_malloc.c
22
h_malloc.c
@ -196,13 +196,16 @@ static inline struct size_info get_size_info(size_t size) {
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if (size <= 128) {
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return (struct size_info){align(size, 16), ((size - 1) >> 4) + 1};
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}
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for (unsigned class = 9; class < N_SIZE_CLASSES; class++) {
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size_t real_size = size_classes[class];
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if (size <= real_size) {
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return (struct size_info){real_size, class};
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}
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}
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fatal_error("invalid size for slabs");
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const size_t initial_spacing_multiplier = 5;
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const size_t special_small_sizes = 5; // 0, 16, 32, 48, 64
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size_t spacing_class_shift = log2u64(size - 1) - 2;
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size_t spacing_class = 1ULL << spacing_class_shift;
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size_t real_size = align(size, spacing_class);
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size_t spacing_class_index = (real_size >> spacing_class_shift) - initial_spacing_multiplier;
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size_t index = (spacing_class_shift - 4) * 4 + special_small_sizes + spacing_class_index;
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return (struct size_info){real_size, index};
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}
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// alignment must be a power of 2 <= PAGE_SIZE since slabs are only page aligned
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@ -1199,10 +1202,7 @@ static size_t get_large_size_class(size_t size) {
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// 512 KiB [2560 KiB, 3 MiB, 3584 KiB, 4 MiB]
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// 1 MiB [5 MiB, 6 MiB, 7 MiB, 8 MiB]
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// etc.
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size = max(size, (size_t)PAGE_SIZE);
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size_t spacing_shift = U64_WIDTH - clz64(size - 1) - 3;
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size_t spacing_class = 1ULL << spacing_shift;
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return align(size, spacing_class);
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return get_size_info(max(size, (size_t)PAGE_SIZE)).size;
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}
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return page_align(size);
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}
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8
util.h
8
util.h
@ -35,6 +35,8 @@ typedef uint32_t u32;
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typedef uint64_t u64;
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typedef unsigned __int128 u128;
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#define U64_WIDTH 64
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static inline int clz64(u64 x) {
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return __builtin_clzll(x);
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}
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@ -43,6 +45,10 @@ static inline int ffz64(u64 x) {
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return __builtin_ffsll(~x);
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}
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static inline u64 log2u64(u64 x) {
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return U64_WIDTH - clz64(x) - 1;
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}
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static inline size_t align(size_t size, size_t align) {
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size_t mask = align - 1;
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return (size + mask) & ~mask;
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@ -50,8 +56,6 @@ static inline size_t align(size_t size, size_t align) {
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COLD noreturn void fatal_error(const char *s);
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#define U64_WIDTH 64
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#if CONFIG_SEAL_METADATA
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#ifdef __GLIBC__
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