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46 lines
794 B
46 lines
794 B
#include <stdlib.h>
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#include <stdint.h>
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#include <limits.h>
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#include <errno.h>
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#include "libc.h"
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uintptr_t __brk(uintptr_t);
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#define ALIGN 16
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void *__simple_malloc(size_t n)
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{
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static uintptr_t cur, brk;
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uintptr_t base, new;
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static int lock[2];
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size_t align=1;
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if (!n) n++;
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if (n > SIZE_MAX/2) goto toobig;
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while (align<n && align<ALIGN)
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align += align;
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n = n + align - 1 & -align;
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LOCK(lock);
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if (!cur) cur = brk = __brk(0)+16;
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base = cur + align-1 & -align;
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if (n > SIZE_MAX - PAGE_SIZE - base) goto fail;
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if (base+n > brk) {
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new = base+n + PAGE_SIZE-1 & -PAGE_SIZE;
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if (__brk(new) != new) goto fail;
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brk = new;
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}
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cur = base+n;
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UNLOCK(lock);
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return (void *)base;
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fail:
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UNLOCK(lock);
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toobig:
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errno = ENOMEM;
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return 0;
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}
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weak_alias(__simple_malloc, malloc);
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