Add a "fork" of musl as //fusl.

fusl/src/malloc/malloc.c

+#define _GNU_SOURCE
+#include <stdlib.h>
+#include <string.h>
+#include <limits.h>
+#include <stdint.h>
+#include <errno.h>
+#include <sys/mman.h>
+#include "libc.h"
+#include "atomic.h"
+#include "pthread_impl.h"
+
+#if defined(__GNUC__) && defined(__PIC__)
+#define inline inline __attribute__((always_inline))
+#endif
+
+void *__mmap(void *, size_t, int, int, int, off_t);
+int __munmap(void *, size_t);
+void *__mremap(void *, size_t, size_t, int, ...);
+int __madvise(void *, size_t, int);
+
+struct chunk {
+        size_t psize, csize;
+        struct chunk *next, *prev;
+};
+
+struct bin {
+        volatile int lock[2];
+        struct chunk *head;
+        struct chunk *tail;
+};
+
+static struct {
+        volatile uint64_t binmap;
+        struct bin bins[64];
+        volatile int free_lock[2];
+} mal;
+
+
+#define SIZE_ALIGN (4*sizeof(size_t))
+#define SIZE_MASK (-SIZE_ALIGN)
+#define OVERHEAD (2*sizeof(size_t))
+#define MMAP_THRESHOLD (0x1c00*SIZE_ALIGN)
+#define DONTCARE 16
+#define RECLAIM 163840
+
+#define CHUNK_SIZE(c) ((c)->csize & -2)
+#define CHUNK_PSIZE(c) ((c)->psize & -2)
+#define PREV_CHUNK(c) ((struct chunk *)((char *)(c) - CHUNK_PSIZE(c)))
+#define NEXT_CHUNK(c) ((struct chunk *)((char *)(c) + CHUNK_SIZE(c)))
+#define MEM_TO_CHUNK(p) (struct chunk *)((char *)(p) - OVERHEAD)
+#define CHUNK_TO_MEM(c) (void *)((char *)(c) + OVERHEAD)
+#define BIN_TO_CHUNK(i) (MEM_TO_CHUNK(&mal.bins[i].head))
+
+#define C_INUSE  ((size_t)1)
+
+#define IS_MMAPPED(c) !((c)->csize & (C_INUSE))
+
+
+/* Synchronization tools */
+
+static inline void lock(volatile int *lk)
+{
+        if (libc.threads_minus_1)
+                while(a_swap(lk, 1)) __wait(lk, lk+1, 1, 1);
+}
+
+static inline void unlock(volatile int *lk)
+{
+        if (lk[0]) {
+                a_store(lk, 0);
+                if (lk[1]) __wake(lk, 1, 1);
+        }
+}
+
+static inline void lock_bin(int i)
+{
+        lock(mal.bins[i].lock);
+        if (!mal.bins[i].head)
+                mal.bins[i].head = mal.bins[i].tail = BIN_TO_CHUNK(i);
+}
+
+static inline void unlock_bin(int i)
+{
+        unlock(mal.bins[i].lock);
+}
+
+static int first_set(uint64_t x)
+{
+#if 1
+        return a_ctz_64(x);
+#else
+        static const char debruijn64[64] = {
+                0, 1, 2, 53, 3, 7, 54, 27, 4, 38, 41, 8, 34, 55, 48, 28,
+                62, 5, 39, 46, 44, 42, 22, 9, 24, 35, 59, 56, 49, 18, 29, 11,
+                63, 52, 6, 26, 37, 40, 33, 47, 61, 45, 43, 21, 23, 58, 17, 10,
+                51, 25, 36, 32, 60, 20, 57, 16, 50, 31, 19, 15, 30, 14, 13, 12
+        };
+        static const char debruijn32[32] = {
+                0, 1, 23, 2, 29, 24, 19, 3, 30, 27, 25, 11, 20, 8, 4, 13,
+                31, 22, 28, 18, 26, 10, 7, 12, 21, 17, 9, 6, 16, 5, 15, 14
+        };
+        if (sizeof(long) < 8) {
+                uint32_t y = x;
+                if (!y) {
+                        y = x>>32;
+                        return 32 + debruijn32[(y&-y)*0x076be629 >> 27];
+                }
+                return debruijn32[(y&-y)*0x076be629 >> 27];
+        }
+        return debruijn64[(x&-x)*0x022fdd63cc95386dull >> 58];
+#endif
+}
+
+static int bin_index(size_t x)
+{
+        x = x / SIZE_ALIGN - 1;
+        if (x <= 32) return x;
+        if (x > 0x1c00) return 63;
+        return ((union { float v; uint32_t r; }){(int)x}.r>>21) - 496;
+}
+
+static int bin_index_up(size_t x)
+{
+        x = x / SIZE_ALIGN - 1;
+        if (x <= 32) return x;
+        return ((union { float v; uint32_t r; }){(int)x}.r+0x1fffff>>21) - 496;
+}
+
+#if 0
+void __dump_heap(int x)
+{
+        struct chunk *c;
+        int i;
+        for (c = (void *)mal.heap; CHUNK_SIZE(c); c = NEXT_CHUNK(c))
+                fprintf(stderr, "base %p size %zu (%d) flags %d/%d\n",
+                        c, CHUNK_SIZE(c), bin_index(CHUNK_SIZE(c)),
+                        c->csize & 15,
+                        NEXT_CHUNK(c)->psize & 15);
+        for (i=0; i<64; i++) {
+                if (mal.bins[i].head != BIN_TO_CHUNK(i) && mal.bins[i].head) {
+                        fprintf(stderr, "bin %d: %p\n", i, mal.bins[i].head);
+                        if (!(mal.binmap & 1ULL<<i))
+                                fprintf(stderr, "missing from binmap!\n");
+                } else if (mal.binmap & 1ULL<<i)
+                        fprintf(stderr, "binmap wrongly contains %d!\n", i);
+        }
+}
+#endif
+
+void *__expand_heap(size_t *);
+
+static struct chunk *expand_heap(size_t n)
+{
+        static int heap_lock[2];
+        static void *end;
+        void *p;
+        struct chunk *w;
+
+        /* The argument n already accounts for the caller's chunk
+         * overhead needs, but if the heap can't be extended in-place,
+         * we need room for an extra zero-sized sentinel chunk. */
+        n += SIZE_ALIGN;
+
+        lock(heap_lock);
+
+        p = __expand_heap(&n);
+        if (!p) {
+                unlock(heap_lock);
+                return 0;
+        }
+
+        /* If not just expanding existing space, we need to make a
+         * new sentinel chunk below the allocated space. */
+        if (p != end) {
+                /* Valid/safe because of the prologue increment. */
+                n -= SIZE_ALIGN;
+                p = (char *)p + SIZE_ALIGN;
+                w = MEM_TO_CHUNK(p);
+                w->psize = 0 | C_INUSE;
+        }
+
+        /* Record new heap end and fill in footer. */
+        end = (char *)p + n;
+        w = MEM_TO_CHUNK(end);
+        w->psize = n | C_INUSE;
+        w->csize = 0 | C_INUSE;
+
+        /* Fill in header, which may be new or may be replacing a
+         * zero-size sentinel header at the old end-of-heap. */
+        w = MEM_TO_CHUNK(p);
+        w->csize = n | C_INUSE;
+
+        unlock(heap_lock);
+
+        return w;
+}
+
+static int adjust_size(size_t *n)
+{
+        /* Result of pointer difference must fit in ptrdiff_t. */
+        if (*n-1 > PTRDIFF_MAX - SIZE_ALIGN - PAGE_SIZE) {
+                if (*n) {
+                        errno = ENOMEM;
+                        return -1;
+                } else {
+                        *n = SIZE_ALIGN;
+                        return 0;
+                }
+        }
+        *n = (*n + OVERHEAD + SIZE_ALIGN - 1) & SIZE_MASK;
+        return 0;
+}
+
+static void unbin(struct chunk *c, int i)
+{
+        if (c->prev == c->next)
+                a_and_64(&mal.binmap, ~(1ULL<<i));
+        c->prev->next = c->next;
+        c->next->prev = c->prev;
+        c->csize |= C_INUSE;
+        NEXT_CHUNK(c)->psize |= C_INUSE;
+}
+
+static int alloc_fwd(struct chunk *c)
+{
+        int i;
+        size_t k;
+        while (!((k=c->csize) & C_INUSE)) {
+                i = bin_index(k);
+                lock_bin(i);
+                if (c->csize == k) {
+                        unbin(c, i);
+                        unlock_bin(i);
+                        return 1;
+                }
+                unlock_bin(i);
+        }
+        return 0;
+}
+
+static int alloc_rev(struct chunk *c)
+{
+        int i;
+        size_t k;
+        while (!((k=c->psize) & C_INUSE)) {
+                i = bin_index(k);
+                lock_bin(i);
+                if (c->psize == k) {
+                        unbin(PREV_CHUNK(c), i);
+                        unlock_bin(i);
+                        return 1;
+                }
+                unlock_bin(i);
+        }
+        return 0;
+}
+
+
+/* pretrim - trims a chunk _prior_ to removing it from its bin.
+ * Must be called with i as the ideal bin for size n, j the bin
+ * for the _free_ chunk self, and bin j locked. */
+static int pretrim(struct chunk *self, size_t n, int i, int j)
+{
+        size_t n1;
+        struct chunk *next, *split;
+
+        /* We cannot pretrim if it would require re-binning. */
+        if (j < 40) return 0;
+        if (j < i+3) {
+                if (j != 63) return 0;
+                n1 = CHUNK_SIZE(self);
+                if (n1-n <= MMAP_THRESHOLD) return 0;
+        } else {
+                n1 = CHUNK_SIZE(self);
+        }
+        if (bin_index(n1-n) != j) return 0;
+
+        next = NEXT_CHUNK(self);
+        split = (void *)((char *)self + n);
+
+        split->prev = self->prev;
+        split->next = self->next;
+        split->prev->next = split;
+        split->next->prev = split;
+        split->psize = n | C_INUSE;
+        split->csize = n1-n;
+        next->psize = n1-n;
+        self->csize = n | C_INUSE;
+        return 1;
+}
+
+static void trim(struct chunk *self, size_t n)
+{
+        size_t n1 = CHUNK_SIZE(self);
+        struct chunk *next, *split;
+
+        if (n >= n1 - DONTCARE) return;
+
+        next = NEXT_CHUNK(self);
+        split = (void *)((char *)self + n);
+
+        split->psize = n | C_INUSE;
+        split->csize = n1-n | C_INUSE;
+        next->psize = n1-n | C_INUSE;
+        self->csize = n | C_INUSE;
+
+        free(CHUNK_TO_MEM(split));
+}
+
+void *malloc(size_t n)
+{
+        struct chunk *c;
+        int i, j;
+
+        if (adjust_size(&n) < 0) return 0;
+
+        if (n > MMAP_THRESHOLD) {
+                size_t len = n + OVERHEAD + PAGE_SIZE - 1 & -PAGE_SIZE;
+                char *base = __mmap(0, len, PROT_READ|PROT_WRITE,
+                        MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
+                if (base == (void *)-1) return 0;
+                c = (void *)(base + SIZE_ALIGN - OVERHEAD);
+                c->csize = len - (SIZE_ALIGN - OVERHEAD);
+                c->psize = SIZE_ALIGN - OVERHEAD;
+                return CHUNK_TO_MEM(c);
+        }
+
+        i = bin_index_up(n);
+        for (;;) {
+                uint64_t mask = mal.binmap & -(1ULL<<i);
+                if (!mask) {
+                        c = expand_heap(n);
+                        if (!c) return 0;
+                        if (alloc_rev(c)) {
+                                struct chunk *x = c;
+                                c = PREV_CHUNK(c);
+                                NEXT_CHUNK(x)->psize = c->csize =
+                                        x->csize + CHUNK_SIZE(c);
+                        }
+                        break;
+                }
+                j = first_set(mask);
+                lock_bin(j);
+                c = mal.bins[j].head;
+                if (c != BIN_TO_CHUNK(j)) {
+                        if (!pretrim(c, n, i, j)) unbin(c, j);
+                        unlock_bin(j);
+                        break;
+                }
+                unlock_bin(j);
+        }
+
+        /* Now patch up in case we over-allocated */
+        trim(c, n);
+
+        return CHUNK_TO_MEM(c);
+}
+
+void *__malloc0(size_t n)
+{
+        void *p = malloc(n);
+        if (p && !IS_MMAPPED(MEM_TO_CHUNK(p))) {
+                size_t *z;
+                n = (n + sizeof *z - 1)/sizeof *z;
+                for (z=p; n; n--, z++) if (*z) *z=0;
+        }
+        return p;
+}
+
+void *realloc(void *p, size_t n)
+{
+        struct chunk *self, *next;
+        size_t n0, n1;
+        void *new;
+
+        if (!p) return malloc(n);
+
+        if (adjust_size(&n) < 0) return 0;
+
+        self = MEM_TO_CHUNK(p);
+        n1 = n0 = CHUNK_SIZE(self);
+
+        if (IS_MMAPPED(self)) {
+                size_t extra = self->psize;
+                char *base = (char *)self - extra;
+                size_t oldlen = n0 + extra;
+                size_t newlen = n + extra;
+                /* Crash on realloc of freed chunk */
+                if (extra & 1) a_crash();
+                if (newlen < PAGE_SIZE && (new = malloc(n))) {
+                        memcpy(new, p, n-OVERHEAD);
+                        free(p);
+                        return new;
+                }
+                newlen = (newlen + PAGE_SIZE-1) & -PAGE_SIZE;
+                if (oldlen == newlen) return p;
+                base = __mremap(base, oldlen, newlen, MREMAP_MAYMOVE);
+                if (base == (void *)-1)
+                        return newlen < oldlen ? p : 0;
+                self = (void *)(base + extra);
+                self->csize = newlen - extra;
+                return CHUNK_TO_MEM(self);
+        }
+
+        next = NEXT_CHUNK(self);
+
+        /* Crash on corrupted footer (likely from buffer overflow) */
+        if (next->psize != self->csize) a_crash();
+
+        /* Merge adjacent chunks if we need more space. This is not
+         * a waste of time even if we fail to get enough space, because our
+         * subsequent call to free would otherwise have to do the merge. */
+        if (n > n1 && alloc_fwd(next)) {
+                n1 += CHUNK_SIZE(next);
+                next = NEXT_CHUNK(next);
+        }
+        /* FIXME: find what's wrong here and reenable it..? */
+        if (0 && n > n1 && alloc_rev(self)) {
+                self = PREV_CHUNK(self);
+                n1 += CHUNK_SIZE(self);
+        }
+        self->csize = n1 | C_INUSE;
+        next->psize = n1 | C_INUSE;
+
+        /* If we got enough space, split off the excess and return */
+        if (n <= n1) {
+                //memmove(CHUNK_TO_MEM(self), p, n0-OVERHEAD);
+                trim(self, n);
+                return CHUNK_TO_MEM(self);
+        }
+
+        /* As a last resort, allocate a new chunk and copy to it. */
+        new = malloc(n-OVERHEAD);
+        if (!new) return 0;
+        memcpy(new, p, n0-OVERHEAD);
+        free(CHUNK_TO_MEM(self));
+        return new;
+}
+
+void free(void *p)
+{
+        struct chunk *self = MEM_TO_CHUNK(p);
+        struct chunk *next;
+        size_t final_size, new_size, size;
+        int reclaim=0;
+        int i;
+
+        if (!p) return;
+
+        if (IS_MMAPPED(self)) {
+                size_t extra = self->psize;
+                char *base = (char *)self - extra;
+                size_t len = CHUNK_SIZE(self) + extra;
+                /* Crash on double free */
+                if (extra & 1) a_crash();
+                __munmap(base, len);
+                return;
+        }
+
+        final_size = new_size = CHUNK_SIZE(self);
+        next = NEXT_CHUNK(self);
+
+        /* Crash on corrupted footer (likely from buffer overflow) */
+        if (next->psize != self->csize) a_crash();
+
+        for (;;) {
+                if (self->psize & next->csize & C_INUSE) {
+                        self->csize = final_size | C_INUSE;
+                        next->psize = final_size | C_INUSE;
+                        i = bin_index(final_size);
+                        lock_bin(i);
+                        lock(mal.free_lock);
+                        if (self->psize & next->csize & C_INUSE)
+                                break;
+                        unlock(mal.free_lock);
+                        unlock_bin(i);
+                }
+
+                if (alloc_rev(self)) {
+                        self = PREV_CHUNK(self);
+                        size = CHUNK_SIZE(self);
+                        final_size += size;
+                        if (new_size+size > RECLAIM && (new_size+size^size) > size)
+                                reclaim = 1;
+                }
+
+                if (alloc_fwd(next)) {
+                        size = CHUNK_SIZE(next);
+                        final_size += size;
+                        if (new_size+size > RECLAIM && (new_size+size^size) > size)
+                                reclaim = 1;
+                        next = NEXT_CHUNK(next);
+                }
+        }
+
+        if (!(mal.binmap & 1ULL<<i))
+                a_or_64(&mal.binmap, 1ULL<<i);
+
+        self->csize = final_size;
+        next->psize = final_size;
+        unlock(mal.free_lock);
+
+        self->next = BIN_TO_CHUNK(i);
+        self->prev = mal.bins[i].tail;
+        self->next->prev = self;
+        self->prev->next = self;
+
+        /* Replace middle of large chunks with fresh zero pages */
+        if (reclaim) {
+                uintptr_t a = (uintptr_t)self + SIZE_ALIGN+PAGE_SIZE-1 & -PAGE_SIZE;
+                uintptr_t b = (uintptr_t)next - SIZE_ALIGN & -PAGE_SIZE;
+#if 1
+                __madvise((void *)a, b-a, MADV_DONTNEED);
+#else
+                __mmap((void *)a, b-a, PROT_READ|PROT_WRITE,
+                        MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED, -1, 0);
+#endif
+        }
+
+        unlock_bin(i);
+}