mirror of
https://github.com/jart/cosmopolitan.git
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fa20edc44d
- Remove most __ASSEMBLER__ __LINKER__ ifdefs - Rename libc/intrin/bits.h to libc/serialize.h - Block pthread cancelation in fchmodat() polyfill - Remove `clang-format off` statements in third_party
78 lines
2.7 KiB
C++
78 lines
2.7 KiB
C++
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/* ----------------------- Direct-mmapping chunks ----------------------- */
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/*
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Directly mmapped chunks are set up with an offset to the start of
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the mmapped region stored in the prev_foot field of the chunk. This
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allows reconstruction of the required argument to MUNMAP when freed,
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and also allows adjustment of the returned chunk to meet alignment
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requirements (especially in memalign).
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*/
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/* Malloc using mmap */
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static void* mmap_alloc(mstate m, size_t nb) {
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size_t mmsize = mmap_align(nb + SIX_SIZE_T_SIZES + CHUNK_ALIGN_MASK);
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if (m->footprint_limit != 0) {
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size_t fp = m->footprint + mmsize;
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if (fp <= m->footprint || fp > m->footprint_limit)
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return 0;
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}
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if (mmsize > nb) { /* Check for wrap around 0 */
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char* mm = (char*)(dlmalloc_requires_more_vespene_gas(mmsize));
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if (mm != CMFAIL) {
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size_t offset = align_offset(chunk2mem(mm));
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size_t psize = mmsize - offset - MMAP_FOOT_PAD;
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mchunkptr p = (mchunkptr)(mm + offset);
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p->prev_foot = offset;
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p->head = psize;
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mark_inuse_foot(m, p, psize);
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chunk_plus_offset(p, psize)->head = FENCEPOST_HEAD;
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chunk_plus_offset(p, psize+SIZE_T_SIZE)->head = 0;
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if (m->least_addr == 0 || mm < m->least_addr)
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m->least_addr = mm;
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if ((m->footprint += mmsize) > m->max_footprint)
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m->max_footprint = m->footprint;
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assert(is_aligned(chunk2mem(p)));
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check_mmapped_chunk(m, p);
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return chunk2mem(p);
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}
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}
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return 0;
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}
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/* Realloc using mmap */
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static mchunkptr mmap_resize(mstate m, mchunkptr oldp, size_t nb, int flags) {
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size_t oldsize = chunksize(oldp);
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(void)flags; /* placate people compiling -Wunused */
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if (is_small(nb)) /* Can't shrink mmap regions below small size */
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return 0;
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/* Keep old chunk if big enough but not too big */
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if (oldsize >= nb + SIZE_T_SIZE &&
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(oldsize - nb) <= (mparams.granularity << 1))
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return oldp;
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else {
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size_t offset = oldp->prev_foot;
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size_t oldmmsize = oldsize + offset + MMAP_FOOT_PAD;
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size_t newmmsize = mmap_align(nb + SIX_SIZE_T_SIZES + CHUNK_ALIGN_MASK);
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char* cp = (char*)CALL_MREMAP((char*)oldp - offset,
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oldmmsize, newmmsize, flags);
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if (cp != CMFAIL) {
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mchunkptr newp = (mchunkptr)(cp + offset);
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size_t psize = newmmsize - offset - MMAP_FOOT_PAD;
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newp->head = psize;
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mark_inuse_foot(m, newp, psize);
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chunk_plus_offset(newp, psize)->head = FENCEPOST_HEAD;
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chunk_plus_offset(newp, psize+SIZE_T_SIZE)->head = 0;
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if (cp < m->least_addr)
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m->least_addr = cp;
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if ((m->footprint += newmmsize - oldmmsize) > m->max_footprint)
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m->max_footprint = m->footprint;
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check_mmapped_chunk(m, newp);
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return newp;
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}
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}
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return 0;
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}
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